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Geological Survey of India

International Geoscience Programme

IGCP-510

Global Correlation of A-type Granites and

Related Rocks, their Mineralization

and Significance in Lithospheric Evolution

(2005-09)

Final Report March 2010

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Final Report on the

IGCP-510

“Global Correlation of A-type Granites and Related Rocks,

their Mineralization and Significance in Lithospheric Evolution”,

conducted in India during 2005-09

- - - - - - - - Report prepared and submitted by

Dr. H. Sarvothaman

Director, Technical Co-ordination

GSI, Southern Region, Hyderabad 500068

in association with

Dr. V.V.Sesha Sai

Jr. Geologist, GSI, NER, Shillong.

- - - - - - - - - -

I. Introduction

International Geoscience Programme is an activity of UNESCO and International

Union of Geological Sciences, IUGS) that provides a common international platform

for joint studies in the field of geology-related topics, especially on society-related

matters. Geoscientific work under the auspices of International Geoscience Programme

(earlier known as International Geological Correlation Programme, IGCP) is taken up

in India, with Geological Survey of India (GSI) as the Nodal Agency; representatives

from different Indian organizations that conduct geoscientific work associate

themselves as Participating Members in the IGCP projects. International Geoscience

Programme, IGCP-510, bearing the title ‗Global Correlation of A-type Granites and

Related Rocks, their Mineralization and Significance in Lithospheric Evolution‘ was

conducted by IUGS during 2005-09 across the globe. In India, the work under IGCP-

510 commenced in November 2006. India was included as a participating country in

this programme in 2007. This report highlights the work done in India under the

auspices of IGCP-510, from November 2006 to December 2009.

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I.1. Aim of IGCP-510: The aim of IGCP-510 is to correlate petrology, geochronology,

geochemistry and metallogeny of A-type granites found in various tectonic settings

through the geological times.

I.2. Objectives of IGCP-510: The objectives of IGCP-510 are to conduct study under

specific themes such as (i) age distribution, petro-tectonic associations and genetic

models of A-type granites and related rocks; (ii) their significance and metallogeny;

(iii) their bearing on granite typology and evaluation of hitherto proposed

classifications; and (iv) their overall role in the evolution of the Earth‘s lithosphere. A-

type granite petrogenesis and nature of hydrothermal processes and different types of

metallogenic provinces and deposits will also be given as inputs to the study.

I.3. Study Group of IGCP-510 in India: As is customary with all IGCP projects in

India, the Indian National Committee (INC) for IGCP had constituted a National

Working Group (NWG) for functioning of IGCP-510. During the tenure (November

2006-December 2009), the work of the NWG of IGCP-510 was monitored by the INC

for IGCP to which the Director-General, GSI (ex-officio) is the Chairman and the

Director, International Division (ex-officio) is the Member Secretary. The composition

of the NWG, IGCP-510 constituted by the INC for IGCP is as follows:

Chairman, NWG:

a. Deputy Director General, Op: MPID, CHQ, GSI, Kolkata (up to July 2007).

b. Deputy Director General, GSI, Southern Region (SR), Hyderabad (from

August 2007 to December 2009.

Convener: Dr. H. Sarvothaman, Director, GSI, Op.MPID, Kolkata / SR, Hyderabad.

Members: 1. Dr. Sambhunath Ghosh, Dy. Director General, GSI, Kolkata / Bangalore.

2. Dr. K. Sashidharan, Director, GSI, Nagpur.

3. Dr. V.V. Sesha Sai, Sr. Geologist, GSI, Hyderabad / Shillong.

4. Dr. Manoranjan Mohanty, Sr. Geologist, Shillong / Bhubaneshwar.

5. Shri Pradeep Mawar, Sr. Geologist, Lucknow (co-opted in June 2007)

6. Shri V.K. Chittora, Sr. Geologist, Jaipur (co-opted in June 2007, but left

NWG in September 2007)

7. Dr. P. V. Ramesh Babu, Scientist-H & Regional Director, Atomic

Minerals Dept., (Dept. of Atomic Energy), Ranchi / Hyderabad

8. Dr. M.E.A. Mondal, Sr. Lecturer, Aligarh Muslim University, Aligarh

9. Dr. D. R. Rao, Scientist-E, Wadia Institute of Himalayan Geology, Dehra

Dun, Uttarakhand (co-opted in June 2007).

I.4. In the following pages, the activities of work conducted in India under the auspices

of IGCP-510, the highlights of those activities and scientific output of the studies of the

NWG of IGCP-510 are presented.

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II. IGCP-510 in India

In India, the work under the IGCP-510 project was conducted from November 2006 to

December 2009. During this tenure, three NWG Meetings, two Field Workshops and

one Open Workshop were conducted. Besides, the progress of work in various stages

of IGCP-510 tenure was highlighted in the 32nd

, 33rd

, 34th

and 35th

INC for IGCP

meetings held between 2006 to 2010, by way of presentations on scientific findings of

the research under IGCP-510, to the esteemed Members of INC for IGCP who monitor

the IGCP projects in India.

II. 1. First Meeting of the NWG, IGCP-510: The First NWG meeting was held at

GSI, CHQ, Kolkata on 14th

November 2006, under the Chairmanship of Shri

P.M.Tejale, DG, GSI & Chairman, INC for IGCP. The Convener, IGCP-510 set out

agenda for work under this IGCP project. Presentations on the field, petrographic and

chemical characteristics, tectonic domains, mineralization and possible ages of A-type

granite occurrences distributed all over in India were made by the NWG of IGCP- 510.

The Chairman advised the NWG Members to work in close association and

communication, and to effectively use the scarce resources available at their disposal

by way of sharing the laboratory facilities.

The Convener set out the following Action Plan for IGCP-510 in this meeting: (i)

Submission of an Integrated Compilation of all information on A-type granites in India

to the DG, GSI by 31 March 2007; (ii) conduct of annual meetings of NWG to assess

the progress and integrate the data generated by the NWG Members; (iii) conduct of

Field Workshops to examine the A-type granites occurring in different tectonic

domains in India (for eg. In (a) a zone of collision, modified into a Marginal Zone

between craton and mobile belt; and (b) a rift zone); (iv) conduct an Open Workshop to

give an opportunity to all scientists, researchers and academia in India to present and

share information on a common / open platform, on the A-type granite occurrences

with which they are associated, by way of their scientific contribution as scientific

presentation; (v) prepare a dossier on A-type granite occurrences of India based on the

Open Workshop deliberations; and (vi) bring out publications.

II.2. Integrated Compilation of information on A-type granites in India: The

integrated compilation was intended as a review of all available information to be made

by the NWG, and to plug the gap in knowledge, as also to launch further study in areas

/ fields identified where there is scope for generating new / additional database. The

Members of the NWG liberally contributed their compilations of the existing database

on Indian A-type granite occurrences up to 2006. The Convener integrated those

compilations and submitted the Integrated Compilation as a single volume to the DG,

GSI, on 30th

March 2007, on the committed date.

II.3. Second Meeting of the NWG & Field Workshop at Prakasam Alkaline

Province: Second NWG meeting was held at D.N.Wadia Hall, GSI, SR, Hyderabad on

18th

December 2007 to review the progress of conducted by the NWG. The Convener

and the Members of NWG made presentations on the nature and field, petrographic and

chemical characteristics of the A-type granite occurrences that came to light in 2007. In

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this meeting, the convener announced the tentative schedule for the Open Workshop to

which the Chairman, INC for IGCP accorded the approval, and requested the Members

to participate in the Open Workshop by making technical paper presentations, which

will be published later. Convener requested the Members to give wide publicity to the

Open workshop so that scientists from all over India could contribute papers and the

database of the NWG was widened.

Field Workshop at Prakasam Alkaline Province, Andhra Pradesh was conducted from

19th

to 21st December 2007. Prakasam Alkaline Province occurs within a Marginal

Zone that occurs between Dharwar craton and the Eastern Ghats mobile belt at the

southeastern part of India in Andhra Pradesh. The Marginal Zone is a reconstituted

zone of collision of Eastern Ghats Granulite (mobile) Belt with the Dharwar craton, and

this zone has witnessed an array of magmatic activity, ranging as ultrabasic, syenitic,

albititic and granitic (including A-type) composition during Archaean and Proterozoic

time. The NWG visited the occurrences of A-type granites and related rocks at Podili,

Kanigiri and Singarakonda, and nepheline syenite (Elchuru) and gabbro plutons (Podile

& Chimakurti) of Prakasam Alkaline Province. Further, the A-type granite occurrences

in Eastern Ghat Granulite Belt in Kondapalle and Pericherla in Krishna and Guntur

districts were also examined.

II. 4. Third Meeting of the NWG: The Third NWG meeting was held on 18th

March

2009, at GSI, Central Region, Nagpur. The NWG reviewed the work carried out by the

Members during 2008. It was observed that until GSI conducts the IGCP projects as

GSI‘s field season programmes, the Members would find it difficult to generate new

database on geochemistry and geochronology, which are essential inputs to projects

like IGCP-510.

II.5. Open Workshop: An Open Workshop was convened on 19th

and 20th

March

2009 at GSI, Central Region, Nagpur. Circular was issued to all research institutions,

universities and professional organizations which carry out geoscientific work and

researches on granite, besides various Regions / Divisions / Units of GSI spread all

over India , inviting scientific papers as scientific contributions in the Open Workshop.

The primary aim of conducting the Open Workshop was to bring all pieces of

information on A-type granite occurrences of India into one single printed volume; and

the secondary aim was to prepare a dossier on the A-type granite occurrences of India

furnishing all available / possible information on those occurrences.

Twenty-eight scientific papers as Abstracts / Extended Abstracts (including two key

presentations) were received as technical contributions to the Open Workshop. They

were presented by their authors in 6 technical sessions spread over two days, followed

by a panel discussion. An Abstract Volume containing all these 28 abstracts was

brought out on this occasion; it was released on 19th

March 2009 by Shri N. K. Dutta,

Sr. Dy. Director General, GSI. This Abstract Volume is attached to this report as

Annexure-I.

II. 6. Dossier on A-type granites of India: Based on the information available from

the Open Workshop Abstract Volume and all other available information on A-type

granites, a dossier has been prepared, which is attached to this report as Annexure-II.

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II. 7. Field Workshop in Narmada Rift Zone: A Field Workshop was conducted in

the Narmada Rift Zone with an aim of comparing the A-type granites occurring in the

modified Collision Zone / Marginal Zone (such as Prakasam Alkaline Province) with

those occurring in the Rift Zone.

Tirodi gneiss (which is regarded in literature as an A-type granite derivative) and

Madan Mahal granite near Jabalpur were examined during this workshop. Field

evidences on the nature of occurrence of Tirodi gneiss and its published peraluminous

geochemistry do not convincingly support its A-type nature. Madan Mahal granite is a

pink, coarse-grained and hypersolvus granite with potash-rich chemistry, and therefore,

it might represent an A-type granite emplaced in a rift environment.

II. 8. Participation by / involvement of the NWG Members in IGCP-510 project

work: Dr. D. R. Rao and Shri Pradeep Mawar, Members from WIGH, Dehra Dun and

GSI, NR, Lucknow respectively were co-opted to the NWG in June 2007, after the First

NWG Meeting. Their participation to the NWG activity was restricted to the Second

NWG Meeting and Field Workshop in Prakasam Alkaline Province. Though they

submitted abstract / paper to the Open Workshop, they could not attend the same, the

Third NWG Meeting and the Narmada Rift Field workshop.

Dr. M.E.A. Mondal, NWG Member representing Aligarh Muslim University had

attended the First NWG Meeting. Despite submitting a paper on Bundelkhand granite

to the Open Workshop, he could not present the findings in the Workshop; nor could he

participate in the other two NWG Meetings and the two Field Workshops.

Under the directive of the DG, GSI & Chairman, INC for IGCP, Shri V. K. Chittora,

Sr. Geologist, GSI, Western Region (part of India enriched in A-type granite

occurrences), Jaipur was co-opted to the NWG in June 2007, on the strength of

nomination from DDG, WR, Jaipur, with a view to compile information on the A-type

granites of Malani, Siwana, Jalor and several other occurrences. He had opted out of

the NWG and could not attend any meeting / workshop. Consequently, the information

on the northwestern Indian A-type granite occurrences was compiled by other Members

/ Convener.

Rest of the Members of NWG participated in all the events of IGCP-510.

II. 9. Acknowledgements: The Convener, NWG, IGCP-510 places on record the

support received from S/Shri P. M. Tejale and N. K. Dutta, Director-Generals, GSI &

Chairmen, INC for IGCP to conduct this project. He acknowledges the assistance

received from the active NWG members and all the authors who submitted / presented

papers in the Open Workshop. The Organizing Committees of Open Workshop, Field

Workshops and various NWG meetings are thanked for their assistance in conducting

those events. Member Secretary & International Division, GSI, Kolkata offered

support to all activities of IGCP-510.

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III. Brief Summary on the A-type granites of India

This part of the report brings out the salient features of the petrographic and

geochemical features of the Indian A-type granite occurrences and tectonic domain in

which those granites are located. The source of information presented in this section of

the report is the Abstract Volume (Annexure-I) which contains the papers presented in

the Open Workshop of 19-20 March 2009.

III. 1. A-type granites in India: A synthesis of the data on the Indian A-type granite

occurrences has brought out that there are three distinct types of alkaline / anorogenic /

anhydrous granites. They types are as follows:

(i) A-type granites bearing sodic-amphibole or -pyroxene such as edenite,

pargasite, riebeckite, arfvedsonite, jadeite, barkevikite, aegirine, aegirine-augite

and acmite, as exemplified by those occurrences as at Podile, Andhra Pradesh

(occurring in a modified Collision / Marginal Zone), and at Siwana, Rajasthan

(located in an intra-plate tectonic setting).

(ii) Hypersolvus granites composed of quartz and K-feldspar, and as described

by Sylvester (1989). Examples: Potash-rich alkaline granite occurrences as at

Kondapalli, Phirangipuram & Perecherla in Eastern Ghats Granulite (Mobile)

Belt, in an anorogenic and anhydrous environment.

(iii) Subsolvus alkali-rich granites occurring at Nalgonda (Dharwar craton),

Singarayakonda (Marginal Zone), Madan Mahal Granite (Jabalpur, in Narmada

Rift Zone) and Jalore Granite (Rajasthan); A-type granite plutons in

Bundelkhand craton, Singhbhum craton (Mayurbhanj, Arkasani, Pal Laharha),

Lingtse Gneiss, Sikkim and Kashmir (Tangmarg-Gulmarg) Himalayas.

III. 2. General geochemical characteristics of A-type granites of India: A synthesis

of a large database that exists in the INAA laboratory, GSI, Pune was made.

Geochemical characters like SiO2 > 66%, Sc < 10 ppm, R1 > 1425 and R2 < 625 are

used for comparative studies of granites from Bundelkhand, Bastar, Dharwar and

Sighbhum cratons. Singhbhum granites have higher range of total REE, Hf ans Ta as

compared to Dharwar and Bundelkhand granites. Geochemical condition of SiO2 >

66%, total Alkali > 9.5%, K2O / Na2O > 2.2, K2O > 5 and CaO < 0.9% are used for

searching for possible post-collisional alkali granites. Samples from (i) Sirohi district,

Rajasthan; (ii) Humboldt, East Antarctica; (iii) Ghosiana (iv) Hamirpur district, UP; (v)

Mainpur kimberlite field, (vi) Raipur district, Chhattisgarh; and (vii) Belamu, Purulia

district, West Bengal are marked from NAA database as A-type granites. They are

show high SiO2, alkalis, Na2O, Fe / Mg, halogens, Zr, Nb, Ga, Y, Ce and low CaO.

Geochemical parameters such as SiO2 > 66%, total Alkali > 9.5%, high Na2O and CaO

< 0.9% are used for locating A-type granites from the database. Median as well as

minimum and maximum values (given in parenthesis) of geochemical parameters of

seven samples of southern parts of India are as follows: SiO2 = 69.65% (67.47-

72.61%) , R1 = 1345 (725-1733), R2 = 345 (282-394) , TiO2 = 0.095%, Al2O3 =

15.42%, CaO = 0.29%, MgO =0.13%, Na2O =6.07, K2O = 4.76%, P2O5 = 0.03% , Co =

1.25ppm, Sc = 2.5ppm Cr = 6.45ppm, Th = 17.5ppm (3.3-34ppm), Ta = 0.34 (0.1-

57ppm), Hf =14.5 (6.2-34ppm), Total REE = 116ppm (26.63-299ppm), Eu/Eu* =

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0.715 (0.08-0.98) indicate granite, quartz syenite and felsite. Geochemical data of

these samples points toward A-type granitoids located in Sholingar, Punjai,

Puliyampatti, Karamadai and Maruda Malai in Tamil Nadu; and Balkere, Sullia district

of Karnataka.

Besides major oxides, total REE < 299ppm, Sc < 10ppm, Co < 8.7ppm, Cr < 13ppm,

Hf < 34ppm and Ta < 57ppm may be used for characterizing A-type granites. High

Hf and Ta indicate possible Zircon and Niobium mineralization in granites.

III. 3. A-type granites in Neoproterozoic Malani Igneous Province, Rajasthan: The

Neoproterozoic Malani Igneous complex of Rajasthan in western part of Peninsular

India is characterised by the presence of voluminous acid volcanic and plutonic rocks,

including A-type granites. The A-type granitiods of Malani Igneous Suite (MIS) are

peralkaline to metaluminous, with minor component of peraluminous granites. The A-

type granites and rhyolites of MIS are characterised by high SiO2, Na2O + K2O, Fe/Mg,

Rb, Zr, Y, Ga, REE and depleted in MgO CaO, P, Ti, Sr, Ni, Cr, Co Eu and V.

Petrographic and geochemical characters suggest that the granite rocks of Malani

Igneous Suite are A- type granite of anorogenic and alkaline character.

A/CNK-A/NK plots show that most of the granitiods of MIS are peralkaline. They are

characterised by high Rb, Nb, Zr, Ga, Y, Hf, Th & U and prominent Eu anomalies with

moderate LREE enrichment and flat HREE patterns. The average incompatible element

values of these granites is Zr – 3116 ppm, Rb - 285 ppm, Ta - 15 ppm, Cs - 4.6 ppm,

Hf - 95 ppm, U - 13.1 ppm and Th – 44 ppm. In tectonic discrimination plot of Y vs

Nb (Pearce et.al. 1984) the granites of MIS appear in Within Plate granite (WPG) field.

III. 4. Mayurbhanj A-type Granite: Mayurbhanj Granite Batholith (MBG), the

youngest acid plutonic event of the Singhbhum-Orissa Iron Ore craton (3.09 Ga) is

characterized by Gabbro-Granophyre bimodal association in the western margin but the

eastern margin the batholith is affected by the southern extension of Singhbhum Shear

Zone (SSZ). MBG is intrusive into the rocks of the Iron Ore Group (IOG), Singhbhum

Granite Batholith (SBG) and Singhbhum Group of metasediments. Except for minor

late – shearing in the east, undeformed and unmetamorphosed MBG batholith is

exposed in four magmatic units separated by younger Simlipal volcano-sedimentary

basin and older Nilgiri Granite. Main unit of MBG is crescent shaped with Kendua-

Kuliana sector in the northeast, Gorumahisani sector in the northwest and Besoi-Asana

sector in the southwest. Other three minor units of the batholith are Notopahar-Poradia,

Nilgiri East and Chakdar Pahar respectively.

The MBG batholith comprises three petrographic units in order of emplacement:

(a) a fine grained granite, essentially granophyric (also designated as microgranite) with

ferrohastingsite, biotite, hornblende and stilpnomelane as accessories;

(b) a coarse grained alkali-feldspar granite grading to porphyritic and gneissic variants

with ferrohastingsite and biotite as accessories; and

(c) a biotite-bearing aplogranite occurring as vein intrusive mainly in the eastern

part.

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III. 5. A-type granite magmatism in Bundelkhand craton, Central Indian shield:

The Bundelkhnad granite-gneiss complex of the central Indian shield is one of the

pristine cratonic block of the Indian plate and is delineated by the Great Boundary Fault

in the west and by the Son Narmada Lineament in the south. The craton is fringed by

the rocks of the Bijawar and the Gwalior Groups and the Vindhyan Supergroup. It

preserves the signatures of several stages of crustal growth in the Archaean-

Paleoproterozoic. Tonalite-trondhjemite-granodiorite gneisses form the oldest rocks of

the craton and occur as a highly deformed greenstone-gneiss terrain profusely intruded

by the undeformed granitoids. Three types of granitoids, viz. hornblende granitoid

(HG), biotite granitoid (BG) and leucogranitoid (LG) are recognized within the massif.

A few phases of LG (~2.1Ga) show A-type granite characteristics.

III. 6. A-type granites to the east of Cuddapah basin: Close to the eastern margin of

the Cuddapah basin, a number of granite bodies of Mesoproterozoic age occur. These

granites occur intermittently over a stretch of about 300 km from Vinukonda in the

north to Sri Kalahasthi in the south. Notable among them are the Vinukonda granite,

Darsi granite, Dekanakonda granite, Kanigiri granite, Podili alkali granite, and

Anumalakonda granite occurring to west of Pamur and Rapur orbicular granite.

Presence of fluorite as a conspicuous accessory mineral in Vinukonda, Darsi, Podili and

Kanigiri granites, their aplitic variants as well as in later emplaced quartzo-feldspathic

veins and high FeOT contents (31.68 to 34.69 %) and very low MgO contents (0.49 to

2.41 %) in biotite is characteristic of anorogenic granites. These Proterozoic granites

are peraluminous to peralkaline in nature and exhibit calc-alkaline trend. Petrochemical

studies indicated that these granitic rocks are characterized by high Zr (280-660ppm),

high Y (105-340 ppm), high Nb (100-220 ppm), high Rb content (245-345 ppm), high

REE content (except Eu), low MgO content (0.01 to 0.22%), low Sr content (20 ppm to

60 ppm) and high Na2O+K2O (8.64 to 9.84). Rare earth element studies reveal a

general enrichment of LREE relative to HREE with pronounced nagitive Eu anomaly.

The field setup, mineralogy and distinct chemical characteristics suggest that these

granite bodies occurring close to the vicinity of the Proterozoic Cuddapah basin are

emplaced essentially in an anorogenic tectonic setup and the trace element contents

along with presence of fluorite in all the granite and interstitial biotite indicates that

these granites are crystallized from a fluorine saturated magma that is derived due

partial melting of dehydrated lower continental crust.

III. 7. Podili alkali granite, Prakasam Alkaline Province: Biotite- and riebeckite-

bearing alkali granite is the predominant rock type of the Podili pluton. It is medium to

coarse grained, porphyritic in nature, crudely foliated in N-S to NNW-SSE directions

and leucocratic in appearance. Petrographic studies revealed that it is composed of

microcline-microperthite, quartz, amphibole and biotite ( astrophyllite and garnet);

zircon, allanite, sphene, monazite, fluorite and opaques are accessory minerals.

Riebeckite is pleochroic in shades of lavender blue.

III. 8. Anorogenic granites of Anantapur and Chittoor districts, Andhra Pradesh:

A-type granites of Palaeoproterozoic age are associated with Dancherla and Pulikonda

alkaline complexes in eastern Dharwar craton (EDC). Their emplacement was

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controlled by conjugate sets of deep seated regional scale trans-lithospheric strike-slip

faults and shear zones (taphrogenic) which were developed immediately after the late-

Archaean calc-alkaline arc magmatism at different time-space episodes, i.e. initially

into the thickened craton interiors and later into the craton margins. Post-orogenic

granites are associated with the Dancherla complex which was emplaced in between the

Kolar-Kadiri suture and Ramagiri-Penakacherla schist belt. These granite bodies are

found at Gooty, Nagasamudram, Singanamala, Salkamcheruvu, Bukkapatnam-

Puttaparthi and Mudigubba- Kadiri, in Anantapur district and in B. Kothakota area in

Chittoor district. Syenites in Dancherla alkaline complex intrude these granites.

A–type granites are emplaced at the junction of two terrane boundaries / sub-block

boundaries or along suture zone under tensional tectonic setting in the craton interior or

at nearer to the craton margin; while A-type granites of Mesoproterozoic age belonging

to Prakasam alkaline province (PAP) emplaced along the junction of EDC and Eastern

Ghats mobile belt (EGMB). A-type granites in EDC are reported at Peravali and

Dorigallu where these plutons intruded into the Julakalva-Kadiri schist belt,

Anantapur district. A-type granites are emplaced into the Pulikonda syenite,

Tsundupalli schist belt and calc-alkaline granitoids of EDC. The granites are derived

from crustal protoliths (granodiorite-tonalite) as well from the mantle. Post-orogenic

granites are derived from extreme fractionation of calc-alkaline magmas generated

from the mantle and emplaced along conjugate sets of strike-slip faults in the thickened

crust at craton interiors under tensional tectonic environment within Dharwar craton.

Episodic reactivation of conjugate sets of deep seated basement faults / shear zones/

fractures in the already thickened and cratonised crust were manifested in the form of

alkaline magmatism, intervened by tholeiite magmatism (mafic dyke swarms).

III. 9. A-type Granite Occurrences in Eastern Dharwar Craton, Eastern Ghats

Mobile Belt and Marginal Zone in Andhra Pradesh: A few occurrences of A-type

granite located in Andhra Pradesh show intrusive relation with pyroxene granulites or

enderbite-charnoenderbite complex or granodiorite-adamellite-granite complex. These

occurrences are situated in Eastern Dharwar Craton (EDC) and Eastern Ghats Granulite

(Mobile) Belt (EGMB). The A-type granites of Andhra Pradesh are characterized by

high SiO2, alkalis, LILE, Ta, Hf and Fe/Mg ratio, and low CaO, MgO, Sr, Ba, Cr, Sc

and Eu. Chondrite-normalized Eu shows negative anomaly. Their Agpaitic index

(molar K2O + Na2O / Al2O3) ranges from 0.81 to 0.97; they are mostly wollastonite-

normative and metaluminous, but are occasionally subaluminous. A-type granites occur

at Jujjuru, Singarayakonda, Kanigiri, Darsi, Podili, Vinukonda and Torakonda areas, as

small plutons and vein-like intrusive bodies within a variety of gneissic or granitic

rocks. Intruding into the same gneissic / granitic rocks is a wide variety of rocks

(including alkaline rocks), petrologically consanguineous to the A-type granites, such

as albitite and trondhjemite, nepheline-, ferro-, quartz-syenites and lamprophyres of

Prakasam Alkaline Province (PAP), Kannegiri carbonatite, gabbros and anorthosite.

All these rocks (and PAP) are located within a Marginal Zone (MZ) which is a tectono-

magmatically modified zone of collision between EGMB and EDC. The gneisses /

granites of MZ that host the PAP as well as the A-type granites and their related rocks

are reconstituted from the granitic rocks of EDC and the granulites of EGMB.

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III. 10. A-type granite occurrences in the area between Dharwar Craton and

Southern Granulite Terrain in Tamil Nadu: The granites of Southern Granulite

Terrain (SGT) can be grouped under two broad categories, viz., the Late Archaean /

Early-proterozoic granites and the Late-Proterozoic / Early-Palaeozoic (Pan-African)

granites. The older granites are restricted to the northern part of SGT, while the

younger Pan-African granites are mostly found in central and southern parts of SGT.

Geochronological studies have yielded isochron age of 534 15 Ma for the Sankari-

Tiruchengodu, 61935 Ma for the Maruda Malai and 471-475Ma for the Punjai

Puliyampatti granites. The field setting, mineralogical and geochemical characters of

most of the Pan-African granitoids of SGT characterize them as Anorogenic A-type

granites.

III. 11. Granites of alkaline affinity (A-type) in Kerala: Intrusive granites of

alkaline affinity have been reported from different localities within the geographic

stretch of Kerala. Prominent among them are the Peralimala Granite, Kalpatta Granite,

Ambalavayal Granite, Munnar Granite, Chengannur Granite and Sholayur Granite.

These granite bodies occur in proximity to major lineaments which coincide with deep

crustal conduits provided by near vertical axial traces of major folds. These intrusive

entities have distinct signatures of post-tectonic emplacement along crustal fractures

which are the results of late-Proterozoic and Pan-African orogeny. The alkali granites

are similar in terms of petrography and petrochemistry. They are also chronologically

and spatially consanguineous as revealed by emplacement geometry and isotopic age

data (around 500Ma) but vary drastically in texture, content and assemblage of

accessory minerals. These granites are rich in potash and have high Fe / Mg ratio.

III. 12. Tamparkola Granite-Rhyolite (TG-TR): TG is an elliptical batholith located

in Deogarh and Sundergarh districts of Orissa. It is intrusive into Kunjar group of

greenstone belt that unconformably rests over Bonai Granite batholith (~3.2Ga) in the

western margin of Iron Ore Craton. TG-TR (~ 2.8 Ga based on Pb- Pb dating on zircon)

is emplaced synkinematically with F2 deformation of Kunjar with development of two

sets of cleavages. Tamparkola Granite is an undeformed and unmetamorphosed unit

though Kunjar group shows an imprint of two deformation phases. Tamparkola rhyolite

(TR) in minor proportions is associated with TG in the peripheral parts of batholith.

The contact between TG & TR is not well defined. Irregular nature of grain size

variation from chilled to porphyritic texture within short distance and presence of

substantial enclaves, absence of contact metamorphic effect suggest a shallow- level

emplacement of magma that largely crystallised at depth. Besides, assimilated units of

TG with country rocks like biotite granite gneiss, tonalite gneiss, granodiorite porphyry

are also present.

III. 13. A-type granites of Purulia, West Bengal and Singhbhum, Jharkhand: Rare

metal-bearing pegmatites of A-type granite affinity is emplaced within a mixed I- and

S-type gneisses in Chhotanagpur Gneissic Complex in Purulia district, West Bengal

and Singhbhum district, Jharkhand. Rare metal-bearing pegmatites are peraluminous.

12

The geochemistry of the rare metal-beraing pegmatoids is similar to that of A–type

granitoids. Rare metal-bearing pegmatites have high SiO2 (71-77%), high alkalis

(Na2O+K2O 8.79-11.55%), low Sr (18-41 ppm), high Nb, high Rb/Sr, low Ba, high

Ga/Al (2.33-7.006) and low CaO (0.03-0.25%), low MgO (0.15-0.37), low K/Rb, and

variable Y/Nb (0.53-2.857) which reveal A –type chemistry. However, these rare

metal-bearing pegmatites have a low FeOt / MgO ratio which is the aberration from A

type granite. A few A-type rare metal pegmatoids plot in the field of A1 type

granitoids. These A1 rare metal pegmatoids indicate mantle differentiates in an

intraplate / rift zone environment and crustal contamination. The associated gneisses

(grey granitoid gneiss, porphyroclastic granitoid gneiss and two mica granitoid gneiss),

leucogranitoid and barren pegmatites bear the imprints of a mixed I and S type

character. Geochemistry reveals that the gneisses along with the associated pegmatoids

are emplaced in a within-plate to syn-collisional tectonic setting. This is characterized

with an extensional tectonic regime (an intracratonic rift setting) with the development

of ductile to brittle-ductile shear zones along with emplacement of granitoids. Two

prominent shear zones, viz. the NPSZ (the North Purulia Shear Zone) and the NML

(the Northern Mega lineament) traverse this part of the CGC.

III. 14. A-type granites at Kondapalle, Phirangipuram and Perecherla areas in

Eastern Ghat Granulite Belt, Andhra Pradesh: A-type granites occur at

Kondapalle, Phirangipuram and Perecherla areas in Eastern Ghat Granulite (Mobile)

Belt, Andhra Pradesh. Leucocratic A-type granite bodies intrude a granulite facies

assemblage comprising charno-enderbite, enderbite and garnetiferous gneiss, as veins

and small plutons; the are about 100 m long and 50 m wide. A-type granite exhibits

sharp contact with the granulitic hosts. Petrographic study reveals hypidiomorphic-

grabular texture and these granites are composed of quartz, K-feldspar (microcline) and

a few grains of plagioclase ± garnet, while zircon and opaques are the accessory

minerals. Quartz is anhedral and exhibits wavy extinction. Presence of deformation

bands is noticed in some quartz grains while neoblast development recrystallisation

around the grain margins is conspicuously noticed in some of the larger anhedral quartz

grains indicating that the rock is subjected to brittle-ductile deformation. K-feldspar is

unaltered and occurs as subhedral laths. At places bleb-type of microperthite is present

in K-feldspar. Plagioclase grains are subhedral with lamellar twinning. At places the

twin lamellae in plagioclase are distorted. Garnet is present in a few samples. Zircon is

accessory mineral.. Minute prismatic grains of zircon (0.05 mm size) at places are

zoned and occur as twin grains. Magnetite occurs as subhedral to irregular grains

ranging in size from 0.1 mm to 0.5 mm.

III. 15. Arkasani Granophyre: Arkasani Granophyre (AG) in Kharswan District,

Jharkhand includes 7 isolated bodies of granitic rocks (largest one being at Arkasani

Hill), located along E-W belt within the Proterozoic Mobile belt following the northern

margin of the Chakradharpur Granite Gneiss Basement (CKPG-I). Arkasani

Granophyre is a medium to coarse-grained rock containing euhedral phenocrysts (max.

10% of volume) of Plagioclase (An22-35) in a groundmass of sodic plagioclase (An 2-15),

K- feldspar, biotite, muscovite and other accessories. Characteristic granophyric texture

suggests its origin from melt.

13

Whole- rock analysis data plot in ―Granite‖ field of normative Or- Ab- An diagram.

Major- and trace-element parameters of AG in comparison to mean A-type granites

(figures in parenthesis) are: SiO2- 66.94 wt.% (73.88%), (Na2O+K2O) - 8.42wt.%

(8.78%), A.I.- 0.85 (0.95), Na2O/ K2O- 0.80 (0.88), (MnO+ MgO+ CaO) – 5.29 wt.%

(1.0 %), (FeO/ MgO)- 2.24(7.38); Rb- 83 ppm (169 ppm), Sr- 31.8 ppm (48 ppm), Ba-

1104 ppm (352 ppm), K/ Rb- 465 (229), Rb/ Sr- 2.61 (3.52), Rb/ Ba- 0.07 (0.48),

Eu/Eu*- 0.465, Ce/ YbN- 3.66 (2.2- 5.5). REE- pattern of AG is slightly fractionated

with moderate to large negative Eu- anomaly and enriched HREE with a concave

downward HREE- pattern. AG was produced by partial melting of a heterogeneous

source comprising 70% deformed cover sediments, 27% trondhjemite basement of

CKPG-I and 3% basic enclaves (both intrusives and extrusives).

III. 16 REE mineralization in A-type granites in Andhra Pradesh, Tamil Nadu,

Orissa and Gujarat: Granites and associated pegmatites in different parts of India

were explored for Rare Metal (Li, Be, Nb, Ta) and Rare Earth (Y, REE) mineral

potential. The granite pluton at Kanigiri, Prakasam district of Andhra Pradesh

constitutes the southernmost part of the Prakasam Alkaline Complex (PAC), which lies

to the east of the eastern margin of the Cuddapah Basin. Kanigiri Granite (KG) is

biotite granite with notable content of accessory minerals like fluorite, columbite,

samarskite, fergusonite, zircon, allanite and thorite. It is low-Ca, metaluminous, highly

fractionated alkali granite with enrichment of Rb, Pb, Ga, Y, Zr, U, Th, Nb and Ta, and

depletion of Ba, Sr, Ti and P. Field, petrological and geochemical studies indicate KG

as A-type granite (anorogenic, within plate) and fertile for rare metals and soils derived

from it are potential for polymetallic (Y, REE, Nb and Ta) minerals.

A-type pink granite of Dorigallu-Timmanayanapallyam area, Anantapur is biotite-

monzogranite with minor chlorite and sericite and accessory allanite, epidote, zircon,

sphene, monazite, apatite, calcite and fluorite. It is characterised by SiO2 69-72 wt%,

high Ca, high alkalis and high content of Rb, Pb, Ga, Ce, Y, Zr, U, Nb and Ta and

depletion of Ti, P, Ba and Sr. Its Rb-Sr whole-rock isochron age is 2262 +-108 Ma

with 87

Sr/86

Sri ratio of 0.7156 ±0.0074.

Geochronological study of stock like bodies of A-type granite occurring en echelon

within the Charnockite and Khondalite group between Nagamalai and Minakshipuram,

west and north of Madurai, Tamil Nadu indicated Rb-Sr whole-rock isochron age of

837 ±34 Ma, with an initial 87

Sr/86

Sr ratio of 0.7120 ± 0.0029. This high initial Sr

isotope ratio, A/CNK ratio of 0.977, high K2O content (5.29 %), depletion of Ba and Sr

in relation to Rb and the high values of Ga/Al, Zr, Y, and Nb suggest that these granites

could belong to the rift-related, A-type granite emplaced along NW-SE trending Vaigai

lineament. Rare earth and rare metal mineralisation represented by fergusonite,

gadolinite and allanite-bearing pegmatites and uraniferous graphite-bearing calc-

granulites and schists have been identified in close proximity to these granites.

Several pegmatitic bodies including rare metal bearing ones hosting columbite-tantalite

and beryl intrude Jharsuguda granite of Orissa. It is a silica rich, metaluminous to

peraluminous and potassic granite. It is enriched in trace elements such as Rb, Nb, Zr,

Y, Ga and Th and depleted in Ba, Sr and Ti resulting in high Rb/Sr, Rb/Ba and Ga/Al

ratios. The petro-mineralogical and geochemical characteristics indicate that

Jharsuguda granite is similar to Niobium-Yttrium-Fluorine (NYF)-bearing A-type

fertile granites.

14

Geochemical study of Idar granite, Umedpur, Sabarkantha district, Gujarat indicated

rare-metal and tin-rich, peraluminous, A-type granite affinity over an area of 0.16 sq.

The average Nb, Y and Sn values in granite are 120, 116 and 31 ppm (n = 10)

respectively which are higher than the mean values for low-Ca granite. The high

content of rare metals in the granite is attributed to the presence of discrete columbite,

betafite, thorite and xenotime. Pegmatites and albitized granite within Umedpur

granitic area have also indicated high RM and REE content.

IV: Current Status of the IGCP-510

The project under IGCP-510 is closed on 31 December 2009. This is the final report

highlighting the outcome of the IGCP-510.

IV. 1. The Proceedings Volume of the Open Workshop conducted on 19-20 March

2009 is to be brought out as hard copy by June 2010. Approval of the DG, GSI has

already been obtained for the publication of this Proceedings Volume. DG, GSI has

approved placing the Proceedings Volume in the public domain in GSI Portal.

V. Recommendations

It is recommended that India participates in any one or more successor programmes

which IUG|S proposes in future. The dossier and the current report along with the

Abstract Volume and Proceedings Volume of the Open Workshop of IGCP-510 will

serve as the starting point for the database for the any such successor programme.

15

Geological Survey of India

International Geoscience Programme

IGCP 510

Global Correlation of A-type Granites and Related Rocks,

their Mineralization, and Significance in Lithospheric Evolution

Open Workshop

19th & 20th March 2009

Nagpur

Abstract Volume

Annexure-I

16

Geological Survey of India

International Geoscience Programme

IGCP 510

Global Correlation of A-type Granites and Related Rocks,

their Mineralization, and Significance in Lithospheric Evolution

OPEN WORKSHOP

19th

& 20th

March 2009

at Geological Survey of India, Central Region, Nagpur

Abstract Volume

17

Geological Survey of India

International Geoscience Programme

IGCP 510

Global Correlation of A-type Granites and Related Rocks,

their Mineralization, and Significance in Lithosperhic Evolution

OPEN WORKSHOP

19th

& 20th

March 2009

At Geological Survey of India, Central Region, Nagpur

Chief Patron Shri P. M. Tejale, DG, GSI & Chairman INC for

IGCP

Co-Patrons

1. Shri N. K. Dutta, Sr. Dy. D.G, IR& HR, GSI Kolkata

2. Shri R. K. Vishnoi, Dy. D.G., GSI, CR, Nagpur

Chairman Dr. R. G. Vijay, Dy.D.G, GSI, SR, Hyderabad

Co-Chairmen

1. Shri K.K. K. Nair, Dy.D.G, Op. Maharashtra, Nagpur

2. Shri H. P. Saxena, Dy.D.G, GSI, Op. AP, Hyderabad

Convener Dr. H. Sarvothaman, Director, GSI & Convener IGCP

510

Co-Convener Shri N. Kutumba Rao, Director, ID & Member-Secretary

INC for IGCP, GSI, Kolkata

Organising Secretary Shri K. Sashidharan, Geologist (Sr) & Member, NWG,

IGCP 510, GSI, Op.Maharashtra, Nagpur

Secretaries, Technical

Committe

Dr. P.V. Ramesh Babu, Scientist (G), Regl. Director,

AMD, Hyderabad & Member, NWG, IGCP 510.

Dr. Sambhunath Ghosh, Dy. D.G, AMSE, Bangalore &

Member, NWG, IGCP 510

Shri M. Mohan, Director, GSI, Op. Maharashtra, Nagpur

Dr. M. E. A. Mondal, Sr Lecturer, AMU, Aligarh &

Member, NWG, IGCP 510

Dr. V.V. Sesha Sai, Geologist (Sr) & Member, NWG,

IGCP 510, GSI, Hyderabad

18

Members, Organizing Committee

1. Dr. D.M. Mohabe, Director-CT, GSI, CR, Nagpur

2 Shri K. V. Rao, Director & HOO, GSI, CR

3 Dr. P. Krishnamurthy, Director & HOO, GSI, Hyderabad

4 Shri S. N. Meshram, Director, GSI, Nagpur

5 Shri G. Gonnade, Geologist (Sr), GSI, Nagpur

6 Shri B.T. Borkar, Geophysicist (Sr), GSI, Nagpur

7 Shri K. N. Sinha, ME (Sr), GSI, Nagpur

8 Shri P.K. Raut, Geologist (Sr),GSI, Nagpur

9 Shri K.C. Mahapatra, Geologist (Sr), GSI, Nagpur

10 Dr. Samuel Sukumar, Geologist (Sr), GSI, Hyderabad

Subcommittees

1. Meeting &Technical

session

Chairman

Members

Dr. D. M. Mohabe, Director-CT, GSI, Nagpur

1. Shri S.N.Meshram, Director, GSI, Nagpur

2. Smt. Aglave, Geologist (Sr), GSI, Nagpur

3. Shri Md. Amjad Ali, Geologist (Sr), GSI,

Hyderabad.

4. Shri S. Sekar, Geologist (Sr), GSI, Nagpur

5. Shri S. K. Basak, Geologist, GSI, Nagpur

2. Reception and

Transport

Chairman

Members

Shri K. N. Sinha, ME (Sr), GSI, Nagpur

1. Shri V. K. Khadse, Geologist, GSI, Nagpur

2. Shri P. Pati, Geologist, GSI, Nagpur

3. Accomodation Chairman

Members

Shri G. Gonnade, Geologist (Sr), GSI, Nagpur

1. Shri R.H. Chavhan, Geologist (Jr) GSI Op.

Maharashtra, Nagpur

2. Shri A.C. Bansod, STA (G), GSI Op.

Maharashtra, Nagpur

3. Dr. D. Roop Kumar, Geologist, GSI,

Hyderabad.

4.Hospitality Chairman

Members

Shri P. K. Raut, Geologist (Sr), GSI, Nagpur

1. Dr. S. Bhattacharjee, Geologist (Sr), GSI

Hyderabad.

2. Shri S.H. Wankhede, Geologist, GSI,

Nagpur

Cover Page: Veins of A-type granite (pink, without mafic minerals) intruding into the

enderbite—charno-enderbite—garnetiferous gneiss complex of Eastern Ghats Granulite

Belt. Location: Kondapalli Hills area, Andhra Pradesh.

19

(Key Presentation)

GRANITE EMPLACEMENT MECHANISM – AN OVERVIEW

Abhinaba Roy

Geological Survey of India

Kolkata

Abstract

“Granite is not a rock which was simple in its origin but might be produced in more

ways than one” — Joseph Beete Jukes in 1863

Granites / granitoids are broadly classified into orogenic and anorogenic types

based on their emplacement in active deformation (and crustal addition) zones or

otherwise. The source region in either case could be crustal, mantle or mixed. The

popular alphabet S-, I-, A- and M- granitoid types are supposed to represent distinctive

tectonic setting, and or source regions.

James Hutton first suggested in 1788 that granite magma developed at great

depths in the earth and was made to invade and break (intrude) into the surrounding

state. Early geologists working on the origin of granitic rocks had not concerned

themselves to any great extent with the mechanism of magma ascent. Daly (1903)

emphasized the importance of brittle processes such as stopping, but it was not until the

detail map of work of Cloos (1925) and the structural studies of Balk (1937) that

geologists became interested in the patters of magmatic flow seen in and around

plutons. During most of the 20th

century, the debate regarding the emplacement of

granitic batholiths was dominated by the theory of diapirism (Wegmann), 1930; Daly,

1933; Cloas, 1941; Rast, 1970; Read and Watson, 1974; Holmen, 1978; Pitcher, 1979).

In this model large bodies of molten magma ascend through the cover rocks by

shoulding aside the material in their path, rising by density contrast, volumetric

expansion, gas coring, or tectonic squeezing (Rast, 1970). The last twenty years has

seen the development of a new range of theories regarding the genesis of granitic

magmas, their mode of emplacement, the form that the intrusive take and the way in

which granite plutons fit into the tectonic framework of various orogenic belts. Modern

theories of granite emplacement have centered on dyke-fed transfer of magma (Cruden,

1998; Petford et al.2000) to higher levels in the crust and the creation of space to form

large intrusions. Recent work has also emphasized that making space at the level of

pluton emplacement is mainly a structural problem.

Geochemical and petrological studies on pluton emplaced at mid to shallow

crustal levels have concluded that (a) magmas have moved significantly from the

source regions and (b) magmas do not incorporate large volumes of wall rock material.

However, the essential mechanism by which granitic magma ascends through the

continental crust is a fundamental problem because there is a lack of clear observational

data on the subject.

20

Synchronicity of pluton emplacement with regional tectonic events in orgenic

belts has been demonstrated in recent years for many orogenic belts. It is most unlikely

that magmatism is a tectonically passive event. In the broadest sense magmatism is

always syntectonic when considered the whole process time involved in the melting,

assembly, intrusion and cooling. Diagnostic criteria for syntectonic magma genesis and

emplacement rely on the observation of synmagmatic structures within granitic rocks.

The mechanism of emplacement of any one pluton may vary from dyking to diapirism,

according to the depth of emplacement, and each pluton is unique in its source,

transport, and emplacement characteristics.

In granitic magma with the application of stress there is a continuous

progression of fabrics in response to changing rheology with time as magmatism given

way to autometamorphism. That means at the initial stages the melt (with crustals) will

produce pre-full crystallization fabric and at a later stage to crystal plastic strain fabric.

Thus a mineral foliation could be formed either by flow or by deformation or a

combination of both during the ascent and emplacement of the magma. Most of the

foliation results from symplutonic deformation. When major tectonic structures (faults

and shear zones) develop, space is created within and around them into which granites

may be emplaced. It has long been recognized that granites are often associated

spatially with large tectonic structures: what has been demonstrated more recently is

that there is often a demonstrable temporal connection between the emplacement of

plutons and tectonic activity on the major structures.

Granite magmas ascend in dykes. There are currently two general models for

granitic ascent in dykes, one involving ascent by magma fracture (Clemens & Mawer

1992), and the other related to ascent in fault-related conduits (Petford et al. 1993,

1994). Although both models are different geologically, with the latter emphasizing the

important role of crustal extension in initiating dyke conduits, their physics are

essentially the same. Dykes can occur at all structural levels on scales from the

millimeter to hundreds of meter, demonstrating the ability of magma to penetrate rocks

by fracture propagation (Hutton, 1992). In dyke intrusion the limiting factor is not

wall rock viscosity, but magma viscosity (Clemens and Petford, 1999; Vigneresse,

1999; Baker, 1998; Dingwell, 1999).

The link between tectonism and plutonism in these models means that rates or

tectonic processes will be a major controlling factor in pluton emplacement. The

emplacement site is largely determined by the magma driving pressure, the lithostatic

load and the nature (inhomogeneous or not) of the crust through which the magma is

passing. Magma will find its own level in response to crustal traps and confining stress,

or will passively fill open-space sites within pull-apart systems; it will also, in other

cases, modify the local stress field to form laccolithic intrusions. Not all intrusions

show evidence of passive emplacement; some may show forceful characteristics, such

as in-situ ballooning, horizontal movement leading to the translation of geological

markers, sometimes over many kilometers.

21

(Key Presentation)

A-type Granite: An Introduction

H. Sarvothaman

Geological Survey of India, Hyderabad &

Convener, IGCP-510, India

Abstract

“We’re just trying to find out how the Lord did it”

---J. Frank Schairer

The study of batholiths in southeastern Australia in the Lachlan Fold Belt had

led to the identification of two major granite types, namely I-type (derived from an

igneous source) and S-type (derived from a source which had been through a

weathering cycle, therefore sedimentary source). A third type of granite derived from

melting of the oceanic crust or directly from mantle is christened as M-type.

Orthopyroxene-bearing granites (occurring as plutons and corresponding to charnockite

composition) are reported both in and outside high-grade metamorphic terrains and

these granites are referred to as C-type.

In the oft-quoted reference which is in the form of an abstract, Loiselle and

Wones (1979) had come out with yet another granite known as A-type. In view of the

pioneering nature of the A-type granite concept, which has now been globally accepted

and is the basic concept for the IGCP-510, this abstract is reproduced below with a

view to benefit all the researchers of IGCP-510 on A-type granites:

―Geological Society of America--Abstracts with Programs. 1979

p.468 V.II CHARACTERISTICS AND ORIGIN OF

ANOROGENIC GRANITES

“ LOISELLE, Marc C., and WONES, David R., Department

of Geological Sciences, Virginia Polytechnic Institute and State

University, Blacksburg, VA 24061

―Granitoid rocks generated along rift zones and within

stable continental blocks (anorogenic or A-Type) are usually

mildly alkaline, with low CaO and Al2O3 contents, high

Fe/Fe+Mg, high K2O/Na2O and absolute K2O contents. Examples

include the Pikes Peak batholith, the White Mountain Magma

Series of New Hampshire, the Nigerian Younger granites, and the

Gardar Province, Greenland. Petrographic studies of

crystallization sequences indicate low H2O fugacity; the F content

of biotites indicates a relatively high HF/H2O ratio in the magma;

oxides and accessories indicate low to moderate oxygen fugacity.

22

A-type granitoids are enriched in the incompatible trace elements

(REE (except Eu), Ar, Nb, Ta) and low in trace elements

compatible in mafic silicates (Co, Sc, Cr, Ni) and feldspars (Ba,

Sr, Eu). Initial 87

Sr / 86

Sr ratios range from 0.703 to 0.712. The

majority of A-type granitoids are produced when alkali basalt

either a) interacts with a granulite facies lower crust (which has

undergone a previous partial melting episode) to generate

magmas with moderate to high initial Sr isotope ratios, or b)

fractionates directly without crustal interaction to yield granites

with low initial 87

Sr/86

Sr. In compressive orogenic zones basaltic

magma (or its latent heat) commonly interacts with a thick crustal

sequence to produce calcalkaline (I-type) or peraluminous (S-

type) granitoids. Continental blocks undergoing rifting or

fracturing provide minimal opportunity for interaction between

basic magma and the crust.”

= = = = = =

A plethora of published information is currently available in the geological

literature on A-type granites based on advanced researches on isotope geology, mineral

chemistry, rare-element chemistry and oxygen-fugacity, but the central and original

idea put forth first by Loiselle and Wones (1979) has not practically undergone any

change. It is fair therefore the researchers currently engaged in A-type granites would

apply the concept advocated by Loiselle and Wones (1979) in their studies while

arriving at decision on this highly focused research project.

Varied views related to the A-type granites as culled out of a large number of

research works world over are put forth as follows:

A-type (Alkaline, Anorogenic, Anhydrous) granites are found in rift

zones (Loiselles and Wones, l979), in zones of crustal uplift and strike-

slip faulting (Whalen et al., 1987), in anorogenic (‗within-plate‘) settings

in tensional regimes (Whalen et al., 1987: Clemens et al., 1986), and in

collision zones (Sylvester, 1989; Radain et al., 1981).

Apart from quartz, K-feldspars and minor plagioclase, sodic mafic

minerals (riebeckite, arfvedsonite, barkevikite and aegirine) are at places

essential components in A-type (and peralkaline) granites as

documented from Pikes Peak batholith (Barker et al., 1975), Topsails

suite (Whalen and Currie, 1984), Gabo suite (Clemens et al., 1989;

Collins et al., 1982), Midian suite (Harris and Marriner, 1980) and

several other suites (see Eby, 1990; Radain et al., 1981 for a review).

Frequently, however, A-type granites are devoid of sodic-pyroxene or –

amphibole (Sylvester, 1989), as exemplified by Mumbulla suite (Collins

et al., 1982) and other similar occurrences in Andhra Pradesh (Banerjee

et al., 1983; Sarvothaman and Leelanandam, 1992; Sarvothaman, 1996;

Sarvothaman et al, 1998).

23

A-type granites are either (a) petrogenetically linked to granulites

(Barker et al., 1975; Collins et al., 1982; Sheraton and Black, 1988;

Barker, 1991), or (b) have crustal lithologies such as diorite and

granodiorite (Anderson, 1983; Creaser et al., 1991), or mafic meta-

tonalites (Sylvester, 1989), as their source. Infrequently, A-type granites

are considered to be differentiates of basaltic magma (Eby, 1990).

Melting experiments on two calc-alkaline rocks, a tonalite and a

granodiorite, demonstrated that shallow dehydration melting of

hornblende- and biotite-bearing granitoids generate A-type granite melt

(Patino Douce, 1997).

A wide variety of rocks occur in intimate relation with A-type granites.

They are: 1. Gabbro, anorthosite, quartz-syenite, fayalite-bearing syenite

and granite, riebeckite-granite as in Pikes Peak Batholith; 2. An array

of syenites (nepheline-bearing and nepheline-free), albitite, trondhjemite

(intruded along with A-type granite) within biotite granite as in

Prakasam Alkaline Province in the southeastern part of India

(Sarvothaman et al, 1998). 3. Enderbite, charno-enderbite and

garnetiferous-granite as in the Eastern Ghats Granulite Belt

(Sarvothaman, 1996). Mostly, A-type granite is intruded as veins in the

related rocks or as plutons or veins in granites (hornblende- and/or

biotite-bearing).

Mineralization: REE (La, Ce, Sm), Zr, Nb, Y, Be, Ta, U, Th, Rb

enrichment; mineralization of columbite, samarskite, tantallite, zircon,

monazite, cassiterite, beryl, fluorite, ilmenite and ilmeno-rutile can be

expected (see Ramesh Babu in this volume)

Full details of references quoted in this abstract (not reprints / copies) can be

obtained from the author through Email id: hari.sarvotham@gmail.com

24

AN OVERVIEW OF A-TYPE GRANITE OCCURRENCES

IN THE AREA BETWEEN DHARWAR CRATON AND

SOUTHERN GRANULITE BELT IN TAMIL NADU

P.K.Muralidharan

Geological Survey of India, Chennai

Abstract

In central Tamil Nadu, several major granite plutons, viz., Sankari –

Tiruchengode, Punjai Puliyampatti, Karamadai and Maruda Malai granites occur in a

linear array within an E – W trending litho tectonic zone widely referred to as Cauvery

Lineament Zone or Cauvery Suture Zone (CSZ), which is bounded by Moyar- Bhavani

–Athur Llineament (MBAL) in the north and Palghat – Cauvery Lineament (PCL) in

the south. These are emplaced within the amphibolite facies gneisses and the associated

pelite – carbonate dominated Sathyamangalam supracrustals and the layered ultramafic

– mafic – anorthosite complexes of Archaean age.

The Sankari – Tiruchengode (ST) granite is emplaced within the Bhavani

gneissic complex (Peninsular gneisses) and the associated supracrustal rocks of

Sathyamangalam Group Two distinct phases, viz., a leucocratic medium grained to

pegmatoidal phase and a pink phase with similar variation in grain size have been

noticed.

The Punjai Puliyampatti (PP) granite is emplaced within the hornblende biotite

gneiss of Bhavani Gneissic Complex with the associated garnetiferous gabbro,

amphibolite, meta pyroxenite, chromiferous pyroxenite and dunite occurring in the

form of linear and lensoid bodies. The PP granite appear to have been emplaced syn-to

post-kinematic with F3 cross folding similar to the emplacement of temporally related

ST granite occurring within the same litho tectonic milieu.

The Karamadai (KM) granite, exposed on either side of the Coimbatore –

Mettupalaiyam Highway, is emplaced within the hornblende biotite gneiss of Bhavani

Gneissic Complex and the associated garnetiferous gabbro and pyroxenite of

Mettupalaiyam Ultramafic Complex of Archaean age.

The Maruda Malai (MM) granite pluton occurring in the western part of central

Tamil Nadu near Coimbatore is an E – W trending linear body, emplaced within a

predominantly hornblende-biotite gneiss terrain with enclaves of amphibolite, meta-

pyroxenite and minor calc-silicate rock. The major oxide chemistry of the MM granite,

in general, corresponds to the composition of granite (sensu stricto). The granite shows

25

alkaline affinity in the western part with high K2O content and higher modal alkali

pyroxene / amphibole.

The granites of Southern Granulite Province (SGP) can be grouped under two

broad categories, viz., the Late Archaean / Early-proterozoic granites and the Late-

Proterozoic / Early-Palaeozoic (Pan-African) granites. The older granites are restricted

to the northern part of SGP (north of MBAL), while the younger Pan-African granites

are mostly found in central and southern parts of SGP south of MBAL.

Geochronological studies have yielded isochron age of 534 15 Ma for the ST,

61935Ma for the MM and 471-475Ma for the PP granites. The field setting,

mineralogical and geochemical characters of most of the Pan-African granitoids of

Southern Granulite Province characterize them as Anorogenic A-type granites of

Whalen, et al (1987). An enriched granulitic protolith occurring at the lower crustal

level might have served as the source for these A-type granites.

26

GRANITES OF ALKALINE AFFINITY (A-TYPE) IN KERALA:

TYPICAL EXAMPLES OF POST-TECTONIC DIFFERENTIATES

M. P. Muraleedharan

Geological Survey of India

Kerala Unit

Thiruvananthapuram

Abstract

Intrusive granites of alkaline affinity have been reported from different

localities within the geographic stretch of Kerala State. Prominent among them are the

Peralimala Granite, Kalpatta Granite, Ambalavayal Granite, Munnar Granite,

Chengannur Granite and Sholayur Granite. These granite bodies occur in proximity to

major lineaments which coincide with deep crustal conduits provided by near vertical

axial traces of mega F2 folds. These intrusive entities have distinct signatures of post-

tectonic emplacement along crustal fractures which are the results of late-Proterozoic

and Pan-African orogeny. The alkali granites are similar in terms of petrography and

petrochemistry. They are also chronologically and spatially consanguineous as revealed

by emplacement geometry and isotopic age data (around 500Ma) but vary drastically in

texture, content and assemblage of accessory minerals. Petrochemically these granites

are rich in potash and have high Fe/Mg ratio. This paper is an attempt to bring to fore,

these characteristics and the details of the different occurrences are discussed and

compared with a holistic approach.

27

A-type granites of Perecherla - Phirangipuram areas

in Eastern Ghat Granulite Belt, Guntur district, Andhra Pradesh

H. Sarvothaman & V. V. Sesha Sai

Geological Survey of India

Hyderabad

Abstract

Occurrences of A-type granites are present at Perecherla and Phirangipuram

area in Guntur district, Andhra Pradesh. In these areas, leucocratic A-type granite

bodies intrude a granulite facies assemblage comprising charno-enderbite, enderbite

and garnetiferous gneiss. At Perecherla, the dimension of these A-type granite

occurrences is about 100 m long and 50 m wide. A-type granite exhibits sharp contact

with the granulitic host rocks.

Petrographic studies reveal that the rock exhibits hypidiomorphic texture and is

mainly composed of quartz, K-feldspar and plagioclase ± garnet, while zircon and

opaques are the accessory minerals. Quartz is anhedral and exhibits wavy extinction.

Presence of deformation bands is noticed in some quartz grains while neoblast

development recrystallisation around the grain margins is conspicuously noticed in

some of the larger anhedral quartz grains indicating that the rock is subjected to brittle-

ductile deformation. Both K-feldspar and plagioclase are unaltered. K-feldspar grains

occur as subhedral laths and at places development of bleb type of microperthite

intergrowth is noticed in K-feldspar. Plagioclase occurs as subhedral laths and exhibit

conspicious lamellar twinning. At places the twin lamellae in plagioclase are distorted.

Presence of garnet has been noticed in some thin sections. Zircon is a conspicious

accessory mineral noticed in the rock. Minute prismatic grains of zircon (0.05 mm size)

at places are zoned and occur as twin grains. Opaque are mainly represented by

magnetite, which occur as subhedral to irregular grains ranging in size from 0.1 mm to

0.5 mm and are distributed throughout the rock.

The major-oxide composition of Perecherla A-type granite is as follows

follows: SiO2 73.38

TiO2 0.39

Al2O3 12.57

Fe2O3 2.1

MnO 0.02

MgO < d.l.

CaO 1.91

Na2O 1.93

K2O 5.75

P2O5 0.16

LOI 0.4

Total 98.61

28

Geochemical traits of post-collisional A-type granites in India

R. S. Bains

Neutron Activation Analysis Laboratory,

Geological Survey of India

Pune.

Email: naarsbains@gmail.com

Abstract

A wide variety of rocks from Indian subcontinent and Antarctica, marine

samples and meteorites have been analyzed by neutron activation analysis (NAA) for

eight rare earth elements (REE) such as La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, and six trace

elements such as Co, Sc, Ta, Hf, Th & Cr . Various REE parameters such as total REE,

Eu / Eu* and Ce / Ce

* anomalies, (LREE / HREE)n and chondrite-normalized profiles

are generated by creation and management of NAA database by in-house dedicated

software.

Geochemical characters like SiO2 >=66%, Sc <=10 ppm, R1 >= 1425 and R2

<= 625 are used for comparative studies of granites from Bundelkhand, southern and

eastern (Singhbhum) parts of India. Singhbhum granites have higher range of total

REE, Hf & Ta as compared to southern and Bundelkhand granites.

Geochemical condition of SiO2 > 66%, total Alkali > 9.5%, K2O / Na2O > 2.2,

K2O >= 5 and CaO < 0.9% is used for searching for possible post-collisional alkali

granites. Eight such granite samples from different areas (Sirohi dist., Rajasthan;

Humboldt, East Antarctica; Ghosiana, dist. Hamirpur, UP; Mainpur kimberlite field,

dist. Raipur, Chhattisgarh and Belamu, dist. Purulia, West Bengal) are marked from

NAA database. A-type anorogenic granites, intruded in non-orogenic settings are

originating from continental rifting hot spot due to partial melting of mantle and/or

lower crust (anhydrous). They are reported to be generally having higher SiO2, alkalis,

Na2O, Fe/Mg, halogens, Zr, Nb, Ga, Y, Ce and low CaO than I-types (Igneous source)

and are diverse both chemically and in term their genesis.

Geochemical characters such as SiO2 > 66%, total Alkali > 9.5%, high Na2O

and CaO < 0.9% are used for searching A-type granites and their locations in India.

Median and minimum and maximum values of some geochemical parameters (given in

parenthesis) of seven samples of southern parts of India i.e. SiO2 =69.65% (67.47-

72.61%) , R1 = 1345 (725-1733), R2 = 345 (282-394) , TiO2 = 0.095%, Al2O3 =

15.42%, CaO = 0.29%, MgO = 0.13%, Na2O = 6.07,K2O = 4.76%,P2O5 = 0.03% , Co =

1.25 ppm, Sc =2.5 ppm Cr = 6.45 ppm, Th = 17.5 ppm(3.3-34 ppm) , Ta = 0.34 (0.1-57

ppm) , Hf 14.5 (6.2-34 ppm), Total REE = 116 ppm (26.63-299 ppm), Eu / Eu*

anomaly = 0.715 (0.08-0.98) indicate granite, quartz syenite, felsite dyke.

29

Geochemical data of these samples points toward A-type anorogenic granitoids

located in Sholingar, Punjai Puliyampatti, Karamadai and Maruda Malai in Tamil Nadu

and Balkere, Sullia district of Karnataka. Low total REE (299 ppm) in anorogenic

granites as compared to other granites of Bundelkhand (1290 ppm), southern region

(697 ppm) and Eastern region (4283 ppm) may be due to comparatively low values of

CaO and P2O5 besides other reasons like fractional crystallization and partial melting. It

is also pointed out that besides major oxides, total REE < 299 ppm, Sc<= 10 ppm, Co <

8.7 ppm, Cr < 13 ppm, Hf < 34 ppm and Ta < 57 ppm may be used for finding and

studying A-type granites. High hafnium and tantalum indicate possible zircon and

niobium mineralisation due to their respective geochemical associations. More

locations need to be searched for studying A-type granites in India by multidisciplinary

approach.

Chemical composition of a granitoid is controlled by the chemical composition

of the source, pressure, temperature, and degree of partial melting, and nature and

extent of subsequent assimilation and differentiation processes.

The variability of source areas, both crustal and mantle, produce considerable

variations in granitoid series. There have been numerous attempts to classify the

diverse spectrum of granitoid rocks. S-I-A-M classification has been advocated. These

can broadly be grouped into orogenic and anorogenic settings. Orogenic is rather

narrowly defined here as mountain building resulting from compressive stresses

associated with subduction. Anorogenic refers to magmatism within a plate or at a

spreading plate margin.

Granitoids occur in a wide variety of settings. S-type (sedimentary source), I-

type (igneous source) and M-type (mantle source) are based on source chemical

characteristics), whereas A-type is based on tectonic regime. So classification basis is

not consistent. We might better be served by placing our emphasis on deciding what

controls the chemical composition of magmas and what chemical signatures indicate a

particular process.

The suites range from quartz diorites to true granites and have distinctive

petrographic and field characteristics as well as chemical differences that can not be

related to one another by any process such as fractional crystallization or

contamination. Only by originating from chemically and isotopically different source

rocks could the differences be explained.

30

ANOROGENIC GRANITES OF

ANANTAPUR & CHITTOOR DISTRICTS, ANDHRA PRADESH.

G. Suresh * #, K. V. S. Reddy

#, A. Anil Kumar

#,

R. C. Hanumanthu +, C. V. Gopalan

@ & N. Jaiswal **

Geological Survey of India, # Hyderabad

*Training Institute; @Marine Wing, Mangalore; **AMSE, Ranchi

+Department of Geology, S.V. University, Tirupati-517502.

Abstract

There are reported occurrences of post-orogenic granites in Anantapur district

(Suresh and Rao, 1995), A-type granites in Nalgonda district, Andhra Pradesh in

Eastern Dharwar Craton (EDC) (Sarvothaman, 1996) and in Dorigallu in Kadiri schist

belt, Anantapur district (Zakaulla et al, 1998). An association of albitite-trondhjemite-

A-type granite is present in Prakasam alkaline province (Sarvothaman et al, 1998).

A-type granites of Palaeoproterozoic age are associated with Dancherla and

Pulikonda alkaline complexes in EDC. EDC is characterised by an episodic alkaline

magmatism interspersed with tholeiitic magmatism with progressively younger

magmatic events towards eastern craton margin. Their emplacement was controlled by

conjugate sets of deep seated regional scale trans-lithospheric strike-slip faults and

shear zones (taphrogenic) which were developed immediately after the late-Archaean

calc-alkaline arc magmatism at different time-space episodes, i.e. initially into the

thickened craton interiors and later into the craton margins.

Post-orogenic granites are associated with the Dancherla complex which was

emplaced in between the Kolar-Kadiri suture and Ramagiri-Penakacherla schist belt.

These granite bodies are found at Gooty, Nagasamudram, Singanamala,

Salkamcheruvu, Bukkapatnam-Puttaparthi and Mudigubba- Kadiri, in Anantapur

district and in B. Kothakota area in Chittoor district. Syenites in Dancherla alkaline

complex intrude these granites.

A–type granites are emplaced at the junction of two terrane boundaries / sub-

block boundaries or along suture zone under tensional tectonic setting in the craton

interior or at nearer to the craton margin; while A-type granites of Mesoproterozoic age

belonging to Prakasam alkaline province (PAP) emplaced along the junction of EDC

and Eastern Ghats mobile belt (EGMB). A-type granites in EDC are reported at

Peravali and Dorigallu where these plutons intruded into the Julakalva-Kadiri schist

belt, Anantapur district. A-type granites are emplaced into the Pulikonda syenite,

31

Tsundupalli schist belt and calc-alkaline granitoids of EDC. The granites are derived

from crustal protoliths (granodiorite-tonalite) as well from the mantle. Post-orogenic

granites are derived from extreme fractionation of calc-alkaline magmas generated

from the mantle and emplaced along conjugate sets of strike-slip faults in the thickened

crust at craton interiors under tensional tectonic environment within Dharwar craton.

Episodic reactivation of conjugate sets of deep seated basement faults / shear zones/

fractures in the already thickened and cratonised crust were manifested in the form of

alkaline magmatism, intervened by tholeiite magmatism (mafic dyke swarms).

Geology, structure and geochemistry of the rocks of the area are described in the paper.

32

Petrographic & petrochemical studies of the granites around

Sri Kalahasthi area, Chittoor district, Andhra Pradesh

V. Balachandrudu 1 and V. V. Sesha Sai

2

Geological Survey of India

1 Op. Andhra Pradesh;

2 Petrology Division; Hyderabad 500068

Email: seshubb@yahoo.co.in

Abstract

Biotite-bearing granite plutons occupying 0.5 to 0.75 sqkm area occur to the

south of Nellore schist belt near Tottambedu and adjoining areas near Sri Kalahasthi.

These biotite-granites are A-type granites that occur within older granite / gneiss of

Peninsular Gneissic Complex. Study of megascopic samples indicates that these

granitic rocks are leucocratic to mesocratic, medium to coarse grained, porphyritic at

places. Petrographic studies indicate that these granitic rocks show hypidiomorphic

texture and mainly composed of microcline, quartz, plagioclase and biotite while

zircon, sphene, fluorite and opaques are the accessory minerals. Quartz is anhedral and

exhibits wavy extinction. Microcline exhibits polysynthetic twinning and occurs as

subhedral laths. Plagioclase is partially sericitised and shows lamellar twinning. Biotite

is pleochroic in shades of green and brown. At places minute grains of titanite occur in

clusters. Titanite is commonly noticed associated with biotite, while minute prismatic

grains of zircon observed within biotite form pleochroic haloes. Biotite is interstitial in

nature and occurs as randomly oriented flakes.

XRF analyses indicate that these granites are characterized by high SiO2

contents ranging from 69.90 to 74.5% while the Al2O3 content ranges from 12.96 to

14.32%. High Na2O + K2O content ranging from 8.38 to 9.71% and low CaO ranging

0.28 to 1.39%. Trace element analyses indicated relatively high Zr content ranging 225

to 525 ppm, moderate Rb contents ranging from 180 to 295 ppm and low Sr ranging

from <10 to 85 ppm, while Y analysed 70 to 100 ppm and Nb 30 ppm.

Fluorine-saturated magmas characteristically produce A-type granites. Presence

of two phases of fluorine bearing minerals in the form of interstitial biotite and fluorite

as accessory mineral gives a petrographic indication of the fluorine saturated nature of

the magma from which these granites are derived.

33

A-type Granite Occurrences in

Eastern Dharwar Craton and Eastern Ghats Granulite Belt

H. Sarvothaman

Geological Survey of India, Hyderabad

Abstract

A few occurrences of A-type granite located in Andhra Pradesh show intrusive

relation with pyroxene granulites or enderbite-charnoenderbite complex or

granodiorite-adamellite-granite (s.s) complex. These occurrences are situated in Eastern

Dharwar Craton and Eastern Ghats Granulite Belt. The petrological traits of the

granites of Dharwar Craton and Eastern Ghats Granulite Belt are described by

Sarvothaman (2003).

The A-type granites of Andhra Pradesh are characterized by high SiO2, alkalis,

LILE, Ta, Hf and Fe/Mg ratio, and low CaO, MgO, Sr, Ba, Cr, Sc and Eu. Chondrite-

normalized Eu shows negative anomaly. Their Agpaitic index (molar K2O + Na2O /

Al2O3) ranges from 0.81 to 0.97, and they are mostly wollastonite-normative and

metaluminous, but are occasionally subaluminous. These A-type granulites have lower

crustal granulites as their source rocks, and their melts are indicated to have been

produced by anhydrous partial melting of granulitic rocks under granulite facies

conditions. A brief summary of individual occurrences is tabulated as follows:

Reference:

Sarvothaman (2003) Precambrian Granites of Eastern Dharwar Craton, Eastern Ghats

Mobile Belt and Marginal Zone: Field and Geochemical Evidence for intracrustal

reworking and mantle-derived granite magmatism in Southeastern India. Hutton

Symposium V. Geol. Surv. Japan Interim Report 29, p-129.

Location Co-

ordinates

Related / host rock Occurs in Tectonic

Setting 1. Northern

part of .301

mound, ~3.5

km SE of

Nalgonda.

17o01‘45‖--

79o17‘15‖

Intrudes enderbite-two

pyroxene granulite &

together occur as

enclaves in

granodiorite-adamellite-

granite

Eastern

Dharwar

Craton

Stable

continental

block

2. 1 km S80E

of Dacharam

17o12‘20‖--

79o43‘20‖

--do--

--do--

--do--

3. ~1.75 km

S50W of

Kondapalli

16o36‘30‖--

80o32‘00‖

Enderbite, charno-

enderbite and

garnetiferous gneiss

Eastern

Ghats

Granulite

Belt

Anorogenic

(within plate)

zone

34

Lingtse Gneiss – Posssible Proterozoic A-type granite in

Sikkim – Darjeeling Himalaya

Subhra Suchi Sarkar, Sandip Bardhan & Sambhunath Ghosh

Geological Survey of India

Abstract

Lingtse Gneiss is two-feldspar biotite granite with mylonitic gneissose structure.

These Proterozoic granites (ca. 1678 Ma) are restricted between the MBT and MCT.

Similar deformed granitoid gneiss have been described from all along the entire length

of the Himalayas, occurring in two modes: (I) as a narrow belt occurring at the base of

the Higher Himalayan Crystallines, following trace of a major ductile shear zone

named as, the Main Central Thrust Zone (MCTZ) and (II) as detached sheets within the

Lesser Himalayan low grade rocks. In Sikkim Himalaya Lingtse Gneiss is continuously

exposed between the chloritic phyllite of Gorubathan Formation of Daling Group and

the garnetiferous mica schist litho package of Paro / Chungthang / Jaishidanda

Formation from south of Aritanr to north of Lingtse via Rongli in the eastern part of the

Daling Dome and from Barmek to Heegaon in the western part. Small patch of Lingtse

Gneiss along the contact of garnetiferous mica schist and migmatites of Darjeeling

Gneiss has also been observed near Barapathing. In addition, there are two small bodies

of Lingtse gneiss which have been observed near Rimbi in the western part and near

Lingtong in the northern part within the garnetiferous mica schist sequence. Within

Gorubathan Formation, there is an elongated north south body of Lingtse Gneis. This

central Lingtse gneiss body is exposed from Ramthang - Phodong sector in the north to

Martam in the south. Apart from these occurrences, three cuspet shaped thin bands of

Lingtse Gneiss are encountered within Daling metapelites near Pandim. Thus, Lingtse

gneiss is exposed at three different tectonic levels - along the Daling- Chungthang

contact, within the Daling and within Chungthang.

Megascopically Lingtse Gneiss is a medium to coarse-grained porphyroclastic

biotite granite with development of strong mylonitic foliation and a strong stretching

lineation which defines its gneissose character with L-tectonite look. Closely spaced

shear bands marked by biotite-rich layers and down dip mineral lineation of biotite

streaks and/or long axes of porphyroclasts of K-feldspar are the distinctive megascopic

feature of the Lingtse Gneiss. Quartz grains are often elongated to form ―Quartz

Roding‖ which is parallel to the strike of the gneissosity plane. K-feldspar grains often

form augens which are at times stretched. The individual augen varies in size from 5

mm to a few centimeters. In rare cases, quartz also forms augens. Biotite flakes are seen

to wrap around these augens. Major part of the rock is dominated by biotite as mafic

mineral. However, towards the eastern margin of the central body, development of

sericite has been observed in place of biotite. The gneisses are traversed by concordant

and discordant pegmatite veins. Amphibolite enclaves are recorded within gneisses

with sharp contact. Mineralogically it is a two-feldspar granite having uniform

assemblage of quartz + microcline + plagioclase (An3-15) + biotite + muscovite +

35

myrmekite with chlorite, tourmaline, Fe-Ti oxides, apatite, epidote, rare garnet and

zircon as accessories.

EPMA data of muscovites, biotites and feldspars from Lingtse Gneiss is

processed with relevant cation end members. It is interpreted that muscovites are

enriched in Phengite composition and the biotite is annite mainly. In other words, both

muscovite and biotite of Lingtse gneiss are Fe rich. Feldspar chemistry of Lingtse

gneiss refers to Na rich Plagioclase (Albite to sodic plagioclase) and K rich Orthoclase.

Two feldspar thermometry indicates a mean temperature in between 660 ° C to 797 ° C.

(Stormer, 1975).

From the Tectonic Discrimination Diagram of Pearce et. al. 1984 almost all the

samples are falling in the field of within plate granite. This character had been observed

by Singh et. al. 2003 for most of the Proterozoic Granites of the western Himalaya.

Lingtse Gneiss is also a Proterozoic Granite (1678 ± 44 Ma Rb-Sr isochron age; from

Paul et. al 1996) and thus shows a similarity with the other Himalayan Proterozoic

granites.

The total rare earth elements (∑ REE) in the samples (Paul et. al. 1996) range

from 67 to 184 ppm. Samples show fractionated REE patern with Lan/Lun varying from

1.2 to 6.8. Most of the samples are enriched in LREE. All samples are characterized by

negative Eu anomalies (Eu/Eu* = 0.06 to 0.65. Although samples are moderately rich in

total REE, as per whalen (1987) A Type granite should have more REE concentration.

However, Mishra et. al. opines that the Total REE can be as low as 100 ppm for A

Type Granite and in that case Lingtse gneiss can be considered to be A Type on Total

REE concentration. The Eu/Eu*

ratio however partially follows A- type character as

Whalen suggested it should be between 0.30 to 0.56. Enrichment of LREE is also a

charteristics of A- Type granite. The Ce – Yb relation shows a strong slope. Thus from

the REE point of view Lingtse Gneiss can be considered as A – Type granite.

Zr+Nb+Ce+Y versus Major element Ratio Plot (whalen 1987) Lingtse gneiss

samples are falling away from 148 A- Type granite average plot but well within the

field where some of the Topsale granite falls. However, in 10000*Ga/Al versus Trace

element Ratio Plot (whalen 1987) two Lingtse gneiss samples plot directly over the

average sample. Others are also not very much away. In 10000*Ga/Al versus Major

element Ratio Plot (whalen 1987) though the samples are away from average plot they

are within the field where topsale granite samples fall. Thus from the Ga/Al related

plots , which considered to be the most significant to charectarise the A – Type granite

Lingtse gneiss seems to be an A - Type granite.

Considering the different major and trace element ratios of Lingtse gneiss and

the average 148 A – Type granite (Whalen 1987), it can be observed that that though

trace element ratios are closer to the average sample, the major elements vary

considerably. This disparity is yet to be resolved. It may be possible that as the Lingtse

gneiss is mylonitic granite the major element chemistry is modified by deformation but

the trace and REE elements retained its original A – Type character.

TAMPARKOLA GRANITE- RHYOLITE:

AN EXAMPLE OF ARCHEAN A- TYPE GRANITE

36

S. N. Behera* & Sambhunath Ghosh**

Geological Survey of India

*Kolkata; **Bangalore

Abstract

Tamparkola Granite-Rhyolite (TG-TR) is an elliptical batholith located in

Deogarh and Sundergarh districts, Orissa. It is intrusive into Kunjar Group of

greenstone belt that unconformably rests over Bonai Granite batholith (~3.2Ga) in the

western margin of Iron Ore Craton. TG-TR (~ 2.8 Ga based on Pb-Pb dating on

Zircon) is emplaced synkinematically with F2 deformation of Kunjar with

development of two sets of cleavages. Bandyopadhyay et al (2001) described TG-

TR as undeformed and unmetamorphosed unit though Kunjar Group shows an

imprint of two deformations.

Tamparkola rhyolite (TR) in minor proportions is associated with TG in

the peripheral parts of batholith. The contact between TG and TR is not well

defined. Irregular nature of grain size variation from chilled to porphyritic

texture within short distance and presence of substantial enclaves, absence of

contact metamorphic effect suggest a shallow-level emplacement of magma that

largely crystallized at depth. Besides, assimilated units of TG with country rocks

like biotite granite gneiss, tonalite gneiss, granodiorite porphyry are also present.

TG comprises three components not separately mappable. Major component is

light pink to grey coloured, fine to medium grained alkali-feldspar microgranite with

granophyric and myrmekitic textures. It is closely associated with a coarse-grained

phase and aplitic phase of similar mineralogy and textures. Evidence of assimilation of

TG with the country rocks like metabasics and metasediments is present as biotite-

granite gneiss, tonalite-gneiss and granodiorite porphyry.

Microgranite consists of quartz, microcline, perthite, albite, anorthoclase,

hornblende, hastingsite, biotite with secondary epidote, chlorite, muscovite and

accessories of zircon, apatite, sphene and magnetite. Phenocrysts of alkali feldspar,

plagioclase, quartz, hastingsite, hornblende and biotite are locally observed.

TR is strongly porphyritic with euhedral phenocrysts of untwinned alkali

feldspar, albitic plagioclase and quartz in a partially embayed fine grained matrix with

devitrified glass shards. Elliptical clots of granite are also present.

Mean composition of TG shows excellent corroboration with mean A-type

characters of EIC except for slightly lower soda and Rb/Sr ratio. TR shows broad

37

similarity in major element composition with TG. In TAS classification TR varies in

composition partly to trachyandesite and due to contamination with wall rocks shows

marginal enrichment in Al, Mg, Ca and depletion in Si.

In Ldf-1 (based on 7 major elements) & Ldf-2 (based on 4 alkali elements)

diagrams TG is exclusively A- type while TR is A- type in Ldf-1 but marginally S- type

in Ldf-2 implying the effects of wall rock alteration or, subsolidus equilibration of

alkali feldspar.

Table: Mean composition of Tamparkola Granite & Tamparkola Rhyolite in

comparison with Mean composition of A-type Granite of East Indian Craton.

Mean TG (11) Mean TR (4) Mean EIC A- Type

SiO2 74.8 68.3 >72

Al2O3 11.5 13.6 <14

Na2O 2.77 3.28 >3

Na2O + K2O 7.77 6.88 >7

K2O / Na2O 1.8 1.1 >1

FeO / MgO 7.98 2.4 >2

MnO + MgO +

CaO

1.28 2.94 <1.5

Rb / Sr 2.68 2.3 >3.5

38

Implications of Mesoproterozoic granite magmatism

to the east of Cuddapah basin, Andhra Pradesh, India.

V. V. Sesha Sai 1 & U. V. B. Reddy

2

1Geological Survey of India, Hyderabad

2 Dept. of Applied Geochemistry, Osmania University, Hyderabad

e-mail : seshubb@yahoo.co.in

Abstract

Close to the vicinity of eastern margin of the Proterozoic Cuddapah basin a

number of granite bodies of mesoproterozoic age occur in Nellore schist belt and

adjoining areas. These granite occur intermittently over a stretch of about 300 km from

Vinukonda in the north to Sri Kalahasthi in the south. Notable among them are the

Vinukonda granite, Darsi granite, Singarakonda-Dekanakonda granite, Kanigiri granite,

Podili alkali granite, and Anumalakonda granite occuring to west of Pamur.

Vinukonda granite is leucocratic, medium to coarse grained, gneissose at

places and essentially a subsolvus two mica, two feldspar granite showing

hypidiomorphic texture and essentially composed of microcline (Or84-95), plagioclase

(Ab85-97), quartz, biotite (FeOT- 31.68% and MgO - 2.33%) and muscovite while zircon,

fluorite, zoisite, allanite, rutile and opaques are observed as accessory minerals.

Microcline microperthite (string and chessboard type, and myrmekite structures are

noticed in the rock. Pleochroic haloes around zircon inclusions in biotite are noticed.

Sericitisation is noticed in few untwinned feldspar grains. Fluorite is noticed as

conspicuous accessory mineral in the host biotite-muscovite granite, leucocratic aplitic

variant and quartzo-feldspathic veins that traverse it.

Hornblende-biotite granite occurring near Dekanakonda area is essentially

composed of microcline (Or96.2), plagioclase (Ab97.1) quartz, hornblende and biotite

(FeOT

- 34.69% and MgO - 0.49%) while zircon, fluorite, epidote, chlorite and opaques

are observed as accessory minerals.

Kanigiri biotite granite is leucocratic to mesocratic, medium to coarse

grained showing hypidiomorphic texture and mainly constituted of microcline, quartz,

plagioclase (Ab96-98.5) and biotite (FeOT

- 32.11% and MgO - 0.92%) while fluorite,

muscovite, zoisite, zircon, sphene and opaques are the accessory minerals.

Microperthite intergrowth texture is commonly noticed in the rock. Biotite is pleochroic

in shades of brown and green and interstitial in nature. Discrete grains of fluorite are

noticed in the rock. The rock falls in granite (sensu stricto) field in QAP plot. Fluorite

is a conspicuous accessory mineral commonly noticed as minor stringers and crystals

within the Kanigiri biotite granite, fine to medium grained aplitic variant and also

within the quartzo–feldspathic veins (Sesha Sai, 2004) that traverse it, indicating that

the parent magma from which these granite were derived is fluorine saturated, a

charecteristic feature of A-type granites.

39

Podili alkali granite is leucocratic to mesocratic, medium to coarse grained,

porphyritic at places, and shows N-S to NNW-SSE crude foliatiation. The rock is

essentially composed of microcline microperthite (Or98.12%), quartz, riebeckite and

biotite, while zircon, allanite, sphene, monazite, fluorite and opaques are noticed as

accessory minerals. Patches of plagioclase occurring in perthite is albite in composition

(Ab99.89%). Riebeckite is pleochroic in shades of lavender blue. Both biotite and

riebeckite occur as interstitial minerals within the felsic phases in the rock indicating

late crystallisation. The rock is subjected to brittle-ductile deformation. At places

neoblast development due to recrystallization of quartz is also noticed. In QAP diagram

(Strieckenson 1976) the Podili granite essentially occupies the field of alkali granite.

Virtual absence of normative anorthite (0.00 to 0.16 %) in the Podili alkali granite

corroborates with its hypersolves nature.

To north and northwest of Pamuru, leucocratic granitic rocks showing

WNW-ESE crude foliation and gneissose characters at places are exposed in the form

of hills around Anumalakonda (∆ 296), Komatigunta, Eguvapalle and

Chandrashekarapuram areas. These granites in general are two mica granites showing

hypidiomorphic texture and essentially composed of quartz, microcline, plagioclase,

muscovite, biotite and chlorite, while titanite and opaques are the accessory minerals.

These granitoids are close to the eastern margin of Cuddapah basin and traverse the

schistose lithounits of middle Nellore Schist Belt.

Petrochemical studies indicated that these granitic rocks are characterized

by high Zr (280-660ppm), high Y (105-340 ppm), high Nb (100-220 ppm), high Rb

content (245-345 ppm), high REE content (except Eu), low MgO content (0.01 to

0.22%), low Sr content (20 ppm to 60 ppm) and high Na2O+K2O (8.64 to 9.84).

Presence of fluorite as a conspicuous accessory mineral in Vinukonda,

Darsi, Podili and Kanigiri granites, their aplitic variants as well as in later emplaced

quartzo-feldspathic veins and high FeOT contents (31.68 to 34.69 %) and very low

MgO contents (0.49 to 2.41 %) in biotite is characteristic of anorogenic granites.

The field setup, minerology and distinct chemical characteristics suggest

that Vinukonda, Darsi, Podili, Kanigiri and Rapur-Kayyuru granite bodies are

emplaced essentially in an anorogenic tectonic setup and the trace element contents

along with presence of fluorite in all the granite and interstitial biotite indicates that

these granites are crystallized from a fluorine saturated magma that is derived due

partial melting of dehydrated lower continental crust.

40

MAYURBHANJ GRANITE: A REVIEW AS A-TYPE GRANITE

Sambhunath Ghosh

Geological Survey of India, AMSE Wing, Bangalore

Abstract

Mayurbhanj Granite Batholith (MBG), the youngest acid plutonic event of the

Singhbhum- Orissa Iron Ore craton (3.09 Ga) is characterized by Gabbro-Granophyre

bimodal association in the western margin but the eastern margin the batholith is

affected by the southern extension of Singhbhum Shear Zone (SSZ). MBG is intrusive

into the rocks of the Iron Ore Group (IOG), Singhbhum Granite Batholith (SBG) and

Singhbhum Group of metasediments. Except for minor late – shearing in the east,

undeformed and unmetamorphosed MBG batholith is exposed in four magmatic units

separated by younger Simlipal volcano-sedimentary basin and older Nilgiri Granite.

Main unit of MBG is crescent shaped with Kendua-Kuliana sector in the northeast,

Gorumahisani sector in the northwest and Besoi-Asana sector in the southwest. Other

three minor units of the batholith are Notopahar-Poradia, Nilgiri East and Chakdar

Pahar respectively.

The MBG batholith comprises three petrographic units in order of

emplacement:

(a) a fine grained granite, essentially granophyric (also designated Microgranite)

with ferrohastingsite, biotite, hornblende and stilpnomelane as accessories;

(b) a coarse grained alkali-feldspar granite grading to porphyritic and gneissic

variants with ferrohastingsite and biotite as accessories; and

(c) a biotite-bearing aplogranite occurring as vein intrusive mainly in the eastern

part.

Petrographic characteristics in support of A-type classification of MBG

batholith are:

(i) early appearance of magnetite and its prolong crystallization in all the units;

(ii) general absence of pegmatitic activity, (c) dominant occurrence of single

primary phase of alkali feldspar;

(iii) late appearance of amphibole and biotite in the paragenetic sequence of the

main unit.

All these suggest a general composition of alkali-granite, relatively anhydrous

condition under fO2 condition and relatively high temperature of the parent magma.

Majority of MBG plots both in terms of major oxides or, their ratios and also in

terms of trace elements lay in the field of A- type after Whalen et al (1987). Major

element chemistry of all three units of MBG is more or less uniform with low MgO and

marginal increase of mean total iron (2.14- 3.33 wt.%). MBG is characterized by high

SiO2: 73.7-74.9 wt%, high (Na2O + K2O): 7.64- 8.17 wt%, widely variable FeOt /

MgO: 3-177 and CaO: 0.45-0.72 wt%.

41

Weak to moderate peraluminous nature is reflected from mean A/CKN values

(1.08-1.20). Trace element chemistry of all MBG units is very characteristic of A- type

magma and it is supported by Rb/Sr ratios (2.46- 6.28), plots in WPG (within plate

granite) field of Y-Nb diagram after Pearce et al (1984) and elemental plots against

Ga/Al. REE pattern of MBG is strongly fractionated (LREE/HREE:18-45), LREE-

enriched (Ce/Sm: 2.08-3.95) with moderate to strong, negative Eu-anomaly (0.1- 0.6)

and flat HREE (Tb/Yb: 0.93-1.1).

MORB-normalized multi-element spider diagram for MBG granite units

explains the trace element fractionation pattern analogous to that of A- type granite in

respect of both strongly incompatible (K, Rb, Sr) and weakly incompatible (Th, Nb, Zr,

Ti, Y) elements in addition to negative peaks at Ba and Ti that represents intraplate

setting. Statistical appraisal based on two linear discriminant functions that involve

major and trace elements together for MBG (Ldf1- Ldf2 diagram after Misra, 1999)

confirms it to be an A-type granite in spite of local variants along the western margin

produced by diffusive type magma mixing between MBG and the gabbroic bodies.

42

LEUCOGRANITOIDS OF

BUNDELKHAND GRANITE-GNEISS COMPLEX,

CENTRAL INDIAN SHIELD:

AN EXAMPLE OF PROTEROZOIC A-TYPE MAGMATISM

M. E. A. Mondal

Department of Geology, Aligarh Muslim University, Aligarh – 202002

Email: erfan.mondal@gmail.com

Abstract

A-type granites are characterized by high Na2O + K2O, Fe/Mg, Ga/Al, Zr, Y,

Nb, and REE (except Eu), and low abundances of CaO and MgO. The magma is

anhydrous and alkaline in character. They are further characterized by anorogenic

tectonic regime and post-date the main intrusion phases of other sorts of granites.

Sometimes these are emplaced at the end of orogenic cycle. So they represent within-

plate magmatism and may point to waning stage of subduction. No specific source or

mode of occurrence has been proposed for the A-type magmatism, i.e. A-type

magmatism can be volcanic and/or plutonic. In contrast to I- and S-type granites, which

are based on composition of the protolith, A-type granite classification is based both on

tectonic and chemical characteristics. Different sources have been proposed for the

origin of A-type granitoids. These include mantle-derived magmas, depleted crustal

sources, metasomatized sources, tonalite-granodiorite sources.

A-type granite magmatism has been recorded in Bundelkhand massif of central

Indian shield. In this paper, data on the A-type leucogranitoids of the Bundelkhnad

massif are presented.

The Bundelkhnad granite-gneiss complex of the central Indian shield is one of

the pristine cratonic block of the Indian plate and is delineated by the Great Boundary

Fault in the west and by the Son Narmada Lineament in the south. The craton is fringed

by the rocks of the Bijawar and the Gwalior Groups and the Vindhyan Supergroup. It

preserves the signatures of several stages of crustal growth in the Archaean-

Paleoproterozoic times. Tonalite-trondhjemite-granodiorite gneisses form the oldest

rocks of the craton and occur as a highly deformed greenstone-gneiss terrain profusely

intruded by the undeformed granitoids.

Three types of granitoids, viz. hornblende granitoid (HG), biotite granitoid (BG)

and leucogranitoid (LG) are recognized within the massif. Pb-Pb zircon ages of the

granitoids reveal an age ranging from 2.50 to 2.45 Ga for the hornblende granitoid and

2.52 to 2.51 Ga for the biotite granitoid. The leucogranitoids yield younger age ranging

from 2.49 to 1.89 Ga.

43

The older hornblende granitoid and biotite granitoid contain higher proportion

of ferromagnesian minerals and plagioclase. Ferromagnesian constituents are minor in

younger leuco-granitoid. Based on elements like Al, Fe, Mg, Ga, Zr, Nb, Ce and Y

which are relatively insensitive to low to moderate degrees of alteration and high values

of Ga/Al ratio which is perhaps the most diagnostic feature, point to A-type characters

of the LG. A-type characters of the later leuco-granitoid phase may be due to increasing

mantle contributions at the late stage of granitoid formation.

The granitoids of the Bundelkhnad massif show a progressive change in

composition from calc-alkaline (compressional) to alkali-calcic (extensional) from

older to younger phases; and as such the younger LG phases are confined in the alkali-

cal;cic (extensional) field and it is proposed that younger A-type LG phases were

emplaced at ~2.1Ga during waning stage of subduction.

44

ARKASANI GRANOPHYRE: A REVIEW AS A- TYPE GRANITE

Sambhunath Ghosh

Geological Survey of India

Bangalore

Abstract

Arkasani Granophyre (AG) in Kharswan District, Jharkhand includes 7 isolated

bodies of granitic rocks (largest one being at Arkasani Hill in the easternmost fringe),

located along E-W belt within the Proterozoic Mobile belt following the northern

margin of the Chakradharpur Granite Gneiss Basement (CKPG-I). It is correlated with

the similar tectonic emplacement of Wolf River Batholith of North America, of 1400-

1500 Ma geological age.

Arkasani Granophyre is a medium to coarse-grained rock containing euhedral

phenocrysts (max. 10% of volume) of Plagioclase (An22-35) in a groundmass of sodic

plagioclase (An 2-15), K- feldspar, biotite, muscovite and other accessories.

Characteristic granophyric texture suggests its origin from melt.

Whole- rock analysis data plots in the ―Granite‖ field of normative Or- Ab- An

diagram and the plots are very close to those of Chakradharpur Granite Pegmatoid

(CKPG-II) phase. Major- and trace- element parameters of AG in comparison to mean

A- type granites (figures in parenthesis) are: SiO2- 66.94 wt.% (73.88%), (Na2O+K2O)

- 8.42wt.% (8.78%), A.I.- 0.85 (0.95), Na2O/ K2O- 0.80 (0.88), (MnO+ MgO+ CaO) –

5.29 wt.% (1.0 %), (FeO/ MgO)- 2.24(7.38); Rb- 83 ppm (169 ppm), Sr- 31.8 ppm (48

ppm), Ba- 1104 ppm (352 ppm), K/ Rb- 465 (229), Rb/ Sr- 2.61 (3.52), Rb/ Ba- 0.07

(0.48), Eu/Eu*- 0.465, Ce/ YbN- 3.66 (2.2- 5.5). REE- pattern of AG is slightly

fractionated with moderate to large negative Eu- anomaly and enriched HREE with a

concave downward HREE- pattern.

Very high Ba, strongly depleted Sr, & higher K/Rb (because of low Rb) of AG

suggest crustal melting in the region under intense deformation bordering the northern

edge of CKPG basement According to Sengupta et al (1984), AG was produced by

partial melting of a heterogeneous source comprising 70% deformed cover sediments,

27% trondhjemite basement of CKPG-I and 3% basic enclaves (both intrusives and

extrusives).

Review of available data on field relations, tectonic setting, petrography,

petrochemistry including the REE modeling on Arkasani Granophyre by the author

clearly deciphers that AG may be classified as A- type Granite for its (a) intra- plate

tectonic setting where tensional stress caused crustal fusion in place of rifting, (b)

alkaline character, (c) major- trace- REE characteristics and (d) Proterozoic age of

emplacement. Deviation in mineralogy and some parameters of petrochemistry are

essentially due to partial melting of a sediment- dominated crustal component.

45

Anorogenic tectonic environment for the emplacement of granitic melts

in the Tangmarg region of Kashmir Himalaya.

D. Rameshwar Rao

Wadia Institute of Himalayan Geology, 33 General Mahadeo Singh Road,

Dehradun, Uttarakhand – 248 001.

Email: raodr@wihg.res.in

Abstract

A-type granites occur worldwide throughout the geological time in a variety of

tectonic settings. In Himalaya region, however, the occurrences of such granites are

very limited. The trans-Himalaya and Karakoram regions are dominated by Andean I-

type granites, while the Higher Himalayan Crystallines and Lesser Himalayas are

characterized by S-type Granites. The Palaeozoics of Kashmir has peraluminous S-

type calc-alkaline granitoid bodies of Lower Ordovician age, e.g., Kangan, Kazinag,

Hant, Polokongka La, Puga, Rupshu and Nyimaling.

A small elongated A-type granite pluton is exposed in the Ferozpur nala of

Tangmarg region in the Baramulla district of Kashmir Himalaya. It has xenoliths of

slate and in its upper part it has injected small tongues and veins into agglomeratic slate

and Panjal volcanics. This unique body of Tangmarg granite has well constrained post

Triassic stratigraphic age compared to early Palaeozoic ages for other granite plutons of

Kashmir Himalaya. The Rb-Sr whole rock dating of which suggests an age of around

161 Ma (Rameshwar Rao et al. 1995).

The Tangmarg granite is medium- to coarse-grained and shows hypidiomorphic

granular texture defined by a mosaic of quartz, K-feldspar and plagioclase. Biotite,

hornblende, + clinopyroxene occur as minor minerals, while opaque, titanite, zircon,

apatite and calcite occur as accessory minerals. Geochemically, they are characterized

by high Si, K, Zr, Nb, Y, Zn, Ga and low concentrations of Ca and Sr. They are

peraluminous to meta-aluminous, and their REE show well defined fractionated trends.

Numerous petrogenetic schemes such as Whalen et al. (1987) and Pearce et al.

(1984) have been proposed for the origin of the chemically distinctive A-type

(Anorogenic Granites). Whalen et al. (1987) has used a factor (10000*Ga/Al) plotted

against elements like Nb, Ce, Zr, Y, Zn, (K2O+Na2O), and against ratios K2O/MgO,

FeOt/MgO, (K2O+Na2O)/CaO to show discrimination of A-type granite from the

general M-, I- and S-type granites. Similarly, he used (Zr+Ce+Y+Nb) against

FeOt/MgO and (K2O+Na2O)/CaO to distinguish A-type granite.

The geochemical data of Tangmarg granite falls distinctly in A-type granite

fields defined by Whalen et al. 1987. Besides, the use of two step linear discrimination

function (LDF) given by Misra and Sarkar (1991) also reflect the A-type nature of the

46

Tangmarg granite of Kashmir Himalaya. On tectonic discrimination diagrams of Y vs

Nb, Yb vs Ta, Y+Nb vs Rb, and Ta+Yb vs Rb defined by Pearce et al. (1984), the

Tangmarg granite plots in the Within Plate Granite fields, suggesting for a post-

orogenic intraplate rift-related environment for their origin.

The geochemical data further suggest that the granite melts were generated at

deeper crustal levels of around 35 km under relatively high temperatures of >750oC.

The melts so generated at lower crustal levels have made their fast ascent probably

guided by reactivated Permo-Triassic rift faults.

References: Misra, S. & Sarkar, S.S. 1991. Indian J. Earth Sci., 18, 84-93.

Pearce, J.A., Harris, N.B.W. & Tindle, A.G. 1984. J. Petrol., 25, 956-983.

Rameshwar Rao, D. Sharma, K.K. & Gopalan, K. 1995. J. Geol. Soc. India, 46, 225-233.

Whalen, J.B. Currie, K.L. & Chappell, B.W. 1987. Contrib. Mineral. Petrol., 95. 407-419.

47

Petrogenesis of A-type Granite from Kashmir Himalaya, India.

D. Rameshwar Rao

Wadia Institute of Himalayan Geology,

33 General Mahadeo Singh Road, Dehradun – 248 001, Uttarakhand, India.

Email: raodr@wihg.res.in.

Abstract

An occurrence of A-type granite is exposed along Gulmarg-Tangmarg road in

the Ferozpur nala, SW of Tangmarg, Kashmir Himalaya (cf. Wadia, 1934). It is a

unique body in the region because of its well-constrained post Triassic stratigraphic age

in comparison to other early Paleozoic granites like Kangan, Kazinag and Hant that are

exposed in Kashmir (Trivedi et al., 1985, 1986; Rameshwar Rao et al., 1990). It

contains biotite, amphibole and occasional pyroxene as mafic minerals, besides quartz

and feldspars.

It plots in the alkaline field on the Wright (1969) alkalinity variation diagram,

and shows higher abundances of Zr, Nb, Ga, Y, Pb, Zn, Th, Sn, Mo Bi and REE and

lower Al, Mg and Ca. The samples are peraluminous to minor meta-aluminous, and the

REE elements in these rocks show enriched LREE, moderately depleted HREE and

negative Eu anomaly. They exhibit relatively high Ga/Al ratios which when plotted

against other elements / elemental ratios show their distinctive identity as ‗A-type

granites‘ (Rameshwar Rao et al., 1995). They plot in A-type fields when plotted on

(Zr+Ce+Y+Nb) against FeOt/MgO and (K2O+Na2O / CaO) diagrams and on

(Zr+Ce+Y) against Rb/Ba diagram (cf. Whalen et al., 1987). In Ta vs Yb and Y+Nb vs

Rb plots after Pearce et al. (1984), the samples plot in the Within Plate Granite field

(WPG). The Rb-Sr isotopic studies of six samples show collinear alignment within the

experimental errors, and define a well spread isochron age of 161+5 Ma with an 87

Sr/86

Sr intercept of 0.714.

The presence of minerals like biotite, hornblende and clinopyroxene also

indicates a mafic source and melt generation at high P-T conditions. The peraluminous

to minor metaluminous nature of the samples, their K/Na ratio ranging from 1.1 to 2.5

and the relatively low Sri ratio of these anatectic granites and their chemistry suggests

that the melts were generated at deeper crustal levels of around 35 km, and that the

melts were generated following mostly biotite and hornblende dehydration curve, at

temperatures of around 750 to 950oC. The small intrusive body, alkaline character,

high SiO2 72-79%, high Nb, REE and Ca/Y ratio of more than 100 also suggest that the

granite was emplaced in a post-orogenic extension rift environment (cf. Hussein et al.,

1982; Neary et al., 1976; Sillitoe, 1977; Petro et al., 1979).

The emplacement of granite in the Tethyan sequence rocks of the NW Himalaya

during Upper Jurassic after the cessation of the rift related volcanic activity is related to

the movement of the Indian Plate. The northward movement of India in response to

initial opening of the Indian Ocean not only provided necessary compression in the

northern margin of India, breaking of the Neo-Tethys oceanic crust and initiation of the

48

island arc in the Ladakh (Sharma, 1991), but also facilitated reactivation of listric faults

(Dubey and Bhatt, 1986) led to pressure release and melt generation at relatively high

temperatures in the lower crustal levels around 35 km depth. The anorogenic alkaline

magma produced was brought to near surface level in the Tethyan basin through fault

channels and crystallized as Tangmarg pluton.

References:

Dubey, A.K. and Bhatt, M.I. 1986. Current Trends in Geology, 9, 265-290.

Hussein, A.A.A., Ali, M.M. & El Ramlu, M.F. 1982. J. Vol. Geotherm. Res., 14, 187-198.

Loiselle, M.C. and Wones, D.R. 1979. Geol. Soc. Amer. Abstr. Prog., 11 (7), 468.

Neary, C.R., Gass, I.C. & Cavanagh, B.J. 1976. Amer. J. Sci., 283, 993-1033.

Pearce, J.A., Harris, N.B.W. & Tindle, A.G. 1984. J. Petrol., 25, 956-983.

Petro, W.L., Vogei, T.A. & Wilband, J.T. 1979. Chem. Geol., 26, 217-235.

Rameshwar Rao, D., Sharma, K.K., Sivaraman, T.V., Gopalan, K. & Trivedi, J.R. 1990. Him.

Geol., 1, 57-63.

Rameshwar Rao, D., Sharma, K.K. & Gopalan, K. 1995. J. Geol. Soc. India, 46, 225-233.

Sharma, K.K. 1991. In: K.K. Sharma (ed.), Geology and Geodynamic evolution of the

Himalayan collision zone, Part-II, Pergamon Press, Oxford, pp. 431-439.

Sillitoe, R. 1977. In: A.Al. Shanti (ed.), Evolution and mineralization of the Arabina-Nubian

Shielf, Pergamon Press, Oxford, pp. 110-120.

Trivedi, J.R., Gopalan, K. & Sharma, K.K. 1985. Third Nat. Sem. Mass Spectrometry, E-4/1-

E-4/6.

Trivedi, J.R., sharma, K.K. & Gopalan, K. 1986. Terra Congita, 6, 144.

Wadia, D.N. 1934. Rec. Geol. Surv. India, 68, 121-176.

Wright, J.B. 1969. Geol. Mag., 106, 370-384.

Whalen, J.B., Currie, K.L. & Chappell, B.W. 1989. Contrib. Mineral. Petrol., 95, 407-419.

49

A-TYPE GRANITES OF

ANDHRA PRADESH, TAMIL NADU, ORISSA & GUJARAT

P. V. Ramesh Babu

Atomic Minerals Directorate for Exploration and Research

Department of Atomic Energy, Hyderabad-500 016

Abstract

Several granites and associated pegmatites in different parts of India were

explored for Rare Metal (Li, Be, Nb, Ta) and Rare Earth (Y, REE) mineral potential.

A-type granites from Andhra Pradesh, Tamil Nadu, Orissa and Gujarat have been

studied with emphasis on geology, petromineralogy, geochemistry, geochronology and

related Rare Metal (RM) and Rare Earth (RE) mineralization.

The granite pluton at Kanigiri, Prakasam district of Andhra Pradesh constitutes

the southernmost part of the Prakasam Alkaline Complex (PAC), which lies to the east

of the eastern margin of the Cuddapah Basin. Kanigiri Granite (KG) is biotite granite

with notable content of accessory minerals like fluorite, columbite, samarskite,

fergusonite, zircon, allanite and thorite. Geochemically, it is low-Ca, metaluminous,

highly fractionated alkali granite with enrichment of Rb, Pb, Ga, Y, Zr, U, Th, Nb and

Ta, and depletion of Ba, Sr, Ti and P. Field, petrological and geochemical studies

indicate KG as A-type granite (anorogenic, within plate) and fertile for rare metals and

soils derived from it are potential for polymetallic (Y, REE, Nb and Ta) minerals.

The A-type pink granite of Dorigallu-Timmanayanapallyam area from

Anantapur district of Andhra Pradesh occurs as isolated plutons within vast peneplanal

Peninsular gneiss. It is biotite-monzogranite with minor chlorite and sericite and

accessory allanite, epidote, zircon, sphene, monazite, apatite, calcite and fluorite.

Geochemically, it is characterised by restricted SiO2 (69-72 wt%), high Ca, high

alkalies and high content of Rb, Pb, Ga, Ce, Y, Zr, U, Nb and Ta and depletion of Ti, P,

Ba and Sr. Its Rb-Sr whole-rock isochron age is 2262 +-108 Ma with 87

Sr/86

Sri ratio

of 0.7156 ±0.0074.

Geochronological study of stock like bodies of A-type granite occurring en

echelon within the Charnockite and Khondalite group between Nagamalai and

Minakshipuram, west and north of Madurai, Tamil Nadu indicated Rb-Sr whole-rock

isochron age of 837 ±34 Ma, with an initial 87

Sr/86

Sr ratio of 0.7120 ± 0.0029. This

high initial Sr isotope ratio, A/CNK ratio of 0.977, high K2O content (5.29 %),

depletion of Ba and Sr in relation to Rb and the high values of Ga/Al, Zr, Y, and Nb

suggest that these granites could belong to the rift-related, alkaline, A-type granite

corroborated further by their emplacement along NW-SE trending Vaigai lineament.

Rare earth and rare metal mineralisation represented by fergusonite, gadolinite and

allanite-bearing pegmatites and uraniferous graphite-bearing calc-granulites and schists

have been identified in close proximity to these granites.

50

Several pegmatitic bodies including rare metal bearing ones hosting columbite-

tantalite and beryl intrude Jharsuguda granite of western Orissa. Geochemically, it is a

silica rich, metaluminous to peraluminous and potassic granite. It is enriched in trace

elements such as Rb, Nb, Zr, Y, Ga and Th and depleted in Ba, Sr and Ti resulting in

high Rb/Sr, Rb/Ba and Ga/Al ratios. The petromineralogical and geochemical

characteristics indicate that Jharsuguda granite is similar to Niobium-Yttrium-Fluorine

(NYF) bearing A-type fertile granites.

Geochemical study of Idar granites indicated rare-metal and tin-rich,

peraluminous, A-type granite affinity over an area of 0.16 sq. km NE of Umedpur,

Sabarkantha district, Gujarat. The average Nb, Y, and Sn values in granite are 120, 116

and 31 ppm (n = 10) respectively which are higher than the mean values for low-Ca

granite. The high content of rare metals in the granite is attributed to the presence of

discrete columbite, betafite, thorite and xenotime. Pegmatites and albitized granite

within Umedpur granitic area have also indicated high RM and REE content.

51

Pal Laharha granite gneiss at the southern margin of the Singhbhum

craton:

a reworked A-type granite

M. Mohanty & P. K. Panda

Geological Survey of India, Bhubaneswar

Email: manoranjanmoha@gmail.com

Abstract

The Rengali Province is a discrete tectonic segment juxtaposed between the

Archaean Singbhum Craton in the north and Proterozoic Eastern Ghats Mobile Belt

(EGMB) to the south and has significantly different tectono-metamorphic imprints.

Northern part of the Pal Lahara Granite Gneiss (PG) forms the major lithocomponent of

this province which differs significantly from the granites occurring at the core of the

Singbhum craton and also the infracrustal Cpx+Gt granite and associated charno-

enderbite of the EGMB to its south. The studied part of the Pal Laharah gneiss (PG)

comprises mainly three variants viz. (i) grey hbl-magnetite bearing granite gneiss(PGG)

(ii) Hbl-magnetite bearing, pink and grey banded (stromatic) gneiss (PBG) and, (iii)

grey, two-mica + garnet migmatitic granite gneiss(MGG).

The PGG is a fine grained grey, weakly gneissic granitic rock containing quartz

(35%), plagioclase (~22-20 %), microcline and perthite (~30%), and hornblende (~9-

10%), as the main mineral constituents with epidote and biotite (~ 3%), magnetite,

allanite, zircon, chlorite and apatite as accessories. Plagioclase composition varies

from almost pure albite (Ab98.3 –90.4) and shows normal zoning. Amphibole is

hastingsite to ferrotschermakite.

The PBG is a heterogenous gneissic granitoid comprising interbanded

mesocratic, grey and leucocratic, pinkish quartzo-feldpathic bands forms the banded

gneiss. Main mineral constituents of mesocratic bands are quartz (~30%), K-feldspar

(40%), plagioclase (~25%) with minor magnetite, garnet and amphiboles cumulatively

forming about 2-3%. In the leucocratic bands the mafic mineral content is low (<2 %).

Monazite, euhedral allanite and sphene occur in traces.

The MGG shows wide variation in the mineral composition having mutually

variable proportion of microcline, minor plagioclase (An30), quartz. Muscovite, biotite,

hornblende and garnet (Alm76.5-78Py13.5-14.4Gros4.6-6.6Spes2.4 And0-1) are present as

accessories. Rare uvarovite component with 10.57% Cr2O3 was recorded from one

grain possibly indicative of its mafic protolith composition.

Co-deformation of the of the granite gneiss with supracrustals (metasedimets

and amphibolites), migmatisation and presence of rafts of supracrustals within the

52

gneiss strongly suggest the younger age of the granite gneiss, whose original protholith

has been reworked during later migmatisation involving widespread partial melting

(dehydration melting of Hb+Bt).

In spite of the variations in petrographic and field characters there is only minor

variation in the chemical composition of different components of the PG. These contain

high SiO2 (>72%), Al2O3 (>10%), total iron, Fe/Mg, Na2O + K2O (>8%), low

CaO(<2%), MgO (0.2%) and Sr (<40 ppm). They are wollastonite and corundum

(<1%) normative. On the basis of Fe number (FeO/FeO+MgO), MALI (Modified alkali

index) and Alumina saturation Index (ASI), these gneisses can be classified as ferroan,

calc-alkalic to alkali-calcic and metaluminous granite and plot in A-type granite field.

Compositionally they show monzogranite to granite affinity. In the variation diagrams

of the granites a negative slope of the regression line in case of alumina and calcium

with respect to silica possibly suggest the role of feldspar (plagioclase) fractionation

during the generation of the melt. The characteristic feature of the granite is the higher

Ba (150-1500 ppm) and lower Sr (5 to 255ppm) & Rb (40 to 150 ppm) leading to lower

Rb/Sr (0.07 to2.75 ) ratio. High initial Rb/Sr (0.802 + 0.015) of the gneiss suggests the

involvement of crustal component in its evolution. REE data in Chondrite normalized

diagram show >5 times LREE enrichment (La varying from 73 to 163 ppm) compared to

HREE (Lu from 0.95 to 1.3 ppm) and a pronounced negative Eu anomaly (Eu*/Eu

ranges from 1.7 to 3.5) in both PGG and mesosome (grey components) PBG. A

uniformly flat HREE characterizes these fractionation diagrams indicating near absence

of hornblende or garnet in the melt. Late-discordant alaskitic quartzo-feldspathic veins

having less enrichment of LREE, least REE fractionation and a positive Eu anomaly

(Eu*/Eu is 0.46) suggest possible plagioclase accumulation. In various tectonic

discriminate diagrams, the granite gneiss plot in composite field of within plate, post-

orogenic, rift related and continental epiorogenic granite fields.

From field and petrographic investigations, it is surmised that the Pal Lahraha

granite gneiss could represent a composite migmatitic gneiss in a high strain zone at the

craton-mobile belt boundary. Their chemical parameters points towards A-type granite

composition. These might have evolved by the partial melting of the lower sialic crust

due to magmatic underplating in an extensional tectonic regime. Rb/Sr age of 1802 +

89 Ma for this gneiss (present study), 2.8 Ga Pb-Pb zircon age of the Tamparkola A-

type granite-felsic volcanic association in the western margin of the craton, 3.1 Ga

anorogenic Mayurbhanj granite in the eastern margin and 2.8 Ga A-type granite

reported from Bhuban area in close proximity to the PG strongly supports the

hypothesis of A-type granite magmatism in the craton margin during a protracted

period of 3.1 to 1.8 Ga.

53

Late-orogenic granitic magmatism from

Chhotanagpur Granite Gneiss Complex,

Northeastern Puruliya, West Bengal

B. Goswami & C. Bhattacharyya

Department of Geology, University of Calcutta,

35 Ballygunge Circular Road, Kolkata-19.

Email: bapigoswami69@yahoo.co.in

Abstract

Middle to Late Proterozoic (1000 ± 100 Ma old) high-K calc-alkaline granitoid

suites are relatively widespread within the Chhotanagpur Granite Gneiss Complex

(CGGC). They occur as mafic enclave-bearing porphyritic granitoid massifs, such as

Porphyritic granite batholith of Raghunathpur (Sen, 1956), northeastern Puruliya. These

rocks emplaced as crystal mushes (K-feldspar megacryst-bearing porphyritic texture) at

mid-crustal levels, represent the "Caledonian type" of Pitcher and indicate a late-

orogenic stage (Batchelor and Bowden, 1985) characterized by rapid uplift.

The geochemical data suggest mixed I-type and M-type nature with some

signatures of S-type and A-type granitoids. Their A-type nature was defined from mafic

and felsic rock compositions. This subalkaline, metaluminous to weekly peraluminous

batholith is made up of a compositionally expanded suite (granodiorite-monzogranite-

syenogranite, scarce alkali feldspar granite, abundance of mafic enclaves) which yields

alkali-calcic to calc-alkalic, magnesian to ferroan (Frost et al., 2001) compositions and

markedly high-LILE, high-HFSE affinities. The total REE content of these granitoids is

high and the REE pattern is fractionated with small negative Eu-anomaly.They mostly

fall in the ―Within-Plate Granites‖ (WPG) field of Pearce et al. (1984) with some

samples within the ―Volcanic Arc Granite‖ (VAG) field. They show similarities to

high-Ba–Sr granitoids with high K2O/Na2O ratios. All samples of these granites fall in

the A-type granite class in the diagrams of Whalen et al. (1987). Zircon saturation

temperatures (Harrison and Watson, 1983) indicate high liquidus temperature (800 to

900oC) of magma.

54

Basic rocks from Raghunathpur porphyritic granitoid batholith represent pure

mantle partial melts, as indicated by high Cr and Ni abundances (Mondal et al., 2007).

In MORB normalized spiderdiagrams, mineral fractionation-cumulation effects are

responsible for Ce-Zr-Nb positive anomalies and, Rb, Sr, Ti negative anomaly. This A-

type suite shows a marked LILE-enrichment which can be induced by flushing of fluids

released by dehydration of mantle metasomatised by fluids issued from older

subduction events, but can be equally ascribed to crustal contamination at the magma

chamber level. Alkali-feldspar accumulation that is measured by the extent of positive

Ba-anomaly suggests high water pressures and/or mid-crustal depths of emplacement.

According to their Y/Nb ratios, these granitoids belong to A1 group of Eby (1992),

which is derived from mantle sources. These data substantiate a specific condition of

continental crust characteristics in CGGC which indicates relatively thick, warm and

hydrated conditions during the late-tectonic stage, promoting crustal contamination of

mantle-derived melts.

55

Neoproterozoic A-type granites of Malani Igneous Province, Rajasthan

M. Mohanty

Geological Survey of India, Bhubaneswar

Email: manoranjanmoha@gmail.com

Abstract

The western Indian shield witnessed widespread post-Delhi magmatism (900

and 700 Ma) commencing with the intrusion of syntectonic S-type Erinpura granite and

culminating with the anorogenic Malani igneous activity. Extending from Kirana hills

in Pakistan in the west to Tosham in Haryana in the north, the felsic dominated effusive

and intrusive rocks occur over a large area (44,500 sq.km) in parts of Pali, Sirohi,

Churu, Jodhpur, Barmer, Jalore and Jaisalmer districts of Rajasthan. At least 15 plutons

of granite covering a cumulative area of 8000 sq.km are recorded within the Malani

Igneous Province(MIS) showing age in a close rang of 731 + 14 Ma to 750+15 Ma.

They can be broadly classified into biotite bearing peraluminous Jalore granite,

riebeckite-aegirine bearing peralkaline Siwana granite and hornblende bearing

metaluminous Malani granite.

Among the seven plutons of Jalore granite covering an area of 7600 sq. km,

Sankra pluton is the largest (3700 sq. km). Jalore granite, best exposed at Jalore town,

is characterised by pink coloured biotite bearing, coarse grained, two feldspar granite

having k-feldspar (perthite-8-10% and orthoclase-27-43%), quartz (22-35%),

plagioclase (5-14%), biotite (8-15%) and minor hornblende (1-6%) with magnetite,

zircon, fluorite, rutile, tourmaline, minor fayalite and apatite as accessories.

Coexistence of both subsolvus peraluminous and hypersolvus peralkaline varieties is

reported from Jalore granite. The subsolvus granite having higher SiO2, very high

Al2O3, high normative quartz, albite and hypersthene is peraluminous in nature. It

straddles the field of alkali to calc-alkali granite. It also shows high abundances of

highly charged cations like Zr (av.596),Y(av.70),U(av.5), Th(av.20) and Ga (av.20).

All the samples plot in A-type granite field as the Ga/Al values range from 1.74 to 4.6.

They are characterized by high REE abundance (subsolvus-962ppm and hypersolvus-

949ppm) with moderate LREE enrichment and mild upward curvature of normalized

HREE. Eu depletion is more pronounced in subsolvus variety suggesting the

involvement of plagioclase and k-feldspar fractionation in magma generation. Its

fractionated REE pattern suggests a differentiated mantle derived magma. Rb-Sr

isochron age of 727+8 Ma is estimated for the Jalore granite with MSWD of 0.64.

Out of the six plutons of Siwana granite (1100 sq. km), two are reported to be

ring dykes. The peralkaline granite at Siwana, Barmer district occurs in an elliptical

ring structure (290 sq. km) formed due to a cauldron subsidence. The Rb/Sr age of this

granite (735 Ma) is younger to the 745+10 Ma Malani rhyolites. The granite is mainly

composed of euhedral phenocrysts of string and braided perthite with aegirine / acmite

and riebeckite as the main mafics. Rutile, zircon, magnetite, ilmenite and apatite occur

as accessories. Low Al2O3, FeO, CaO, and TiO2 and high SiO2, Fe2O3, MgO and

alkalies (Na2O + K2O) are the characteristic features. Chemically Siwana granite

56

resembles alkaline granites of Nigeria and Kola peninsula. It shows enrichment of Nb,

Zr, Sn, Be, La, Y and Ce and on plots against Zr, all the granites plot in the peralkaline

field . The subsidence at Siwana possibly facilitated the residual magma enrichment in

alkalies and volatiles thus giving rise to peralkaline granite generation. Since regional

uplift and alkaline magmatism are considered characteristic features of continental rifts,

the peralkaline granite of Siwana suggests the zones of active rifting in a tensional Late

Proterozoic tectonic regime. On the basis of Sr, Pb and Nd isotope studies, it is

surmised that Siwana alkaline magma is mantle derived. However, crustal

contamination is indicated by higher initial Sr87

/Sr86

(0.7062 + 0.0020). This is being

substantiated by oxygen isotope studies on Malani rhyolites. Although the genetic

relationship between the subsolvus (peraluminous) and hypersolvus (peralkaline)

varieties is not resolved, it is suggested that limited plagioclase fractionation of an A-

type magma might have contributed to the derivation of hypersolvus alkaline variety.

Only two small plutons of hornblende bearing granite occur within the MIS

covering 70 sq. km area. These are porphyritic with coarse to very coarse phenocrysts

of alkali feldspar, vitreous quartz and hornblende (15.3%). It is characterized by high

Fe-enrichment.

Several theories have been invoked by the workers regarding the evolution of

MIS. Some believe that the large scale felsic magmatism is the result of hot spot

activity in the western Indian carton. However, the parallelism between the trend of the

fissures with the Aravalli orographic axis has led others to believe that the Malani

magmatism is the result of reactivation of earlier weak zones during epirogenic

movement. It is also suggested that low angle subduction of Delhi oceanic/transitional

crust beneath the western Rajasthan craton and related distensional tectonics during

Late Proterozoic led to the wide spread felsic magmatism.

Although the granites lack significant economic mineralization, anomalous

values of light and middle REE, Zr (av.3032 ppm), La (650 ppm), Y (1145 ppm), Ce

(1520 ppm), Yb (55 ppm) and Nb (av.212 ppm) is reported from peralkaline Siwana

granite.

57

A-type Granites & Related Rocks in the Prakasam Alkaline Province,

a Petrology Museum in the Marginal Zone—A Reconstituted Zone of

Collision between Eastern Ghats Mobile Belt & Dharwar Craton

H. Sarvothaman

Geological Survey of India, Hyderabad

Abstract

This paper describes the A-type granites and related rocks of Jujjuru and

Singarayakonda and their magmatic history relative to their consanguineous rocks.

These A-type granites are petrologically different from the A-type granites of Eastern

Ghats Mobile Belt (EGMB) and Dharwar craton (DC), as discussed by Sarvothaman

(2003).

A-type granites occur at Jujjuru, Singarayakonda, Kanigiri, Darsi, Podile,

Vinukonda and Torakonda areas as small plutons and vein-like intrusive bodies within

a variety of gneissic or granitic rocks. Intruding into the same gneissic / granitic rocks

is a wide variety of rocks (including alkaline rocks), petrologically consanguineous to

the A-type granites, such as albitite and trondhjemite (Sarvothaman et al, 1998),

nepheline-, ferro-, quartz-syenites and lamprophyres of Prakasam Alkaline Province

(PAP; Leelanandam, 1989), Kannegiri carbonatite (Sarvothaman et al, 1996), gabbros

(Vijaya Kumar & Ratnakar, 1995) and anorthosite.

All these rocks (and PAP) are located within a Marginal Zone (MZ) which is a

tectono-magmatically modified zone of collision between EGMB and DC. A

description of this MZ is given by Sarvothaman (2001). The gneisses / granites of MZ

that host the PAP as well as the A-type granites and their related rocks are reconstituted

from the granitic rocks of DC and the granulites of EGMB.

A description of the A-type granites of Jujjuru and Singarayakonda is furnished

in the Table below:

Location Co-

ordinates

Related / host rock Occurs in Tectonic

Setting 1 Jujjuru 16

o45‘30‖--

80o25‘20‖

Intrudes greasy

garnetiferous

pyroxene granulite &

gneiss

Marginal

Zone

Collision

zone

2.Singarayakonda Δ 314 hill Trondhjemite, albitite;

hosted by gneiss.

Marginal

Zone

Collision

zone

58

PAP refers to an area hosting rocks of alkaline magmatic suite, whereas MZ

refers to a tectonic domain that has resulted due to the collision of EGMB with DC.

This zone of collision has accommodated an array of lithounits (as mentioned above)

derived from a peridotitic magma source of lithosphere / magmatic underplate / upper

mantle.

References:

1. Sarvothaman, Srinivasan and Suresh (1998) The Albitite-Trondhjemite-A-type

granite

association in the Prakasam Alkaline Province. J. G. Soc. India, 51, 471-474.

2. Leelanandam, C (1989) The Prakasam Alkaline Province in Andhra Pradesh, India.

J. G. Soc. India, 34, 25-45

3. Sarvothaman, Srinivasan and Suresh (1996) Tectono-magmatism related to the

granulitic terrain of Kannegiri massif east of Khammam, AP. Internatl. Symp.

On Charnockite and Granulite Facies Rocks, Chennai. 135-144

4. Vijaya Kumar, K & Ratnakar, J (1995) The gabbros of Prakasam Alkaline Province,

Andhra Pradesh, India. J. G. Soc. India, 46, 245-254

5. Sarvothaman (2001) Terrain characterization of Marginal Zone and Mapping of a

Terrain Ensemble on the Eastern side of AP by Remote-Sensing. Natl. Symp.

on Advances in Remote Sensing Technology with special emphasis of High

Resolution Imagery. Dec. 11-13, 2001, ISRS, Ahmedabad.

6. Sarvothaman (2003) Precambrian Granites of Eastern DC, EGMB and MZ: Field and

Geochemical Evidence for intracrustal reworking and mantle-derived granite

magmatism in Southeastern India. Hutton Symposium V. Geol. Surv. Japan

Interim Report 29, p-129.

59

A-type Granites of Central Indian Shield

K. Sashidharan

Geological Survey of India

Central Region, Nagpur

Abstract

Syn- to post-kinematic sheetlike granitoids occupy large areas along the

southern contact of Mahakoshal belt in the Central Indian Tectonic Zone. These include

Barambaba granite (2.045Ga), Jhirgadandi monzodiorite- quartz syenite (1.75Ga),

Rihand-Makhrohar-Sigrauli granodiorite (1731±36Ma, Sarkar et al 1998), Madanmahal

granite and Harda granite, emplaced along ENE-WSW to E-W trend, characteristic of

the Central Indian Tectonic Zone (CITZ). This paper mainly deals with the granitoids

exposed in and around Jabalpur and Harda areas in Madhya Pradesh. As they are

confined to the course of Narmada River, these bodies have been clubbed as Narmada

River Granite (NRG). Generally coarse grained, these granites show variable amounts

of strain and have been inferred to be syntectonic multipulse intrusives emplaced along

the deep seated Son Narmada South Fault (SNSF). Geochemical data suggest that the

~1.8 Ga granites had their source in both crust and mantle, which supports the older

continental crust on the southern side.

Granitoids of batholithic dimension are exposed in the terrain south of Central

Indian Shear Zone (CIS). The important bodies include the shallow level Malanjkhand

(MG) and Dongargarh granitoids (DG). The MG hosting a giant Cu ± Au ± Mo deposit

is disposed in a general N-S alignment characteristic of the southern crustal block lying

south of CIS.

Mineralogically, NRG at Jabalpur and Harda contain equigranular

interstitial quartz (25-45%), megacrysts of euhedral to subhedral K-feldspar both

microcline and microcline-microperthite (30-60%) and plagioclase (15-35%). The

accessories include biotite, minor hornblende, zircon, apatite, and tourmaline.

Two types of granite dominate the Malanjkhand mine area. Close to the mine area

it is medium to coarse, porphyritic, mesocratic slightly foliated granite with

quartz, plagioclase, K feldspar, bluish green hornblende, minor yellow brown

biotite, chlorite, zircon, apatite etc. The granite exposed at Darbaritola to the east

is relatively medium to fine grained, more leucocratic, with quartz, plagioclase, K-

feldspar, relatively less (<5%) blue green hornblende, minor biotite. Like NRG,

MG is also subsolvus granites. Hornblende is the main accessory mineral present

up to 10% which increases locally with decrease of silica and alkali minerals.

60

The accessory mineralogy of biotite, hornblende, sphene and magnetite and

absence of aluminous minerals indicate the NRG and MG to be similar to A- type

granite. Their low to moderate Alumina saturation index, low Ca content coupled

with depletion in Sr, P and Ti, moderate to high La, Nb, Y indicates them to have

affinity with A- type granite of Loiselle and Wones (1979). Based on the

relationship of 104Ga / Al vs Nb, Ce, Zr and Y, all the samples of NRG and MG

fall in the A-type granite field. Thus, combined mineralogical and chemical

features suggest A-type nature for both the granites. Trace elemental plots of the

granites indicate the NRG consistent with "within plate granites" and MG plot as

"synorogenic" or "volcanic arc" granites. The Y/Nb ratio of MG is <1.2 implying

intra plate rift environment, whereas the NRG with the ratio >1.2 clearly indicates

Post-Orogenic setting.

A-type granite magmatism usually, though not exclusively, occurs in rift

related environments in continental crustal regions. The emplacement of NRG

and MG are believed to be syn- to post-tectonic with respect to the deformational

events in the respective terrane. However, this differs from the common inference

that A-type granites world-wide are anorogenic. This precludes the common belief

that A-type magmatism commonly form late in a tectonic or magmatic cycle which

is not always the case but is only an ideal case.

61

PETROCHEMISTRY AND TECTONIC SETTING OF

A-TYPE GRANITE OF SANKARI-TIRUCHENGODE AREA

IN CENTRAL TAMIL NADU

N. P. Nathan*, E. Balasubramanian* & S. Ghosh#

Geological Survey of India

* Op: Tamil Nadu, Pondicherry & Kerala, Chennai #

Geochronology & Isotope Geology Division, Kolkata

Abstract

The Granulite-Gneiss terrain of Central Tamil Nadu, representing the marginal

zones of Dharwar craton, witnessed wide spread Neoproterozoic acid magmatism. This

event is marked by the emplacement of several granitoids (viz. Sankari-Tiruchengode,

Punjai Puliyampatti, Karamadai and Madura Malai granites) in a linear array within the

E-W trending Cauvery Shear Zone / Cauvery Suture Zone (CSZ) which is bound by

Moyar-Bhavani Attur Lineament (MBAL) in the north and Palghat-Cauvery Lineament

(PCL) in the south.

The Sankari-Tiruchengode (ST) granite, occurring at the intersection of the

MBAL with the NNE-SSW trending Mettur lineament, is emplaced within the Bhavani

Gneissic Complex and the associated supracrustal rocks of Sathyamangalam Group.

The ST granite comprises two distinct phases, viz. a leucocratic phase and a pink phase.

The leucogranites, showing grain size variation from medium grained to pegmatoidal,

occur in the peripheral parts of the ST pluton while the pink granites (coarse to

pegmatoidal) occupy the core.

Pegmatoidal leucogranites (WPGr) are made up of sodic plagioclase (An10-12)

and quartz with minor potash feldspar (microcline). Muscovite, biotite, garnet and

magnetite represent the accessory phases. Pink granites, on the other hand, contain

quartz, microcline, microcline-microperthite and plagioclase (albite-oligoclase) with

accessory biotite, magnetite, zircon and allanite. The modal composition of ST granites

indicates that the WPGr is tonalitic in composition, while all other variants of

leucocratic and pink granites fall in the fields of syenogranite and monzogranite in the

IUGS classification of Le Bas and Streckeisen (1991).

Petrochemical studies indicate that the WPGr is distinctly showing a tonalite /

trondhjemite composition with higher Na2O / K2O ratio of 3.96. The other variants of

the ST granite show granite to quartz-monzonite composition. The WPGr is showing

distinct geochemical signatures of low Ba, Sr and high Rb compared to the other

varieties of ST granite. It is also enriched in High Field Strength Elements (HFSE) such

as Nb, Ta, Zr and Y besides Pb. The concentration of Nb and Y over Li and Cs

characterize the WPGr as ‗NYF‘ – type granite of Cerny (1991). In the REE

distribution too, the WPGr shows a HREE and U dominated pattern with pronounced

negative Eu-anomaly (Eu / Eu* = 0.21 to 0.39) while the pink granites show LREE and

Th enrichment without any marked Eu anomaly.

The ST granites, in general, show the geochemical affinity towards Post-

orogenic and Within-Plate Granite of Maniar and Piccoli (1989) and Pearce et al.,

62

(1984) in conformity with their predominantly undeformed nature. The higher content

of SiO2, total alkalis, Nb, Zr, Y, Sn, Zn and REE (except Eu) and low Ba and Sr

characterise the leucogranites (WPGr) of the ST pluton as A-type granite. Although the

pink granites of ST pluton analyse higher Ba and Sr, the other chemical characters such

as higher SiO2, total alkalis, Zr and REE are comparable with that of the known A-type

granites.

An enriched granitic source at the deeper tectonic level might have served as the

source for the ST granite. The location of the ST pluton at the intersection of the NNE-

SSW trending Mettur Fault with the E-W trending MBAL suggests that its

emplacement might have been controlled by these lineaments. Reactivation of these

lineaments and shearing might have facilitated the ore-bearing fluids to migrate and get

concentrated within these granites at structurally favourable locales.

63

Rare-metal-bearing pegmatites:

a probable A-type granitoid suite emplaced within a mixed

I- & S-type gneisses in Chhotanagpur Gneissic Complex (CGC)

in Purulia district, West Bengal and Singhbhum district, Jharkhand.

Sukhendu Ray, Bhrigu Shankar & P.K. Mukhopadhyay

Geological Survey of India

Eastern Region, Kolkata

Abstract

The CGC is mostly a migmatitic complex with amphibolite and mica schist

occuring as melanosomes. Three distinct granitoid gneisses have been demarcated in

the area. All these gneisses are characteristically garnetiferous. These gneisses contain

deformed restites / enclaves of metasedimentaries and metabasites. Homophanous

leucogranite, locally porphyritic, is also a characteristic feature of the terrain.

In the Chhotanagpur Gneiss Complex (CGC) numerous pegmatites are

emplaced in different directions. The pegmatites are classified geochemically into two

broad types on the basis of their rare metal (viz. Cs, Li and Rb) content. These are viz.

the rare metal bearing pegmatites and the barren pegmatites. The latter group is devoid

of any rare metal. Both these pegmatites have distinctive mineralogy.

All the granitoid gneisses and pegmatites are essentially peraluminous to

rarely metaluminous. The rare metal bearing pegmatites are highly peraluminous with

A/CNK value ranges from 1.076 to 1.86. The major and trace element geochemistry of

these rare metal bearing pegmatoids are very similar to that of A–type granitoids. It

reveals that the rare metal bearing pegmatites have essentially high SiO2 (71-77%),

high absolute alkali (Na2O+K2O 8.79-11.55%), low Sr (18-41 ppm), high Nb, high

Rb/Sr, low Ba, high Ga/Al (2.33-7.006) and low CaO (0.03-0.25%), Y/Nb (0.53-2.857)

which are very similar to A –type granitoids. However, these rare metal bearing

pegmatites have a low FeOt / MgO ratio which is the aberration from the true A type

granitoid. Furthermore, some of the A-type rare metal pegmatoids are plotted in the

field of A1 type granitoids. These A1 rare metal pegmatoids may indicate a mantle

differentiates in an intraplate / rift zone environment and is associated with some

amount of crustal contamination. Interestingly, all the associated granitoid gneisses

(viz. grey granitoid gneiss, porphyroclastic granitoid gneiss and two mica granitoid

gneiss), leuco-granitoid and the barren pegmatites bear the imprints of a mixed (I- and

S-type) character. Though some components of grey granitoid gneiss, porphyroclastic

granitoid gneiss, leucogranitoid and barren pegmatoid are found to plot in the field of

A2 type granitoids which may suggest that these are probably the sub-type of I-type

granitoids. It may indicate a continental margin set up with an apparent crustal source

(not metasedimentary).

64

The granitoid gneisses, both the types of pegmatoids and the associated

metabasic rocks (amphibolite) all have shown a characteristic calc-alkaline affinity in a

continental environment. Major and trace element geochemistry is also revealed that

the granitoid gneisses along with the associated pegmatoids may have been emplaced in

a within plate to syn-collisional tectonic setting. This is characterized with an

extensional tectonic regime (i.e. in an intracratonic rift setting) with the development of

ductile to brittle-ductile shear zones along with emplacement of granitoids.

Two prominent shear zones, viz. the NPSZ (the North Purulia Shear Zone)

and the NML (the Northern Megalineament) are found to traverse within this part of the

CGC. The terrain is also manifested by three phases of folding episodes (viz. F1, F2 and

F3) and it has been suffered amphibolite to granulite grade of metamorphism with

episodes of melting. Effects of retrogression metamorphism have also been noticed

significantly within the terrain.

65

GRANITE OCCURRENCES IN

JAMMU & KASHMIR, AND UTTAR PRADESH – A

COMPILATION

Pradeep Mawar

Geological Survey of India

Lucknow

Abstract

Northern Indian States of Jammu & Kashmir, and Uttar Pradesh

have occurrences of granites which have been documented by several

workers till date. The major occurrences of granites are:

1. Ladakh Granitoid Complex, Kargil and Leh Distts, Jammu

& Kashmir;

2. Dudhi Granitoid Complex, Sonbadhra Distt, Uttar Pradesh;

Ladakh Granitoid Complex exposed north of Indus tectonic

zone is overlain by the sediments of Indus Group by a pronounced

regional unconformity, extends from to west in the Northern part of

Jammu and Kashmir, comprising two genetically related by distinctly

separable granitoid phases viz

(i) Hanugoma granitoid and

(ii) Garkhun granitoids,

besides, the pre-granitoid metasedimentaries of Bilargu Formation

and post-Hanugoma but pre-Garkhun granitoid, Lalung volcanics and

intrusive dykes.

Dudhi Granitoid Complex, occurring in Kirwani-Muirpur-

Kirwil block, Sonbhadra district of Uttar Pradesh, comprises a wide

zone of supracrustal enclaves and associated granitoids in its northern

parts, a monotonous zone of medium to coarse grained, pink granitoid

gneiss in its central part and fine grained banded grey granitoid gneiss

in its southern part. Based on characters such as colour, grain size,

mineral assemblage and mutual relationship, two types of granite

gneisses and five phases of granites have been identified. These

granites and five phases of Granites have been identified. These are

described in detail.

66

Annexure -II

DOSSIER ON THE OCCURRENCES OF A-TYPE GRANITES IN INDIA

Name of

occurrence

State Host Rocks Related

Rocks

Tectonic

domain

Geological

Domain

Chemistry Radiometric

data

Mineralisation / Remarks /

References

A-type

granites of

Malani

Province

Rajasthan,

(western

India)

Metasedimentary

rocks of Delhi

Super Group

Rhyolites and

peralkaline

granites of

Siwana

Complex

Aravalli-

Craton

Western

Indian

Sheild

Granites of Malani

Province are

charecterised by high Rb,

Nb, Zr, Ga, Y, Hf, Th &

U and prominent Eu

anomalies with moderate

LREE enrichment and

flat HREE patterns.

Neoproterozoic

age of 750 ±10

Ma (Dhar, et. at.

1996) for

granites of

Malani Felsic

Province

Average values of trace

elements Zr – 3116 ppm

Rb-285 ppm, Ta-15 ppm

Cs-4.6 ppm, Hf- 95 ppm

U- 13.1 ppm & Th – 44 ppm

Dhar.S et.al. (1996) : Sr, Pb

and Nd isotope studies and

their bearing on the

petrogenesis of the Jalore and

Siwana Complexes, Rajasthan.

Jour. Geol. Soc. Ind. Vol.48

(2) pp.151-160

Tamparkola

Granite as A-

type granite

Orissa

(eastern

India)

Archean Kunjar

Group--

greenstone belt

lithologies

Rhyolite and

alkali-

feldspar

microgranite

Singhbhum

Craton

Kunjar

Group

(greenstone

belt)

High SiO2 -73.5 to 79.89

%, High K2O 4.52 to

6.67 % Moderate Na2O-

3.46 % and low MgO -

0.01 to 0.15 % and low

CaO-0.34 to 1.15 %

~ 2.8 Ga

(Bandyopadhyay

et al, (2001).

Reference: Bandopadhyay

P.K., Chakraborty A.K.,

Desmusani M. & Misra S.;

2001; 2.8 Ga old anorogenic

granite acid volcanics

association from western

margin of the Singhbhum-

Orissa Craton, Eastern India;

Gondwana Research, vol.4

no.3; pp. 465-475, 2001.

A-type granite

around

Banda,

Hamirpur and

Sonbhadra

Uttar

Pradesh

(northern

India)

Granitic rocks

and gneisses.

Monzo-

granite and

syenite

Archean-

Proterozoic

Craton

Bundhel-

khand

Craton

Peraluminous to

peralkaline. High SiO2,

Na2O and K2O. Negative

europium anomaly. High

REE. High Chlorine 445

ppm. High Hf, Ta and Th

--

Geochemical traits of post-

collisional A-type granites in

India. By R. S. Bains, H.

Sarvothaman, R. K. Sinha,R.

S. Alte, K. K. Deshmukh & S.

N. Janbandhu. Proceedings

Volume on the Open

Workshop of IGCP-510,

March 2009

67

68

Details of A-

type granite

State Host Rock Related Rock Tectonic

domain

Geological

Domain

Chemistry Radiometric data Mineralisation / Remarks /

References

A-type

granites and

pegmatites in

Chotanagpur

Gneissic

Complex

(CGC)

West

Bengal

and

Jharkha

nd

(eastern

India)

Gneisses and

migmatite

Rare metal

bearing

pegmatites /

megacrystic

granitoid gneiss

and biotite

granite gneiss

Singhbhum

Craton

Chotanagpur

Gneissic

Complex

(CGC)

High SiO2 69.73%

to 75.56%,

moderate K2O

(1.79- 4.75%) and

moderate Na2O

(2.45-3.57%). Low

MgO (0.51-1.59%)

and low CaO 1.57-

2.91%

Porphyroblastic granite

870 ± 40 Ma and

leucogranite 810 ± 40 Ma.

Ref: Baidya, T.K. et.al.

(1987): New

Geochronological data on

some granitic phases of

the Chotanagpur granite

gneiss complex in the NW

Purulia district, West

Bengal. Indian Jour. Earth

Sci., v.14 (2), pp.136-141.

Mineralisation: Lithium –

Cesium and Rubidium

Mineralisation in Proterozoic

Zoned Pegmatites of Beku,

West Bengal.

Reference: Som, S.K.,

Bandyopadhyay, K.C., Basu,

S.K., Santra, D.K., and Ghosh,

R.N. (2002): Li-Cs-Rb

Mineralisation in Proterozoic

Zoned Pegmatites of Beku,

West Bengal. Jour. Geol. Soc.

India, v.60, pp.493-503.

Sankari

Tiruchengod,

Punjai

Puliyampatti,

Karamadai

and Maruda

Malai granites

Tamil

Nadu

(south

India)

Amphibolite

gneisses,

Sathyamangalam

supracrustals and

the layered

ultramafic–mafic

anorthosites of

Achaean age.

Leuco-granites

and pegmatites

Granulite

Belt

South Indian

Granulite

Belt

These granite

shows alkaline

affinity high K2O

content and higher

modal alkali

pyroxene /

amphibole.

Field, mineralogical and

geochemical characters

indicate

A-type

A-type granites

in Southern Granulite Belt,

Tamil Nadu.

P.K.Muralidharan.

Proceedings Vol. Open

Workshop of IGCP-510,

March 2009

69

Details of A-

type granite

State Host Rock Related

Rock

Tectonic domain Geological

Domain

Chemistry Radiometric

data

Mineralisation / Remarks /

References

Banda,

Hamirpur,

Sonbhadra

Bundhelkhand

area

U.P. Precambrian

Granites and

gneisses

Monzogranite

and

syeno-

granite

Archean

Bundhelkhand

Craton

Bundhelkhad

Craton

Peraluminous to

Peralkaline

-

These granites exhibity

negative europium

anomalies and the

magnitude of negative

europium anomalies

increase with increase in

total REE

A-type

granites of

Perecherla -

Phirangipuram

areas

Andhra

Pradesh

Granulites - Mobile Belt Eastern Ghat

Granulite

Belt

High SiO2- 73.38 %

High K2O-5.75 %

Na2O-1.93 %

Low MgO- < 0.1 %

-

Ref: A-type granites of

Perecherla - Phirangipuram

areas in Eastern Ghat

Granulite Belt, Guntur district,

Andhra Pradesh. H.

Sarvothaman & V. V. Sesha

Sai. Proceedings Vol. Open

Workshop of IGCP-510,

March 2009

-

Mayurbhanj

Granite

Orissa Gabbro-

Granophyre

association

Alkali-

feldspar

granite and

granophyre

Craton Singhbhum-

Orissa Iron

Ore craton

High SiO2: 73.70 to

74.90 %, high (Na2O

+ K2O): 7.64 to 8.17

%, and Low CaO:

0.45 % to 0.72 %.

REE is strongly

fractionated LREE /

HREE:18 to 45),

LREE-enriched

(Ce/Sm: 2.08-3.95)

with moderate to

strong, negative Eu-

anomaly and flat

HREE

3.09 Ga Rb/Sr ratios (2.46- 6.28), plots

in WPG (within plate granite)

field of Y-Nb diagram after

Pearce et al (1984) and

elemental plots against Ga/Al.

70

Details of A-

type granite

State Host Rock Related

Rock

Tectonic domain Geological

Domain

Chemistry Radiometric

data

Mineralisation / Remarks /

References

Kanigiri

granite

Andhra

Pradesh

57M/9

Quartz-chlorite

schist and

quartzites of

Nellore schist

belt

Alkali

granite

Close to the vicinity

of eastern margin of

Cuddapah basin and

Nellore schist belt

Nellore

schist belt

Nb - 100-220 ppm

Y 105-340 ppm

Zr 280-660 ppm

1120±25 Ma

dating

(Gupta.et.al.

1984)

Reference :Gupta, J.N.,

Pandey, B.K., Chabria, T.,

Banerjee, D.C., and Jayaram,

K.M.V. (1984). Rb-Sr

geochronological studies of the

granites of Vinukonda and

Kanigiri, Prakasam district,

Andhra Pradesh, India.

Precambrian Research, vol.26

pp. 105-109.

Vinukonda

granite

Andhra

Pradesh

57 P/12

Schistose rocks

of Nellore schist

belt

Close to the vicinity

of eastern margin of

Cuddapah basin and

Nellore schist belt

Nellore

schist belt 1615±25

dating

(Gupta.et.al.

1984)

Reference: Gupta, J.N.,

Pandey, B.K., Chabria, T.,

Banerjee, D.C., and Jayaram,

K.M.V. (1984). Rb-Sr

geochronological studies of the

granites of Vinukonda and

Kanigiri, Prakasam district,

Andhra Pradesh, India.

Precambrian Research, vol.26

pp. 105-109.

Podili alkali

granite

Andhra

Pradesh

57M/9

Quartz-chlorite

schist and

quartzites of

Nellore schist

belt

Syenite

Close to the vicinity

of eastern margin of

Cuddapah basin and

Nellore schist belt

Nellore

schist belt

Nb - 100-220 ppm

Y 105-340 ppm)

Zr 280-660 ppm

-

Mineralisation :Astrophylllite

(High Ti Nb mineral) Nb2O5

6.04% and TiO2 7.52%. By

Reference : V.V.Sesha Sai,

et.al. National Seminar on

Tectonism, Magmatism and

Mineralisation (MTM-2007)

Kumaun University, Nainital.

71

Details of A-

type granite

State Host Rock Related

Rock

Tectonic domain Geological

Domain

Chemistry Radiometric

data

Mineralisation / Remarks /

References

Arkasani

Granophyre

Jharkhand Basement rocks

represented

mainly by

Chakradharpur

granite and

associated rocks

-

Proterozoic

Mobile belt

Archean

rocks of

Singhbhum

Craton

Average values

SiO2- 66.94 %

Na2O+K2O - 8.42%

Rb- 83 ppm), Sr-

31.8 ppm, Ba- 1104

ppm, K/ Rb- 465, Rb/

Sr- 2.61, Rb/ Ba-

0.07.

REE- pattern is

slightly fractionated

with moderate to

large negative Eu-

anomaly and

enriched HREE with

a concave downward

HREE- pattern.

Arkasani

granophyre is

correlated

with the Wolf

River

Batholith of

North

America, of

1400- 1500

Ma

The Arkasani granophyre is

made of seven isolated bodies

of granitic rocks (largest one

being at Arkasani Hill in the

easternmost fringe), located

along E-W belt within the

following the northern margin

of the Chakradharpur Granite

Gneiss Basement

Ref: Arkasani granophyre: A

review as a- type granite. By

Sambhunath Ghosh.

Proceedings Vol. Open

Workshop of IGCP-510,

March 2009

Tangmarg

granite

Jammu-

Kashmir

Rocks of

Kashmir

Himalayas

- Orogenic belt Kashmir

Himalayas

High Si, K,Zr,Nb, Y,

Zn, Ga and low Ca

and Sr.

Minerologically

quartz, K-feldspar

and plagioclase with

subordinate biotite

and amphibole.

Accessories are

titanite, zircon,

apatite and calcite

161 Ma Ref: Anorogenic tectonic

environment for the

emplacement of granitic melts

in the Tangmarg region of

Kashmir Himalaya. .

Rameshwar Rao. Proceedings

Vol. Open Workshop of IGCP-

510, March 2009

72

Details of A-

type granite

State Host Rock Related Rock Tectonic domain Geological

Domain

Chemistry Radiometric

data

Mineralisation / Remarks /

References

Peralimala,

Kalpatta ,

Munnar,

Chengannur

and Sholayur

Granites

Kerala Precambrian

rocks

-

South Indian Sheild Craton Petrochemically

these granites are

rich in potash and

have high Fe/Mg

ratio.

~ 500Ma

A-type

granites of

Chittoor

district

Andhra

Pradesh

Gneisses and

granites of

Peninsular

Gneissic

Complex

Syenites Gneissic Complex

of

Dharwar Craton

Craton High SiO2, high

(Na2O + K2O)

and low CaO. REE is strongly

fractionated LREE-

enriched with flat

HREE patterns

Paleo

Proterozoic

age

A-type granites of

Chittoor are emplaced

into the Pulikonda

syenite, Tsundupalli

schist belt and calc-

alkaline granitoids of

Eastern Dharwar Craton. Bundelkhand

granite-gneiss

Complex

Uttar

Pradseh

granite-gneiss

Complex

hornblende

granitoid ,

biotite

granitoid and

leucogranitoid

,

Central Indian shield

Craton high Na2O + K2O,

Fe/Mg, Ga/Al, Zr, Y,

Nb, and REE (except

Eu), and low

abundances of CaO

and MgO

-

The granitoids of the

Bundelkhnad massif show a

progressive change in

composition from calc-

alkaline (compressional) to

alkali-calcic (extensional)

from older to younger phases

73

Details of A-

type granite

State Host Rock Related Rock Tectonic domain Geological

Domain

Chemistry Radiometric

data

Mineralisation / Remarks /

References

Pal Laharha

granite gneiss

Orissa Hornblende-

magnetite

granite

gneiss(PGG)

(ii) Hbl-

magnetite

bearing, pink

and grey

banded

(stromatic)

gneiss (PBG)

and, (iii) grey,

two-mica +

garnet

migmatitic

granite

gneiss(MGG).

Singhbhum craton:

Craton High SiO2 (>72%),

Al2O3 (>10%), total

iron, Fe/Mg, Na2O +

K2O (>8%), low

CaO(<2%), MgO

(0.2%) and Sr (<40

ppm).

Rb/Sr age of

1802 + 89 Ma

The characteristic feature of

Pal Laharha granite is the

higher Ba (150-1500 ppm) and

lower Sr (5 to 255ppm) & Rb

(40 to 150 ppm) leading to

lower Rb/Sr (0.07 to2.75 )

ratio. High initial Rb/Sr (0.802

+ 0.015) of the gneiss suggests

the involvement of crustal

component in its evolution.

Barambaba,

Rihand-

Makhrohar,

Madanmahal

and Harda

granites

Maharasht

ra and

Madhya

Pradesh

Mahakoshal belt,

Betul belt,

Sausar belt and

undifferentiated

gneisses

Mon

zodiorite-

quartz syenite

and

granodiorite

Mahakoshal belt Central

Indian

Shield

Mineralogically

interstitial quartz (25-

45%), megacrysts

microcline and

microcline-

microperthite (30-

60%) and plagioclase

(15-35%) with

accessory biotite,

hornblende, zircon,

apatite, and

tourmaline.

Chemically low to

moderate Alumina

saturation index, low

Barambaba

granite

(2.045Ga),

Jhirgadandi

monzodiorite-

quartz syenite

(1.75Ga),

Rihand-

Makhrohar-

Sigrauli

granodiorite

(1731±36Ma,

Sarkar et al

1998)),

Madanmahal

Granites in Narmada Rift zone

are mostly syn- or post-to late

tectonic in nature. Though

restricted in extent unlike the

ubiquitous S and I type

granites, these A –type

granites are characterized by

distinct petrographic and

geochemical features and

anorogenic nature.

74

Ca content coupled

with depletion in Sr,

P and Ti, moderate to

high La, Nb, Y

granite, Harda

granite

75

Details of A-

type granite

State Host Rock Related Rock Tectonic domain Geological

Domain

Chemistry Radiometric

data

Mineralisation / Remarks /

References

Malanjkhand

and

Dongargarh

granitoids

(DG). The MG

hosting a giant

Cu± Au± Mo

deposit is

disposed in a

general N-S

alignment

characteristic

of the southern

crustal block

lying south of

CIS.

Central

Indian

Shield

The Malanjkhand granite

hosting a giant Cu± Au± Mo

deposit is disposed in a general

N-S alignment characteristic of

the southern crustal block

lying south of Central Indian

Shield

Lingtse granite Sikkim Low grade rocks

of Lesser

Himalayas

- Orogenic Belt Himalayan

Orogenic

Belt

High REE and

enriched LREE.

Lan/Lun varying from

1.2 to 6.8.

1678 ± 44 Ma

Rb-Sr

isochron age;

from Paul et.

al 1996

This is a two-feldspar biotite

granite