1

CHAPTER ONE: INTRODUCTION

1.1 Background

The Sefwi Greenstone Belt and its adjacent Sunyani Basin are found in the western

part of Ghana, situated in the Proterozoic Birimian terrane of the West African Craton

(Figure 1.1).

Fig. 1.1. Geological map of the West Africa Craton (Africa map, insert) showing the

Paleoproterozoic Birimian terrane with the Sefwi and Sunyani Basin in red (Lampo,

2009)

Figure 1. Geological map of West African Craton (Africa map, insert) showing the Paleoproterozoic Birimian terrane with the Sefwi and Sunyani Basin in red (Lampo, 2009)

0 100 200

kilometres

830000m

830000M

1100000mN

280000mW

280000mW

1100000mN

MALI

NIGER

BENIN

TOGO

SENEGAL

LIBERIA

SIERRA

LEONE

GUINEA

Granitoids

greenstone

belt

Phanerozoic

cover

Pale

o

pro

tero

zo

ic

Archean

Study area

2

The Birimian terrane in Ghana has been a focus of commercial gold exploration since

the 1900’s. This is usually within the so-called chemical facies, defined as cherts,

manganiferous and carbon-rich sediments, Fe-Ca-Mg carbonates, and sulphide

mineral disseminations, intermittently developed at the transition between the

volcanic belts and metasedimentary basin (Leube et al. 1990, Taylor et al., 1991). The

gold usually occurs as disseminated sulphide associated with arsenopyrite, quartz

veins and stockwork free gold associated with polymetallic sulphides such as pyrite,

chalcopyrite and pyrrhotite (Milési et al., 1989; 1992). Structurally, most of the gold

deposits are hosted in shear zones or fault systems, except for the Tarkwaian deposit

which is hosted in alluvium deposits.

Currently, exploration work has been extended into the leucogranites, with the Sefwi

belt and the Sunyani basin being the primary areas of interest. For efficient gold

exploration, understanding the regional tectonic evolution of the area is critical.

However, the stratigraphy and structural evolution of the terrane remains the subject

of debate (Hasting, 1982, Ledru et al., 1988, Leube et al., 1990, Feybesse et al. 2006,

Vidal et al. 2009). This is due to the small number of local studies carried out in the

terrane. The significant paucity of outcrops and limited access are a result of dense

vegetation and laterized regolith soil cover.

This study attempts to address the general lack of structural information within the

study area, establish the sequence and style of deformation within the leucogranites,

as well as the timing of their emplacement and the deformation that affected them.

This was carried out by geologically mapping the study area, the undertaking of

detailed microstructural analysis of the leucogranites as well as other rock bodies in

the study area. Laser ablation- inductively coupled mass spectrometry (LA-ICP-MS)

3

was used to better constrain the ages of the deformation the rocks have undergone by

dating associated granites. In addition, potential field geophysical data was used to

help elucidate the subsurface structural and tectonic architecture of the study area.

The aim of this study is to:

1. Produce a geological map of the study area using both geological field mapping

data and geophysical data.

2. Study the deformations the rocks have experienced under macroscopic, mesoscopic

and microscopic scales

3. Analyse the field structural data in order to establish the deformation geometry and

develop a regional interpretation of the system with respect to known gold

occurrences.

1.2 Study Area and Accessibility

The study area is located within the Brong Ahafo and Western Regions of Ghana,

specifically the Asunafo-North and Bia districts. This lies between the co-ordinates

7o00’N, 3

o00’W (NW corner), 7°00’N, 2°45’W (NE corner), 6°38’N, 3°00’W (SW

corner) and 6o38’N, 2

o45’W (SE corner) of longitude/latitude (WGS 84 datum &

ellipsoid). It covers a total area of 1130 km2

and straddles the Sefwi belt and its

adjoining Sunyani basin in the Birimian terrane as shown in Figure 1.2 below. The

study area is about 600km from Accra and connected by feeder roads, which are often

destroyed by the rains and erosion during the raining season. Large portions of the

4

area lie within the Subin and Bia forest reserve, thereby making access even more

difficult.

Fig.1. 2. 1:1,000,000 Geological map of the Birimian Terrane in Ghana showing the

study area in red (Einslohr and Hirdes, 1991)

N

5

1.3 Physiography

1.3.1 Relief and Drainage

Extensive erosion has flattened the area, leaving only a few scattered hills. The

highest topographic point is 350 metres, and the lowest point is 196 metres. The study

area is well drained, with the River Bia being the largest river. The River Bia divides

the study area into two equal eastern and western halves. The River Bia is fed by

many affluent rivers in the study area such as the Bewiadwe, Alakatrufo, Awiwuhu,

Anankasu, Domeabra, Kasapen, Subin and Mansamakoma.

1.3.2 Climate

The study area falls within the Wet Semi Equatorial Climatic Region. The area has

two rainfall maxima with a mean annual between 125 and 200 centimetres. The first

rainy season is from May to June every year, with the heaviest in June; the second

rainy season is from September to October. The highest mean monthly temperature of

about 30o

C occurs between March and April and the lowest of 26oC in August. The

average monthly humidities are highest (75-80%) during the two rainy seasons and

lowest (70-80%) during the rest of the year (Dickson and Benneh, 1988).

6

1.3.3 Vegetation and Soils

Moist semi-deciduous forest characterizes the whole study area, and overall in Ghana

this vegetation type covers 20% of the total land area (Christiansen and Awadzi,

2000). Most of the upper and lower layers of the forest exhibit deciduous

characteristics during the long dry season from November to March and do not shed

their leaves throughout the year.

The principal soil in the study area is the forest ochrosols, a brightly coloured soil

from highly weathered parent mafic and felsic materials. The nature of the soil

impedes downward drainage and causes water logging during the dry season (Dickson

and Benneh, 1988).

7

CHAPTER TWO: LITERATURE REVIEW

2.1 Summary of Geology of the Birimian Terrane

The Birimian Paleoproterozoic terrane, also known as the Baoule-Mossi Domain,

outcrops in the southeastern portion of the Man-Shield of the West Africa Craton

(WAC). It extends across the western half of Ghana, Cote D’Ivoire, southern Mali,

Burkina Faso, Senegal and the west of Niger (Figure 2.1).

The Baoule-Mossi domain section of the West African Craton comprises Birimian

rocks and minor Tarkwaian rocks. The Birimian consists of metavolcanics that

includes meta-andesites, meta-basalts and meta-gabbros. It is also made up of

metasediments such as greywackes, quartzites and carbonaceous phyllites. The

Fig.2.1. Regional geological map of the west African Craton (Milési et al., 1989 and Vidal

et al., 1996)

8

metasediments and metavolcanics have been intruded by granitoids. The Tarkwaian

rocks consist of coarse clastic sedimentary rocks that include conglomerates, arkoses,

sandstones and minor amount of shales. Pebbles in the conglomerates include

volcanic and sedimentary clasts derived from the Birimian rocks and granitoids

(Eisenlohr and Hirdes, 1991), and are considered as molasses deposits. Most of the

rocks in the Birimian were dated 2.25-2.05 Ga and were deposited during the

Eburnean orogeny (Taylor et al., 1988; Abouchami et al., 1990; Liégeois et al., 1991;

Boher et al., 1992; Hirdes et al., 1992). Some portions of the Proterozoic Birimian

terrane in the WAC have some Archean basement terranes exposed through them.

Sedimentation in the Tarkwaian terrane occurred from 2.244 Ga. to 2.132 Ga. (Davis

et al., 1994). The Eburnean Orogenic event tectonically accreted, metamorphosed and

deformed the volcanic and sedimentary rocks into belts and basins, respectively.

2.2 Summary of the Geology

The Birimian terrane in Ghana forms an extensive part of the Paleoproterozoic

domain of the West African Craton (Einslohr and Hirdes, 1991; Hirdes, 1991; Davis

et al., 1992; Vidal et al., 2009), and covers the western half of Ghana. The Birimian

Supracrustal rocks in Ghana are composed of volcanic-plutonic units and subordinate

epiclastic sedimentary rocks which were emplaced between 2.25 and 2.17 Ga. These

rocks were intruded by the 2.16-2.15 Ga monzogranitic rocks (Feybesse et al., 2006).

Between 2.13-2.00 Ga there was emplacement of syn-tectonic crustal and calc-

alkaline anatectic crustal melt during the Eburnean Orogeny (Davis et al., 1994;

Oberthur et al., 1998). The Eburnean Orogeny completed the cratonization process

through tectonic accretion of Paleoproterozoic rocks onto a more deformed Archean

9

crust (Feybesse and Milési, 1994, Hirdes 1996, Feybesse et al., 2000, Feybesse et al.,

2006). A range of tectonic models for the Birimian terrane have been proposed by

various authors. Abouchami et al. (1990), Boher et al. (1992), Dia et al. (1997) and

Pouclet et al. (2006) all proposed a Paleoproterozoic juvenile continental crust

formed during the Eburnean orogenic event, most probably from oceanic materials in

an intraplate ocean plateau. Also, from intra-cratonic rift to oceanic spreading and

accretion related setting (Leube et al., 1990). Sylvester and Attoh (1992) also

proposed an immature island arc environment built on an oceanic crust.

Regionally the Birimian in Ghana has experienced greenschist facies metamorphism

with typical metamorphic assemblage in the pelitic rocks being quartz+ muscovite+

rare biotite; the volcanic rocks consist of chlorite+ actinolite+ epidote (Eisenlohr and

Hirdes, 1991).

The Birimian terrane has been faulted, folded and sheared with most of the units

striking northeast-southwest with vertical to sub vertical dips.

2.3 Geology of Western Ghana

2.3.1 Architecture

The Birimian terrane in Ghana consists of five northeast-southwest trending and one

north-south trending volcanic belts with intervening sedimentary basins (Davis,

1994). The volcanic belts are lithologically composed of mainly tholeiitic basalts,

dacites, andesites and rare rhyolitic rocks. From the south to north, the volcanic belts

in Ghana are the Kibi-Winneba, Ashanti, Sefwi, Bui, Bole-Navrongo and Lawra.

Interpretation of gravity and magnetic data showed north-easterly extension of these

10

volcanic belts below the Neoproterozoic/Palaeozoic Voltaian sediments and in

adjoining countries, thus reaching several 100 kilometres in length (Hastings, 1983;

Leube et at., 1990). These belts are 15-40 km wide and 60-90 km apart, trend

northeast-southwest and decrease in width north-westward across the country (Taylor

et al., 1991) with intervening sedimentary basins. The intervening sedimentary basins

from south to north lie in between the volcanic belts. These basins and belts have been

intruded by various granitoids. Four types of Paleoproterozoic granitoids suites are

present in Ghana (Hirdes et al, 1991) known as the Winneba, Cape Coast, Dixcove

and Bongo granitoids (Junner, 1940; Kesse, 1985). The Birimian terrane is highly

eroded, therefore giving the terrane a general flat topography (Dickson and Benneh,

1988).

2.3.2 Sediments

The name Birimian was introduced by Kitson (1928) to describe the Paleoproterozoic

rocks in the valley of the Birim River in Ghana (Kesse, 1985). It is bounded to the

east by the Dahomeyan Pan African belt and Voltaian basin (Kennedy, 1964), and to

the west by the Archean portion of the Man Shield. The early research into the

stratigraphic designation of the Birimian terrane defined an Upper and Lower

Birimian (Kitson, 1928; Junner, 1940). The Lower Birimian was thought to be made

up primarily of sedimentary rocks and the Upper Birimian of volcanic rocks. The

stratigraphy of the Birimian established by early authors has been an issue of debate,

due to different evidence seen in other countries where the Birimian is also exposed.

Both the Upper and Lower Birimian have been intruded by granitoids. Lying on top

of the Birimian is the minor Tarkwaian terrane. The sediments within lower Birimian

11

outcropped basically within the basins. These are the Cape-Coast, Kumasi, Sunyani

and the Maluwe Basins. The sediments are composed of volcano-clastic rocks,

turbidity related greywackes, argillitic rocks and chemical sediments.

Feybesse in 2006 proposed a stratigraphy for the Birimian terrane that is placed in the

context of the crustal evolution of the West African Craton during the Eburnean

Orogenic event. Feybesse proposed a coeval deposition between the Birimian

volcanic and sedimentary units not conforming to the stratigraphy proposed by earlier

workers. A summary of Feybesse’s stratigraphy shown in Table 1.1

Table 1.1. Chronological order of deposition of sediments and emplacement of

volcanic and plutonic rocks in the Birimian terrane

Order Activity Age

1. Deposition of Banded Iron Formation from Paleoproterozoic volcano-

sedimentary rocks

unknown

2. Emplacement of volcanic-plutonic units and subordinate epiclastic

sedimentary rock of the Sefwi, Ashanti and Kibi Belts during the early

stages of the Birimian cycle

2.25 and 2.17

Ga.

3. Emplacement of monzogranitic intrusions around 2.16-2.15 Ga

4. Deposition of sediments in the Sunyani, Kumasi-Afema Basins 2.15 and 2.10

Ga

5. Emplacement of syn-tectonic crustal and calc-alkaline intrusions

between 2.13-2.00 Ga. Certain portions of these intrusions intersect the

Tarkwaian sediments deposited

2.13-2.09 Ga

12

2.3.3 Magmatism

The granitoids intruding the Birimian belt and basin have been characterized into two

groups, the group that intrudes the basin and the group that intrudes belt. The former

is known as the basin-type granitoids and the latter also referred to as the belt-type

granitoids. Hirdes et al. (1991) described the belt granitoids as metaluminous,

hornblende-rich medium-sized plutons and have geochemical characteristics similar

to tholeiitic basalts whilst the basin-granitoids are peraluminous, biotite-rich

batholithic with no geochemical similarities of tholeiitic basalts. In contrast Leube et

al. (1990) and Feybesse et al. (2006), proposed a coeval deposition between the

Birimian volcanic and sedimentary units not conforming to the stratigraphy proposed

by earlier workers.

U-Pb dating done on zircon, monazite and rutile minerals from the granitoids rocks in

the Sefwi belt and Sunyani basin yielded ages of 2179.2 ± 2.9 Ma and 2087.6 ±1.4

Ma, respectively (Hirdes, 1991). More recent innovations of the U-Pb methods for

dating rocks have led to significant improvements in both precision and accuracy.

Therefore, the re-evaluation of these ages has become very crucial in order to better

evaluate the timing between leucogranite emplacement, deformation and gold

mineralization.

The previous ages assigned to the granitoids in the belts generally agree with Sm-Nd

whole rock isochron age of 2166 ± 66 Ma for the tholeiitic basalt in the Birimian

volcanic belt (Taylor et al, 1988). This implies coeval magmatism for the

emplacement of these rocks (Hirdes et al., 1991).

This research incorporates new in-situ Laser Ablation Inductively Coupled Plasma

Mass Spectrometry (LA-ICP-MS) data for U-Pb age determinations on zircon from

13

the two hornblende-biotite granodioritc samples located in the extreme south eastern

portion of the study area. The metasediments lie unconformably on this granitoids

(Feybesse, 2006).

2.3.4 Tectonic Evolution

The structural evolution of the Birimian terrane has been described by many workers

as polycyclic events (Ledru et al, 1988; Cozens, 1988; Ledru et al., 1990; Milési et al.,

1991; Eisenlohr and Hirdes, 1991; Feybesse et al., 2006).

Ledru et al. (1988), Cozens (1988) and Milési et al. (1991) proposed that there were

two major phases of deformation; the Pre-Tarkwaian (D1) and Post Tarkwaian (D2).

Eisenlohr and Hirdes (1991) also recognised two phases or intensities of deformation.

They recognised low strain and high strain phases of deformation. In the low strain

phase, the rocks developed northeast-trending subvertical foliation (S1). This is sub-

parallel, or at a small angle, to bedding and contain a subhorizontal intersection

lineation (L1). Rocks belonging to the high strain phase occur predominantly along

the northwestern margins of the volcanic belts and are characterized by the presence

of a penetrative northeastern trending foliation (S2) and a south-west plunging

stretching lineation.

Feybesse et al. (2006) distinguished three phases of deformation within the Birimian

terrane in Ghana. The D1 deformation was defined by S1 foliation parallel to the axial

plane of microfolds and by an L1 stretching lineation. Penetrative fabrics developed

during this stage vary according to the intensity of metamorphism and the relative

proportion of co-axial strain associated with the deformation. Where the evidence of

co-axial deformation was pronounced a weak stretching lineation and symmetrical

pressure shadows were produced and the bedding was not transpose. The D2

14

deformational phase represents the maximum strain, manifested by F2 folds with

horizontal or slightly plunging hinges, associated with a general east-northeast to

west-southwest striking S2 cleavages and north-east to south-west sinistral ductile

faulting that variably included components reverse thrusting. D3 is defined by folds

generally associated with brittle shears, indicating that the crust was already exhumed

to higher structural levels.

Most of these structural evolution models of the Birimian supergroup were developed

without taking careful account of the Sunyani Basin. This is due in large part to the

fact that the basin lacks outcrop exposures. This work seeks shed light on the

structural evolution of the Sunyani basin and examines its role in the overall

deformation history of the region using a multi-scale and multidisciplinary approach.

2.4 Geophysical Data

The regional-scale structural distribution and patterns of mineralization of many

regions have been determined based on integrated interpretation of potential field

geophysical data and airborne gamma-ray survey (Airo, 2004; Airo, 2007). Recent

improvements in navigation, data acquisition, processing, image capabilities, coherent

and high-quality aero-geophysical data offer an important addition to field geological

mapping and defining the regional compositional and structural variation of bedrock

(Finn and Morgan, 2001; Airo, 2004). Structural analysis is an effective method at the

local scale, but at the regional scale becomes less reliable, particularly if exposure is

sparse, because of the uncertainty in correlating the observations from dispersed

exposures into a coherent model (e.g. Betts et al., 2003; Wade et al., 2008). Potential

field geophysical data such as aeromagnetic and gravity data are widely used. This

15

thesis work takes into consideration the field observations, aeromagnetic data and

magnetic susceptibility measurements.

2.4.1 Magnetic Data

Aeromagnetic geophysical surveys are widely used to characterize the variations in

magnetic minerals (magnetite, pyrrhotite, mag-hematite etc.). The expediency of the

geophysical aeromagnetic survey data in the interpretation of regional geological

structures is an aspect of its spatial coverage, cost-benefit ratio, resolution and its

depth penetration (Aitken and Betts, 2009).

Even though aeromagnetic geophysical surveys, have advantages such as mapping

lithologies, rock types, deformations style and boundaries, faults, fracture, shear zones

(Airo, 2007) and seeing through surficial layers (Finn and Morgan, 2001), there is

always geological ambiguity due to the fundamental nature of potential fields. They

thereby lack sensitivity to the geometry of structure at depth (Aitken and Betts, 2009).

There is also an issue of remnant magnetisation that may need to be taken into

account when modeling specific anomalies, as the rocks sometimes have magnetic

direction that differs from the normal magnetic field (Baranov and Naudy, 1964).

The aeromagnetic geophysical survey data over the Birimian terrane was acquired in

1999/2000 by High Sense Geophysics at an altitude of 60 metres with flight line

trending east to west spaced 400m apart. The geophysical aeromagnetic image used

for this work has already been processed to show total magnetic intensity (TMI)

(Figure 2.2).

16

2.5 Data Processing and Integration

Gridding process preferred for this work was after Chandler and Lively (2007).

Options like minimum curvature, bi-directional gridding, tinning and kriging were

used in gridding the magnetic data from the OASIS MONTAJ geophysical

programme. The truthfulness of each data was done by considering the look of the 2nd

Fig. 2.2. Total magnetic intensity image of the study area which has been reduce to pole and

shading from northwest. The unit for the colour bar is in nT.

17

vertical derivative enhancement. This is due to the fact that the 2nd

vertical derivative

resolves the effect of adjacent anomalies and gets rid of the high frequencies.

2.5.1 Reduce To Pole

The shape of any magnetic anomaly depends on the inclination and declination of the

main magnetic field of the earth. Thus the same magnetic body will produce an

anomaly of different shape depending were it happens to be and its orientation. The

reduction to the pole filter reconstructs the magnetic field of a data set as if it were at

the pole. This means that the data can be viewed in map form with a vertical magnetic

field inclination and a declination of zero. In this way the interpretation of the data is

made easier as vertical bodies will produce induces magnetic anomalies that are

centred on the body symmetrically (Telford et al., 1990).

2.5.2 Vertical Derivatives

The first vertical derivative filter computes the vertical rate of change in the magnetic

field. Where the downward continuation achieves spatial resolution by increasing the

amplitude of the high frequencies (shallow sources), the derivative filter suppresses

the long wave lengths. The vertical derivative or gradient of a magnetic field is

calculated by multiplying the amplitude spectra of a field by a factor of a form

Where n is the order of the vertical derivative.

18

First vertical derivative is physically alike to the measurement of the magnetic field at

two points perpendicularly above each order; subtracting the data and dividing the

outcome by the vertical spatial separation of the measurement points. The second

vertical derivative is the vertical gradient of the first vertical derivative. This process

improves higher frequencies relative to lower frequencies. The second vertical

derivative gets rid of the longer wavelength and resolves the effects of adjacent

anomalies (Milligan and Gunn, 1997).

2.5.3 Analytical Signal

Analytical signal is a function related to a magnetic field by the derivatives

Where m is the magnetic anomaly

Analytical signal is not a measurable quantity and is not dependent on the direction of

magnetisation and the direction of the earth magnetic field. All bodies with the same

geometry have the same analytical signal (Milligan and Gunn, 1997).Analytical signal

is efficient for mapping edges of three dimensional magnetic sources by treating those

edges as two dimension features, an example is contacts.

19

2.5.4 Automatic Gain Control

Automatic Gain Control converts waveforms of variable amplitude into waveforms of

semi constant amplitude. The net result is to remove the amplitude information from

the data sets, producing a representation of the data that gives an equal emphasis to

the signal with both high and low amplitudes (Milligan and Gunn, 1997).

20

CHAPTER THREE: METHODOLOGY

Three major subdivisions of work were performed in order to achieve the various

goals of this study: Pre-Field work, Field work and Post-Field work.

3.1 Pre-field work

A desk study and literature review was done to have a fair knowledge of previous

work performed in the study area. Thus the necessary literature linked with the

research were assembled and assessed by way of books, scientific journals and

searching electronic data base. Acquisition of base maps and organising field logistics

were done at this stage. Also regional magnetic geophysical data were acquired for

further analysis and to aid in the interpretation of the subsurface geology.

3.1.1 Field work

The field stage entailed geological mapping and sampling. The geological mapping

was done at a scale of 1:50,000. The first stage of the geological mapping process was

reconnaissance mapping. The purpose of this activity was to get a sense of the

available outcrops and their distribution throughout the map area, and to learn as

much as possible about the geology of the study area. The reconnaissance mapping

was assisted by reference to satellite imagery, shaded relief map provided by Shuttle

Radar Topography Mission (SRTM), and integration of known geology from

available reports. The satellite image used was a LANDSAT image with a true colour

(RGB) band combination as shown in Figure 3.1. The SRTM images were used to

21

recognise and identified the general topography, spot heights, active and dry rivers,

streams and available outcrops in the area. The SRTM shaded image as shown in

Figure 3.2 was used to identify probable outcrop localities as well as places of higher

elevations.

Fig.3.1. LANDSAT true colour (RGB) band combinations image used for the

reconnaissance mapping.

(7°00'N)

(2°45'W)

(6°38'N)

(2°45'W)

(7°00'N)

(3°00'W)

(3°00'W)

(7°00'N)

22

Fig 3.2. A regional SRTM digital elevation image with sun shading to show the

general topography and possible outcrop present (regions with white tone). Insert in a

black box is the study area

Some degree of ground truth work was also done along roads, streams and footpaths.

This was to have a better idea of whether outcrops interpreted from the remotely

sensed images were present and distinctive enough to map. This reconnaissance

mapping method provided the best possible chance of finding outcrop, and it provided

experience on how to orient and locate oneself in the field, and formulate a plan of

how to go about the mapping.

(8°0'25.2''N)

(2°0'00''W)

(2°0'00''W)

(5°59'38.4''N)

(4°1'1.2''W)

(4°1'1.2''W)

(8°0'25.2''N)

(5°59'38.4''N)

23

The reconnaissance mapping was followed with more detailed geological mapping.

The methods applied during the geological mapping process were pace and compass

mapping, tape and compass mapping, systematic traversing and sampling and

measuring of magnetic susceptibilities. The pace and compass method is one of the

most efficient and inexpensive methods employed during the field mapping process.

From a known datum point, the number of steps taken is multiplied by an individual’s

pace to give an idea of the total distance covered to a given outcrop. Whilst pacing,

the compass is used alongside to give accurate direction. This was done hand in hand

with systematic traversing. Traversing always controlled the progress of the mapping,

so that one does not have to relocate oneself every time an observation is made at an

outcrop. It also makes certain the ground necessary to carry out the goals of the study

is covered. The Global Positioning System (GPS) was used to help in the traverse.

The GPS showed the position in terms of WGS 84 georeference coordinates at any

point in the field. The GPS to a large extent became problematic due to the fact that

the study area was densely vegetated. In order not to accumulate unacceptable levels

of errors, traverses were made basically along rivers and streams. Finding the position

of streams and rivers on base maps is relatively easy due to their unique shapes,

direction of bends and the streams or river junction.

Structural attitudes were measured by the use of the geological compass and

measuring tape. The structures measured were joints, lineations, faults, foliation, fold

axes, fold limbs and axial planes. The structural measurements were plotted on a map

as well as stereographic projections. This facilitated a structural analysis that provided

insight into how structures were distributed in the mapped area. Photographs, sketches

and isometric drawings of various geological structures and rock units were done

24

during the field work. In particular, the sketches made in the field helped to clarify

various structural relationships that were difficult to interpret.

Soils, provided they have not been transported, reflect the rock beneath. This

observation has been used over the years to draw geological boundaries on many

geological maps; especially in areas were outcrop exposures are sparse and scrubby.

Changes in terms of colour and textures of the soils also reflect the change from one

outcrop type to another. Soils could not be used in this study due to the extent of

erosion and the level of weathering. The weathering was about 100 metres deep. This

is evident in the rock cores drilled in the area by Keegan resources limited. The soils

throughout the study area were red and clayey.

Oriented samples were collected using grab method. Thus structural attitudes of the

samples were measured and marked on the samples before the samples were

hammered out from the outcrop. A total of about 50 samples were collected within the

hornblende-biotite granodiorite, leucogranites and metasedimentary rocks within the

Sunyani basin for petrologic, microstructural and geochemical studies. The samples

used for the analysis were taken from areas where fresh rocks could be obtained. The

samples were then placed in sample bags with marked names corresponding to the

station number and measured structural attitudes. These rocks were representatives of

structural aspects and mineral types.

3.1.2 Post-Field Work

The post-field work included thin-section preparation, Petrographic studies, and

preparation of samples for LA-ICP-MS. LA-ICP-MS and further processing of

geophysical aeromagnetic and gamma ray survey data.

25

3.1.2.1 Thin-Section Preparation

A rock saw with a diamond blade was used to cut the rocks into rectangular blocks

(referred to as ―billets‖ or ―chips‖) that are 46 by 26 millimetres with a thickness of

about 1 centimetre. Both surfaces of the sample were made ground flat and smooth.

The softer rocks were impregnated with epoxy to make them hard for cutting. The

thin section was prepared by Vancouver Petrographics, Canada using the following

techniques: A slurry of coarse grit and water placed on a polishing lap. One of the flat

sides of the billet was polished with 200 grit to smooth out any imperfections or

scratches. After the first polish, the lap was cleaned, and the billet was further

polished using finer grit. The sample was then washed and set on a hot plate to

become perfectly dried. A large drop of an epoxy mix was placed at the centre of the

slide and warmed until it bubbled. Then the polished side of the billet was placed on

the warm slide. Any excess epoxy residue was carefully cut and scraped away using a

blade. The thin section was further ground using the 600 grit to 30 microns. A glass

cover slip was then attached to the thin section slide using Canada balsam.

A total of 50 oriented and un-oriented thin sections were produced and examined

using an optical cross-polarizing microscope for petrologic and microstructural

analysis. The microstructures of the rocks that were investigated on a thin section

were cut orthogonal to the foliation and parallel to lineation if a lineation was present.

3.1.2.2 Petrography and Microstructural analysis

The petrographic descriptions of the thin sections made were both quantitative and

descriptive. The quantitative description incorporated point counting or modal

analysis, grain size of each mineral species (thus the main primary and secondary

phases), grain shape, inclusions of mineral grains, noting of overgrowth and

26

intergrowth textures and mineral associations. For the purpose of this thesis work,

grains with diameters lesser than or equal to 0.03 millimetres were considered

groundmass and above 0.03 millimetres as porphyroclast and phenocrysts. The total

volume percent for the mineral species depends on the total number of phenocryst

counted. No value in percentage was given for accessory minerals and the grain

distribution was dependent on the phenocryst or the primary mineral phases.

3.1.2.3 Mineral Separation

The initial steps for the mineral separation prior to the LA-IC-PMS analysis included

crushing and grinding the samples down to individual grain size and then passed over

a Wilfley Table™ for initial density separation. The mineral separation was done at

Simon Fraser University, Burnaby, Canada. Approximately 2 kg of each sample was

crushed using a Chipmunk™ jaw crusher. First, the jaw crusher was thoroughly

cleaned with a vacuum, wire brush, sponged with soapy water, sprayed with ethanol

(to expedite the drying), wiped with a paper towel and sprayed with compressed air.

Each sample was crushed into gravel size fragments. The crushed samples were then

placed in a labelled sample bag. The jaw crusher was thoroughly rewashed and dried

after each sample run to avoid sample contamination. The crushed samples were then

ground in a Bico™ disk mill. Prior to and following the running of each sample, the

disk mill was thoroughly cleaned similar to that described above for the jaw crusher.

Each crushed sample was slowly fed through the disk mill. The sample was run about

three times in the disk mill to get it down to silt to clay sized particles in order to

reduce the samples to approximately individual grain size.

Each ground sample was then poured over a Wifley™ table which facilitated gravity

separation of the minerals according to their specific gravity. The flow of water over

27

the table, and the inclination angle and oscillation frequency of the Wifley™ table can

be adjusted to maximize the separation and yield of heavy minerals (e.g. zircon,

monazite, titanite). The separated samples were then dried under a heat lamp. Once

dry, a rare earth element magnet was passed over the heaviest fraction of each sample

to remove the most magnetic minerals (e.g. magnetite), as well as any iron filings that

may have been incorporated from the crusher and grinder.

Methylene Iodide, a heavy liquid with a specific gravity of 3.32, was used to separate

zircon (s.p. ~4.6) from less dense minerals with a s.p. < 3.32. To further concentrate

the zircon, a Frantz™ LB-1 magnetic separator was used, which can be used to

separate minerals based on their magnetic susceptibility (Zircon typically has the

lowest magnetic susceptibility versus other heavy minerals). The separation

procedures used for the heavy liquids and magnetic separation were according to

those followed at Simon Fraser University and the Boise State University (BSU)

isotope geology laboratory (2008). The zircon separates for each sample were then

placed into individual small glass vials and sent to the Boise State University LA-IC-

PMS lab for U-Pb analysis.

3.1.2.4 LA-ICP-MS Analysis

Zircon grains were separated from rocks using the technique described above and

mounted in epoxy and polished until the centres of the grains were exposed.

Cathodoluminescence (CL) images were obtained with a JEOL JSM-1300 scanning

electron microscope and Gatan MiniCL. The images were used to guide the

placement of analysis spots during laser ablation inductively coupled plasma mass

spectrometry (LA-ICP-MS). U-Pb isotope systematics and trace element

compositions were analyzed by LA-ICP-MS using a ThermoElectron X-Series II

28

quadrupole ICPMS and New Wave Research UP-213 Nd:YAG UV (213 nm) laser

ablation system. In-house analytical protocols, standard materials, and data reduction

software were used for simultaneous acquisition and real-time calibration of U-Pb

dates and a suite of HFSE and REE elements. Zircons were ablated with a laser

diameter of 25 microns using fluence and pulse rates of 12 J/cm2 and 5 Hz,

respectively, during a 60 second analysis (15 sec gas blank, 45 sec ablation) that

excavated a pit ~25 µm deep. Ablated material was carried by a 1 L/min He gas

stream to the nebulizer flow of the plasma. Dwell times were 5 ms for Si and Zr; 100

ms for 49

Ti and 207

Pb, 40 ms for 238

U, 232

Th, 202

Hg, 204

Pb, 206

Pb and 208

Pb isotopes;

and 10 ms all other HFSE and REE elements. Background count rates for each

analyte were obtained prior to each spot analysis and subtracted from the raw count

rate for each analyte.

For U-Pb dates, instrumental fractionation of the background-subtracted 206

Pb/238

U

and 207

Pb/206

Pb ratios was corrected, and dates were calibrated with respect to

interspersed measurements of the Plesovice zircon standard (Slama et al., 2008).

Signals at mass 204 were indistinguishable from zero following subtraction of

mercury backgrounds measured during the gas blank (<1000 cps 202

Hg), and thus

dates are reported without common Pb correction. Radiogenic isotope ratio and age

error propagation for each spot includes uncertainty contributions from counting

statistics and background subtraction. For concentration calculations, background-

subtracted count rates for each analyte were internally normalized to 29

Si and

calibrated with respect to NIST SRM-612, USGS BCR-2, and BIR-1 glasses as the

primary standards.

Errors on U-Pb dates are given at 2 and presented as follows: weighted mean date ±

x [y], where x is the internal error and y is the error including the uncertainty on the

29

standard calibration, which are propagated in quadrature. The standard calibration

uncertainties for this experiment are 0.96% and 0.78 % (2) for the 207

Pb/206

Pb and

206Pb/

238U dates, respectively. Internal errors should be used when comparing

weighted mean dates that were measured in the same analytical session, and the errors

including the calibration uncertainties should be used when comparing against all

other dates. Weighted mean calculations were performed using Isoplot 3.0 (Ludwig,

2003).

The FC-1 zircon standard was measured as an unknown during the experiment as a

quality control standard. The 14 spots measured yield weighted mean 207

Pb/206

Pb and

206Pb/

238U dates of 1089 ± 17 [20] and 1097 ± 11 [14], respectively. These dates agree

with the chemical abrasion - isotope dilution thermal ionization mass spectrometry

weighted 207

Pb/206

Pb and 206

Pb/238

U dates of 1098.3 ± 0.3 and 1095.4 ± 0.2 Ma,

respectively (internal errors at 2unpublished data, Boise State University).

3.1.2.5 Geophysical Data Processing

Gridding was the first step used to level the magnetic data. This method quality

controlled the data by way of their display as enhanced images. The gridding provided

smooth surfaces to the original point located data. This was done by using the

minimum curvature and bi-directional line gridding tools from the Oasis Montaj 7.0

geophysical program.

Several enhancement tools and processes from the Geosoft Oasis Montaj software

package were used to enhance the data to produce located profiles and grid versions in

the form of images for the total magnetic intensity (Milligan and Gunn, 1997). These

enhancement processes applied to the aeromagnetic data, Automatic Gain Control,

30

first vertical derivative, reduction to the equator. The World Geodetic System (WGS)

84 Universal Transverse Mercator (UTM) Zone 30 coordinate system was used as the

projection system for the processing with the units in metres. The datum used is WGS

84 (world). The limits used for the processing were:

Minimum X: 468500, Minimum Y: 663200, Maximum X: 583100 Maximum Y:

829100 with grid size of 100 metres.

Pre-processing by way of linear filtering process was done on the geophysical

magnetic image to remove magnetic anomalies from the initial grid data based on the

disparity in the average frequency content of the noise anomaly (Milligan and Gunn,

1997). This was done since irregularities from superficial sources have higher

frequencies than anomalies from deeper sources. The linear filtering was done by

running a series of Fourier transforms on the magnetic grid data set. The pre-

processed magnetic grid data or image was reduced to the pole (Figure 3.3a) using

inclination and declination values of -16.11 and -6.14 respectively. The reduction to

pole transforms the inclined magnetic field to be equivalent to one with latitude at the

magnetic poles. The data was also reduced to the equator (Figure 3.3b). The reduction

to the equator and reduction to the pole both centre the peaks of the magnetic

anomalies over the source. This makes the data easier to interpret without losing any

geophysical meaning. At lower latitudes a separate amplitude correction is usually

required for reduction to pole calculations, therefore, there will be less loss of

information in reducing to equator data than reduce to pole (Ram et al., 2008).

31

Fig. 3.3. Processing applied to the total magnetic intensity data of the central western part of the Birimian terrane in Ghana (a) Reduce

to pole, with the study area outlined in blue (b) Reduce to the equator, with the study area outlined in blue

32

3.1.2.5.1Vertical Derivatives

The first vertical derivative filter was applied to magnetic field intensity data to

enhance shallow geological structures from the data. As with other filters the vertical

derivative enhances the higher wave number components of the spectrum. The first

vertical derivative values of the magnetic field were computed directly from the

gridded total magnetic field using fast Fourier transform. The second vertical

derivative was applied to the total magnetic field to enhance near surface features,

anomalies and to remove higher frequency from the image. This helped to mark out

features with different susceptibilities. The vertical derivatives were important

because lithologic contacts with contrasting magnetic susceptibilities are easy to

delineate precisely (Figure 3.4).

33

Fig. 3.4. (a) First vertical derivative of a section of the Birimian terrane in Ghana in greyscale (b) A pseudocoluor first vertical derivative

of a section of the Birimian terrane in Ghana (c) A pseudocoluor second vertical derivative image of a section of the Birimian using a

0.75 Gaussian filter. The study area in the blue insert.

34

3.1.2.5.2 Automatic Gain Control

For the Automatic Gain Control (AGC) the GRIDAGC GX of the Oasis Montaj

programme was used to apply automatic gain compensation to the grid. It isolated the

background component in the input grid for the window size. A correction was

applied to equalize the amplitude over the grid. Automatic gain control is very

important in structural mapping, since all structural trends and alignments are done in

a true amplitude data (Figure 3.5). For this matter it requires that the data should have

a zero base average base level (Milligan and Gunn, 1997).

35

Fig. 3.5. Automatic gain control images of a section of the Birimian terrane in Ghana. (a) is a pseudocoluor image and (b) is an image in

greyscale

(a) (b)

36

CHAPTER FOUR: RESULTS

The regional structural design of an area where outcrops are sparse can be brought to

light by incorporating microscopic and macroscopic studies of outcrops, analysing

field structural data and interpreted geophysical data. This chapter discusses the

results and various interpretations done during the field work and laboratory work.

The results are grouped into petrography, structures and geochronology.

4.1 Lithological and Petrographical Studies of the study area

4.1.1 Metagreywacke

Metagreywacke outcrops within the central-northern parts of the study area (Figure

4.1), and were observed in four unoriented drill holes drilled by Keegan resources in

the southern part of the study area. Most of the metagreywacke outcrops found in the

study area are about 10 to 20 metres in length and 10 to 20 metres in width. On a

mesoscopic scale, the rock is fine- to medium-grained. The metagreywacke shows

subvertical to vertical penetrative foliation (Figure 4.3a), and is composed of

muscovite, biotite and chlorite. Most of the greywacke from the drill core samples are

calcite altered. The metagreywacke outcrops mainly occur within the shear zone in

the study area with some showing mineral lineations (Figure 4.3b) mainly trending

040° and plunging 20°. Location of samples for thin section analysis can be seen in

Figure 4.2.

37

Fig.4.1. An outcrop map showing the general distribution of rocks in the study area.

Elevation contours at 50m intervals.

38

MANU 002( FIG 16b & 16d)

MANU001( FIG 15b (TS) & 16a)

ASU002

FIG 16c (TS)

FIG 33 & 34

NF002

MANU003

FIG 15a (HS)

ANTWI002

KADD100254

FIG 13a & 13b (HS)

FIG 14a & 14b (TS)

FIG 12e (TS)

FIG 12c & 12d (TS)

FIG. 12a & 12b (TS)

ANTWI001

FIG 11a (HS)

AKYE003

ADIN001

FIG 11b (HS)

BIA002

KWA001

FIG 17a (HS)

FIG 18a (TS)

FIG. 12f (TS)

NDOBEM002

KKRA001

FIG 18b (TS)

FIG 18a (HS)

HS - HAND SAMPLE

TS - THINSECTION

(2°45'W)(7°00'N)

(6°38'N)

(2°45'W)

(7°00'N)

(3°00'W)

(3°00'W)

(6°38'N)

Fig.4.2. A map showing localities of samples that were used in the thesis work as thin

section, field shots and geochronology.

39

(a) (b)

Fig.4.3. Photographs showing (a) metagreywacke showing vertical penetrative

foliation in Antwiagyei Township and (b) metagreywacke illustrating mineral

lineation formed on the surface of the foliation plane.

Under the microscope, the metagreywacke has a fine to medium grain texture. It is

compose mainly of quartz, chlorite and micas with plagioclase feldspar, sphene,

pyrites and tourmaline as accessory minerals. The metagreywackes at some locations

are calcic altered. The Table 4.1 below shows the location and modal percentages of

metagreywacke in the study area.

The minerals within the thin section show schistose textures mostly exhibited

preferred orientation. The minerals also show abundant clastic quartz grains in a mica

rich matrix. Quartz exhibits undulose extinction which is the result of

40

Table 4.1 Location and mineral modal or volume percentages of greywacke in the study area

Minerals Modal

%

Modal

%

Modal

%

Modal

%

Modal

%

Modal % Modal % Modal

%

Modal % Modal % Modal % Modal %

Quartz 50 60 56 55

34

60

65

60

50

50

10

50

Biotite 2 5 10 10

30

10

5

10

8

10

7

10

Muscovite 6 5 15 15

30

10

5

10

10

20

7

10

Calcite 15 5 6 -

-

-

10

-

10

10

20

10

Chlorite 20 10 4 15

-

-

-

-

8

-

35

-

Plagioclase - 10 2 1

-

10

10

13

10

-

-

5

Pyrite 1 1 3 4

2

5

-

5

2

-

2

2

Sphene 2 2 2 1

2

-

3

-

2

-

2

3

Tourmaline 3 1 1 2

2

-

2

4

-

-

-

-

Locations AKYE

003

ANTWI

001

ANTWI

002

BIA

001

BIA

002

KADD100243

97.5m-97.7m

KADD100243

113m-

113.05m

BETH

001

KADD100244

121m-121.7m

KADD100245

62.5m-65.36m

KADD100246

181m-181.1m

KADD100245

132m-132.2m

41

crystal plastic deformation that likely accompanied the development slaty-induced

cleavage. According to Vernon (2004) and Durney and Kisch (1994), slaty cleavage

in low grade metamorphic rocks is characteristically developed as axial surfaces of

folds. A secondary metamorphic foliation defined by biotite within a vein is oblique

to the main S1 foliation and the pressure shadows around porphyroclasts (Figure 4.4f).

This kind of foliation was not observed in outcrops. Also a pressure shadow is formed

on one side of the pyrite mineral which provides insight into the type of deformation

the rock had experienced. The pressure shadow extends in the direction of schistosity

(Figure 4.4f)

(a) (b)

42

(c) (d)

(e) (f)

Fig.4.4. (a) Thin section cut perpendicular to strike of foliation and lineation seen in

the outcrop showing the minerals present in the metagreywacke; (b) showing some

elongated and rounded quartz minerals in white with biotite minerals (green)

wrapping around it; (c) S1 foliated greywacke showing elongated quartz and

43

feldspars; (d ) Elongate quartz grains showing shearing (e) metagreywacke showing

preferred orientation of quartz indicating S1 foliation (f) Greywackes showing

secondary metamorphic foliation of biotite in the lower section of the

photomicrograph. It does not resemble any S1 seen elsewhere within the study area.

All the thin sections have been cut parallel x-z-orientation of the finite strain ellipsoid.

4.1.2 Phyllites

Outcrops of phyllites were mostly observed within the south-eastern portion of the

map area. All phyllite outcrops were observed in erosional gullies along the feeder

road and small streams. The phyllites are highly weathered, brick red and fine-

grained. They are composed mainly of micas and iron oxides. The phyllites within the

drill cores which are in contact with the leucogranites are slightly harder, which may

be the result of contact metamorphism associated with the emplacement of the

granite. The majority of the phyllites that outcrop in the study area are about two to

three metres in size. The phyllites also show subvertical to vertical penetrative

foliation. The phyllites were very difficult to observe and describe due to the extent of

weathering in the area. For instance, in drill core the depth of weathering

demonstrated by the loose pebbly ferruginous layer to the saprolite is about seventy to

eighty metres. Fresh samples of the phyllites were obtained in five drill cores samples.

Here the phyllite has a grey colour, sheared (Figure 4.5a), and composed mostly of

quartz, micas, pyrite and graphite. The phyllites are commonly intercalated with the

metagreywackes in the drill samples (Figure 4.5b) and are usually altered to quartz

and calcite. In all the drill samples the phyllites occurred at a depth of about 130 to

250 metres.

44

Under the microscope, the phyllites are fine- to medium-grained and composed

mainly of quartz, mica, calcite, pyrites and graphite (Table 4.2). The phyllites show

somewhat schistose texture. The larger grains of quartz demonstrated sweeping

undulose extinction and are anhedral in shape. This indicates that the mineral had

experienced crystal plastic ductile deformation. The smaller quartz grains do not

exhibit undulose extinction, but do have serrated edges which may indicate

deformation-induced dynamic recrystallization (Figure 4.6a). The thin section also

shows S1 foliation and S2 crenulation cleavages (Figure 4.6a).

Table 4.2 Location and mineral modal percentages of phyllite in the study area

Minerals Modal %

Mica

Quartz

Calcite

Graphite

Sphene

40

20

20

15

2

Sample Numbers KADD100245

143.6m-143.7m

45

S2

quartz vein

F

F

(a) (b)

Fig.4.5. Photographs showing (a) graphitic phyllites showing folds and S2 foliation

and quartz veins which are faulted. The fault planes are marked by the letter F, and (b)

core box showing intercalations of graphitic phyllite and metagreywacke. The

metagreywacke are the lighter grey zones and the graphitic phyllites are the darker

grey ones.

46

(a) (b)

Fig. 4.6. (a) Phyllites exhibiting S1 foliation and S2 crenulation cleavage and quartz

minerals at the bottom right showing larger grains with undulose extinction and

smaller grains with serrated edges indicating recrystallization (b) Showing the

subhedral to euhedral calcite and pyrite (opaque under the polarizing microscope)

minerals formed in veins.

4.1.3 Hornblende-Biotite Granodiorite (HBG)

These rocks only outcrop within the Sefwi belt, within the extreme southeastern

corner of the study area (Figure 4.1). The hornblende-biotite granodiorite (HBG) was

phaneritic, slightly weathered and composed mainly of hornblende, plagioclase,

quartz and biotite (Table 4.3). The HBG occur as mostly small rounded mounds, have

an oval shape, mostly trend northeast- southwest and are very hard (Figure 4.7). The

HBG has a crystalline texture, massive and is jointed. The rocks are also crosscut by

different generations of randomly oriented veins.

47

(a) (b)

Fig.4.7. Photograph 4.7(a) and (b) shows the trend of relatively small rounded

outcrops of hornblende- biotite granodiorite pluton. Photos taken facing the NE

direction.

From microscopic observation, the rock is phaneritic and composed of plagioclase

feldspar, quartz, hornblende, epidote and biotite, and includes accessory minerals such

as sphene, microcline, zircon (Figure 4.8d and Table 4.3). Generally the minerals

within the thin section are less deformed compared to that of the phyllites and

metagreywackes, except that the some grains of the quartz exhibited undulose

extinction. Two forms of plagioclase were detected; one that shows polysynthetic

twinning and the other with oscillatory zoning. The oscillatory zoning (Figure 4.8b)

may be formed due to alternation in the plagioclase liquid phase equilibrium as a

consequence of variable changes in the temperature, pressure and partial pressure.

The undulose extinction and polysynthetic twinning also suggest the rock had

undergone some crystal plastic deformation. Mymerkitic texture (Figure 4.8a) was

48

observed at the boundary between the quartz and plagioclase feldspar mineral as a

result of quartz and feldspar intergrowth.

Table 4.3. Location and mineral modal or volume percentages of Hornblende-Biotite

Granodiorite in the study area

Minerals Modal % Modal % Modal % Modal %

Plagioclase

Quartz

Hornblende

Epidote

Biotite

Sphene

Zircon

65

10

8

5

5

1

<1

65

10

8

8

6

1

<1

60

20

5-7

5

5

1

<1

50

25

5

5

5

1

<1

Sample Numbers MANU 001 MANU 002 ASU 002 NF002

49

(a) (b)

(c) (d)

Fig.4.8. (a) Mymerkitic texture formed at the centre of the thin section. This is as a

result of intergrowth of the quartz and plagioclase feldspar at the quartz and

plagioclase feldspar boundary; (b) Plagioclase feldspar exhibiting oscillatory zoning

50

and granular texture; (c) The hornblende-biotite granite showing quartz veins. The

quartz within the veins have serrated edges, which implies dynamic recrystallization

has taken placed; (d) Plane nicols of the thin section showing hornblende, sphene,

epidote and biotite.

4.1.4 Leucogranites

The leucogranites outcrop mainly in the northeast to northwestern portion of the study

area, within Subin and Bia forest reserve and Bia River. The rock is whitish grey,

phaneritic and composed mainly of quartz, plagioclase feldspar, muscovite and

biotite. They are slightly weathered and have quartz and pegmatite veins intruding

through them. Some of the outcrops are fairly rounded (Figure 4.9b) and others were

lensoidal (Figure 4.9a).

(a) (b)

Fig.4.9. (a) Showing lensoidal shape of the two mica pluton; (b) Shows a rounded

leucogranites

51

(a) (b)

Fig.4.10. (a) Euhedral to subhedral shape plagioclase, quartz and muscovite (b) thin

section of leucogranites showing granular texture

Under microscopic observations, the rock is coarse-grain, with a granular texture,

composed of euhedral to subhedral (Figure 4.10a) quartz, plagioclase, microcline,

muscovite, biotite and accessory minerals such as sphene and zircons (Figure 4.9b and

table 4.4).Some of the quartz mineral showed preferred orientation and exhibited

undulose extinction (Figure 4.26).

52

Table 4.4. Location and mineral modal percentages of leucogranites in the study area

Minerals Modal % Modal % Modal % Modal % Modal % Modal %

Plagioclase

Quartz

Microcline

Biotite

Muscovite

Sphene

Zircon

Pyrite

50

10

18

8

10

1

1

1

48

12

15

10

10

1

1

1

50

10

12

10

12

1

<1

<1

50

20

5

10

10

2

1

<1

48

15

10

10

15

1

1

1

52

10

12

10

12

2

1

1

Sample

numbers

SEB001 KWA001 KWA002 SEBEBIA001 SEBEBIA

002

NDOBEM001

53

4.2 Metamorphism

Metamorphism refers to the changes in a rock’s mineralogy, texture, and or

composition that occur predominately in the solid state under the conditions between

those of diagenesis and large-scale melting (Winter, 2001). Two forms of

metamorphism were identified in the study area within the Sunyani Basin,

1. Regional Metamorphism

2. Contact Metamorphism

Pursuing the guide of Turner and Weiss (1963), the metamorphic phase (Mn) will be

related to the deformational phase (Dn) and S- tectonites (Sn) in the study area, where

n is the nth term. Due to the paucity of outcrops, most of the metamorphic phase

descriptions were based on thin section textures and only a few from outcrops.

4.2.1 Regional Metamorphism

Regional metamorphism is any metamorphism that affects large bodies of rock on a

regional scale or large extent (Winter, 2001). The type of regional metamorphism in

the study area is the dynamo-thermal type of metamorphism. This category of

metamorphism occurs in places were deformation and heat coalesce. M1

metamorphism within the study area was probably synchronous with D1 deformation

and the development of the vertical to subvertical penetrative foliation (S1; Figure

4.3a). In thin section S1 is defined by the alignment of quartz and mica (biotite) within

the metagreywacke and phyllitic rocks (Figures 4.4d, 4.4f and 4.6a).

54

4.2.2 Contact Metamorphism

Contact metamorphism occurs adjacent to igneous intrusions as a result of the thermal

effects of hot magma intruding cooler rock (Winter, 2011). Contact metamorphism

(M2) that occurred within the study area was due to the leucogranites intruding into

the metasediments. The metamorphism in the study area is graphically represented

below (Figure 4.11).

Fig.4.11. Graphical representation of the relationship between generations of

deformation (D) and, metamorphism (M) in the study area

55

4.3. Geological interpretation of aeromagnetic data of the study area

Rocks that outcrop in the study area consist of metagreywackes, phyllites,

leucogranite and hornblende-biotite granodiorite. A geological map was constructed

with the aid of the aeromagnetic grid data (Figure 4.12). The few outcrops found in

the study area were overlain on the total magnetic intensity data to better constrain the

geological map that was made.

Fig. 4.12.Geological map of the study area constructed from the geophysical and

geological field mapping data.

56

Faults (blue lines in the map above) with the aeromagnetic image were picked in areas

where there were abrupt breaks in the trend of the magnetic signatures. These faults

were basically not observed in the field. The blue dash lines within the map indicate a

fault that has been inferred as a result of measurement made on a linear grid. The dip

direction of S1 along those linear grids varies. The Sunyani basin is largely

characterized by low to high magnetic anomalies. From the reduce to pole data, the

metagreywackes and the hornblende-biotite granodiorite show high magnetic

anomalies ranging from 31754nT to 31035.4nT, meaning the rocks possibly have

high magnetite content. The phyllites in the study area appear to have medium

magnetic anomalies ranging from 31800.9nT to 31761.1nT.

The study area was divided into four main domains based on the reduce-to-pole

magnetic image (Figure 4.13). The south-eastern domain, or domain 1, is

characterized by high magnetic anomalies mostly associated with the hornblende-

biotite granodiorite. The southern portion, domain 2, has medium to high magnetic

intensity and generally composed of phyllites. The central portion, domain 3 mainly

composed of metagreywackes has high and intervening low magnetic anomalies.

Domain 3 is dominated by a subparallel, northeast-southwest trend of relatively low

and high magnetic intensities. The overall magnetic intensity of the domain is

relatively high. The striped magnetic patterns show what is likely the varied

distribution of magnetite or other magnetic minerals. There is a clear trend in the

magnetic anomalies within Domain 3 are oblique to its boundaries, and appear to

indicate the presence of a sinistral sense shear across Domain 3. Is sinistral sense of

shear can be seen in a thin section of leucogranite picked within that domain (Figure

5.2). Thus, Domain 3 within the study area is interpreted as a distributed sinistral

shear zone .The structural grain of the magnetic anomalies trends mostly northeast-

57

southwest as evident in first vertical derivative. The first vertical derivative increases

the sharpness and visibility of structural grain in the magnetic grid data by

emphasising higher amplitudes and higher frequencies. The sudden break in a

magnetic intensity may be as a result of discontinuities or faults within the rock body.

Fig.4.13. First vertical derivative image of a reduce-to-pole data of the study area

showing the various domains within the study area, and highlighting the sinistral

shear zone across domain 3

58

4.3.1 Geological and geophysical modelling

Geological and geophysical modelling of the study area was better constrained using

the magnetic susceptibility (k) measurement of each rock unit. The susceptibility

measurement was done on both outcrop and drill core samples to know the magnetite

distribution in the area so they could be compared to, or possibly correlated with, the

aeromagnetic data to aid in the constructing of a more accurate geologic map of the

region. Magnetic susceptibility measurement was done for twenty five samples (Table

4.5 and Appendix 2).

Table 4.5. Magnetic susceptibility of various rock units in the study area

Sample Number Rock Name K1

SI Units

K2

SI Units

K3

SI Units

K4

SI Units

K5

SI Units

K average

SI Units

ASU002 HBG 0.04 0.03 0.03 0.04 0.01 0.03

MANU001 HBG 0.67 0.68 0.67 0.69 0.68 0.68

ANTWI002 metagreywacke 13.6 13.9 13.3 13.9 14.8 13.9

NF002 HBG 0.17 0.19 0.17 0.17 0.22 0.18

ANTWI001 metagreywacke 0.79 0.78 0.80 0.86 0.87 0.82

BIA002 metagreywacke 8.75 8.76 8.74 8.74 8.75 8.74

AMPM005 HBG 0.03 0.01 0.00 0.01 0.02 0.01

KWA003 HBG 0.92 0.97 0.95 1.04 1.03 0.98

BIA001 metagreywacke 7.66 7.94 8.33 8.68 8.85 8.29

BETH001 metagreywacke 3.55 3.66 3.64 3.69 3.50 3.61

AKYE003 metagreywacke 0.11 0.11 0.10 0.14 0.13 0.12

MANU002 HBG 1.32 1.32 1.35 1.41 1.42 1.36

KADD100244

77.5m-77.7m

HBG 0.02 0.02 0.03 0.02 0.03 0.02

KADD100244 HBG 0.00 0.04 0.01 0.00 0.00 0.01

59

121-121.17m

KADD100244

161.-161.21m

Phyllites 0.09 0.09 0.08 0.07 0.09 0.08

KADD100243

113-113.05m

HBG 0.09 0.05 0.05 0.04 0.03 0.05

KADD100243

97.5-97.7m

HBG 0.07 0.08 0.09 0.10 0.10 0.09

KADD100245

132-132.2m HBG 0.06 0.06 0.08 0.06 0.07 0.07

KADD100245

65.2-65.36m

Phyllites 0.04 0.06 0.04 0.05 0.04

0.05

KADD100245

40.5-40.65m HBG 0.03 0.04 0.03 0.03 0.05 0.04

KADD100254

143.6-143.7m Phyllites 0.09 0.10 0.09 0.14 0.10 0.10

KADD100254

94.5-94.63m HBG 0.52 0.53 0.52 0.62 0.41 0.52

KADD100246

181-181.1m metagreywacke 10.8 10.9 11.1 11.3 11.2 11.1

KADD100246

176-176.1m HBG 0.00 0.06 0.04 0.04 0.02 0.03

KADD100246

164-164.1m HBG 0.06 0.04 0.04 0.02 0.00 0.03

KADD100246

98-98.1m metagreywacke 20.4 19.7 19.8 20.0 20.1 20.2

60

From the susceptibility readings, the metagreywackes have considerably higher

magnetic susceptibility than the other rock units in the study area. The granitoids

display a lower magnetic susceptibility with smaller variation. The phyllites also

displayed a lower magnetic susceptibility but, have a higher magnitude than the

granitoids. The low and high bands or strips, seen in the magnetic grid data can be

correlated with the susceptibility measurements done in the laboratory. This can be

seen, in station ANTWI002, ANTWI 001, BIA001, BETH001 and AKYE 003.

4.4 Geological structures in the study area

The few outcrops exposed in the study area have provided some level of information

about the structural settings. The various structures encountered have been

statistically analysed and their probable cause and relations has been established. The

structures that characterized the rock in the study area in the Sunyani basin are

foliations, joints, quartz veins, faults, crenulations, mineral lineations and boudins.

The general distribution of structures in the study area is shown in the map below

(Figure 4.14).

61

Fig.4.14. 1: 50,000 structural map showing the distributions of structures observed in

the study area

62

4.4.1 Foliations

Foliations in the study area mark the first phase of deformation in the study area.

These represent a penetrative planar fabric seen both at the mesoscopic scale and

microscopic scale in rocks such as metagreywackes, phyllites and some of the

leucogranite outcrops. The rocks in the study area exhibited vertical to subvertical

foliations (Figure 4.15a and 4.15b). The foliation thickness within the phyllites and

greywackes ranges from 0.1 to 0.2 and 0.01 to 0.1 centimetres, respectively. Most of

the foliation surfaces were marked by the growth of platy minerals such as muscovite

and biotite. The regional strike for the foliation ranges from northeast and southwest

with moderate to steep dips (Kesse, 1985). Locally, the general mean strike for

foliation in the phyllite is 064° and the minimum dip is 64° (Figure 4.16).

(a) (b)

Fig. 4.15. Greywacke showing vertical foliation in 4.15a and subvertical foliation in

4.15b

63

N=19

Fig.4.16.Lower hemisphere equal area projection of poles to foliation within the

phyllites

N=48

Fig.4.17. Plot of poles to foliation within the metagreywackes

64

The average strike of foliations amongst the greywacke outcrop is 057° and dip

ranging from 56° to 85° (Figure 4.17). Most of the rocks had generally steep dips.

Under the microscope most of the phyllites and greywacke showed preferred

orientation of minerals such as quartz, feldspar and biotite (Figures 4.4d, 4.6a and

4.8c). Thus, the two rocks show the same foliation orientations and were likely

deformed by the same event. The data used to determine these mean values can be

seen in appendix 3 and 4.

4.4.2 Joints

Joints within the study area were well developed, evenly spaced and had a T-

intersection pattern, thus the joints had orthogonal relationships. The parallel, or

concordant, joint to the foliation surface had a mean strike of 052° and dip a of 67°,

and that strike of the discordant joint is 334° with a mean dip of 79° (Figure 4.19).

Two orientations of joints were also observed in the both the leucogranites and the

hornblende-biotite granodiorite, thus the primary joint and the secondary joint. The

primary set of joints had a mean strike of 314° and a mean dip of 63°, and the

secondary joints had a mean strike of 039° and a mean dip of 48° (Figure 4.18). The

data used to determine these mean values can be seen in appendix 7.

65

N=19

Fig.4.18. Lower hemisphere equal area projection of poles to joints within the

leucogranites and hornblende-biotite granodiorites in the study area

N=11

Fig.4.19. Lower hemisphere equal area projection of poles to joints within the

metasediments in the study area.

66

4.4.3 Veins

Veins found in the Sunyani basin were associated with all the rock units in the study

area, but are predominately associated with both of the leucogranite and hornblende-

biotite granodiorite. The veins in the study area consist of quartz and pegmatite veins.

The pegmatite veins were exclusively associated with the leucogranites. The

pegmatite veins had tourmaline mineralization in them. The average thickness of the

veins was 0.5 to 10 centimetres and they had variable lengths up to 10 metres. Most of

the quartz and pegmatite veins were seen in Godom, Fosukrom, Ndobem and

Kwabenakra and are faulted (Figure 4.20a). The quartz veins observed in Akaakrom

shows F2 folding (Figure 4.20b). Most of the veins cross cut each other which indicate

that there were at least two episodes of remobilization.

67

(a) (b)

(c) (d)

Fig. 4.20. Various veins found in the study area. (a) Faulted quartz vein observed at

Fosukrom (b) Quartz veins affected by F2 folding in Akaakrom; (c) Pegmatite veins

crosscutting each other at Ndobem Township; (d) Tourmaline in a pegmatite vein.

68

4.4.4 Folds

Basically only one mesoscopic fold was observed at the study area, along with some

crenulations. The fold was observed in Fosukrom at the station AMPM005. The fold

observed in the study area is reclined, with a vertical fold axis and axial plane (Figure

4.20c). It is interpreted as an F2 fold. The fold had a length of 12 centimetres and

amplitude of 45 centimetres. The fold was formed as a result of ductile deformation.

The fold was affected by later faulting.

Three crenulations were observed at outcrop level within the metagreywacke. They

are second generation folds (F2) that have affected the foliations within the

metagreywackes. The F2 fold hinges have variable trends of 110°, 140°, 072° and

plunge 70°, 80° and 15°, respectively (Figure 4.21a , 4.21b and appendix 6).

69

(a) (b)

(c)

Fig.4.21. (a) Quartz vein that has been affected by F2 fold in the metagreywacke; (b)

metagreywacke showing F2 folding which is oblique to pre-existing foliation; (c) A

70

fold with a vertical fold axis and vertical axial plane. The black line marks the fault

plane.

4.4.5 Faults

Faulting is the fundamental brittle mechanism for achieving shear displacement

(Davis and Reynolds, 1996). A mesoscopic fault was observed within the

leucogranites in the study area. It is a normal fault and was observed at the station

TOGO001. The fault plane had a strike of 320°, dip of 88°, and a fault throw of 40

centimetres. Some faults were inferred in the northwestern part of the study area and

bounding Domain 3 (Figure 4.22b). The fault was inferred since it cannot be seen

clearly on the earth surface and also due to how the rocks have been tectonised by

way of changes in dip directions of foliation along a linear grid in the study area.

Faults in the study area were also picked from the aeromagnetic total intensity image

where there is a sudden break in a magnetic data. Most of the faults picked out of the

magnetic intensity image trend northwest- southeast.

(a)

71

(b)

Fig.4.22. (a) Normal fault exhibited in the two mica granite (b) Total magnetic image

showing faults as black lines in domain 3. The faults trend NW-SE, and oblique to the

main regional structures.

72

4.4.6 Mineral Lineations

The mineral lineations in the study area were observed in the foliation plane of the

metagreywacke at station ADIN001. The mineral lineations imparted a fibrous

appearance on the rock (Figure 4.23). The mineral lineation may have formed as a

result of preferred directional crystallization or from the stretching of grains by

deformation (Davis and Reynolds, 1996). The mineral lineations measured in the

study area trend between 040°- 030° and plunge 25°- 20°, respectively.

Fig.4.23. A photograph showing a mineral lineation on the surface of a

metagreywacke.

73

4.4.7 Boudins

Boudins form as a response to the layer parallel extension of a stiff layer enveloped

by mechanically softer layers. The way in which it stretches depends mainly on the

ductility contrast of the participating layer and the magnitude of stretching (Davies

and Reynolds, 1996). Boudins observed within the study area were symmetrical in

profile, with their long axes oriented parallel to the S1 foliation, and are interpreted to

have formed within the shear zone (Figure 4.24). The trend of the boudin neck is

045°.

Fig.4.24. Boudin oriented parallel to the S1 foliation in the study area.

74

4.5 LA-IC-PMS U-Pb and Pb-Pb geochronological results

Age determination was carried out for two samples within the study area using LA-

IC-PMS. The samples analysed were from the hornblende-biotite granodiorite. The

ages obtained from these samples span 10Myr. The samples analysed were ASU002

and NF002 with coordinates 6°42’19.8’’N, 2°46’02’’W and 6°41’06.5’’N,

2°46’08’’W, respectively.

4.5.1 Sample ASU002

This hornblende-biotite granodiorite outcrops in the southeastern portion of the study

area, within a cocoa farm, as a relatively small lensoidal shaped outcrop. The rock is

coarse-grained, exhibits granular texture, has an intermediate composition, and is

mineralogically composed of quartz, hornblende, epidote, plagioclase and biotite.

Most of the plagioclase in the rock exhibited oscillatory zoning and only a few

exhibited polysynthetic twinning. Twenty one spots analyses on zircon separated from

the rock yielded a weighted mean 207

Pb/206

Pb age of 2136±11Ma (Figure 4.26). From

the Cathodoluminescence image (Figure 4.25) the zircon crystals have oscillatory

zoning, which is typical of igneous zircon. The ages of these zones showed no real

age difference.

75

The summary of the data that was used for the age determination can be seen

appendix 8.

Fig.4.25. Cathodoluminescence image of representative zircon crystals from sample

ASU002. Circles show locations for the LA-IC-PMS spot analyses for U-Pb

Fig. 4.26. Zircon U-Pb concordia plot for sample ASU002 (hornblende –biotite

granodiorite)

76

4.5.2 Sample NF002

NF002 is also a hornblende-biotite granodiorite that was sampled in the town of

Nfanti. The outcrop is lensoidal in shape, coarse-grained, with a granular texture both

in thin section and in outcrop, and showed no deformation. The rock is composed of

quartz, plagioclase feldspar, hornblende and epidote. Twenty LA-IC-PMS spot

analyses were made on the zircon crystals that were separated from NF002 and

yielded a weighted mean 207

Pb/206

Pb age of 2135±9 Ma (Figure 4.28). From the

Cathodoluminescence image (Figure 4.27) the zircon are oscillatory zoned, which is

typical of igneous zircon. The ages of these zones showed no real age difference.

The summary of the data that was used to determine the ages can be seen in appendix

9.

Fig. 4.27. Cathodoluminescence image of representative zircons from sample NF002.

Circles show locations of LA-ICPMS spot analyses for U-Pb

77

Fig.4.28. Zircon U-Pb concordia plot for sample NF002 (hornblende –biotite

granodiorite)

78

CHAPTER FIVE: DISCUSSION

This section of the report discusses the results enumerated in chapter four. This is

based on the structural and geochronological data, petrographic analysis,

interpretation of geophysical data set and field relationships.

5.1 Stratigraphy of the Study area

Ages reported by earlier workers based on U-Pb dating on zircon for the hornblende-

biotite granodiorites yielded ages of 2.25 to 2.17 Ga (Feybesse, 2006) and 2178± 2.3

Ma (Hirdes, 1991). Zircon in the hornblende-biotite granodiorite analysed in this

study yielded ages of 2135±9 Ma and 2136±11 Ma. This mean, the magmatism

interpreted to be responsible for the formation of the hornblende-biotite granodiorite

is within the same time range.

Feybesse (2006) reported an age of 2.1 Ga for the deposition of metasediments of the

Sunyani basin. Vidal et al. (2006) and Oberthür et al. (1998) suggested the

metasediments within the study area lie unconformably above the hornblende-biotite

granodiorite of the Sefwi belt, which is corroborated by the ca. 2136 Ma age

determined in this study.

From geochronological relations it can be inferred that the metagreywackes and

phyllites have been intruded by leucogranites, which agrees with the U-Pb ages

determined from zircon and monazite on the leucogranites that yielded an age of

2087± 1.4 Ma (Hirdes, 1991). The metagreywackes were basically younger than the

phyllites based on the cross section and field observations, and in some areas within

the drill core they were intercalated. This therefore makes the overall structure of the

basin in this area a synform. Generally on an outcrop level, almost all the

79

metagreywackes were fine grained, with a few being medium grained. In thin section,

most of the quartz and feldspar grains are angular (Figure 5.1).

Fig.5.1. A photomicrograph of a greywacke showing angular grains of quartz and

feldspar

This may indicate that the sediments were not transported from a long distance from

its source area and deposited in a low energy environment, perhaps close to the

erosional source and with a moderate relief, as suggested by Vidal (1996) and Alric et

al. (1987).

80

No metamorphic aureoles were observed in the southeastern portion of the study area

(i.e., Asumura), where the hornblende-biotite granodiorite come into contact with the

metasediments (phyllites). This implies that the hornblende-biotite granodiorite was

emplaced prior to the deposition of the sediments, which agrees well with their

respective ages summarized above. The hornblende-biotite granodiorite and the

leucogranites outcropped as lensoidal and small rounded mounds, but are thought to

be part of a larger batholithic body as seen in the aeromagnetic images.

Outcrops of the leucogranites within the study area show no visible fabric such as

foliation or cleavage development apart from its lensoidal and oval to ellipsoidal

shape. In thin section, the quartz minerals within the leucogranites show some

preferred orientation fabric. Some section of the thin sections of the leucogranites also

exhibited phaneritic and granular texture, and most of the quartz grains did not show

undulose extinction, meaning the rock had experienced minimal strain. The intensity

of deformation within the leucogranites was low due to the cryptic texture seen. The

general strike of the foliation within the leucogranites was about 045°, which

indicated the maximum stretching direction. The lensoidal shaped leucogranites trend

mostly in the northeast-southwest direction, the same as the strike of the foliation in

the metasediments. This may indicate that emplacement of the leucogranites was

coeval with and influenced by the deformation within the study area.

81

Fig.5.2. Showing preferred orientation of quartz mineral within the leucogranites. The

oblique orientation of the long axes of the quartz grains with respect to the microcline,

plagioclase and muscovite compositional layering. The quartz show C-fabric which is

oblique to the shear plane boundaries (inferred to be approximately parallel to the

compositional layering) indicates a sinistral shear sense.

The phyllites and the greywacke on the other hand exhibit foliation, strained minerals

(e.g., quartz showing undulose extinction) and schistose texture.

A cross-section from A-B (Figure 5.3b) constructed from the geological map (Figure

40a), and from all the observations and data collected in this study, suggests that the

hornblende-biotite granodiorite is the oldest rock in the study area, followed by the

N

82

deposition of the phyllites, then the metagreywackes and the later intrusion of the

leucogranites.

Fig.5.3. (a) Geological map constructed from geological field work (b) Cross section

from A to B.

83

5.2 Geophysical interpretation and mineralization

The aeromagnetic geophysical grid data have provided a clearer interpretation of the

geology of the Sunyani basin.

Since outcrops were sparse within the study area, the magnetic signatures from the

magnetic image in conjunction with the magnetic susceptibilities measured from the

various lithologies helped in constraining the location of the lithological boundaries,

and thereby aided in producing a more sensible and accurate geological map. The

various lithologies within the study area have been captured on the geophysical map

and are shown to be trending mostly northeast- southwest.

The striped pattern in the central portion of the magnetic image showing alternating

low and high magnetic signatures maybe as a result of tight folding of a single

magnetic layer and hydrothermal alteration that have hitherto introduced or destroyed

magnetite or other magnetic bearing mineral within the study area or. The tight

folding within the high strain zone is also indicated by the variation in dip direction

(mostly NW and SE). The hydrothermal alteration may be seen in the field area as

quartz, calcite and quartzo-feldspathic veins being mineralized with sulphide minerals

(e.g. pyrite and ankerite). The hydrothermal alterations hypothesis may be supported

by the fact that gold mineralization as, well as active gold mining has taken place

along that same trend or anomaly by Newmont Ghana Gold Limited. The gold is

associated with hydrothermal fluid formed usually along faults zones in the

leucogranites (Subika pit). Also, assaying done on auger samples within the central

part of the study area where this stripped pattern anomaly is found, reportedly gave

higher values for gold (the data is proprietary and is being withheld by Keegan

Resources Ghana Limited). Unoriented drill core from that same area showed highly

84

strained structures within the study area. The foliations within the graphitic phyllites

are tightly spaced and folding was also observed (Figure 5.4). Measurements were not

done due to the fact that the bottom and the top of the holes could not be determined.

In the area where the shearing was intense, the rocks were altered with quartz and

calcite veins that contained disseminated with cubic sulphides (pyrites) (Figure 5.4a).

(a)

85

(b)

Fig.5.4.(a) A drill core of phyllites and metagreywacke affected by alteration showing

sulphide mineralization (yellow shinny mineralization in the middle core); (b) Thin

section of a strained phyllite showing S 0-1 overprinted by F2 folding and S2 cleavage ,

as well as faulted quartz and calcite veins .

The leucogranites exhibit relatively medium to high magnetic signatures. On a

regional scale, the magnetic image showed a large batholithic body over 70

kilometres in length, and has a lensoidal or oval shape trending northeast-southwest.

A 1 kilometre width of high magnetic signature can be seen wrapping around the

leucogranite. This could be a metamorphic aureole or the distribution of magnetic

mineral within the leucogranites. As with the metasediments described above,

disseminated pyrite also occurs within the leucogranites.

86

5.3 Structures

This subsection deals with the structures observed at outcrop-scale, thin section-scale

and those interpreted from the processed magnetic image in order to characterize the

deformational history of the study area. The structures observed were foliations,

joints, lineation, folds, faults and mineral lineations. Due to the paucity of outcrop

within the study area, identification of large-scale structures was difficult.

The tectonic foliations (S1) within the study area were basically observed within the

phyllites and metagreywackes. The stereographic plots in Chapter 4 show that both

rocks strike in the NE-SW direction and show vertical to subvertical dip. The

intermediate to high dips of S0 and S1 indicate they were parallel to the axial plane of

a probable F1 (?) tight isoclinal fold. This meant both rock types likely experienced

the same deformation event. S1 within the metasediments parallels the bedding (S0).

S1 in thin section for the sediments was defined by elongate grains of quartz and

feldspar minerals. S2 foliations within the study area consist of crenulation cleavages

that were identified in thin sections of the phyllites.

All the folds observed within the study area were F2 folds and their axial planes were

mostly orthogonal to the subvertical to vertical dipping foliations. These folds were

only observed within the metasediments, although we can infer a synformal large-

scale fold from the overall stratigraphy of the region.

The central half of the study area marks the zone of most intense deformation where

all the major structures are found. This zone is focused within the greywackes and

phyllites, which suggests the deformation was partitioned into the less competent

metasediments versus the stronger plutons. The metagreywacke and phyllites within

this area exhibit near vertical dips of S1 whose dip directions vary from southeast to

87

northwest. Two faults are inferred within the zone of intense deformation that are

interpreted to bound an ~15km wide sinistral strike-slip shear zone. This is based on

the discreet change in dip direction along a particular linear trend of about 20

kilometres in length, which also coincides with macroscopic shear structures observed

in the aeromagnetic map.

The hornblende-biotite granodiorite within the study area showed no evidence of

deformation. The rock had granular texture and showed myrmekitic textures. The

wartlike myrmekite can be interpreted as preservation of a primary igneous texture

that represents the intergrowth between quartz and plagioclase probably formed

during magmatic crystallization of the rock.

The area is interpreted to have undergone two main phases of deformation, D1 and D2,

based on the structures discussed above. The D1 event involved produced the

penetrative S1 foliation observed throughout much of the study area, which is axial

planar to a probable F1 (?) fold (probably a tight isoclinal fold); unfortunately, this F1

fold was not observed in the study area due to paucity of outcrop. S1 contains mineral

lineations (L1) which is defined by quartz. D2 is marked by faulting, a folding event

and a probable shear zone in the central portion of the study area. From the central

portion of the geophysical magnetic data, the striped pattern of the magnetic

signatures is oblique (S-fabric) to the main bounding regional magnetic signatures (C-

fabric), which is interpreted as a macroscopic C-S fabric within a distributed sinistral

shear zone. Microscopic evidenced for sinistral shear sense in this high strain zone

comes from a thin section of the leucogranite that contains a preferentially oriented

quartz fabric oblique to microcline, plagioclase and muscovite (Figure 5.2). The

leucogranites was found in the high strain zone. The boundary magnetic signature

88

strikes about 040° with the high and low magnetic signatures striking averagely about

070°.

Fig.5.5. Reduce-to-pole magnetic image showing oblique and sinistral movement of

magnetic anomaly. This sense of movement is shown in the black lines.

040° 080°

89

The hornblende-biotite granodiorite magmatic emplacement (2135±9Ma) pre-dates

both the deposition of the sediments and emplacement of the leucogranite, which was

followed by the D1 and D2 deformation events. As such, the D1 and D2 events must

have occurred after 2087± 1.4 Ma, the age of the leucogranites. For this reason, both

the sediments and the leucogranite had the same north-eastern orientation.

90

CHAPTER SIX: CONCLUSION AND RECOMMENDATIONS

This work has provided a new insight about the architecture of the Sunyani basin. The

various deformations within the study area have been constrained by absolute

geochronological ages and the strip pattern of the magnetic signatures may be

explained as the addition or the possible destruction of magnetic minerals within the

study area by the introduction of hydrothermal fluids.

By way of the regional architecture structure four different conclusions can been

drawn

The study area has undergone two kinds of deformation. Thus D1 and D2 event

which occurred after the emplacement of the leucogranites as a result of the

same strike and trend direction of the rocks. This observation made within the

Sunyani basin in Ghana was almost the same as Vidal et al. (2009) observed

within the Comoè basin in La Cote D’Ivoire.

The Hornblende-Biotite granodiorites were emplaced 48Ma prior to the

deposition of sediments in the Sunyani basin

The leucogranites were emplaced during 2087±1.4Ma and were mineralized.

This may be partly responsible for the hydrothermal fluid within the study

area.

The sediments (metagreywackes and phyllites) were mostly fine grained with

only a few being medium grained. The quartz and feldspar minerals observed

within thin sections were generally angular. This indicated the sediments are

first cycle in origin. This observation was also in line with Vidal et al. (2009)

observation in the Comoè basin in La Cote D’Ivore.

91

6.1 Recommendations

To have a good picture of the regional structural architecture of the Sunyani basin

with will be imperative to map the whole Sunyani basin, rather than just a small

section.

92

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97

APPENDICES

Appendix 1. Table showing the coordinates and figure numbers of various hand

sample and thin section used.

Location longitudes Latitudes

Figure

number Outcrop Thin-Section

Drill

Sample

ANTWI001 -2.8595 6.7201 11a metagreywackes

ADIN001 -2.8571 6.816 11b metagreywackes

AKYE003 -2.8908 6.6826 12a

metagreywacke

AKYE003 -2.8908 6.6826 12b

metagreywacke

ANTWI001 -2.8595 6.7201 12c

metagreywacke

ANTWI001 -2.8595 6.7201 12d

metagreywacke

ANTWI002 -2.861 6.7209 12e

metagreywacke

BIA002 -2.9424 6.6816 12f

metagreywacke

KADD100254 -2.8328 6.6377 13a Phyllites

KADD100254 -2.8328 6.6377 13b Phyllites

KADD100254 -2.8328 6.6377 14a Phyllites

KADD100254 -2.8328 6.6377 14b Phyllites

MANU003 -2.7645 6.6416 15a HBG

MANU001 -2.7656 6.6463 15b HBG

MANU001 -2.7656 6.6463 16a HBG

MANU002 -2.7622 6.64305 16b HBG

ASU002 -2.7672 6.7055 16c HBG

MANU002 -2.7622 6.64305 16d HBG

KWA001 -2.9701 6.849 17a Leucogranite

KKRA001 -2.9659 6.9756 17b Leucogranite

KWA001 -2.9701 6.849 18a Leucogranite

NDOBEM002 -2.9729 6.9565 18b Leucogranite

98

Appendix 2.Table showing the location and magnetic susceptibilities of outcrops in

the study area

Sample

Number

Rock Name

K1 K2 K3 K4 K5 K

average

longitude(W) latitude(N) SI

Units

SI

Units

SI

Units

SI

Units

SI

Units

SI

Units

ASU002 -2.7672 6.7055 HBG 0.04 0.03 0.03 0.04 0.01 0.03

MANU001 -2.7656 6.6463 HBG 0.67 0.68 0.67 0.69 0.68 0.68

ANTWI002 -2.861 6.7209 metagreywacke 13.6 13.9 13.3 13.9 14.8 13.9

NF002 -2.7688 6.6847 HBG 0.17 0.19 0.17 0.17 0.22 0.18

ANTWI001 -2.8595 6.7201 metagreywacke 0.79 0.78 0.8 0.86 0.87 0.82

BIA002 -2.9424 6.6816 metagreywacke 8.75 8.76 8.74 8.74 8.75 8.74

AMPM005 -2.9076 6.7545 Leucogranite 0.03 0.01 0 0.01 0.02 0.01

KWA003 -2.7896 6.6629 HBG 0.92 0.97 0.95 1.04 1.03 0.98

BIA001 -2.9636 6.6854 metagreywacke 7.66 7.94 8.33 8.68 8.85 8.29

BETH001 -2.9113 6.6798 metagreywacke 3.55 3.66 3.64 3.69 3.5 3.61

AKYE003 -2.8908 6.6826 metagreywacke 0.11 0.11 0.1 0.14 0.13 0.12

MANU002 -2.7622 6.6430 HBG 1.32 1.32 1.35 1.41 1.42 1.36

KADD100244 -2.8311 6.6407 HBG 0.02 0.02 0.03 0.02 0.03 0.02

77.5m-77.7m

KADD100244 HBG 0 0.04 0.01 0 0 0.01

121-121.17m

KADD100244 Phyllites 0.09 0.09 0.08 0.07 0.09 0.08

161.-161.21m

KADD100243 -2.8247 6.6473 HBG 0.09 0.05 0.05 0.04 0.03 0.05

113-113.05m

KADD100243 HBG 0.07 0.08 0.09 0.1 0.1 0.09

97.5-97.7m

KADD100245 -2.8328 6.6377 HBG 0.06 0.06 0.08 0.06 0.07 0.07

132-132.2m

KADD100245 Phyllites 0.04 0.06 0.04 0.05 0.04 0.05

65.2-65.36m

KADD100245 HBG 0.03 0.04 0.03 0.03 0.05 0.04

40.5-40.65m

KADD100245 Phyllites 0.09 0.1 0.09 0.14 0.1 0.1

143.6-143.7m

KADD100245 HBG 0.52 0.53 0.52 0.62 0.41 0.52

94.5-94.63m

KADD100246 metagreywacke 10.8 10.9 11.1 11.3 11.2 11.1

181-181.1m -2.8171 6.6547

KADD100246 HBG 0 0.06 0.04 0.04 0.02 0.03

176-176.1m

KADD100246 HBG 0.06 0.04 0.04 0.02 0 0.03

164-164.1m

KADD100246 metagreywacke 20.4 19.7 19.8 20 20.1 20.2

98-98.1m

99

Appendix 3. Table showing the locations of various S1 foliations measurement made

in the study area

S1 foliation

STATION longitude Latitude outcrop type strike dip dip direction

NF001 2° 46' 09'' 6° 41' 03'' HBG

NF002 2° 46' 06'' 6° 41' 06'' HBG 36 30 295

38 50 290

KWA003 2° 47' 22'' 6° 39' 46'' HBG 40 62 300

42 60 298

BOA001 2° 48' 20'' 6° 40' 45'' metagreywacke 40 50 120

38 52 118

ANW001 6°42'41.2'' 2°49'35.2'' Phyllite 40 60 300

ANW002 6°43'17.4'' 2°48'32.2'' Phyllite 70 52 320

68 52 310

50 48 312

63 51 314

ASU001 6°42'24.1'' 2°46'07.6'' Phyllite 75 62 162

75 60 160

74 60 158

75 60 155

ANTWI001 6°43'12.6'' 2°51'34.3'' metagreywacke 45 40 320

46 39 318

45 70 319

42 52 140

45 54 142

ANTWI002 6°43'15.3'' 02°51'39.8'' metagreywacke 40 60 320

350 42 70

352 38 74

350 38 76

40 20 140

ANTWI003 6°43'43.6'' 2°50'52.7'' metagreywacke 45 85 125

ANTWI004 6°43'48.6'' 2°50'07.6'' Phyllite 30 60 110

40 80 120

AMPM001 6°42'16.6'' 2°52'43.2'' metagreywacke 45 75 130

46 74 140

30 68 120

AMPM003 6°44'20.7'' 2°52'59'' HBG 36 62 270

40 60 120

45 62 350

AMPM004 6°42'44.9'' 2°53'57.1'' metagreywacke 40 60 130

38 58 128

AKYE001 6°41'13.6'' 2°52'25.2'' metagreywacke 58 68 350

60 67 348

62 70 348

AKYE002 6°40'07.6'' 2°53'51.9'' metagreywacke 60 80 140

65 80 145

65 84 145

AKYE003 6°40'57.5'' 2°53'26.9'' metagreywacke 65 80 155

62 80 152

BETH001 6°40'47.6'' 2°54'36.9'' metagreywacke 60 70 160

58 72 158

BETH002 6°42'40.9'' 2°55'15.1'' metagreywacke 60 68 150

BETH003 6°41'29.1'' 2°53'55.8'' metagreywacke 55 40 145

100

60 80 150

60 82 150

SEB002 6°46'33.4'' 2°50'45.5'' Leucogranite 20 80 110

45 80 135

33 80 123

ADIN001 6°48'58.4'' 2°51'25.4'' metagreywacke 40 75 135

30 80 120

35 78 128

ADIN002 6°48'40.8'' 2°51'51.8'' metagreywacke 40 80 130

VERE001 6°47'10.1'' 2°52'45.5'' metagreywacke 48 72 138

CAMP001 6°49'22.4'' 2°54'26.6'' metagreywacke 10 80 275

KWA003 6°51'28.4'' 2°57'24.0'' Phyllites 46 65 136

KWA004 6°50'23.4'' 2°54'16.7'' metagreywacke 38 75 128

AKAA001 6°50'37.7'' 2°53'49.6'' metagreywacke 40 50 290

80 70 170

50 80 140

65 75 155

KOJO001 6°52'57.2'' 2°52'27.4'' Phyllites 354 60 86

GOKA001 6°54'08.3'' 2°51'17.2'' metagreywacke 30 50 120

SEBEBIA003 6°57'10.9'' 2°59'09.4'' Leucogranite 280 22 360

NDOBEN001 6°57'02.6'' 2°58'52.3'' Leucogranite 360 30 92

Appendix 4. Table showing the locations of various S2 foliations measurement made

in the study area.

S2 foliation

STATION longitude Latitude outcrop type strike dip dip direction

ANTWI001 6°43'12.6'' 2°51'34.3'' metagreywacke 45 80 318

45 78 320

AKAA001 6°50'37.7'' 2°53'49.6'' metagreywacke 70 20 160

Appendix 5. Table showing the locations of mineral lineation measurement made in

the study area.

Mineral lineation

STATION longitude latitude outcrop type Trend Plunge

ADIN001 6°48'58.4'' 2°51'25.4'' metagreywacke 40 30

25 20

101

Appendix 6. Table showing the locations of various F2 folds and quartz veins

measurement made in the study area.

Folds axis(F2) Quartz veins

STATION Longitude Latitude outcrop type Trend plunge Trend Plunge

NF001 2° 46' 09'' 6° 41' 03'' HBG 90 28

BOA001 2° 48' 20'' 6° 40' 45'' metagreywacke 95 52

92 50

MANU005 6°38'36.7'' 2°47'09.8'' HBG 80 5

30 20

ANW001 6°42'41.2'' 2°49'35.2'' Phyllite 10 50

ANW002 6°43'17.4'' 2°48'32.2'' Phyllite 60 50

ANTWI003 6°43'43.6'' 2°50'52.7'' metagreywacke 50 54

AMPM003 6°44'20.7'' 2°52'59'' HBG 110 70

AMPM004 6°42'44.9'' 2°53'57.1'' metagreywacke 142 72 40 60

BETH001 6°40'47.6'' 2°54'36.9'' metagreywacke 35 78

AKAA001 6°50'37.7'' 2°53'49.6'' metagreywacke 72 82

NDOBEN002 6°57'23.4'' 2°58'22.6'' 310 20

320 10

272 2

Appendix 7. Table showing the locations of various joints measurement made in the

study area.

Joints

STATION Longitude Latitude outcrop type Strike Dip Dip

direction

NF001 2° 46' 09'' 6° 41' 03'' HBG 272 42 2

20 42 290

NF002 2° 46' 06'' 6° 41' 06'' HBG 20 30 200

350 58 272

KWA001 2° 47' 23'' 6° 38' 56'' HBG 20 30 70

BOA001 2° 48' 20'' 6° 40' 45'' metagreywacke 310 60 38

KW004 2° 47' 11'' 6° 39' 45'' HBG 40 50 310

40 52 320

MANU001 2° 46' 49'' 6° 38' 49 HBG 352 64 110

270 64 180

MANU004 6°38'14'' 2°45'55'' HBG 40 75 120

320 80 210

MANU005 6°38'36.7'' 2°47'09.8'' HBG 275 76 180

270 64 180

30 76 290

ANW002 6°43'17.4'' 2°48'32.2'' Phyllite 32 74 240

102

ANTWI001 6°43'12.6'' 2°51'34.3'' metagreywacke 350 75 250

ANTWI002 6°43'15.3'' 02°51'39.8'' metagreywacke 40 60 320

ANTWI003 6°43'43.6'' 2°50'52.7'' metagreywacke 320 15 220

ANTWI004 6°43'48.6'' 2°50'07.6'' Phyllite

320 80 50

AMPM003 6°44'20.7'' 2°52'59'' HBG 85 70 360

AMPM004 6°42'44.9'' 2°53'57.1'' metagreywacke 330 76 50

328 80 52

AMPM005 6°45'16.3'' 2°54'27.6'' Granite 320 80 48

318 78 46

AKYE001 6°41'13.6'' 2°52'25.2'' metagreywacke

AKYE002 6°40'07.6'' 2°53'51.9'' metagreywacke 320 88 220

BETH002 6°42'40.9'' 2°55'15.1'' metagreywacke 342 80 85

SEB002 6°46'33.4'' 2°50'45.5'' Leucogranite 345 75 250

30 70 120

103

Appendix 8. Summary of LA-IC-PMS U-Pb on zircon- ASU002

U Th Pb* 206Pb* ±2σ 207Pb* ±2σ 207Pb* ±2σ 208Pb* ±2σ 207Pb* ±2σ 207Pb* ±2σ 206Pb* ±2σ "Best

age"

%

Laser spot ppm ppm ppm 238U (%) 235U* (%) 206Pb* (%) 232Th (Ma) 206Pb* (Ma) 235U (Ma) 238U* (Ma) (Ma) disc.

ASU002 S

31

144.76 74.46 180 0.39 2.72 7.04 3.06 0.13 1.39 2125.7 37.9 2108 24.5 2117.09 27.19 2126.7 49 2107.79 1.05

ASU002 S

32

111.84 58.3 90.2 0.39 2.81 7.16 3.44 0.13 1.98 2121.7 53.1 2137 34.6 2131.72 30.64 2126.1 51 2137.18 0.61

ASU002 S

33

88.24 56.14 112 0.37 2.59 6.94 3.21 0.14 1.9 1933.9 122 2169 33.2 2103.43 28.5 2036.8 45 2169.2 7.11

ASU002 S

34

158.68 121.13 231 0.38 2.53 7.07 2.8 0.13 1.2 1996.8 61.2 2160 20.9 2119.96 24.91 2078.4 45 2160.46 4.43

ASU002 S

35

123.64 77.91 181 0.43 6.5 7.72 6.71 0.13 1.66 2351.7 208 2107 29.1 2198.84 60.33 2298.2 126 2107.46 10.76

ASU002 S

36

160.22 53.02 141 0.36 2.61 6.7 3.03 0.13 1.54 2160.7 66.6 2150 27 2072.75 26.79 1996 45 2149.92 8.31

ASU002 S

37

114.16 41.99 120 0.39 2.53 7.14 3.04 0.13 1.69 2145.2 70.2 2133 29.6 2129.59 27.1 2126.1 46 2132.94 0.37

ASU002 S

38

98.99 35.69 89.3 0.39 3.11 7.16 3.59 0.13 1.8 2246.9 72.3 2118 31.6 2131.16 32 2145.2 57 2117.6 1.53

ASU002 S

39

158.49 141.6 158 0.35 3.33 6.37 3.76 0.13 1.75 1029.2 101 2115 30.6 2028.58 32.97 1944.3 56 2115.39 9.35

ASU002 S

41

28.05 15.58 30.1 0.39 3.29 7.38 4.09 0.13 2.43 2206.1 81.5 2161 42.4 2158.99 36.61 2157.2 60 2160.71 0.19

ASU002 S

42

31.7 19.15 39.9 0.39 3.42 7.17 4.49 0.13 2.92 2157.3 97.2 2163 50.9 2132.56 40.02 2101.6 61 2162.52 3.3

ASU002 S

45

175.99 111.45 202 0.35 3.45 6.37 4.15 0.13 2.31 1790.1 58.4 2132 40.5 2028.21 36.45 1928.2 58 2131.51 11.02

ASU002 S

46

66.22 13.3 39.3 0.41 4.05 7.36 4.79 0.13 2.57 2225.5 141 2105 45.2 2156.17 42.88 2210.5 76 2104.81 5.93

ASU002 S

47

136.47 66.06 160 0.35 6.18 6.4 6.63 0.13 2.41 2143.9 151 2155 42.1 2032.61 58.26 1914.5 102 2154.74 12.87

ASU002 S

48

102.9 59.39 148 0.38 7.21 6.93 7.67 0.13 2.6 2441.7 205 2146 45.5 2102.12 68.05 2057.8 127 2145.81 4.79

ASU002 S

49

90.32 36.78 102 0.37 2.88 6.78 3.59 0.13 2.14 2554.7 162 2133 37.5 2082.76 31.77 2032.3 50 2133.07 5.5

104

U Th Pb* 206Pb* ±2σ 207Pb* ±2σ 207Pb* ±2σ 208Pb* ±2σ 207Pb* ±2σ 207Pb* ±2σ 206Pb* ±2σ "Best

age"

%

Laser spot ppm ppm ppm 238U (%) 235U* (%) 206Pb* (%) 232Th (Ma) 206Pb* (Ma) 235U (Ma) 238U* (Ma) (Ma) disc.

ASU002 S

50

58.43 29.34 63.1 0.42 3.69 7.88 4.56 0.14 2.67 2461.3 113 2178 46.5 2217.74 41.05 2261 70 2177.99 4.52

ASU002 S

51

237.39 138.11 366 0.42 4.13 7.56 5.18 0.13 3.12 2433.1 101 2102 54.8 2179.74 46.44 2263.2 79 2102.07 9.09

ASU002 S

52

64.66 31.92 75.1 0.41 3.32 7.49 4.49 0.13 3.02 2252 65.5 2149 52.8 2172.02 40.24 2196.4 62 2149.06 2.6

ASU002 S

53

206.81 110.48 236 0.39 3.07 7.01 3.74 0.13 2.12 1837.3 62.3 2106 37.3 2112.51 33.2 2119.7 56 2105.56 0.78

Appendix 9. Summary of LA-IC-PMS U-Pb on zircon- NF002

U Th Pb* 208Pb* ±2σ 206Pb* ±2σ 207Pb* ±2σ 206Pb* ±2σ 207Pb* ±2σ 207Pb* ±2σ "Best

age"

%

ppm ppm ppm 232Th (%) 207Pb* (%) 235U* (%) 238U (%) 206Pb* (Ma) 235U (Ma) (Ma) disc.

Laser

spot

NF002 L

2

116.63 53.82 113.55 0.11 2.3 7.55 1.25 6.84 3.4 0.37 3.15 2129 22 2092 30 2129 4

NF002 L

3

85.24 19.96 76.46 0.13 4.21 7.53 1.64 7.35 3.31 0.4 2.87 2133 29 2156 30 2133 3

NF002 L

4

103 44.01 116.795 0.12 2.77 7.51 1.42 7.16 3.31 0.39 2.99 2139 25 2132 30 2139 1

NF002 L

5

109.73 55.08 73.14 0.12 3.34 7.58 1.55 7.16 3.75 0.39 3.42 2122 27 2133 33 2122 1

NF002 L

6

154.67 57.97 173.01 0.14 3.66 7.47 1.45 7.91 3.12 0.42 2.75 2149 25 2222 28 2149 9

NF002 L

7

120.89 41.65 140.65 0.13 2.7 7.6 1.68 7.45 3.09 0.41 2.59 2118 30 2167 28 2118 6

NF002 L

8

144.66 85.75 180.62 0.11 5.44 7.41 1.53 7.32 4.3 0.39 4.02 2163 27 2152 38 2163 1

NF002 L 130.22 44.3 135.9 0.12 2.87 7.65 1.65 7.03 3.08 0.39 2.59 2107 29 2115 27 2107 1

105

10

NF002 L

11

360.25 156.8 354.93 0.1 4.76 7.42 1.9 7.32 4.77 0.39 4.37 2161 33 2152 43 2161 1

NF002 S

13

48.86 1.67 15 0.14 12.64 7.54 2.34 7.55 4 0.41 3.24 2133 41 2180 36 2133 5

NF002 S

14

255.78 205.41 480.14 0.11 2.24 7.55 1.94 7.58 4.6 0.41 4.17 2129 34 2183 41 2129 6

NF002 S

15

56.52 0.79 8 0.16 18.27 7.66 2.02 7.12 3.5 0.39 2.861 2105 35 2127 31 2105 2

NF002 S

17

307.78 26.66 153.73 0.12 4.68 7.6 2.76 7.12 5.13 0.39 4.32 2118 48 2128 46 2118 1

NF002 S

18

135.46 46.89 134.72 0.11 3.22 7.46 3.5 7.2 5.11 0.39 3.72 2151 61 2137 46 2151 2

NF002 S

20

126.13 19.21 84.72 0.12 5.33 7.43 1.79 7.39 5.78 0.39 5.49 2156 31 2160 52 2156 0

NF002 S

21

105.38 40.18 106.45 0.12 4.55 7.66 1.72 7.38 4.34 0.41 3.98 2104 30 2160 39 2104 6

NF002 S

22

150.67 48.99 157.37 0.14 6.26 7.39 1.8 7.44 3.6 0.39 3.11 2167 31 2166 32 2167 0

NF002 S

23

114.01 8.66 64.66 0.11 7.23 7.57 2.33 7.38 5.7 0.4 5.2 2125 41 2159 51 2125 4

NF002 S

26

128.51 73.76 202.67 0.12 5.19 7.4 2.18 8.32 8.24 0.44 7.94 2166 38 2267 75 2166 12

NF002 S

30

503.23 144.01 427.24 0.11 3.6 7.53 2.88 6.91 5.07 0.37 4.18 2135 50 2101 45 2135 4

106