J. Petrology-1997-King-371-91

8/10/2019 J. Petrology-1997-King-371-91

1/21

JOURNAL OF PETROLOGY VOLUME 38 NUMBER 3 PAGES 371391 1997

Characterization and Origin of Aluminous

A-type Granites from the Lachlan Fold Belt,Southeastern Australia

P. L. KING1, A. J. R. WHITE2, B. W. CHAPPELL1 AND C. M. ALLEN1

1DEPARTMENT OF GEOLOGY, AUSTRALIAN NATIONAL UNIVERSITY, CANBERRA, A.C.T. 0200, AUSTRALIA

2VIEPS, DEPARTMENT OF EARTH SCIENCES, MELBOURNE UNIVERSITY, PARKVILLE, VIC. 3052, AUSTRALIA

RECEIVED APRIL 22, 1996 ACCEPTED OCTOBER 9, 1996

The metaluminous to weakly peraluminous A-type granites of the INTRODUCTIONLachlan Fold Belt are a distinctive group of igneous rocks, on the

Rock classification schemes are useful, not only for char-basis of chemical and mineralogical criteria. Those granites that

acterizing rocks, but also because they potentially bringcontain ~6572% SiO2 can be distinguished from other types on us closer to understanding fundamental rock-formingthe basis of higher abundances of Fetotal/(Fetotal+ Mg), high processes. One of the most common methods of defining

field strength elements, trivalent rare earth elements, Ga and Zn.granite types is in terms of mineralogical and/or chemical

Mineralogically, they contain Fe-rich hydrous mafic minerals andcompositions, which are measurable and non-genetic

primary ilmenite, and hence are reduced relative to the NiNiOparameters (e.g. cordierite granite, peraluminous granite).

buffer. However, the extremely felsic A-type granites (SiO2 > ~72%)A chemicaltectonic approach to granite classification

have the same chemical and mineralogical characteristics as felsic, has been taken by some researchers, where chemicalfractionated I-type granites. Recent analyses indicate that the Lachlan

parameters are taken as indicative of the tectonic en-Fold Belt A-type granites have Sc, F, alkali element, trace transition

vironment in which the granite formed (e.g. Pearce et al.,element and H2O contents similar to those of other unfractionated1984). Others have inferred magma source compositionsI-type granites. RbSr and NdSm isotopic compositions arefrom chemical and mineralogical features, for examplehighly variable, probably reflecting source region heterogeneity. Thethe I- and S-type classification of Chappell & Whitemetaluminous to weakly peraluminous A-type granites of the Lachlan(1974, 1992). The proliferation of classification schemesFold Belt are distinct from peralkaline rocks in terms of chemicalhas been reviewed by Clarke (1992) and Pitcher (1993),composition, petrography and field associations, although these rocksand reflects both the difficulty of choosing definitivehave been grouped together as a single type in current classificationcriteria for classification and the complexity of granites.schemes. We propose that the metaluminous to weakly peraluminous

The term A-type was proposed in an abstract byA-type granites, such as those of the Lachlan Fold Belt, should beLoiselle & Wones (1979) to distinguish mildly alkalinedefined as aluminous A-type granites and should not be grouped

rocks (high K2O + Na2O) from typical calc-alkaline (I-with peralkaline granites. The Lachlan Fold Belt aluminous type) rocks. Other distinctive features that those workersA-type granites have relatively high calculated zircon saturationproposed were high ratios of Fetotal/(Fetotal + Mg) andtemperatures. We suggest that these granites were produced by high-F/H2O ratios, high abundances of high field strengthtemperature partial melting of a felsic infracrustal source.elements (HFSE) and trivalent rare earth elements

(REE3+), and low abundances of FeMg trace elements

(Cr, V, Ni, Cu), Ba, Sr and Eu. Loiselle & Wones

(1979) included peralkaline, metaluminous and weakly

peraluminous rocks in their A-type group. In addition,

they noted that A-type granites are characterized byKEY WORDS:A-type granite; aluminous A-type; peralkaline; Australia

Corresponding author. Present address: Department of Geology, Box

87-1404, Arizona State University, Tempe, AZ 85287-1404, USA. Oxford University Press 1997

8/10/2019 J. Petrology-1997-King-371-91

2/21

8/10/2019 J. Petrology-1997-King-371-91

3/21

8/10/2019 J. Petrology-1997-King-371-91

4/21

JOURNAL OF PETROLOGY VOLUME 38 NUMBER 3 MARCH 1997

Fig. 1. Map showing the location of the I-, S- and A-type granites in the Lachlan Fold Belt, along with andalusite to sillimanite grademetamorphic rocks, gabbros and bimodal rift complexes. The A-type granites have a wide distribution and make up ~06% of the granites

exposed in the belt. The names of the granite units are given in Table 1.

374

8/10/2019 J. Petrology-1997-King-371-91

5/21

KING et al. ALUMINOUS A-TYPE GRANITES

Such complexities imply that although A-type granites alteration, typical of intrusive rocks, is common, withsecondary minerals including chlorite, muscovite, fluorite,commonly form late in a tectonic and magmatic cycle,

that is not always the case; therefore anorogenic cannot epidote, sphene, siderite, magnetite, hematite, stilp-nomelane and amorphous iron oxides.be used as a general term to characterize these rocks.

Also, the term anorogenic is used with various meanings. Enclave types in the A-type granites of the LFB haveabundances that are suite-specific. Granites of the GaboSome workers have applied the term anorogenic mag-

matism to magmatism postdating major episodes of gran- Island and Mumbulla suites contain rare enclaves, xeno-crysts and phenocrysts. In contrast, the Wangrah Suiteitic magmatism (e.g. Bonin et al., 1978). Other workers

define orogeny to include both magmatic and structural contains phenocrysts, rapakivi texture and microgranularenclaves, with considerable textural heterogeneity at allactivity. Furthermore, it can be difficult to constrain an

orogeny to a specific time period, owing to lateral vari- scales.ations in the intensity of structural activity within aterrane, some of which may result from orogenic activityin adjacent terranes (e.g. the LFB and New England

CHEMICAL COMPOSITIONSFold Belt; Chappell, 1994).Chemical compositions of 13 selected LFB A-type gran-ites and the average composition are listed in Table 2.Major element data were obtained by X-ray spectrometry

PETROGRAPHY using fused discs (Norrish & Hutton, 1969). The traceelements Rb, Sr, Ba, Zr, Nb, Y, V, Ni, Cu, Zn, Ga, As,In the LFB, A-type granites are commonly pink, owingSn and Pb were measured on pelletized powder samplesto abundant brick red K-feldspar, but creamwhite K-using the X-ray spectrometric methods described byfeldspar is also present (Wangrah, Ellery and MongaChappell (1991). Instrumental neutron activation analysissuites and the A-type granites of the Wyangala Batholith).(Chappell & Hergt, 1989) was used to determine Cs, Hf,Plagioclase is normally zoned (commonly An4015) and noREE, Sc, Cr, Co, Th and U contents. Wet chemistrycores with higher anorthite contents have been identified.techniques from Peck (1964) were used to determine FeOAs with other near-surface granites, quartz occurs ascontent. Comprehensive chemical data for the Gaboembayed bipyramidal crystals in some rocks and quartzIsland and Mumbulla suites were previously given byfeldspar intergrowths are common. In many of the gran-Collins et al. (1982). On the basis of petrographic in-ites, quartz and feldspar proportions are close to near

vestigations and the techniques described by Chappell &minimum-temperature melt compositions for pressures White (1992), no altered samples are included in the dataof 100200 MPa. All A-type granites of the LFB contain

presented.annite and the majority contain small amounts of am-phibole. Amphibole compositions are summarized inTable 1. The crystal habits of mafic minerals tend to be

specific to individual plutons. Both annite and amphiboleOXYGEN FUGACITY AND VOLATILEare observed as anhedral and euhedral crystals and areCONTENTSfound interstitially, individually, and in mineral ag-

gregates. Annite rarely pseudomorphs Fe-rich amphibole. Ilmenite, typically found within mafic minerals, is theNotably, in the LFB, the aluminous A-type granites most common FeTi oxide mineral in the LFB A-type

never contain pyroxene or olivine, although some Ba- granites. Ourdata indicate that the hematite andMnTiO3rich A-type volcanic rocks contain pyroxene. This differs components in ilmenite are very low (generally

8/10/2019 J. Petrology-1997-King-371-91

6/21


Table2:ChemicalanalysesofA-typegranitesfromtheLachlanFoldBelt

Averageof55

AB412

GI1

AB239

WB140

BG20

BG15

AB422

VB203

AB421

AB118

AB238

AB401

WB121

A-typesamples 1

wt%

SiO2

7383

245

7045

7360

7095

7206

6985

7192

7253

7587

7532

7700

7638

7667

76

69

TiO2

028

016

054

038

050

025

052

024

037

013

015

015

018

009

0

06

Al2O3

1279

066

1326

1272

1317

1319

1377

1354

1308

1229

1271

1183

1214

1210

12

60

Fe2O3

084

046

093

199

161

056

072

064

088

088

051

040

081

060

0

34

FeO

154

084

332

082

228

192

314

217

171

050

116

105

078

038

0

62

MnO

005

002

008

004

005

005

005

006

005

003

006

004

002

002

0

03

MgO

029

023

061

020

046

019

091

027

048

014

023

004

009

005

0

04

CaO

104

055

193

083

146

119

209

152

131

070

090

061

029

053

0

54

Na2O

342

033

339

362

348

352

283

325

332

380

336

306

316

325

4

16

K2O

467

043

398

411

416

527

465

490

488

460

461

498

513

512

4

60

P2O5

007

006

018

008

011

004

019

008

012

002

005

002

005

270 p.p.m.); both defined by Chappell & White (1992). Complete analyses of WB140, WB121 andthe LFB A-type average are given in Table 2.

identified using the more mafic members (Whalen et al.,COMPOSITIONAL COMPARISON1987; Chappell & White, 1992).

WITH I-TYPE GRANITESIn the case of discriminating the A-type granites from

Many felsic, highly fractionated I-type granites have other granites we are principally concerned with I-typecompositions that overlap those of the intrinsically felsic rocks. A-type granites can be easily discriminated from

A-type granites. When dealing with the more felsic gran- S-type granites because the latter have much higherites, there are difficulties with most genetic schemes,

P2O5, lower Na2O contents, and show increasing P2O5mainly because such rocks tend to be close to haplogranite

with fractionation, which contrast with A-type trends(near minimum-temperature melt) compositions. Thus,

(Chappell & White, 1992). The felsic S-type granites

felsic granites typically have converging major element are always peraluminous and become strongly so withcompositions and similar mineral compositions, with

fractionation (two-mica granites), thus mineralogical cri-quartz and two feldspars occurring in subequal amounts

teria alone will distinguish the two types.(Table 3). This immediately leads to problems; for in-Collinset al. (1982) and Whalenet al. (1987) comparedstance, classification schemes dependent on mineralogy

the Gabo Island and Mumbulla A-type suites with otherbecome meaningless for the more felsic rocks (SiO2 >granites, and in doing so created classification criteria72%). The so-called alkali-feldspar granites are a goodthat many workers use to distinguish A-type character.example of this: Pitcher (1993) suggested that these areLandenberger & Collins (1996) similarly compared dataA-type rocks, whereas other workers have demonstratedfrom I- and A-type granites from the Chaelundi Complex,that some are I-type (MacKenzie et al., 1988, 1990). ToNew South Wales, Australia. We now have a largeruse chemical classification schemes when dealing withdatabase of LFB granites (1939 analyses with SiO2>57%)felsic rocks it is necessary to use distinctive granite as-

sociations where the granite type can be most readily that allows us to better describe the compositional effects

380

8/10/2019 J. Petrology-1997-King-371-91

11/21


Fig. 4. K2O vs Na2O for I-type and A-type granites of the Lachlan Fold Belt. Both K2O and Na2O increase with increasing SiO2 content forboth granite types; thus high K2O + Na2O is a characteristic of both I- and A-type felsic granites. It should also be noted that the A-type rocksare more potassic than sodic. Three extreme outliers of the I-type granites have not been included in the fields for the I-type granites. Theseare from the Urialla and Jungle Creek plutons (both 7075% SiO2; Na2O contents of 202% and 264%, and K2O contents of 378% and

225%, respectively) and the Coles Bay pluton (Freycinet, >75% SiO2, Na2O and K2O contents of 491% and 371%, respectively).

of fractionation in the LFB. As fractionation changes the Suite (average 73% SiO2) and Mumbulla Suite (average77% SiO2) granites have relatively high average Bacompositional features used for determining granite type,it is useful to undertake this kind of comparison. Average contents (767 and 575 p.p.m., respectively). In contrast,

granites of the Wangrah and Yewrangara Suites havechemical data for the LFB A-type granites, and un-fractionated and fractionated I-type granites are pre- Ba contents that decrease from ~820 p.p.m. to ~40

p.p.m., while SiO2 increases from ~70% to 77%. Basented in Table 3.Relative to typical I-type granites, LFB A-type granites contents in granites may reflect differences in source

regions or pyroxene-dominated fractionation; however,have higher Fetotal/(Fetotal+Mg), although compositionalconvergence occurs for the most felsic rocks. This feature we currently do not fully understand the variations that

are observed. Sr and Ca levels are generally lower in thecould be a function of the relatively reduced nature of A-type magmas. The LFB A-type granites are not unusually A-type than the I-type granites ( Table 3).

Zirconium content is relatively high (commonly >300alkaline compared with other granites with similar silicacontents; as Na2O + K2O increases with SiO2 content p.p.m.) in the less felsic A-type granites (6572% SiO2)

and decreases with fractionation in both the A- and I-in any granite suite these elements are not diagnostic(Fig. 4; Table 3). The LFB A-type granites are only type granites (Fig. 5; Tables 2 and 3). Y and Nb are alsorelatively abundant in the less felsic A-type granites, butclearly more K2O rich than the I-type granites at SiO2

contents of 6570%. At higher silica contents, the A- show no clear trends with fractionation, while in theI-type granites those elements generally increase withtypes are weakly peraluminous as a result of fractionation.

The perception that A-type granites are extremely fractionation (Table 3). Zn decreases with fractionationin both granite types, but average Zn content for A-typealkaline seems to have arisen from the convenient as-

sociation of the letter a with alkaline, although A- granites is higher than that observed for the most felsicI-type granites. Thus, Zn is an indicator of A-type char-type granites were originally defined as mildly alkaline

(Loiselle & Wones, 1979) or somewhat alkaline (Collins acter, but not a complete discriminant. Ga does not varygreatly with fractionation in the A-type granite suiteset al., 1982).

Ba contents appear to be suite-specific for both the A- from the LFB, except in the Yewrangara Suite, where itincreases (Table 3). However, Ga contents increase withand I-type granites in the LFB. For example, the Gabo

381

8/10/2019 J. Petrology-1997-King-371-91

12/21


fractionation in many I-type granites, which results in fields on geochemical plots (compare with Whalenet al.,1987). In some cases, rocks may plot in the A-type fieldGa/Al trends that can be readily discerned from theof one chemical discrimination diagram, but will not plotmajority of LFB A-type granites (Whalen et al., 1987).in the A-type field of another chemical discriminationThe REE behave similarly with fractionation in bothdiagram, owing to fractionation (e.g. the aluminousA- and I-type granites, although the more mafic A-typesubsolvus A-type rocks from Corsica; Poitrasson et al.,granites have flatter REE3+ patterns and much higher1994, 1995). In the absence of a close relationship withREE contents than typical I-type granites (Tables 2 andunfractionated rocks, distinction of strongly fractionated3). The LREE (LaSm) decrease with fractionation in

A-type granites from similarly fractionated I-type granitesboth types. The most mafic rocks do not have a strongis difficult. At present, classification of very felsic rocksnegative Eu/Eu anomaly (e.g. Gabo Island and Mum-can only be made confidently when there is an associationbulla suites; Collins et al., 1982). However, Eu decreaseswith less evolved rocks within the same suite. Thus aas the rocks become more felsic, resulting in a strongsmall proportion of very felsic and fractionated rocks arenegative Eu/Eu anomaly (e.g. WB121), indicative ofambiguous in terms of I- or A-type character as a resultfeldspar fractionation. The HREE (GdYb) increaseof their prolonged evolution. Compositional separationslightly, or remain constant with fractionation in bothbetween the two types is very clear in less evolved rocks,the I- and A-type granites. Sample BG20 (Murrungowar)and mineralogical criteria can be used to discriminatehas strikingly different REE geochemistry from the otherthe types. Therefore, the A-type concept is valid.LFB A-type granites, with a steeper chondrite-normalized

slope, and lower concentrations of HREE. We attribute

these differences to BG20 being the most mafic rockanalyzed with annite as the sole mafic mineral (amphibole Granites problematic for classificationis present in all of the other less felsic compositions). As noted above, the extremely felsic granites are difficult

The A-type granites of the Gabo and Mumbulla suites to classify using chemical data. Altered, felsic granitescontain high abundances of Sc (1418 p.p.m.), and high are even more problematic for classification and, as anSc was cited as a diagnostic feature of A-type granites example, we present data on the Freycinet and Housetopby Collinset al. (1982). However, the Sc content of other granites of Tasmania. These are felsic, strongly frac-

A-type granites is variable and generally lies within the tionated (Rb > 270 p.p.m.) granites that are difficult torange observed for I-type granites of the same SiO2 classify as either fractionated I- or A-type granites. Theycontent. Within a particular SiO2 range, the average were designated I-type by Chappell et al. (1991) simply

value for Sc in the A-type granites is slightly higher than because that is by far the more common type of granitethe average for the I-type granites and so, for this element, throughout the belt, although chemical compositionsthe average value is misleading and high Sc contents are overlap with those of A-type granites for some elementsnot diagnostic for LFB A-type granites. (e.g. Zr and Ce; Fig. 5). The Tasmanian rocks appear

Low abundances of trace transition elements have also to be altered, on the basis of petrographic evidence, suchbeen cited as characteristic of LFB A-type granites by as an abundance of albitic plagioclase, and compositionalCollins et al. (1982), but this feature is also a reflection evidence (e.g. most have extremely low CaO abundancesof the inherently felsic nature of A-type granites; felsic I-

8/10/2019 J. Petrology-1997-King-371-91

13/21


peralkaline rocks. Peralkaline rocks are unequivocally A- with the LFB aluminous A-type granites. The Narraburratype in this sense, whereas the metaluminous to weakly Suite rocks have much more variable Zr contents thanperaluminous A-type rocks are more ambiguous. We those observed for the LFB aluminous A-type granitescontend that there are distinctive features of the per- and some of them have substantially higher Zr contents.alkaline granites that are not shared with the aluminous World-wide, peralkaline granites commonly contain 1000

A-type granites, such as indeed their peralkalinity, con- p.p.m. Zr (Eby, 1990), but contents as great as ~5000sequent distinctive mineralogy, characteristic field as- p.p.m. have been reported (e.g. Habd-Aldyaheen com-sociations and general chemical compositions. plex, Arabian Peninsula; Radain et al., 1981). This is

Many of the peralkaline rocks are hypersolvus (with consistent with experimental evidence that Zr is morealkali feldspar the only feldspar) and the mafic minerals soluble in peralkaline than metaluminous melts (Watson,include fayalite, hedenbergite, aegirine, ferrorichterite, 1979). Zr content increases with fractional crystallizationriebeckite and arfvedsonite. These features indicate that in the peralkaline rocks if the magma reaches the granitethe peralkaline magmas had an anhydrous origin. In stage of fractionation at high enough temperatures andgeneral, the peralkaline rocks are associated with vo- the solubility of Zr has not been exceeded.luminous basalt, syenite and/or anorthosite. In contrast, The chemical trends observed for many peralkalinethe LFB aluminous A-type granites do not include any rocks could be achieved by Al2O3 depletion of either anhypersolvus rocks and those mafic minerals are not I- or A-type parent magma or basaltic magma by extremeobserved, excepting riebeckite, which is rare (Table 1). crystal fractionation of plagioclase and clinopyroxeneWe argue above that the LFB A-type granites have (Tuttle & Bowen, 1958) or Ca-bearing alkali feldsparnormal H2O contents and these petrographic ob- (Carmichael & McKenzie, 1963). These mechanismsservations support this proposal. In addition, the LFB appear consistent with peralkaline rock compositionsaluminous A-type granites are only associated with minor (H2O-poor, high Ba, Sr and HFSE, strong negative Eu/basalt and gabbros and never associated with syenite or Eu) and field associations (common mafic rocks), andanorthosite. have been proposed by many workers (e.g. Baker, 1974;

Previous workers have discussed the differences be- Walsh et al., 1979; Turner et al., 1992).tween peralkaline and aluminous A-type rocks. Whalen The differences between the metaluminous to weakly& Currie (1990) studied large metaluminousperalkaline peraluminous A-type rocks and the peralkaline rocks arecomplexes, emphasizing the Topsails Complex, New- such that they should not be grouped together in rockfoundland. They suggested that those rock associations classification schemes. In grouping these two different

have a diff

erent petrogenesis from other smaller, highly types of granite together, Loiselle & Wones (1979) hadfractionated A-type granites. We contend that the metal- access to many fewer data than now available. The nameuminousperalkaline complexes differ from the smaller peralkaline should be retained for a group of rocks thatmetaluminousweakly peraluminous granites of the LFB have long been regarded as distinctive. The aluminousand that the latter rocks need not be highly fractionated. A-type granites of the LFB and elsewhere are differentIn other regions, metaluminous A-type rocks and the from peralkaline rocks, and as the two types are likelylarger peralkaline A-type rock associations have been to have different origins, it is inappropriate to groupgrouped together. For example, Eby (1992) divided A- them together. We recommend using the term aluminoustype granites from around the world into A1 and A2 A-type in reference to the LFB rocks and similar rocksgroupings on the basis of tectonic affiliations and the Y/ elsewhere. Retaining the A term is useful because ofNb and Yb/Ta ratios of the rocks. If a wider group of the extensive literature on those rocks using that name,trace elements are examined [e.g. the figures of Eby even though some A characteristics are not distinctive in(1992)], then compositions of the A1, A2, peralkaline and the LFB and probably elsewhere (e.g. extremely alkaline,

metaluminous rocks overlap. This is due to the inherently anhydrous and anorogenic). Perhaps A should nowfractionated nature of many of the peralkaline granites, refer to anomalous in the LFB, in reference to thewhich leads to great compositional variation within a anomalously high HFSE contents of the aluminous A-suite. However, if the most mafic member of a suite is type granites (compare with Hogan et al., 1992).examined, the peralkaline rocks typically contain more

Ba, Sr, HFSE and REE3+ and strong negative Eu/Euanomalies relative to metaluminous A-type granites. Wesubmit that these differences result from different pe-

ISOTOPIC WORKtrogenetic schemes for the peralkaline rocks (fractionationIsotopic compositions were measured using a multi-from a mafic source; below) and the aluminous rockscollector VG354 thermal ionization mass spectrometer(partial melting of an infracrustal source; below).at the Centre for Isotope Studies, North Ryde, NewIn Fig. 5, we show some of the variation in Ebys A2

group by comparing the peralkaline Narraburra Suite South Wales. For each analysis, a 100 mg sample was

383

8/10/2019 J. Petrology-1997-King-371-91

14/21


Fig.

5.

(a)ZrvsSiO2

forI-type,pera

lkalineandA-typegranitesoftheLachlanFoldBelt.Theoutlinearbitrarilyencloses~98%

oftheI-typegranites.TheI-typegranitesthathaveZr

contents>300p.p.m.includetheBurrinjuckandYeovalgranites,whichbelongtotheBoggyPlainSupersuite(discussedintext;Wybornetal.,1987).Also,theGobonderyandYackandandah

graniteseachhaveoneanalysiswith>

300p.p.m.Zr.NoneofthosegranitesareconsideredtobeA-type,asothercriteriaarenotsatisfied.Itshouldbenotedthattheperalkaline

Narraburra

Granite(Wormald&Price,1988;Wormald,1991)hasextremelyvariableZrcont

ents,withsomegraniteshavingveryhighcontents.

TwoperalkalinerocksfromtheNarra

burraSuite

werenotplottedinthediagram(from

theBoginderraGranite;Wormald,1991).ThoserockshaveZrcontentsof638and799p

.p.m.,andSiO2contentsof7395and7548%

.(b)Cevs

SiO2

forI-type,peralkalineandA-typ

egranitesoftheLachlanFoldBelt.Theoutlinearbitrarilyencloses~994%oftheI-typegranites.TheI-typegranitesthatplotoutoftheoutlined

areaincludetheBurrinjuckandJacksongranitesoftheBoggyPlainSupersuite(disc

ussedintext;Wybornetal.,1987);alsotheJindera,MumbedahandButmaroogranites.Th

osegranites

arenotconsideredtobeA-typebe

causeothercriteriaarenotsatisfied.Oneana

lysisfromtheJinderaGranitewasnotplotted

onthediagram(SiO2=

7067%,

Ce=

422

p.p.m.).

384

8/10/2019 J. Petrology-1997-King-371-91

15/21


dissolved in an open beaker on a hot plate employing al., 1982; Clemens et al., 1986; Whalen et al., 1987;Peterson et al., 1991; Skjerlie & Johnston, 1992). OurHF, HNO3 and HClO4. Sr was separated using a one-

step ion exchange column in a BioRad AG50W-X8 resin data indicate that other petrogenetic models are necessaryto explain the LFB A-type granites and possibly otherand dilute HCl. Sr isotopic compositions were corrected

for mass fractionation with an 86Sr/84Sr value of 01194. aluminous A-type granites world-wide.Granites, as felsic rocks of minimum-temperature meltNd was extracted using a single column pass process (see

Korsh & Gulson, 1986). Both Sr and Nd isotopic ratios composition, represent either products of fractional crys-

tallization of quartz, feldspars and mafic minerals fromfor a single dissolution were collected at least 50 timessuch that 2 values were at most 00015%. Procedural a more mafic melt, or primary melts derived from a source

containing quartz and feldspars. Within the constraintsblanks were 790 pg of Nd and 250 pg of Sm. For RbSranalyses, 10 runs of a standard (SRM987) gave 84Sr/ imposed by these two broad mechanisms, the distinctive

features of the aluminous A-type granites could reflect86Sr = 00564895, 86Sr/88Sr = 0120182196, 87Sr/86Sr = 07102623. For Nd isotopic analyses, 27 dis- either a characteristic parent magma composition and/

or source rock, or differences in the physical and/orsolutions of Onions standard gave 146/144Nd =0721396320 (2), 145Nd/144Nd = 03484072, chemical conditions of melting, magma separation or

crystallization. We briefly review some of the arguments143Nd/144Nd = 05111122.Isotopic ratios are potentially useful indicators of gran- previously made for the genesis of I-type and peralkaline

rocks, in the context of evaluating the potential geneticite source regions; however, in the case of the SmNdand RbSr systems, the A-type granites are ambiguous, schemes for the aluminous A-type rocks.

as ratios overlap with those of I-type and peralkalinerocks (Table 4, Fig. 6). None the less, no sedimentarycomponent is indicated by isotopic data. The A-typeshave relatively high initial 143Nd/144Nd ratios with Nd

values (at 400 Ma) varying from +501 to 315; thereInvolvement of a mafic magmais a range from mantle to crustal values. This variationFractional crystallization, generally of a mantle-derivedis consistent with Nd isotope heterogeneity in granitesmagma, to produce I-type granites or peralkaline com-from eastern Australia and from Corsica (Chappellet al.,positions has been proposed by many workers (e.g.1990; Turner et al., 1992; Poitrasson et al., 1994, 1995).Bowen, 1928; Baker, 1974; Walsh et al., 1979). AnIn both cases, isotope heterogeneity has been interpretedexample of such a process in the LFB is the I-type Boggy

to reflect magma source region heterogeneity. These Plain Supersuite (Wyborn et al., 1987). Those rocks doresults illustrate some of the difficulties in applying Ndnot share the chemical features of the LFB A-types,isotopes to elucidate the genesis of extremely felsicexcept at their most felsic compositions, where we havemagmas, such as the A-type granites.seen that there is overlap between I- and A-type com-Calculated initial 87Sr/86Sr ratios (at 400 Ma) are inpositions. At the more mafic compositions, where A-typethe range 07002070888, excluding sample AB401.granite chemical features are distinctive, the fractionatedSample AB401 has extremely low initial 87Sr/86Sr that isgranites can be easily distinguished from the Boggy Plainthought to reflect an inaccurate age correction owing toSupersuite rocks. For example, Zr contents are generallythe very high Rb/Sr ratio. We do not consider that thelower in the Boggy Plain Supersuite because they areSr initial ratios are meaningful in the case of the LFBderived from a mafic magma that was undersaturatedA-type granites, owing to their relatively low Sr contentswith respect to Zr (exceptions are listed in Fig. 5). Onceand thus their high sensitivity to changes of Rb/Sr or SrZr becomes saturated in a magma, high Zr contentsisotopic compositions.

cannot be reached via fractional crystallization, especiallyif zircon is one of the fractionated minerals and tem-perature falls during fractionation. A few granites do

have high Zr contents in the Boggy Plain Supersuite(>300 p.p.m.; Fig. 5), but they are not considered to be

PETROGENESIS A-type as other criteria are not satisfied.The LFB metaluminous to weakly peraluminous A-type One argument against a mechanism of fractional crys-

tallization of a mafic magma to produce the aluminousgranites have chemical and mineralogical attributes

which must reflect a somewhat different petrogenesis A-type granites of the LFB is that some of the least

evolved rocks have Eu, Rb, Sr and Ba contents thatfrom typical I-type granites. Previously, the distinctivefeatures of the A-type granites, such as high HFSE and preclude extensive feldspar fractionation from a mafic

source. The composition of the very felsic MumbullaGa, were explained in terms of high F, low H2O andhigh alkali element contents in the source (e.g. Collins et Suite rocks [high SiO2, ~77%; high Ba, 500655 p.p.m.;

385

8/10/2019 J. Petrology-1997-King-371-91

16/21


Table4:RbSrandSmN

disotopicdataforselectedA-typegranitesfromtheLachlanFoldBelt

AB412

GI1

AB239

WB140

BG20

B

G15

AB422

VB203

AB421

AB118

AB238

AB401

W

B121

87Rb/86Sr

3309

4778

3522

1449

4562

7617

8323

11231

13416

19510

39443

63068

87Sr/86Sr

0724632

0736103

0725114

0716215

0733704

0745348

0750039

0763997

0780686

0815897

0909173

1067880

SriT

070579

070888

070505

070796

070772

070196

070263

070002

070426

070476

06845

070864

147Sm/144Nd

011601

0146

02

011856

012091

008441

011893

011419

011854

014442

015022

014056

018877

018412

143Nd/144Nd

0512527

0512

431

0512331

0512496

0512223

0512369

0512540

0512690

0512500

0512355

0512350

0512779

0512681

Ndo

217

404

599

277

810

525

191

101

269

552

562

275

084

InitialNdT

051222

0512

05

051202

051218

0512000

051206

051224

051238

051212

051196

051198

051228

051220

SrT

977

1421

872

1289

1

254

430

526

153

760

831

2068

1

385

NdT

195

146

200

110

237

128

23

501

003

315

276

315

148

ModelNd

813

1370

1139

904

969

1

084

779

583

1191

1640

1436

1589

1

845

ThesubscriptTreferstothevaluecalculatedat400Ma.

Thesubscriptoreferstothein

itialvalue.

TheCHURvaluesusedwere14

7Sm/144Nd=

01966and143Nd/144Nd=

0512638(Jacobsen&Wasserburg,

1980

).

386

8/10/2019 J. Petrology-1997-King-371-91

17/21


Fig. 6. Plot of Nd vs initial 87Sr/86Sr (both calculated for 400 Ma) showing the LFB A-type granites. Also shown are the fields for I- type and

S-type granites from the LFB [data from Chappell et al. (1990)] and the field for peralkaline rocks from the Padthaway Ridge, South Australia(Turner et al., 1992). It should be noted that the A-type granites overlap isotopically with the I-type and peralkaline rocks. The sample AB401

(Dunskeig pluton, Wangrah Suite) has been excluded from this plot, as explained in the text.

moderate Rb, 225261 p.p.m.; and low to moderate Eu, Partial melting121168 p.p.m. (Collins et al., 1982)] indicates that Many workers have suggested that A-type granites arethere has been no appreciable feldspar fractionation. The produced by combined partial meltingfractionationmost mafic members of the Yewrangara and Wangrah from source regions of slightly different composition thanSuites (WB140 and AB412, Table 2) similarly have those for I-type granites (e.g. Anderson & Cullers, 1978;compositions that were probably not produced by frac- Cullers et al., 1981; Collins et al., 1982; Anderson, 1983;tionation from a mafic source, but appear to be the result Clemens et al., 1986; Whalen et al., 1987; Wormald &of partial melting.

Price, 1988; Creaseret al., 1991; Landenberger & Collins,Magma mixing is a process that has been advanced 1996). Proposed source compositions that have beenby some workers to produce A-type granites (e.g. Bedard, favored are lower crustal, including tonalite, granodiorite,1990). However, as many of the intrinsically felsic A- peraluminous granulite, charnockite and granulitic re-type granites of the LFB are weakly peraluminous, very siduum from melting of I-type granites. On the whole,little strongly metaluminous mafic magma could have the researchers listed above have discussed granites withbeen added to the granite magma, especially considering similar compositions to the LFB A-type granites. Thethat the mafic magmas have higher concentrations of Al general approach has been to try and account for anand (Ca + Na + K). Also, magma mixing seems H2O-poor, F-rich source. These models, or any othersunlikely in the LFB, on the basis of the occurrence that invoke a distinctive source for the A-type granites,of bimodal A-type rock associations and the restricted have to be reconciled with the fact that A-type granites

miscibility of the two magma types (Sparks & Marshall, may be adjacent to or intrusive into other granite types

and, in the LFB, have a very limited distribution. This1986).

387

8/10/2019 J. Petrology-1997-King-371-91

18/21


means that if the sources for A-type granites are dis- aluminous A-type granites such as those of the LFB. Thistinctive, then those source regions had to be either identification of aluminous A-type rocks has petrogenetic

very localized and/or separated vertically from adjacent implications.granite source regions. (2) Aluminous A-type granites commonly have Fe-rich

mafic minerals and primary ilmenite. The more mafic

(~6572% SiO2) granites are distinguished chemically

from I-type granites by relatively high Fe total/(Fetotal +

Mg), HFSE (especially Zr, Nb, Y), REE3+, Ga and Zn.Synthesis

The RbSr and NdSm isotopic compositions for theIn assessing the possible genetic schemes for the LFB A- LFB A-type granites overlap with those of peralkalinetype granites, the most important single feature is their and I-type granites from elsewhere.high Zr contents relative to the I-type granites, which, (3) More evolved A-type granites are difficult or im-as we have noted above, is related to higher calculated possible to distinguish from fractionated I-type granites.zircon saturation temperatures. Zr is an ideal discriminant To characterize any kind of felsic granite it is necessaryfor the aluminous, unfractionated LFB A-type granites. to compare suites of rocks in which less evolved rocksIn addition, its behavior in granite magmatic systems

are also present. New data indicate that some featureshas been characterized experimentally (Watson, 1979;

of LFB aluminous A-type granites, which were previouslyWatson & Harrison, 1983). We suggest that the otherconsidered diagnostic of the type, are actually similar to

HFSE that are relatively abundant in the A-type granitesthose of many felsic I-type granites; for example, Na2Ohave partition coefficients that are similarly dependent+ K2O, Sc and trace transition element contents.on temperature.

(4) The LFB aluminous A-type granites generally haveThe critical observation that A-type magmas existed

reduced compositions relative to the NNO buffer, whichat higher calculated zircon saturation temperatures than

most probably reflects the character of the source region.other felsic granites implies that they were derived from

Our data also show that those granites do not have higha fertile felsic source region that required a high tem-

F contents compared with fractionated granites. Thereperature before an extractable magma was produced.is no evidence that H2O contents are lower than for felsicWe favor a felsic infracrustal source that could overlap inI-type granites; thus the term anhydrous in referencecomposition with I-type sources, on the basis of similaritiesto the A-type rocks is misleading. These intensive para-between the two rock types. The major difference be-meters have a key role in the petrogenesis of this granitetween petrogenetic schemes for the aluminous A-typetype.magmas and the I-type magmas is that different physical

(5) Calculated zircon saturation temperatures for al-conditions prevailed. Limited availability of H2O anduminous A-type granites are higher than those of otherrelatively low oxygen fugacity during partial melting, andgranite types. We suggest that the other HFSE that aretherefore high temperatures, may be all that is requiredrelatively abundant in the aluminous A-type granitesto produce aluminous A-type granites. As melt viscosityhave partition coefficients that, like Zr, are dependentis reduced at high temperatures, an extractable melt mayon temperature.be generated at smaller degrees of partial melting than

(6) The term anorogenic is unclear and thus shouldneeded for other granite types. The necessarily highnot be used for characterizing A-type granites. Geo-temperatures required to produce an extractable magmachronological evidence suggests that LFB aluminous A-may have been initiated by mantle upwelling or mafictype granites can be emplaced at any time during amagma influx into a localized area. Although we cannottectonicmagmatic episode. In the LFB, aluminous A-rule out magma mixing as a factor in petrogenesis, theretype granites are found adjacent to I-type granites ofis no direct evidence to support it, therefore we do notsimilar age and have similar field relations.favor it.

(7) We favor a petrogenetic scheme in which the

aluminous A-type granites were derived by small degrees

of partial melting of a felsic, infracrustal source region.

The source region was probably relatively reduced, withCONCLUSIONS water and F contents similar to those of I-type source

regions. The A-type source regions could be either very(1) The term A-type as proposed by Loiselle & Woneslocalized or separated from other granite source regions(1979) is too broad to succinctly define rocks world-wide.

vertically in the crust. The necessarily high temperaturesWe recommend using the term aluminous A-typerequired to produce an extractable magma may havein reference to the LFB rocks and similar rocks else-been initiated by mantle upwelling or mafic magmawhere. The peralkaline rocks should be known as

such, and differ from the metaluminous to weakly per- influx into a localized area.

388

8/10/2019 J. Petrology-1997-King-371-91

19/21


Carmichael, I. S. E. & McKenzie, W. S., 1963. FeldsparliquidACKNOWLEDGEMENTSequilibria in pantellerites: an experimental study.American Journal of

This manuscript benefited from constructive reviews by Science261, 382396.Champion, D. C., 1991. Felsic granites of far north Queensland.John Hogan, John Foden and an anonymous reviewer.

Unpublished Ph.D. Thesis, Australian National University, Can-We appreciate Tony Ewarts careful editorial assistance. berra, A.C.T.We are grateful for helpful conversations and data fromChappell, B. W., 1991. Trace element analysis of rocks by X-ray

Phillip Blevin, Ian Williams, David Champion, Dennisspectrometry. Advances in X-ray Analysis34, 263276.

Pogson, and Anthony Budd. Discussions with Phillip Chappell, B. W., 1994. Lachlan and New England: fold belts ofCandela, the late Robert Hill, Cal Barnes and Doone contrasting magmatic and tectonic development. Journal and Pro-Wyborn were also useful. John Holloway and Lee Silver ceedings, Royal Society of New South Wales127, 4759.

Chappell, B. W. & Hergt, J. M., 1989. The use of known Fe contentare thanked for providing facilities during the final stagesas a flux monitor in neutron activation analysis.Chemical Geology 78,of manuscript production. Nick Ware, Tony Phimphisane151157.

and Geoff Denton are thanked for help with analyticalChappell, B. W. & White, A. J. R., 1974. Two contrasting granite

work. Figure 1 was drafted by the Cartographic Servicestypes.Pacific Geology 8, 173174.

Unit at AGSO. Financial support from the Australian Chappell, B. W. & White, A. J. R., 1992. I- and S-type granites in theResearch Council Grant A39232908 is acknowledged. Lachlan Fold Belt.Transactions of the Royal Society of Edinburgh: Earth

Sciences83, 126.

Chappell, B. W., Williams, I. S., White, A. J. R. & McCulloch, M. T.,1990. Granites of the Lachlan Fold Belt. ICOG 7 Field Guide

Excursion A-2. Bureau of Mineral Resources, Geology & Geophysics Record

1990/48.

Chappell, B. W., English, P. M., King, P. L., White, A. J. R. & Wyborn,

D., 1991. Granites and related rocks of the Lachlan Fold Belt (1:1 250 000

scale map). Canberra: Bureau of Mineral Resources, Geology andREFERENCESGeophysics.Anderson, J. L., 1980 . Mineral equilibria and crystallization conditions

Chen, Y. D. & Williams, I. S., 1990. Zircon inheritance in maficin the late Precambrian Wolf River rapakivi massif, Wisconsin.inclusions from the Bega Batholith granites, southeastern Australia:American Journal of Science280, 289332.an ion microprobe study.Journal of Geophysical Research95B, 17787Anderson, J. L., 1983. Proterozoic anorogenic granite plutonism of17796.North America. Geological Society of America Memoir161, 133154.

Clarke, D. B., 1992. Granitoid Rocks. London: Chapman and Hall.Anderson, J. L. & Cullers, R. L., 1978. Geochemistry and evolution

Clemens, J. D., Holloway, J. R. & White, A. J. R., 1986. Origin of anof the Wolf River Batholith: a late Precambrian rapakivi massif in

A-type granite: experimental constraints. American Mineralogist 71,north Wisconsin, U.S.A. Precambrian Research7, 287324.

317324.Atkinson, P., 1976. Geology and geochemistry of the Victoria ValleyCollins, W. J., 1977. Gabo Island Granite Suite. Unpublished

Batholith, Grampians Ranges, south-eastern Australia. UnpublishedB.Sc. Honours Thesis, Australian National University, Canberra,

B.Sc. Honours Thesis, La Trobe University, Melbourne, Vic.A.C.T.

Baker, P. E., 1974. Peralkaline acid volcanic rocks of oceanic islands.Collins, W. J., Beams, S. D., White, A. J. R. & Chappell, B. W., 1982.

Bulletin of Volcanology38, 737754.Nature and origin of A-type granites with particular reference to

Barker, F., Wones, D. R., Sharp, W. N. & Desborough, G. A., 1975.southeastern Australia. Contributions to Mineralogy and Petrology 80,

The Pikes Peak Batholith, Colorado Front Range, and a model for189200.

the origin of the gabbroanorthositesyenitepotassic granite suite.Creaser, R. A., Price, R. C. & Wormald, R. J., 1991. A-type

Precambrian Research2, 97160.granites revisited: assessment of a residual-source model.Geology 19,

Barron, L. M., Scheibner, E. & Suppel, D. W., 1982. The Mount163166.

Hope Group and its comagmatic granites on the Mount Allen 1:Cullers, R. L., Koch, R. J. & Bickford, M. E., 1981. Chemical evolution

100 000 Sheet, New South Wales. Quarterly Notes New South Wales of magmas in the Proterozoic Terrane of the St. Francois Mountains,Geological Survey 24. Southeastern Missouri. 2. Trace element data. Journal of Geophysical

Bedard, J., 1990. Enclaves from the A-type granite of the Megantic Research86, 1038810401.Complex, White Mountain magma series: clues to granite mag-

Czamanske, G. K., Ishihara, S. & Atkin, S. A., 1981. Chemistry ofmagenesis.Journal of Geophysical Research95 (B11), 1779717819. rock-forming minerals of the CretaceousPaleocene batholith inBonin, B., Grelou-Orsini, C. & Vialette, Y., 1978. Age, origin and Southwestern Japan and implications for magma genesis.Journal of

evolution of the anorogenic complex of Evisa (Corsica): a K Geophysical Research86, 1043110469.LiRbSr study. Contributions to Mineralogy and Petrology 65, 425432. Dodd, S. J., 1981. The deformation, metamorphic and intrusive history

Bowen, N. L., 1928. The Evolution of the Igneous Rocks. Princeton, NJ: of the Kuark Metamorphic Belt, Southeast Gippsland. UnpublishedPrinceton University Press. B.Sc. Honours Thesis, La Trobe University, Melbourne, Vic.

Budd, A. R., 1992. Internal differentiation and mineralization of the Eby, G. N., 1990. The A-type granitoids: a review of their occurrenceBanshea pluton, New South Wales. Unpublished B.Sc. Honours and chemical characteristics and speculations on their petrogenesis.Thesis, Australian National University, Canberra, A.C.T. Lithos26, 115134.

Burnham, C. W. & Ohmoto, H., 1980. Late-stage processes of felsic Eby, G. N., 1992. Chemical subdivision of the A-type granitoids:

magmatism.Mining Geology, Special Issue8, 111. petrogenetic and tectonic implications.Geology 20, 641644.

Camacho, A., 1987. Geochemistry of some fractionated western Tas- Fergusson, C. L. & Glen, R. A. (eds), 1992. The Palaeozoic eastern

manian granites. Unpublished M.Sc. Thesis, La Trobe University, margin of Gondwanaland: tectonics of the Lachlan Fold Belt,

southeastern Australia and related orogens.Tectonophysics214.Melbourne, Vic.

389

8/10/2019 J. Petrology-1997-King-371-91

20/21


Greenberg, J. K., 1990. Anorogenic granite associations as products of Poitrasson, F., Duthou, J-L. & Pin, C., 1995. The relationship between

progressive continental evolution. In: Gower, C. F., Rivers, T. & petrology and Nd isotopes as evidence for contrasting anorogenic

Ryan, B. (eds) Mid-Proterozoic LaurentiaBaltica. Geological Association of granite genesis: example of the Corsican Province (SE France).

Canada, Special Paper38, 447457. Journal of Petrology36, 12511274.

Hogan, J. P., Gilbert, M. C. & Weaver, B. L., 1992. A-type granites Radain, A. A. M., Fyfe, W. S. & Kerrich, R., 1981. Origin of peralkalineand rhyolites: is A for ambiguous? EOS, Transactions, American Geo- granites of Saudi Arabia. Contributions to Mineralogy and Petrology 78,physical Union (newsletter)73, 508. 358366.

Jacobsen, S. C. & Wasserburg, G. J., 1980. SmNd isotopic evolution Richards, D. N., 1967. The Geology of the Jerangle District. Un-of chondrites. Earth and Planetary Science Letters50, 139155. published B.Sc. Honours Thesis, Australian National University,

Johnson, M. C. & Rutherford, M. J., 1989 . Experimentally determined Canberra, A.C.T.conditions in the Fish Canyon Tuff, Colorado, magma chamber. Rogers, J. J. W. & Greenberg, J. E., 1990. Late-orogenic, post-orogenic,Journal of Petrology30, 711737. and anorogenic granites: distinction by major-element and

King, P. L., 1992. A-type granites from the Lachlan Fold Belt: a trace-element chemistry and possible origins. Journal of Geology 98,case study and reassessment. Unpublished B.Sc. Honours Thesis, 291310.Australian National University, Canberra, A.C.T.

Skjerlie, K. P. & Johnston, A. D., 1992. Vapor-absent melting at 10King, P. L., Chappell, B. W., White, A. J. R. & Williams, I. S., 1992.

kbar of a biotite- and amphibole-bearing tonalitic gneiss: implicationsA-type granites from the Lachlan Fold Belt, eastern Australia.EOS,

for the generation of A-type granites.Geology 20, 263266.Transactions, American Geophysical Union 73, 346.

Sparks, R. S. J. & Marshall, L. A., 1986. Thermal and mechanicalKorsch, M. J. & Gulson, B. L., 1986. Nd and Pb isotopic studies of

constraints on mixing between mafic and silicic magmas. Journal of

an Archaean layered maficultramafic complex, Western Australia, Volcanology and Geothermal Research29, 99124.and implications for mantle heterogeneity.Geochimica et Cosmochimica

Sylvester, P. J., 1989. Post-collisional alkaline granites.Journal of GeologyActa50, 110.

97, 261280.Landenberger, B. & Collins, W. J., 1996. Derivation of A-type granites

Turner, S. P., Foden, J. D. & Morrison, R. S., 1992. Derivation offrom a dehydrated charnockitic lower crust: evidence from the

some A-typemagmas by fractionation of basaltic magma: an exampleChaelundi Complex, Eastern Australia.Journal of Petrology 37, 145from the Padthaway Ridge, South Australia.Lithos28, 151179.170.

Tuttle, O. F. & Bowen, N. L., 1958. Origin of granite in the light ofLeake, B. E., 1978. Nomenclature of amphiboles.American Mineralogistexperimental studies in the system NaAlSi3O8KAlSi3O8SiO2H2O.63, 10231052.Geological Society of America Memoir74, 153 pp.Lewis, P. C., Glen, R. A., Pratt, G. W. & Clarke, I., 1994. Bega-

Walsh, J. M. N., Beckinsale, R. D., Shelhorn, R. R. & Thorpe, R. S.,Mallacoota 1:250 000 Geological Sheet SJ/554, SJ/558: Explanatory1979. Geochemistry and petrogenesis of Tertiary granitic rocks fromNotes. Sydney: Geological Survey of New South Wales.the island of Mull, NW Scotland. Contributions to Mineralogy and PetrologyLoiselle, M. C. & Wones, D. R., 1979. Characteristics and origin of71, 99116.anorogenic granites.Geological Society of America, Abstracts11, 468.

Watson, E. B., 1979. Zircon saturation in felsic liquids: experimentalMacKenzie, D. E., Black, L. P. & Sun, S-S., 1988. Origin of alkali-

feldspar granites: an example from the Poimena Granite, north- data and applications to trace element geochemistry.Contributions toeastern Tasmania, Australia.Geochimica et Cosmochimica Acta 52, 2507 Mineralogy and Petrology70, 407419.2524. Watson, E. B. & Harrison, T. M., 1983. Zircon saturation revisited:

MacKenzie, D. E., Sun, S-S. & Black, L. P., 1990. Reply to N. C. temperature and composition effects in a variety of crustal magmaHiggins Comment on Origin of alkali-feldspar granites: an example types. Earth and Planetary Science Letters64, 295304.from the Poimena Granite, northeastern Tasmania, Australia. Whalen, J. B. & K. L. Currie, 1990. The Topsails igneous suite, westernGeochimica et Cosmochimica Acta54, 23132322. Newfoundland; fractionation and magma mixing in an orogenic

Maniar, P. D. & Piccoli, P. M., 1989. Tectonic discrimination of A-type granite suite. Ore-bearing Granite Systems; Petrogenesis andgranitoids.Geological Society of America Bulletin 101, 635643. Mineralizing Processes. Geological Society of America, Special Papers 246,

Merzbacher, C. & Eggler, D. H., 1984. A magmatic geohygrometer: 287300.application to Mount St. Helens and other dacitic magmas.Geology Whalen, J. B., Currie, K. L. & Chappell, B. W., 1987. A-type granites:12, 587590.

geochemical characteristics, discrimination and petrogenesis. Con-Naney, M. T., 1983. Phase equilibria of rock-forming ferromagnesian

tributions to Mineralogy and Petrology 95, 407419.silicates in granitic systems.American Journal of Science283,9931033.

Williams, I. S., 1992. Some observations on the use of zircon UPbNorrish, K. & Hutton, J. T., 1969. An accurate X-ray spectrographic

geochronology in the study of granitic rocks.Transactions of the Royal

method for the analysis of a wide range of geological samples. Society of Edinburgh: Earth Sciences83, 447458.Geochimica et Cosmochimica Acta33, 431453.Williams, I. S., Chappell, B. W., McCulloch, M. T. & Crook, K. A.

Pearce, J. A., Harris, N. B. W. & Tindle, A. G., 1984. Trace elementW., 1991. Inherited and detrital zirconsclues to the early growth

discrimination diagrams for the tectonic interpretation of graniticof crust in the Lachlan Fold Belt.Geological Society of Australia, Abstractsrocks. Journal of Petrology 25, 956983.29, 58.Peck, L. C., 1964. Systematic analysis of silicates. US Geological Survey,

Wones,D. R., 1989. Significance of theassemblage titanite+magnetiteBulletin1170.+ quartz in granitic rocks.American Mineralogist74, 744749.Peterson, J. W., Chako, T. & Kuehner, S. M., 1991. The effects

Wormald, R. J., 1991. The petrology and geochemistry of Mid toof fluorine on the vapor-absent melting of phlogopite+ quartz:Late Palaeozoic magmatism in the Temora region, New Southimplications for deep-crustal processes.American Mineralogist76, 470Wales. Unpublished Ph.D. Thesis, La Trobe University, Melbourne,476.Vic.Pitcher, W. S., 1993. The Nature and Origin of Granite. London: Blackie.

Wormald, R. J. & Price, R. C., 1988. Peralkaline granites near Temora,Poitrasson, F., Pin, C., Duthou, J-L. & Platevoet, B., 1994. Aluminous

southern New South Wales: tectonic and petrological implications.subsolvus anorogenic granite genesis in the light of Nd isotopic

heterogeneity.Chemical Geology 112, 199219. Australian Journal of Earth Sciences35, 209221.

390

8/10/2019 J. Petrology-1997-King-371-91

21/21


Wyborn, D. & Owen, M., 1986. Araluen, N.S.W.1:100 000 Geological economic significance in the Lachlan Fold Belt.Australian Journal of

Earth Sciences34, 2143.Map Commentary. Canberra, A.C.T.: Australian Government Pub-

lishing Service. Yacopetti, C. M., 1987. The A-type granites of the Lachlan Fold Belt.

Unpublished B.Sc. Honours Thesis, Australian National University,Wyborn, D., Turner, B. S. & Chappell, B. W., 1987. The Boggy Plain

Supersuite: a distinctive belt of I-type igneous rocks of potential Canberra, A.C.T.

J. Petrology-1997-King-371-91

Documents

Transcript of J. Petrology-1997-King-371-91