carbonate alteration of serpentinite in the murchison
TRANSCRIPT
CARBONATE ALTERATION OF SERPENTINITE IN THE MURCHISON
GREENSTONE BELT, KAAPVAAL CRATON : IMPLICATIONS FOR
GOLD MINERALIZATION
by
Moropa Ebenezer Madisha
DISSERTATION
submitted in fulfilment of the rquirements for the degree of
MASTERS of SCIENCE
in GEOLOGY
Faculty of Science at the
Rand Afrikaans University
Promotor : Prof. D.D. van Reenen
Johannesburg, November 1996
LIST OF CONTENTS Page number
ACKNOWLEDGEMENTS
ABSTRACT
CHAPTER 1 : INTRODUCTION 1
1 ARCHAEAN GREENSTONE BELTS 1
1.1 Introduction 1
1.2 Evolution of greenstone belts 1
2 ARCHAEAN LODE GOLD DEPOSITS AND THEIR RELATION TO DEFORMATION AND
WALL ROCK ALTERATION 2
2.1 Introduction 2
2.2 Metamorphism 2
2.3 Host rock lithology 2
2.4 Deformation 3
2.5 Systematics of wall rock alteration associated with ultramafic rocks 3
2.6 Fluid inclusion and stable isotope studies 5
3 SUMMARY 5
CHAPTER 2 : MURCHISON GREENSTONE BELT 6
1 INTRODUCTION 6
2 REVIEW OF PREVIOUS WORK 6
2.1 Locality 6
2.2 Regional geological setting 6
2.2.1 Lithology 6
2.2.2 Mineralization 9
2.2.2.1 The Antimony Line 9
2.3 Structural Geology 10
2.3.1 Pre-deformational structures 10
2.3.2 D 1 deformation 10
2.3.3 02 deformation 11
2.3.4 D3 deformation 11
3 PREVIOUS STUDIES RELATING TO ALTERATION AND MINERALIZATION 11
4 PRESENT INVESTIGATION 13
4.1 Statement of the problem and purpose of present study 13
4.2 Areas of investigation 14
4.3 Methods of investigation 14
4.3.1 Mapping and sampling 14
4.3.2 Petrography 14
4.3.3 Petrochemistry 15
4.3.4 C-isotope analyses 15
4.3.4 Fluid inclusions 15
CHAPTER 3 : FIELD RELATIONS AND PETROGRAPHY OF THE MAJOR LITHOLOGIES
AT THE PIONEER LOCALITY 16
1 INTRODUCTION 16
2 FIELD RELATIONS 16
3 PETROGRAPHY 23
3.1 Serpentinite and ophicarbonate 23
3.1.1 Metamorphic history of serpentinite 31
3.1.2 Serpentine veins 33
3.1.3 Fabric development in serpentinite and ophicarbonate 33
3.1.4 The nature of the precursor igneous rock 36
3.2 Talc-chlorite and talc-amphibole lithology 38
3.3 Quartz-carbonate rocks 38
3.3.1 The nature of the fabric in quartz-carbonate rocks 42
3.4 Mafic schists 45
3.3.1 Quartz-chlorite schist 45
3.3.2 Chlorite schist 45
3.3.3 Chlorite-amphibole schist 47
3.3.4 Epidote-bearing schist 47
4 SUMMARY 48
CHAPTER 4 : FIELD RELATIONS AND PETROGRAPHY OF THE MAJOR LITHOLOGIES
AT THE PIKE'S KOP LOCALITY 49
1 INTRODUCTION 49
2 FIELD RELATIONS 49
3 PETROGRAPHY 53
3.1 Serpentinite and ophicarbonate 53
3.2 The origin of the fabric in the serpentinite 56
3.2.1 The magnetite fabric in the massive serpentinite 56
ii
3.2.2 'The foliated serpentinite 56
3.5 The mafic schists 59
3.5.1 Chlorite-Ca-amphibole schist 59
3.5.2. Epidote-bearing schist 59
4 SUMMARY 59
CHAPTER 5 : FIELD RELATIONS AND PETROGRAPHIC DESCRIPTIONS OF THE
MAJOR ROCK TYPES AT COUNTY DOWN 60
1 INTRODUCTION 60
2 FIELD RELATIONS 60
3 PETROGRAPY 60
3.1 Chlorite-carbonate schist 60
3.1.1 The nature of the foliation in chlorite-carbonate schist 64
3.2 Quartz-carbonate rocks 64
3.2.1 The nature of the fabric in quartz-carbonate rocks 66
3.3 Mafic schists 68
3.3.1 Chlorite-Ca-amphibole schist 69
3.3.2 Epidote-bearing schist 69
4 SUMMARY 69
CHAPTER 6 : LITHOLOGICAL DESCRIPTIONS OF THE MAJOR ROCK TYPES AND
THE OCCURRENCE OF MINERALIZATION AT THE MONARCH SHAFT 70
1 INTRODUCTION 70
2 LITHOLOGICAL RELATIONS OF THE MAJOR ROCK TYPES FROM THE MONARCH SHAFT 71
3 PETROGRAPHY 72
3.1 Chlorite-quartz-carbonate schist 72
3.1.1 The nature of the foliation in chlorite-quartz-carbonate schist 74
3.2 Quartz-carbonate schists 74
3.2.1 The nature of the foliation in quartz-carbonate schists 79
3.3 Massive quartz-carbonate rock 79
4 TEXTURAL RELATIONSHIP BETWEEN CHLORITE AND FUCHSITE 81
5 MINERALIZATION 82
6 SUMMARY 88
CHAPTER 7 : MINERAL CHEMISTRY 89
1 Serpentine minerals 89
iii
2 Chromite 89
3 Talc 89
4 Chlorite 90
5 Carbonate minerals 92
CHAPTER 8 : BULK ROCK CHEMISTRY 93
1 INTRODUCTION 93
2 QUARTZ-CARBONATE ROCKS 93
3 SERPENTINITE AND OPHICARBONATE 95
4 COMPARISONS BETWEEN QUARTZ-CARBONATE ROCKS, SERPENTINITE AND
OPHICARBONATE ROCKS 95
5 DISCUSSION 95
CHAPTER 9: THE NATURE OF THE FLUID PHASE INVOLVED DURING SERPENTINIZATION
AND CARBONATE ALTERATION OF THE ULTRAMAFIC LITHOLOGIES FROM THE MGB 97
1 INTRODUCTION 97
2 THE NATURE OF THE FLUID PHASE ASSOCIATED WITH SERPENTINIZATION AND PEAK
METAMORPHIC CONDITIONS 97
2.1 Peak metamorphic assemblage of serpentinite 97
2.2 Composition of the fluid phase during serpentinization and peak metamorphism 100
3 THE COMPOSITION OF THE FLUID PHASE ASSOCIATED WITH THE CARBONATIZATION
OF THE SERPENTINITE 103
4 THE FLUID PHASE ASSOCIATED WITH MINERALIZED VEINS FROM THE MONARCH
MINE 104
5 SUMMARY 105
CHAPTER 10 : FLUID INCLUSION AND STABLE ISOTOPE STUDIES 106
1 INTRODUCTION 106
1.1 Sample selection for fluid inclusion study 106
1.2 Fluid inclusion types 107
1.3 Sample selection for stable isotope studies 107
2 PETROGRAPHY OF FLUID INCLUSIONS 108
2.1 Ophicarbonate rocks (Sample P20) 108
2.2 Quartz-carbonate rocks (Sample P14) 108
2.3 Mineralized quartz-carbonate rocks (Sample 05) 111
3 HEATING AND FREEZING RESULTS 115
iv
3.1 Ophicarbonate rocks 115
3.2 Quartz-carbonate rocks 118
3.3 Mineralized quartz-carbonate rocks 118
4 STABLE ISOTOPE DATA 122
5 DISCUSSION 125 6 SUMMARY 128
CHAPTER 11 : SUMMARY AND CONCLUSIONS 130
REFERENCES 133
APPENDICES I - IV 147
v
ACKNOWLEDGEMENTS
Dr. J.F. van Schalkwyk is thanked for giving me the opportunity to do this project and for his
continuous support, encouragement and supervision. Prof. D.D. van Reenen is thanked for taking
over as my supervisor after the departure of Dr. J.F. van Schalkwyk and for his encouragement and
support towards the completion of the project. Prof., without your "get finished" push I doubt I could
have completed the project.
Financial support from FRD, RAU and EOC is gratefully acknowledged. Special thanks to JCI for
providing access to their prospects, accommodation during field work and helpful information
(including surface and underground maps). Anglovaal is also thanked for providing some valuable
information. The Geological Survey and Rocklabs provided XRF analyses for bulk rock
compositions. The stable isotope data was provided by Dr. C. Hards from UCT.
The following people are thanked for their technical support and contribution during the project; Prof.
C. Roering, Prof. J.M. Barton, Mr H. Jonker, K. Mokgatlha, M. Ruygrok, H. Dirr, S. Theron, M.
Buxton, V. Naidoo, N. Day, P.A. Pitts, A. Bellenbach, M. Baloyi, D. Selepe and H. Leteane.
Finally I want to thank my father, mother and sisters, Mabatho, Lebogang and Busisiwe, for their
undying support throuhgout my carreer. To Moeletsi and Mpho, your assistence in many different
ways is appreciated. Many thanks to my colleagues and friends for their encouragement.
vi
ABSTRACT
The Murchison Greenstone Belt, like other greenstone belts, has a complex history which involves
intense deformation, extensive alteration and mineralization. It is known for its stibnite and gold deposits
which are hosted by a semi-brittle-ductile shear zone, the Antimony line. The mineralization occurs
dominantly as vein-filled fractures hosted by more competent quartz-carbonate rocks and, therefore,
resembles the occurrence of other Archaean lode gold deposits hosted by ultramafic rocks. The
ultramafic lithologies display a characteristic alteration pattern consisting of serpentinite talc-
carbonate —> quartz-carbonate-(±fuchsite) rocks. The alteration zonation generally displays an
increasing intensity of carbonatization towards the mineralization hosted by quartz-carbonate rocks.
Petrographic studies of the serpentinite from the Murchison Greenstone Belt indicate that it has been
subjected to prograde metamorphism. The phase relation studies suggests that the peak metamorphic
assemblage characterized by the presence of antigoritettalc i tchlorite ±tremolite eqilibrated in the
presence of an H 20-rich fluid phase containing <30 mol % CO 2. The peak metamorphic assemblage is
progressively replaced by carbonate-bearing assemblages as a result of interaction with a CO 2-rich fluid
phase. Quartz-carbonate rocks which comprise of quartz+magnesite+ dolomite, therefore, represent the
final alteration products of the serpentinite and equilibrated at X c02 >0.7 at 550°C. The carbonatization
process could have also been accompanied by the introduction of K, Na and possibly CaO. The
alteration fluids were channelled through microshear zones and fractures indicating the significance of
deformation. The deformation can be correlated to Boocock's D 1 event which trends ENE and has
subvertical dips.
The mineralization occurs in the form of quartz-carbonate veins which are restricted to the more
massive and competent quartz-carbonate rocks. These mineralized veins occupy brittle fractures
developed as a result of later deformation. The presence of dolomite in these veins that cut across the
quartz-carbonate assemblages cannot be explained by the phase relations. The occurrence of
mineralization is largely controlled by the physical or mechanical properties of the rocks which are
influenced mainly by alteration. The favourable occurrence of mineralization in the quartz-carbonate
rocks relative to the serpentinite and talc-carbonate rocks indicates the significance of alteration and
deformation in the localization of mineralization.
vii
Stable isotope and fluid inclusion studies indicate that the alteration zonation, serpentinite talc-
carbonate -+ quartz-carbonate rocks, is a result of a single alteration event considered to be induced
by fluids of marine origin characterized by 6 13C signatures between -1.64 to 0.90 per mil and salinity
values ranging from 3.46 to 13.45 wt % NaCI. The stable isotope and fluid inclusion data further show
that the fluid phase associated with the stibnite-gold mineralization is characterized by light 6 13C
values, ranging from -6.83 to -5.76 per mil, typical of either a deep-seated mantle or a magmatic
source and a high salinity dominantly between 24.24 and 25.85 wt% NaCI equivalent. Such high
salinity fluids of mantle or magmatic origin associated with vein hosted gold mineralization are rarely
documented in literature.
A comparison of the fluid phase associated with the carbonate alteration of the serpentinite with the
fluid phase associated with the mineralized veins clearly indicate different sources. High salinity and
lighter 6 130 values clearly distinguish the mineralizing fluid from the lower salinity fluid with heavier
6 13C signatures that caused the carbonatization of the serpentinite. This suggests that the carbonate
alteration assemblages of the precursor serpentinite and the mineralized veins evolved as a result of
interaction with fluids of different salinities and source, i.e. different fluids.
viii
CHAPTER 1 : INTRODUCTION
1 ARCHAEAN GREENSTONE BELTS
1.1 Introduction
Greenstone belts represent the oldest volcano-sedimentary sequences preserved on the earth's crust.
They occur on Archaean cratons and range in age from 3.4 - 2.3 Ga (Windley, 1977). Greenstone belts
vary considerably in size but are commonly long, narrow and linear in shape. They consist mainly of
ultramafic, mafic and felsic volcanics, intruded by minor syntectonic plutons and surrounded by massive
to foliated trondhjemitic-tonalitic-granodioritic granitoids. Some of the plutonic rocks represent the
basement onto which the volcanics were extruded (Condie, 1981). Late intrusions include both felsic
and mafic igneous rocks (Colvine et al., 1988). The volume of sedimentary sequences associated with
greenstone belts is variable and overlie the volcanics (igneous succession) structurally and / or
stratigraphically (Hunter, 1991).
1.2 Evolution of oreenstone belts
A major controversy exists as to the origin and the regional tectonic setting of the greenstone belts and
a number of models have been proposed to account for their evolution. The classical and earlier models
generally considered greenstone belts to be extremely thick volcanic and sedimentary stratigraphic
successions, metamorphosed at greenschist facies and characterized by synforms enclosed within
granitic and gneissic rocks (Anhaeusser, 1971). According to these models, density inversion and
induced diapirism account for the present day structure of greenstone belts.
Recent studies have, however, shown that greenstone belts are extremely complicated and that their
component volcanic and sedimentary successions have formed in different tectonic settings (De Wit &
Ashwal, 1986) that vary from continental platforms to oceans (Veamcombe, 1991). Some of the recent
investigations (Condie, 1980a, 1981; Card, 1986; Hoffman, 1991; Veamcombe, 1991; De Wit, 1991; De
Wit et a, 1992) suggest that plate tectonic-related processes that involve regional thrusting can
account for the evolution of greentone belts. The plate tectonic models are supported by compositional
similarities between the Archaean greenstone belts and modem arcs systems (Percival & Card, 1986).
Although details of the models vary depending on the stratigraphic sections (volcanics overlain by
sediments) and on the tectonic environment, they are generally associated with convergent plate
1
boundaries. Archaean greenstone belts have been interpreted as back-arc basins (Tamey et al., 1976;
Condie & Harrison, 1976; Windley, 1977) and island arcs (Veamcombe, 1991).
2 ARCHAEAN LODE GOLD DEPOSITS AND THEIR RELATION TO DEFORMATION AND WALL
ROCK ALTERATION
2.1 Introduction
Greenstone belts account for some of the world's economical mineral productions (Windley, 1977;
Candle, 1981) and are important hosts to lode gold deposits, which are responsible for a significant
proportion of the world's gold production (Robert et al., 1991).
2.2 Metamorphism
Assemblages from greenstone sequences display a wide range of metamorphic conditions, varying from
greenschist to granulite fades. The majority are, however, characterized by sub-greenschist to
greenschist facies (Windley, 1977) with amphibolite facies conditions more common as contact aureoles
surrounding intrusive plutons. Most of the gold mineralization appear to be hosted by sequences that
recorded greenschist and amphibolite fades conditions and only a few deposits have been reported
from upper-amphibolite to granulite facies terranes (Phillips, 1990; Groves et al., 1989; Groves, 1991).
2.3 Host rock litholoqv
Although it has been suggested that certain lithologies are more favourable host rocks for gold
mineralization (eg. Phillips and Groves, 1983; Groves et al., 1989), a number of studies have shown
that mineralization is not restricted to a specific lithological unit or stratigraphic level within a greenstone
succession (eg. Kerrich and Fyfe, 1981; Colvine, 1983; Kishida and Kerrich, 1987; Colvine et al., 1988).
Archaean lode gold deposits are, however, characterized by zones of intense deformation associated
with extensive wall rock alteration. This demonstrates that gold mineralization is a function of the
interaction between deformation and alteration, rather than lithological control (Kerrich, 1983, Kerrich et
al., 1984; Kishida and Kerrich, 1987).
2
2.4 Deformation
Greenstone belts are characterized by intense deformation, commonly displaying a polyphase history of
faulting and folding that often resulted in structural repetition (Lowe and Byerly, 1986). Gold
mineralization is associated with zones of anomalous high strain characterized by linear shear zones of
brittle-ductile nature (Kerrich and Allison, 1978; Boocock et al., 1984; Nesbit et aL, 1986; Eisenlorhr et
al., 1989; Golding et aL, 1989). Small scale structures within these deformational zones, e.g. fractures,
shear surfaces, cracks and fold hinges, can be shown to have played an important role in localizing the
gold mineralization (Colvine et al., 1988). Deformational zones that host gold deposits are closely
associated with and comprise zones of extensive wall rock alteration (Fyon and Crocket, 1982; Kishida
and Kerrich, 1987; Colvine et aL, 1988). Deformation is, therefore, of fundamental importance to the
localization of mineralization as it provides the pathways along which alteration fluids flow and also
controls both the rate and the volume of fluid transport. Secondary permeability is, therefore, related to
the dimensions and intensity of alteration (Cox et al., 1986; Colvine et al., 1988).
2.5 Systematics of wall rock alteration associated with ultramafic rocks
Most Archaean gold deposits display a consistent wall rock alteration zonation which is characterized by
variation in carbonate and silicate mineralogy, suggesting a strong influence of CO2 and alkali (K and
Na) contents of the alteration fluids on the subsequent mineral equilibria from respective alteration
zones (Dube et aL, 1987; Clark et aL, 1989). The alteration zonation envelopes the orebody and the
intensity of alteration increases with proximity to the mineralization (Kerrich, 1983; Robert and Brown,
1986; Dube et aL, 1987; Neal and Phillips; 1987; Colvine et al., 1988; Moritz and Crocket; 1991). This
indicates a close relationship between the mineralization (mostly contained in quartz and quartz-
carbonate veins) and hydrothermal alteration of the wall rock.
In all the occurrences where a serpentinite represents the host rock, a prominent alteration pattern
consisting of serpentinite talc-carbonate quartz-carbonate is evident (eg. Pearton, 1980 -
Murchison Greenstone Belt; Kishida and Kerrich, 1987 - Kerr Addison deposits, Ontario; Bohlke, 1989 -
Alleghany deposits, Califonia; de Ronde et aL, 1992 - Barberton greenstone belt). Pearton (1980) and
de Ronde et aL (1992) suggested that this alteration pattern is a result of at least two stages of
alteration; an early sea-floor event which resulted in talc-carbonate alteration of the serpentinite and a
later hydrothermal event which produced quartz-carbonate assemblages. Kishida and Kerrich (1987)
and Bohlke (1989), however, considered the alteration pattern as the result of the interaction of a
serpentinite with CO2-rich fluids during a single event. The different zones of the alteration sequence
reflect variations (increase) in fluid-rock ratios.
3
with CO2-rich fluids during a single event. The different zones of the alteration sequence reflect
variations (increase) in fluid-rock ratios.
Pearton (1980) and De Ronde et aL (1992) generally considered the mineralization as the result of a late
hydrothermal alteration that also formed quartz-carbonate alteration. Kishida and Kerrich (1987)
considered alteration and associated gold mineralization to result from repeated cycles of hydraulic
fracturing, fluid penetration, and fluid-rock interaction.
Detailed metamorphic studies of the wall rock alteration which could provide useful information on the
physical and chemical conditions of the mineralization were, however, done only in a few cases (e.g.
Kishida and Kerrich, 1987; Bohlke, 1989, Davies et al., 1990; Schandl and Wicks, 1990). These
investigations related the alteration zonation (serpentinite --> talc-carbonate —> quartz-carbonate) to
isobaric divariant fields in T- X co2 phase diagrams and suggested that it is the result of the introduction of
an externally derived CO 2-bearing fluid. The variation in CO 2 content of the co-existing fluid phase is
explained by a combination of the intensity of deformation and the rate of infiltration of the external fluid.
Although these studies made an important contribution to the understanding of the wall rock alteration
associated with lode gold deposits, they stil neglected the wealth of information contained by the
precursor lithology (unaltered or semi-altered serpentinite). This could allow a better understanding of
the relative timing of the events through an intergration of the tectono metamorphic evolution of the host
rock with alteration and associated mineralization.
Mineralization along the Antimony line in the Murchison greenstone belt is characterized by the fact that
it (mineralization) is hosted virtually exclusively by quartz-carbonate rocks which represent carbonatized
ultramafic lithologies (serpentinites).
In the present investigation, the alteration of ultramafic rocks is considered because they (ultramafic
rocks) are generally characterized by simple bulk rock compositions, contained almost entirely within the
system Si02-CaO-MgO-(H 20-0O2). The composition of ultramafic rocks is susceptible to changes in T-
P-X condition and they can also record deformation events at various stages of their history (Williams,
1979; Wicks, 1984a). It is a known phenomenon that ultramafic rocks in the Archaean greenstone belts
have undergone extensive serpentinization and carbonatization. Serpentine minerals have a limited
stability in the presence of CO 2-bearing fluids and this should contribute to the understanding of the
existing fluid phase of variable CO 2 content during carbonatization. Ultramafic rocks are, therefore,
suitable to study the tectono-metamorphic history of greenstone belts (Evans, 1977; Dymek etal., 1988;
van Schalkwyk, 1991).
2.6 Fluid inclusion and stable isotope studies
Archaean lode gold deposits have been studied in great detail during the last decade. The majority of
these studies concentrated on mineralized quartz-carbonate veins while the wall rocks that host these
veins received little attention. Fluid inclusion and stable isotope studies from the mineralized veins
suggest that Archaean auriferous fluids are characterized by the following fluid composition :
low salinity (5 - 6 wt% NaCI equiv.), although earlier studies (Ho et al., 1985; Hendequist and Henley,
1985) indicated salinity values of <2 wt % NaCI in the fluid.
15 - 30 mol % CO 2 .
0.7 - 0.9 g/cm 3 density.
Temperature and pressure of entrapment in the range of 200 - 400°C and 1 - 2 kbar, respectively.
613C signatures generally vary between -2 and -4 per mil (eg. Golding and Wilson, 1983; Kishida and
Kerrich, 1987; Groves et al., 1988; Golding et al., 1989; Schandl and Wicks, 1991; de Ronde et al.,
1992). Groves et al. (1988) have documented two distinct 6 13C values for carbonates in the Norseman-
Wiluna greenstone belt (W. Australia). They associate isotopically light carbonates (-3 to -7 per mil) to an
earlier CO2 alteration and the heavier carbonates (-2 to -4 per mil) with the gold mineralization. Some
researches did, however, show that the 513C values of the wall rock alteration and mineralization are
similar (eg. Kishida and Kerrich, 1987; de Ronde et al., 1992).
3 SUMMARY
Most of the published isotope and fluid inclusion studies have not been related to detailed metamorphic
studies of the wall rock. An exception is the work by Kishida and Kerrich (1978) who integrated detailed
metamorphic studies with stable isotope data to constrain the nature of the fluid system and the possible
role of fluids in precipitating gold deposits. Detailed metamorphic studies of the alteration integrated with
stable isotope and fluid inclusion studies of the wall rock and mineralization should provide a better
understanding of the Archaean lode gold deposits.
5
CHAPTER 2 : MURCHISON GREENSTONE BELT
1 INTRODUCTION
The Murchison Greenstone Belt (hereafter referred to as MGB), like other greenstone belts, has a
complex history which involves deformation, serpentinization, prograde recrystallization and
carbonatization, as a result of interaction with CO 2-bearing fluids (Viljoen, 1979; Muff and Saager, 1979;
Pearton, 1980). The MGB is known for its stibnite and gold deposits, which are hosted within a shear
zone (the Antimony line) that is characterized by highly altered rock assemblages. The mineralization
occurs as vein-filled fractures hosted by more competent quartz-carbonate rocks (Viljoen, 1979;
Boocock et al, 1984; Vearncombe et al, 1988) and, therefore, is similar to other lode gold deposits
hosted by ultramafic rocks.
2 REVIEW OF PREVIOUS WORK
2.1 Locality
The MGB is located in the north-eastern part of the Kaapvaal craton, South Africa (Fig. 2.1). It
represents the second largest greenstone belt, after the Barberton greenstone belt, on the granite-
greenstone terrane adjacent to granulite facies Southern Marginal Zone (SMZ) of the Limpopo Belt (Fig.
2.1). It is approximately 150 km in length and has a maximum width of 15 km.
2.2 Regional geological setting
The MGB, flanked by Archaean granite and granitoid gneisses in the south and north, is partially overlain
by Lower-Proterozoic sediments and volcanics of the Transvaal Supergroup in the west. In the east, it
breaks up into two enclaves and is unconformably overlain by the Upper-Palaeozoic and Mesozoic rocks
of the Karoo Sequence in the Kruger National Park (Vearncombe, 1992; Fig. 2.2).
2.2.1 Lithology
The MGB consists of a sequence of schistose carbonated ultramafic, mafic and felsic lavas and
subvolcanic rocks, and sedimentary rocks and in the north, the Rooiwater meta-igneous complex
6
• Jonannesourg
ZIMBABWE
BOTSWANA it•
./*
•
• . ■ ,..•
7• 6.•
REPUBLIC OF SOUTH AFRICA
0 100 200 400 km
Fig. 2.1. Location of the MGB on the Kaapvaal Craton. BGB - Barberton Greenstone Belt; SMZ -Southern Marginal Zone.
(Vearncombe et al., 1986, 1987. 1988; Fig. 2.2). Various dyke intrusions have also been recognized
(Pearton, 1980). The metamorphic grade in the Murchison sequence varies from greenschist to upper-
amphibolite facies (Pearton and Viljoen, 1986; Vearncombe at al., 1988).
The Murchison Belt can be divided into subregional domains on the basis of lithology, metamorphism
and structure (Fig. 2.2). A brief description of these domains, from north to south, is given below :
The Silwana's amphibolite unit comprises highly deformed hornblende schists, amphibolite gneisses
and minor biotite schists of the Letaba strike-slip shear zone (Fripp et al., 1980; Vearncombe et al.,
1988).
The Rooiwater meta-igneous Complex is a layered, differentiated body which intruded along the
northern flank of the Murchison Belt and, is in turn, intruded by the surrounding granites (Pearton and
7
8
Fig.
2.2
. Reg
ion
al g
eolo
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al m
ap o
f the
MG
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Aft
er V
iljoe
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197
8).
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a C ,...
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Viljoen, 1986). the Rooiwater Complex consists of two units, the Novengilla Gabbro-anorthosite series
which contains discontinuous magnetite and sulphide-bearing layers, and the intrusive Free State
homblende granite. The Rooiwater complex has been metamorphosed to amphibolite facies
(Veamcombe et al., 1988).
The Rubbervale Formation comprises quartz-porphyroclastic schist interpreted to be quartz-feldspar
porphyry (Vearncombe, 1988) and felsic volcanic schists. Copper-zinc massive sulphide deposits have
been reported in the felsic schists (Vearncombe, 1988; Pearton and Viljoen, 1986).
The Murchison schist unit consists of altered ultramafic, mafic, and metasedimentary schists and
forms the largest domain of the MGB. Rock types present include serpentinites, a variety of mafic
schists, chert, iron formations and quartz-mica schists. Biotite schists derived from ultramafic precursor
commonly occur in contact with intrusive granitoids (Vearncombe, 1988).
The La France schist unit comprises intensely deformed quartzite, conglomerate and quartz-mica
schist. Garnet and kyanite occur locally in quartz-mica schists.
2.2.2 Mineralization
The MGB hosts a wide range of mineral deposits that include gold, antimony, copper-zinc massive
sulphides, emeralds, mercury and titaniferous magnetite. Economically, the most important are the gold
and antimony mineralization, concentrated along a linear zone called the Antimony line.
2.2.2.1 The Antimony Line
The Antimony line forms a central feature of the Murchison schists unit (Vearncombe, 1988) (Fig 2.2). It
trends ENE and is 50 to 250m wide. It also represents a semi-brittle zone in a ductile shear zone
(Boocock et al., 1984, 1988; Vearncombe et al., 1988) characterized by intensely deformed and
carbonatized mafic and ultramafic units of the greenstone sequence. These include quartz-chlorite, talc-
chlorite, talc, talc-carbonate and quartz-carbonate schists.
The Antimony line, therefore, represents a zone of high strain, associated with extensive alteration and
gold and antimony mineralization. The host rock and alteration zonation resemble the occurrence of
Archaean lode gold deposits hosted by ultramafic rocks in greenstone belts (eg. Kishida and Kerrich,
1987; Colvine et al., 1988; Bohlke, 1889; de Ronde et al., 1992).
9
2.3 Structural Geology
The MGB, like other granite-greenstone belts, has experienced intense deformation and a number of
deformation events have been recognized (Viljoen et al., 1978). The Antimony line is considered to
have developed early in the deformation history (as a result of Di event) of the greenstone belt
(Boocock, 1984; Boocock et al., 1984; Veamcombe et al., 1988).
The earliest account of the structural geology of the MGB was given by Van Eeden (1939) who
interpreted it as a major, tightly folded, syncline and regarded the Antimony line as a fault.
Viljoen et al. (1978) and Viljoen (1979) investigated the structural relationships along the Antimony line.
They recognized two major deformation events and a later minor event, and suggested that the first
event (D1) is represented by ENE-trending isoclinal folds and associated pervasive axial planar
cleavage. The second deformational event (D 2) resulted in E-W-trending folds with an associated axial
planar cleavage, while the third event (D 3) is represented by northward-trending small scale kink bands
and chevron folds.
More recent structural investigations along the Antimony line by Boocock (1984), Boocock et al. (1984),
Veamcombe (1988); Veamcombe et aL (1988) also recognized three deformational events (D1, D2 and
D3) that are summarized below (Boocock, 1984 and Boocock et aL, 1984).
2.3.1 Pre-deformational structures
Pre-deformational features, interpreted as bedding, have been recognized. These include graded units
that are commonly separated by thin shale partings within the quartzites, and coarse-grained pebble
bands that form scour channels which may truncate the bedding planes in the underlying units.
2.3.2 Di deformation
The Di deformation event is represented by isoclinal folding about ENE-trending axial planes. The
heterogeneous strain distribution during Di led Boocock et aL (1984) to sub-divide the Antimony line into
low, intermediate and high strain domains. The low strain domain is developed in the most competent
lithologies (including banded iron-formation, chert and massive quartz-carbonate rocks) that have been
folded around F 1 folds with ENE trending axes. Si axial planar cleavage, which is the most dominant
structural feature of the Antimony line, is associated with these fold axes. It trends ENE-WSW to E-W
and dips between 80°N to 80°S over most of the area (Boocock, 1984). Competent lithologies are also
10
strongly boudinaged in the S i plane. Both small and large scale F, folds have been observed. Brittle
fractures that developed in competent quartz-carbonate rocks led to quartz and quartz-carbonate veining
in tensional fractures.
In the intermediate strain domain, largely confined to banded chlorite phyllite, small scale folding with a
related axial planar cleavage is dominant.
The high strain domain, restricted to zones of highly schistose chlorite phyllite, talcose schist and
schistose quartz-carbonate rocks, is characterized by a pervasive steeply dipping ENE-trending
schistosity. F, folds may be completely overprinted by the S i schistosity. Folded quartz veins with
boudinaged limbs and detached fold closures are preserved as isolated rodded structures in the S i
cleavage planes (Boocock et al., 1984).
2.3.3 D2 deformation
During D 2 , S i was folded and crenulated about the E to ESE-trending axes. The F 2 folds and the S 2
crenulations display an 's' shaped asymmetry and generally plunge subvertically. F 2 folds vary from
open to tight, and are characterized by small wavelengths which are well-manifested in more competent
rocks. The S2 schistosity trends E to ESE and dips dominantly between 80°N and 80°S. S 2 becomes
more prominent from east to west in the region of the Antimony line and is the dominant structural
feature in the Gravelotte quarry (Boocock, 1984).
2.3.4 D3 deformation
The third deformation event, D 3 , is characterized by vertical conjugate kink bands trending NNE and NW.
Small scale box folding has also been observed (Boocock et al., 1984).
Brittle fracturing, folding and dyke intrusion are common and may be considered to represent the post-D 3
deformation structures.
3 PREVIOUS STUDIES RELATING TO ALTERATION AND MINERALIZATION
Since the first discovery of gold in 1869, there has been a number of geological investigations in the
MGB. Most of these investigations focused on the general geology, structural geology and occurring
mineral deposits, although some also made contributions to the alteration and its relationship to gold and
antimony mineralization.
11
Earlier studies considered the mineralization to have originated from hydrothermal solutions related to
the intrusion of a magmatic body, the 'Old Granite' (Le Grange, 1929; Willemse, 1935; Mendelssohn,
1938; Van Eeden et aL, 1939). These authors also recognized a close spatial association of high
concentrations of antimony mineralization with extensive carbonate alteration zones. Mendelssohn
(1938) and Van Eeden et al. (1939) noted that these extensively carbonated zones occur within a
pervasively deformed zone, the Antimony line. A sedimentary origin was suggested for the carbonate-
bearing rocks.
Muff (1976) and Muff and Saager (1979) considered the alteration and associated mineralization as the
result of two carbonatization events. The primary carbonatization occurred during a very early stage of
rock formation, i.e. a syn-sedimentary and / or diagenic process during deposition and, therefore,
represents a pre-metamorphic occurrence of the carbonate horizons. The authors suggested that the
hydrothermal process was related to late-stage volcanic activity in a subaqueous environment. The
secondary carbonatization stage occurred syn- to post-metamorphism and resulted in the remobilization
and reconstitution of carbonates and quartz, which formed quartz-carbonate and fracture-filled veins.
These authors considered mineralization to have been effected by late stage volcanic activity. Minnit
(1975) proposed a similar model in which mineralization was formed by hydrothermal activity in an
exhalative volcanogenic hot-spring environment, coeval with the formation of the Murchison sequence.
Subsequent work by Viljoen et aL (1978), Viljoen (1979), Pearton (1980), Pearton and Viljoen (1986)
and Abbot et aL (1986) generally indicated that the mineralization is associated with extensive wall rock
alteration located in areas of structural disturbances, along the Antimony line. They noted the following
alteration pattern : talc and talc-carbonate zone -3 quartz-carbonatetfuchsite zone, with the
mineralization being restricted to the latter zone.
Pearton (1980) interpreted the alteration pattern to be the result of the alteration of a peridotitic
komatiite by two carbonatization events. The first event resulted into the formation of talc-carbonate
schists by chemical decomposition induced by percolating sea waters, and the second event resulted in
the formation of quartz-carbonate rocks from talc-carbonate schists by hydrothermal alteration. The
potassic-metasomatism, described by Pearton (1978), and associated mineralization are thought to
have occurred during the second event of carbonatization.
Boocock (1984) studied the lithologies, structure and mineralization along the Antimony Line. He
considered the carbonate and silica alteration of the Antimony Line and the enrichment of antimony and
12
gold to be the result of convection of sea water through the rock pile in a sub-sea environment, with
minor remobilization of the mineralization during subsequent deformation.
4 PRESENT INVESTIGATION
4.1 Statement of the problem and purpose of present study
The previous work on the MGB covered the general geology, structural investigation and mineralization
in the area. However, these studies made limited contributions to the relationship between deformation,
alteration and associated mineralization, a significant feature of Archaean greenstone belts.
Earlier studies (eg. Mendelssohn, 1938; van Eerden et al., 1939) on alteration and mineralization along
the Antimony line considered the carbonate rocks to be of sedimentary origin and, therefore, largely
ignored the ultramafic nature of the carbonate-bearing rocks and the occurrence of alteration zonation
associated with these rocks.
Recent studies (eg. Viljoen, 1979; Pearton, 1980) considered the quartz-carbonate rocks to represent
altered ultramafics, with the alteration being a result of two carbonatization events. Mineralization is
considered to be associated with the later carbonatization event. Also, stable isotopes and fluid
inclusions related to the mineralization and altered wall rock, have not been studied in detail.
The purpose of the present investigation is to integrate the metamorphic, stable isotope and fluid
inclusion studies of the wall rock and associated mineralized veins in an attempt to explain the
occurrence of mineralization. A detailed metamorphic study of serpentinite is done in order to relate its
alteration (carbonatization) and deformation history. This data will contribute to a better understanding of
the relative timing of, and the chemical and physical conditions of, the mineralization.
The following aspects were therefore examined in detail :
the timing of alteration (carbonatization) of serpentinite with respect to peak metamorphic conditions
and deformation
the alteration pattern associated with ultramafic rocks (serpentinite to quartz-carbonate±fuchsite)
the relative timing of mineralization with respect to alteration and deformation
the evolution of mineralization as a result of either the same alteration fluids or of a different fluid
event.
13
4.2 Areas of investigation
To establish the alteration pattern associated with the serpentinite and the timing of alteration relative to
peak metamorphic conditions, localities which contain serpentinite and quartz-carbonate rocks were
selected. These localities include Pioneer, Pike's Kop and County Down (Fig. 2.2).
To determine the relationship of the alteration zonation with mineralization, a well-known mineralized
complex, the Monarch Mine (Fig. 2.2), was selected.
4.3 Methods of investigation
4.3.1 Mapping and sampling
A total of 95 representative samples of all major lithologies were carefully selected from Pioneer, Pike's
Kop and County Down. Oriented samples were collected from surface outcrops and from trenches. A
number of uncontrolled samples were also collected from old diggings. Maps provided by JCI were used
to locate the samples at the Pioneer and County Down localities. Detailed mapping was also undertaken
and the existing maps were modified where necessary (Figs 3.1 and 5.1). At Pike's Kop, a sketch map
was used to locate the samples (Fig. 4.1). At the Monarch Mine, a total of 44 samples were collected
from underground exposures and from two borehole cores; Monarch 2534 from the 21 st level and
Monarch 2458 from the 9th level. Monarch 2458 intersected the Free State ore body. Underground
sampling and mapping of the contact of the Free State ore body with the surrounding rocks was done in
the cross-cut no. 5, block 956, 9 th level. Photographs of specific exposures were taken. Planar fabrics
were also measured and plotted on the maps.
4.3.2 Petrography
A detailed petrographic study of thin sections and polished thin sections (a total of 143) was carried out.
This was done in order to establish a temporal relationship between the metamorphic and deformational
events and the introduction of the metasomatizing fluids that altered the serpentinite and resulted in the
formation of gold-bearing quartz-carbonate veins.
The P-T-X conditions that prevailed during metamorphism, carbonate alteration and mineralization were
estimated with reference to an isobaric T- Xc0 phase diagram. This diagram was calculated for pure
phases using the program GEOCALC (Perkins et al., 1986).
14
4.3.3 Petrochemistry
To supplement the field and petrographical studies, 23 carefully selected samples were used for
microprobe analyses. A total of 232 chemical compositions of the important minerals were determined
with a Cameca Camebax electron microprobe located in the RAU Geology Department. A 15kV
accelerating potential was used with a 10nAmp beam current and beam diameter of approximately
31.im. Structural mineral formulae were calculated using the MINFILE program (Afifi and Essene, 1988).
A complete list of microprobe analyses is included in appendix I.
Bulk rock analyses of major and minor elements of 33 representative samples from different localities
were done by the Councel for Geosciences. Bulk rock compositions for major elements of 4 samples
were also determined by Rock Labs. A list of bulk rock analyses is included in appendix II.
4.3.4 C-isotope analyses
CO2 was extracted from carbonate minerals in ophicarbonate and quartz-carbonate rocks (19 samples)
and in mineralized veins (2 samples), and was analyzed for 8 13C isotopes in order to constrain the
possible origin of CO2-bearing alteration and mineralization fluids. The 8 13C isotope analysis was was
done by Dr. C. Harris at the department of Geochemistry, University of Cape Town.
4.3.4 Fluid inclusions
Double polished thin sections from both the wall rock alteration assemblages and mineralized veins
were prepared for fluid inclusion studies. Heating and freezing experiments were carried out using a
fluid inclusion adapted USGS HF stage in combination with a Nikon microscope located in the RAU
geology department. Both heating and freezing experiments were done on the same inclusions, with low
temperature experiments done first so as to avoid possible decrepitation or leakage.
15
CHAPTER 3 : FIELD RELATIONS AND PETROGRAPHY OF THE MAJOR
LITHOLOGIES AT THE PIONEER LOCALITY
1 INTRODUCTION
The Pioneer prospect is located approximatelly 33 km ENE of Gravelotte (Fig. 2.2). Rock types at the
locality include serpentinite, ophicarbonate (characteristically an inhomogeneous rock with serpentine
and carbonate components; terminology after Trommsdorff and Evans, 1977), talc-chlorite and talc-
amphibole-bearing lithologies and quart-carbonate rocks. Outcrops of these rock types are
enveloped by a variety of mafic schists with intercalated banded iron-formation. Quartz and/or
carbonate veins are not uncommon in the area (Fig. 3.1).
2 FIELD RELATIONS
The exposure is generally poor and outcrops of schistose and carbonate-bearing lithologies are
intensely weathered. Outcrops of serpentinite and ophicarbonate are restricted to the south-western
portion of the prospect where they occur as massive lensoid body elongated subparallel to the fabric
displayed by the surrounding rocks. Field relationships and sample positions within serpentinite and
ophicarbonate bodies are shown in figures 3.1 and 3.2. Outcrops of serpentinite and ophicarbonate
weather to a brownish colour and the ophicarbonate commonly displays a pitted surface representing
weathered carbonate porphyroblasts (Fig. 3.3). Pods of relatively massive ophicarbonate with fewer
isolated porphyroblasts are also present (Fig. 3.4). Serpentinite and ophicarbonate outcrops
frequently display a faint fabric defined by oriented stringers of magnetite which can be up to 2.5 mm
thick and 20 cm long (Fig. 3.5). Towards its southern contact with the surrounding weathered mafic
schists (Fig. 3.1), outcrops of serpentinite and ophicarbonate contains a stockwork of carbonate-filled
veins (Fig. 3.6). There also appear to be an increase of thin (< 0.5 cm) cross-fibre serpentine veins
towards the contact. Both the carbonate-filled and serpentine veins are randomly orientated.
Talc-chlorite and talc-amphibole-bearing lithologies crop out in close proximity to outcrops of massive
porphyroblastic serpentinite and ophicarbonate (Fig. 3.1). As a result of poor exposure, the field
relationships of these lithologies with the serpentinite or ophicarbonate are uncertain. Talc-chlorite
and talc-amphibole-bearing lithologies are characterized by the apparent absence of a fabric. Due to
their similar dark green colour and texture it is difficult to distinguish between talc-chlorite and talc-
amphibole-bearing lithologies in the field.
16
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El Massive porphyroblastic serpentinite
4.q Massive and relatively uncarbonated serpentinite
ss Massive porphyroblastic serpentinite with extensive serpentine and carbonate veining
Figure 3.2. A sketch map showing sample locations and their relationship with serpentinite and ophicarbonate. Width of view = 20m.
Figure 3.3. Weathered and pitted surface of the ophicarbonate.
18
Figure 3.4. A fresh surface of massive ophicarbonate.
Figure 3.5. Fabric defined by sub-parallel orientation of magnetite stringers in an outcrop of massive porphyroblastic ophicarbonate (sample P20, Fig 3.1).
19
Outcrops of quartz-carbonate rocks, characterized by a brownish-red weathering colour, but
displaying a grey colour along freshly broken surfaces, occur in the vicinity of serpentinite and
ophicarbonate outcrops. The presence of fuchsite (chromian muscovite) in quartz-carbonate rocks
explains the green colour that is characteristic of these rocks. Outcrops of quartz-carbonate rocks
occur as lensoid bodies that are elongated sub-parallel to the foliation in the area (Fig. 3.1). The
cores of quartz-carbonate outcrops are generally massive but they display a foliation along their
margins. The massive cores of this rock type are characterized by numerous carbonate
porphyroblasts but locally display narrow (<15 cm) foliated zones which occasionally contain quartz
veins (Fig. 3.7). The orientation of these zones are sub-parallel to the foliation in the surrounding
quartz-carbonate schist. Undifferentiated quartz-carbonate rocks (Fig. 3.1) consist of a combination
of both massive porphyroblastic and schistose quartz-carbonate rocks that could not be differentiated
due to the high degree of weathering. Small lenses (15 - 30cm thick and 1 - 2m long) of grey quartz-
carbonate schist (depleted in fuchsite) occur within green quartz-carbonate schist (fuchsite-bearing)
(Fig. 3.8). The grey variety appears to be less deformed than the green one.
Quartz- and/or carbonate-filled veins are present in outcrops of quartz-carbonate rocks (Fig. 3.1).
Interesting relationships between vein type and host litholgy can be summarised as follows:
quartz-filled veins are the most abundant
both quartz and carbonate-filled veins occur in quartz-carbonate outcrops with most of the large
quartz veins orientated sub-parallel to the foliation (Fig. 3.1)
outcrops of serpentinite and ophicarbonate contain only randomly orientated carbonate-filled
veins and never quartz-filled veins.
Highly weathered mafic schists appear to surround outcrops of quartz-carbonate rocks, serpentinite
and ophicarbonate. Quartz-chlorite schist appear to be the most dominant mafic lithology that
underlies a large part of the area. Porphyroblasts of quartz + albite are visible in outcrop (Fig. 3.9).
The contacts between the mafic schists, serpentinite and quartz-carbonate rocks are rarely exposed.
Where it can be observed, the contact between quartz-chlorite schist and quartz-carbonate rocks is
characterized by a striking colour change from green (of the former) to the reddish-brown weathering
colour of the latter rock type.
The dominant foliation in the area trends ENE with subvertical dips that vary between 70°N and 80°S.
In the eastern part of the area (Fig. 3.1), another foliation is developed oblique to the dominant
foliation. It trends in an NE direction and its relationship with the main foliation could not be
established due to weathering. A slight variation in trend of the two foliations is shown by the strike
20
Figure 3.6. Afresh surface of massive porphyroblastic ophicarbonate displaying carbonate-filled veins.
Figure 3.7. Thin foliated zones, accompanied by quartz veining, developed in the massive quartz-carbonate rock.
21
Figure 3.8. A lense-shaped body of a relatively more massive grey quartz-carbonate schist (sample P51) within a highly deformed green quartz-carbonate schist.
Figure 3.9. A sample of a quartz-chlorite schist with quartz + albite porphyroblasts.
22
and the dip of foliation and by the plots of the poles to the foliation in stereographic plots (Fig. 3.1).
Boocock (1984) described the ENE trending foliation with subvertical dips varying between 80°N to
80°S, which is considered to be the most common structural feature of the Antimony line, as a result
of the Di deformation event. The dominant ENE trending foliation with subvertical dips at the
Pioneer locality can be correlated with Boocock's (1984) D i foliation.
3 PETROGRAPHY
3.1 Serpentinite and ophicarbonate
In thin section, serpentinite and ophicarbonate are characterized by the metamorphic assemblage :
serpentine + talc + magnesite t dolomite t chlorite + opaque minerals (samples P1, P4, P7, P8, P9,
P15, P16, P19, P20, P28, P30, P62).
Serpentine in all samples defines pseudomorphic textures composed of lizardite (Fig. 3.10). The
serpentine minerals are identified according to optical characteristics described by Wicks et al.,
(1977) and Wicks and O'Hanley (1988) (Table 3.1). Lizardite is present as alpha-serpentine
consisting of length-fast fibres. The pseudomorphic textures resemble a banded or curtain-like
growth texture described by Wicks et al., (1977) (Fig. 2d). This texture consists of sets of bipartite
veins with a subparallel orientation in which distinct mesh textures are observed. The
pseudomorphic textures appear to be relatively undeformed and display sub-parallel orientation of
the central partings (Fig. 3.10). Lizardite occurs commonly in low-grade serpentinite as the principal
serpentine mineral, and is formed by the pseudomorphic replacement of pre-existing silicates (Wicks
and Whittaker, 1977; Wicks and O'Hanley, 1988). The pseudomorphic textures described above are
characteristic of serpentine pseudomorphs after olivine (Wicks et al., 1977). Hourglass textures
composed of lizardite are also present in sample P62 (Fig. 3.11). In samples P20, P62 and P8,
serpentine also occurs as fine-grained interlocking textures that appear to be replacing the
pseudomorphic textures (Fig. 3.12).
In areas of intense deformation (represented by microshear zones, see section 3.1.4) and extensive
carbonate veining (sample P8), serpentine defines non-pseudomorphic interpenetrating textures
composed of antigorite (Fig. 3.13). Antigorite is identified by its bladed morphology and length-slow
optical character (Wicks and Whittaker, 1977; Wicks et. al., 1977; Wicks and O'Hanley, 1988).
23
Figure 3.10. Photomicrographs showing the banded or curtain-like growth pseudomorphic textures composed of lizardite(Lz) (sample P62; X Nicols).
;11
Figure 3.11. Photomicrograph showing the hourglass texture (arrow) composed of lizardite(Lz) (sample P62: X Nicols).
24
Optical
Texture
Characteristics
Mineralogy
Pseudomorphic
Mesh rim length-fast lizardite
length-slow chrysotile
Mesh center, isotropic lizardite, antigorite
fine-grained or chrysotile
Mesh center, length-fast lizardite
hourglass length-slow chrysotile or antigorite
Hourglass length-fast lizardite
Ribbon length-fast lizardite
Non-pseudomorphic
Transition isotropic lizardite, chrysotile
or antigorite
Interlocking length-fast lizardite
length-slow antigorite, chrysotile
or lizardite
Serrate veins length-fast lizardite
length-slow antigorite
Interpenetrating length-slow antigorite, rarely
chrysotile or lizardite
Table 3.1. Serpentine texture and mineralogy. Optical characteristics are based on elongation of fibres or apparent fibres (After Wicks and O'Hanley, 1988).
25
Figure 3.12. Photomicrograph showing the pseudomorphic textures being replaced by the non-pseudomorphic interlocking textures (arrow) (sample P62; X Nicols).
Figure 3.13. Photomicrograph showing the non-pseudomorphic interpenetrating blades of antigorite(Atg) (sample P8; X Nicols). The microshear zones are discussed in section 3.1.4; Fig. 3.23.
26
Serpentine veins are also common in serpentinite and ophicarbonate, and these are discussed in
section 3.1.2.
Magnesite is the most abundant carbonate phase present in ophicarbonate, while dolomite was
identified only in sample P19. The absence of tremolite and the rare occurrence of dolomite in the
samples of serpentinite and ophicarbonate can be explained by their low CaO content which vary
between 0.02 and 1.21 wt% (Appendix II, Table C). Tremolite and dolomite are common Ca-bearing
phases in serpentnites and ophicarbonates. Bulk rock compositional control on the formation of
carbonate minerals in serpentinite is dicussed in chapter 9. Magnesite is present in all the samples
and occurs commonly as porphyroblasts containing inclusions of lizardite, talc, chromite and
magnetite (Fig. 3.14). Magnesite, in samples P8 and P28, is also present as veins and appears to
replace serpentine veins (Fig. 3.15).
The occurrence of dolomite and magnesite that progressively replace serpentine minerals indicate
that the serpentinite has been subjected to carbonate alteration as a result of the interaction with
CO2-bearing fluids. The occurrence of carbonates filling stockwork veins (Fig. 3.6) and the increased
carbonate content in areas associated with zones of deformation represented by microshear zones
(discussed in section 3.1.4) suggest that deformational structures acted as pathways through which
externally derived CO2-bearing fluids were transported.
The peak metamorphic assemblage of serpentinite, characterized by the presence of antigorite, is
being replaced by carbonate-bearing assemblages. This indicates that the carbonatization event
postdates or occurred very close to the peak metamorphic conditions represented by the serpentinite
at the Pioneer locality.
Talc occurs in two textural forms; as relatively coarse idioblastic to subidioblastic grains associated
with and commonly included in lizardite pseudomorphs, and as fine-grained aggregates between the
lizardite pseudomorphs (Fig. 3.16). It is possible that coarse-grained talc formed during the hydration
of the igneous precursor as talc commonly replaces enstatite under these conditions (Evans and
Guggenheim, 1988). The fine-grained variety is frequently associated with magnesite (Fig. 3.15)
which suggests that it could have formed during carbonatization of serpentine as a result of the
reaction 1:
Reaction 1: serpentine + CO2 = talc + magnesite + H2O.
This is supported by the occurrence of magnesite porphyroblasts with talc and lizardite inclusions
surrounded by the matrix comprized almost entirely of fine-grained talc (sample P19 and P16; Fig.
3.14).
27
Figure 3.14. Photomicrograph of an ophicarbonate composed of magnesite(Mst) porphroblasts within the talc(Ta) matrix. Lizardite(Lz) and talc also occur as inclusions in magnesite (sample P19; X Nicols).
Figure 3.15. Photomicrograph showing the serpentine(S) veins being replaced by magnesite(Mst) veins (sample P28; X Nicols).
28
Chlorite is present in samples P15, P16, P19 and displays two different textural associations;
xenoblastic flakes intergrown with lizardite and talc, and
subidioblastic grains closely associated with chromite and rimmed by magnetite (Fig. 3.17).
Chlorite can form during the prograde recystallization of a serpentinite by
a polymorphic transformation of lizardite (Chemosky et al., 1988), or
according to the reaction; lizardite = antigorite + chlorite (Wicks and O'Hanley,1988).
At high temperatures (above 500°C) lizardite with composition >9.25 wt % A1 203 (or x>0.5) slowly
recrystallizes to chlorite (Nelson and Roy, 1958; Gillery, 1959; Chemosky et al., 1988). Lizardite in
serpentinite from the Pioneer locality is characterized by an alumina content that vary from 0.04 to
10.7 wt % (Appendix 1, Table Ala) (i.e. x<5 and x>5). Although lizardite is dominantly characterized
by compositions x<0.5, the production of chlorite by a polymorphic transformation of lizardite during
prograde recrystallization is preferred as chlorite has not been identified in association with
antigorite.
In the second textural association, chlorite surrounds the chromite core which is rimmed by
magnetite (Fig. 3.17). Magnetite also forms an outer rim around chlorite and talc (Fig. 3.17). This
textural association resembles textures developed during the "pseudomorphic replacement" of
chromite (spinel) by chlorite described by Pinsent and Hirst (1977) in the Blue River Ultramafic Body,
British Columbia, Canada and by Van Schalkwyk (1991) from the serpentinite of the Pietersburg
Greenstone Belt. Similar chromite-chlorite association in serpentinite have also been described by
Loferski (1986) from the Red Lodge District, Montana. Pinsent and Hirst (1977) suggested that the
chlorite was produced by the reaction 2:
Reaction 2: spine! + serpentine + brucite = ferritchromit + chlorite.
They also suggested that the above reaction was compositionally controlled as only the Al-rich
spinels, with a Crx100/(Cr+Al) ratio between 32 and 58, from the peridotitic part of the ultramafic
body were susceptible to the reaction. The Cr-rich spinels with a Crx100/(Cr+Al) ratio of 58 to 82
from the dunitic part were not affected. Contrary to the data of Pinsent and Hirst (1977) the cores of
chromite in the Pioneer serpentinite body have Crx100/(Cr+Al) of 78.1 to 79.6. Beeson and Jackson
(1969) also suggested that the alteration of chromite to ferritchromit accompanied by the formation
of chlorite occurred in the ultramafics of the Stillwater Complex, Montana. They used the reaction 3:
Reaction 3: chromite + olivine + H2O = ferritchromit + magnetite + chlorite
to explain the association. Wicks (1984a) suggested that the high temperature reaction 4:
Reaction 4: forsterite + 2 enstatite + 4 1120 = clinochlore
produced the lenses and stringers of chlorite and magnetite in the Glen Urquhart Serpentinite,
Scotland.
29
Figure 3.16. Photomicrograph showing coarse-grained talc(Ta) associated with the pseudomorphic textures and fine-grained talc occuring in the interspaces between the pseudomorphs (sample P30; X Nicols).
, ,1_ ..4.. _ . • . 1
!4. 0.05 mm it',.. • -
!)
„..
W '-' " ‘11r.an--:-.../. It ... ..,. ,...._ ... -.. vt.•., • . ..-1 ;'•*4.. %I. v
- .. s- ,. : . • -:-.1%-gf-..-.;APN:44 4-'1
Figure 3.17. Photomicrograph showing the association of chromite(Chr), chlorite(Chl), magnetite(Mt) and talc(Ta) within a talc matrix. Chlorite flakes not associated with chromite and magnetite also occur within talc (sample P19; X Nicols).
30
It is uncertain which of the above reactions produced the chlorite associated with chromite in the
serpentinite from Pioneer locality, but the absence of relics of high-grade silicates (eg. enstatite,
green spine!, forsterite) eliminates the possibility that it formed as a result of the high temperature
hydration reaction. The fact that chromite is the only relic phase associated with chlorite suggests
that the reaction of Pinsent and Hirst (1977) is favourable for the production of chlorite.
Opaque minerals present include chromite, magnetite, and sulphide minerals with magnetite being
the most abundant phase. It occurs in two textural forms ;
sub-idioblastic to idioblastic grains disseminated throughout the rock, and
finely-granular grains commonly arranged in the form of stringers.
The orientation of the magnetite stringers is controlled by the pseudomorphic textures as they occur
along the central partings. According to Wicks and Whittaker (1977), the concentration of magnetite
along the central partings is a result of the serpentinization process. The thicker and longer
magnetite stringers which are readily visible in outcrop (Fig. 3.4) are associated with serpentine
veins (Fig. 3.18). They are generally oriented subparallel to the stringers of magnetite that occur
along the central partings of the lizardite pseudomorphs. Magnetite is also present in pseudomorphic
textures of chlorite after chromite as described above. Chromite also occurs in the form of
disseminated subidioblastic to idioblastic grains commonly surrounded by a rim of magnetite. The
chromite core seems to be mostly preserved in large grains. Pyrite is the most common sulphide
phase in the serpentinite and ophicarbonate. The sulphide minerals are generally disseminated
through the rock but, in places, appear to be associated with the carbonate-bearing veins.
3.1.1 Metamorphic history of serpentinite
Wicks and Whittaker (1977) classified serpentinites into eight types based on increasing or
decreasing temperature, the presence or absence of antigorite and penetrative deformation (Table
3.2). O'Hanley et aL (1989) reduced the eight regimes under which serpentinites formed into four
according to the following criteria;
the stability of antigorite is a function of temperature, and
the presence of a foliation does not affect serpentine stability (O'Hanley, 1991).
O'Hanley (1991) related the four regimes of serpentinite stability to three distinct serpentinization
sub-processes namely hydration, serpentine recrystallization and deserpentinization (Table 3.2). The
first sub-process (A and B; Table 3.2) occurs during a decrease in temperature and involves the
hydration of olivine to either antigorite or lizardite. This produces retrograde serpentinites
characterized by pseudomorphic textures. The second sub-process (C; Table 3.2) occurs during an
increase in temperature and involves recrystallization of lizardite into a new lizardite-bearing texture
31
( Min
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32
or to either chrysotile or antigorite and result in prograde serpentinites characterized by hourglass
and interlocking textures. The final sub-process, deserpentinization, involves a prograde
metamorphism of hourglass and interlocking textures into interpenetrating antigorite textures.
The serpentinite at the Pioneer locality is characterized by lizardite as the principal serpentine mineral
defining the pseudomorphic textures. Transitional serpentine textures in the form of hourglass
textures composed of lizardite (Fig. 3.11) and fine-grained interlocking textures of serpentine (Fig.
3.12) also occur. Antigorite in the form of non-pseudomorphic interpenetrating textures (Fig. 3.13) is
also present. This transition from pseudomorphic textures through hourglass and interlocking
textures to non-pseudomorphic interpenetrating textures can be related to the classification of
serpentine in table 3.2 and, therefore, indicates a prograde metamorphism of the serpentinite at the
Pioneer locality.
3.1.2 Serpentine veins
In thin section, both simple (a single vein composed of fibres that are continuous from wall to wall)
and composite (a single vein composed of more than one set of fibres) serpentine veins are
observed. Both vein types may have sharp and linear or serrated boundaries. Vein types with sharp
and linear boundaries may be interpreted as fracture-filling while those with serrated boundaries are
interpreted as replacement veins (Cogulu and Laurent, 1984). Examples of these veins are shown in
figures 3.19 and 3.20. Simple cross-fibre fracture-filled veins (with sharp and linear boundaries) are
composed of chrysotile, identified as a fibrous gamma-serpentine with positive elongation. Optical
properties of serpentine minerals are presented in table 3.1. Simple veins with serrate boundaries
(Fig. 3.19) are composed of gamma-serpentine with length-slow apparent fibres and this may either
be lizardite or antigorite. Composite veins (Fig. 3.20) consist of alpha-serpentine with length-fast
apparent fibres (lizardite) in the centre and gamma-serpentine with length-slow fibres (chrysotile) in
the rim. The serpentine veins associated with magnetite (Fig. 3.18) consist of interlocking textures.
Textural evidence shows that the serpentine veins predate the formation of carbonate veins as they
are frequently cross-cut (Fig. 3.21) and also replaced by the carbonate veins (Fig. 3.15).
3.1.3 Fabric development in serpentinite and ophicarbonate
Planar fabric (observed in outcrop) in these rocks is generally defined by magnetite stringers
occurring along the central partings of the pseudomorphic textures (bipartite veins). Wicks and
Whittaker (1977) attributed this phenomenon to progressive serpentinization during which magnetite
33
\
Figure 3.18. Photomicrograph showing the association of magnetite(Mt) with serpentine(S) veins (sample P20; X Nicols).
Figure 3.19. Photomicrograph showing a simple serpentine vein with serrated boundaries in talc (sample P15; X Nicols).
34
4 • •
4 • e • s
a C.
7, .1.
. • 2 . ,
• V-
" . s .• •..
0.1 mm
Figure 3.20. Photomicrograph showing a composite serpentine vein with sharp and linear boundaries (sample P28; X Nicols).
Figure 3.21. Photomicrograph showing a serpentine(S) vein that is cut by a carbonate(C) vein (sample P28; X Nicols).
35
migrates into the central partings of the mesh cells. The length and thickness of the stringers vary
from thin section to thin section. The stringers display a number of orientations with an angle of 30 to
40° between different orientations (Fig. 3.22).
The subparellel bipartite veins from the pseudomorphic textures and the consistent orientation of
magnetite stringers along their central partings possibly reflect a fracture pattern in the serpentinized
olivine grains (Wicks et al., 1977; Wicks, 1984c). Studies on olivine petrofabrics in peridotites
(Lappin, 1971; Ave Lallemant and Carter, 1970; Nicolas et al., 1971 & 1973; Mercier and Nicolas,
1975; Ragan, 1967) showed that olivine grains may be orientated as a result of igneous flow textures
or as a result of syntectonic recrystallization.
Ophicarbonate lithologies also contain narrow microshear zones which are oblique to the orientation
of pseudomorphic textures (Fig. 3.23). Highly flattened lizardite pseudomorphs comprise these
microshear zones. This indicates that deformation postdates serpentinization. The microshear zones
are associated with zones of extensive carbonate alteration indicating a close association between
deformation and carbonatization. Deformation could have possibly resulted in the formation of
pathways through which CO2-rich fluids, that were responsible for carbonatization, were transported.
3.1.4 The nature of the precursor igneous rock
Although the composition of igneous ultramafic rocks could have been altered during
serpentinization (Hostetler et al,,1966; Gresens, 1967; Thayer, 1967; Page, 1967, Blais and Auvray,
1990), the nature of the precursor igneous rock can, however, be estimated on the basis of the co-
existing mineral assemblages. Pseudomorphic textures described above are characteristic of
serpentine after olivine (Wicks et a, 1977, Wicks and O'Hanley, 1988). The absence of
pseudomorphic bastite textures which form after pyroxenes and amphiboles (Wicks and Whittaker,
1977) indicates an apparent lack of these minerals in the precursor ultramafic rock.
The presence of minor amounts of coarse-grained talc might indicate the presence of enstatite in the
precursor rock (as discussed in section 3.1.1). Virtual absence of dolomite in ophicarbonate indicate
that the rocks contained insignificant amounts of CaO. This is also reflected by bulk rock
compositions with very low CaO contents that vary from 0.02 to 1.21 wt (Appendix II, Table C).
An igneous ultramafic precursor for the serpentinite from the Pioneer locality can, therefore, be
estimated to have consisted mainly of olivine and minor amounts of orthopyroxene, i.e. a dunite or
harzburgite.
36
..e
,011.-•••••
•
0.2 mm
lark . 7 14.■:.. .,;4W" '
•
Figure 3.22. Photomicrograph showing the orientation of the magnetite stringers controlled by the pseudomorphic textures (Sample P17; X Nicols).
Figure 3.23. Photomicrograph showing the localized shear zones (arrows) which have an oblique orientation relative to the relatively undeformed lizardite(Lz) pseudomorphs (sample P8; X Nicols).
37
3.2 Talc-chlorite and talc-amphibole litholoqies
The talc-chlorite lithology is characterized by the assemblage; talc + chlorite + opaque minerals
(sample P22). Talc occurs as medium- to coarse-grained blades with a random orientation. Chlorite
is brown and occurs as scattered concentrations of fine-grained aggregates within talc (Fig. 3.24).
The talc-amphibole lithology is characterized by the assemblage talc + Ca-amphibole + chlorite +
opaque minerals (samples P3 and P21). The Ca-amphibole has an actinolitic composition and
occurs as stubby grains and elongated grains intergrown with talc (Fig. 3.25). Small subrounded
grains with a high birefringence represent the cross sections of elongated amphibole grains that are
scattered throughout the rock. Talc occurs as randomly oriented medium- to coarse-grained blades
while chlorite is present as medium- to coarse-grained blades disseminated within the talc and Ca-
amphibole matrix.
A higher abundance of opaque minerals occur in the talc-chlorite rock and include rutile, chromite,
magnetite, ilmenite and hematite. Rutile commonly occurs in a stallate form. Ilmenite, magnetite and
chromite occur as subidioblastic to idioblastic grains that are disseminated throughout the rock.
Magnetite commonly replaces and forms a rim around the chromite core while magnetite is in turn
replaced by hematite in a similar relationship.
The abundance of actinolite in the talc-amphibole rock and its general absence from serpentinite
indicates that these lithologies represent metamorphosed equivalents of different igneous rocks. This
is supported by other mineralogical variations such as the absence of relics of serpentine minerals
and the absence of carbonate minerals from talc-amphibole rock.
In thin section, the talc-chlorite and talc-amphibole rocks show no evidence of foliation.
3.3 Quartz-carbonate rocks
Quartz-carbonate rocks generally consist of the assemblage; quartz + dolomite + magnesite +
chlorite t fuchsite t albite t tourmaline + opaque minerals.
Massive quartz-carbonate rocks are characterized by the presence of numerous magnesite
porphyroplasts that appear to be overgrowing the foliation (samples P36-1, P36-2, P48, P49, P55,
P59, P60 and P61), or by the presence of magnesite porphyroblasts occurring within quartz and
38
Figure 3.24. Photomicrograph showing the occurrence of chlorite(Chl) within a talc(Ta) matrix in the talc-chlorite schist (sample P22; X Nicols).
0.2 mm
PirMite 27:
Figure 3.25. Photomicrograph showing the elongated and stubby tremolite(Tr) grains in a talc(Ta) matrix in the talc-tremolite schist (sample P21; II Nicols).
39
carbonate minerals with no foliation visible (sample P49) (Fig. 3.1). Schistose quartz-carbonate rocks
are characterized by the presence of a well-defined foliation (sample nos; P5, P10-1, P10-2, P11,
P13, P14, P38, P48 and P58) (Fig. 3.1). Scattered magnesite porphyroblasts are also present in
these rocks. Relatively more massive lenses of fine-grained grey quartz-carbonate rock
characterized by the absence of fuchsite (sample P51) occur locally within schistose quartz-
carbonate rocks.
Foliation in the rocks, where present, is mainly defined by the orientation of chlorite, fuchsite and/or
tourmaline. Details of the foliation are discussed in the following section. The microlithons, separated
by the foliation planes, are mainly composed of quartz and carbonate minerals"(Fig. 3.26). The
microlithons (originally described by DeSitter, 1954) are zones of commonly less well oriented
minerals separated by zones of strongly preffered mineral orientation.
Quartz generally occurs in three textural varieties;
as fine- to medium- grained grains in the microlithons,
as elongate 'ribbons' that display undulatory extinction along the foliation (Fig. 3.26), and
in lense-shaped bodies and veinlets orientated subparallel to the foliation.
Quartz commonly contains inclusions of dolomite, magnesite, chlorite, fuchsite and opaque minerals.
Quartz grains from the veinlets are commonly larger and can be readily distinguished from those
occurring in the matrix by the lack of mineral inclusions. The veinlets display evidence of deformation
as grains along their boundaries with the surrounding matrix are generally elongated subparallel to
the foliation.
The carbonate minerals occur in various grain sizes. The microlithons consist of medium-grained
dolomite and magnesite, with magnesite being the dominant phase. The bulk rock compositional
control on the formation of dolomite and magnesite in these rocks is discussed in chapter 9. Both
dolomite and magnesite also occur as elongate grains along narrow foliation planes (Fig. 3.26).
Magnesite is also present as relatively undeformed porphyroblasts, which together with quartz,
frequently cut across and overgrow the chlorite + fuchsite foliation (Fig. 3.27). Quartz and opaque
minerals commonly occur as inclusions in carbonate grains.
Chlorite occurs in two textural forms;
as stringers or elongated grains which define the foliation, and
less commonly as small randomly oriented laths scattered throughout the rock (Fig. 3.28). The
laths also commonly occur as inclusions in quartz and carbonates.
40
Figure 3.26. Photomicrograph showing microlithons separated by a chlorite(Chl) ± fuchsite(F) foliation. Quartz(Q) and carbonate(C) grains along the foliation are elongated parallel to the foliation (sample P61; X Nicols).
A 0.2 mm liocwriP., •
Figure 3.27. Photomicrograph showing magnesite(Mst) porphyroblasts and quartz(Q) overgrowing and obliterating the foliation (sample P61; X Nicols).
41
Fuchsite occurs closely associated with chlorite and is present in the form of elongated grains along
narrow foliation zones. Detailed textural relationships between chlorite and fuchsite are described
under section 3.4 in chapter 6.
Tourmaline occurs in quartz-, dolomite-, magnesite- and albite-bearing veins and as elongated grains
defining the foliation (Fig. 3.29). Tourmaline grains are closely associated with chlorite suggesting
that the quartz-carbonate rocks have been subjected to metasomatism (Fig. 3.30).
Albite occurs in three textural associations;
as relatively undeformed subidioblastic grains intergrown with quartz and carbonates forming a
minor constituent of the microlithons (Fig. 3.28),
in quartz-carbonate veins, and
as elongate grains along the foliation planes.
In sample P5, both albite and dolomite (with which it is associated) are deformed within localized
microshear zones (Fig. 3.31). These microshear zones are overgrown by relatively undeformed
grains of magnesite and quartz. The associated occurrence of deformed albite and dolomite
suggests a close temporal relationship between Na-metasomatism and the production of dolomite.
The opaque minerals present in the quartz-carbonate rocks include rutile, magnetite, chromite and
sulphides. Rutile occurs both as acicular grains along the foliation and also in a stallate form.
Chromite grains are subidioblastic and consist of a core surrounded by a magnetite rim similar to its
occurrence in serpentinite and ophicarbonate and can, therefore, support the ultramafic derivation of
these rocks. Pyrite is the most common sulphide mineral in the rocks. It usually occurs as coarse
grains surrounded by a magnetite rim. Chalcopyrite is frequently found as inclusions in pyrite.
3.3.1 The nature of the fabric in quartz-carbonate rocks
The foliation in quartz-carbonate rocks is mainly defined by chlorite and fuchsite. S-shaped grains
and "fishes" of chlorite indicate that the foliation is of tectonic origin. The foliation zones, which
separate individual microlithons, are commonly 1 - 3 mm apart and frequently anastomoze around
porphyroblast of magnesite. The opaque minerals tend to form traces along the chlorite ± fuchsite
foliation.
Although grains of quartz, dolomite and magnesite are frequently deformed, magnesite
porphyroblasts and also quartz-magnesite bearing assemblages overgrow and obliterate the foliation
(Fig. 3.27). Remnants of foliation defined by chlorite t fuchsite is often found enclosed within quartz
42
Figure 3.28. Photomicrograph showing chlorite(Chl) stringers defining the foliation in the quartz-carbonate rock. Chlorite also occurs as fine-grained scattered laths in the microlithons. Note the occurrence of albite(Ab) associated with quartz and carbonate minerals in the microlithons (sample P61; X Nicols).
4144 4/1 foi Figure 3.29. Photomicrograph showing elongated tourmaline(T) grains along the foliation. An arrow points at the foliation that is obliterated by fine-grained quartz and grains of carbonate minerals with the relics of chlorite(Chl) being preserved (sample P11; X Nicols).
43
-A,esir • " 4
t• ' ,
•
. or- 414
...•
Figure 3.31. Photomicrograph showing deformed albite(Ab) grains together with dolomite(Do) in microshear zones (sample P5; X Nicols).
44
and carbonate minerals, and display a parallel orientation to the main foliation (Figs 3.29 and 3.32).
Deformed stringers of chlorite ± fuchsite are also found between carbonate grains which could
probably be a result of compression induced by the growth of the carbonate grains (Fig. 3.33).
Textural relationships, in which grains of quartz, dolomite and magnesite are deformed along the
foliation, but where quartz-magnesite-bearing assemblages overprint this foliation indicate a complex
relationship between carbonatization and deformation. This suggests that carbonate alteration
outlasted deformation.
Samples P10-1 and P38, are characterized by a foliation that is developed obliquely to the main
foliation.(Fig. 3.34). This oblique foliation can be correlated to a similar foliation observed in outcrop
(section 3.2). The absence of cross-cutting relationships between these foliations suggest a
syntectonic development of these fabrics.
3.4 Mafic schists
Mafic schists surround the quartz-carbonate rocks, serpentinite and ophicarbonate (Fig. 3.1). The
mafic lithologies at all studied localities have apparently not been affected by the carbonatization
process and, as a result, are briefly discussed.
3.3.1 Quartz-chlorite schist
Quartz-chlorite schist is the most abundant mafic schist and consists of chlorite + quartz + opaque
minerals (samples P53 and PL1).
Chlorite forms a major constituent of the rocks and it commonly occurs as stringers and elongate
grains that define the foliation. It also occurs as "fishes" within the chlorite matrix. Quartz occurs as
fine grains within the chlorite-rich matrix. It is also associated with porpnyroblasts of albite that
overgrows and obliterates the chlorite foliation.
Opaque minerals include rutile, magnetite and sulphides. They commonly occur elongated within the
foliation.
3.3.2 Chlorite schist
This schist consists mainly of chlorite (samples P6 and P23), which defines the foliation and occurs in
a fibrous form. Magnetite occurs as an accessory mineral and is commonly elongated along the
foliation.
45
T:
: :21 41.40.9 1'...vg . 14'0 • CP
. 4.•
Figure 3.33. Photomicrograph showing the folded chlorite(Chl) ± fuchsite(F) fabric within carbonates(C) and quartz(Q) (sample 11, II Nicols).
0.2 Mm
-4'LtAtitito.
Figure 3.32. Photomicrograph showing the preserved chlorite(Chl) foliation within magnesite(Mst) and quartz(Q) (sample P38; X Nicols).
46
Figure 3.34. Photomicrograph showing the relationship of the two foliations (dashed lines) developed in quartz-carbonate schists (sample P10-1; X Nicols).
3.3.3 Chlorite-amphibole schist
This lithology consists of Ca-amphibole + chlorite + magnetite (samples P26, P31, P24, P27 and
P34). The Ca-amphibole occurs as stubby and elongated grains of various sizes. Chlorite is fibrous
and it often defines the foliation in the rocks. The modal proportions of Ca-amphibole and chlorite
varies. In sample P31 magnetite occurs as coarse subhedral grains with chlorite inclusions. Sample
P26 is characterized by alternating chlorite-rich and Ca-amphibole-rich bands. Undeformed grains of
Ca-amphibole in the chlorite-rich bands are often found growing pushing apart the chlorite indicating
a late development of Ca-amphibole.
3.3.4 Epidote-bearing rocks
The epidote-bearing rocks are characterized by the assemblage : Ca-amphibole + Epidote + Na-
feldspar + Calcite + Chlorite (sample nos. P32 and P33). Ca-amphibole occurs both as stubby and
elongated grains with a random orientation. The fine-grained mosaic grains of Na-feldspar occur in
47
the interspaces between other minerals in the rock. Epidote is closely associated with calcite and
may occur as porphyroblasts. Chlorite is found as brownish flakes associated with Ca-amphibole.
No fabric is observed in the rocks.
4 SUMMARY
The transition from dominant pseudomorphic textures composed of lizardite through hourglass and
interlocking textures to non-pseudomorphic interpenetrating textures composed of antigorite
suggests that the serpentinite is the result of prograde metamorphic processes. The peak
metamorphic assemblage of the serpentinite (antigorite ± talc ± tremolite ± chlorite) is progressively
replaced by carbonate-bearing assemblages as a result of the interaction with CO 2-bearing fluids.
The serpentinite is deformed along narrow microshear zones. The increased carbonate content along
these microshear zones suggest that deformation could have resulted in the formation of pathways
through which the CO 2-bearing fluids were transported.
Deformed quartz and carbonates concentrated along the foliation in quartz-carbonate rocks which is
also obliterated and overgrown by relatively undeformed quartz-magnesite assemblages and
magnesite porphyroblasts, indicate that carbonatization occurred during deformation but also
outlasted deformation. This foliation trends ENE and has subvertical dips between 70°N and 80°S
and can be correlated with Boococks D i deformation.
48
CHAPTER 4 : FIELD RELATIONS AND PETROGRAPHY OF THE MAJOR LITHOLOGIES
AT THE PIKE'S KOP LOCALITY
1 INTRODUCTION
Pike's Kop is an L-shaped hill covering an area of 800m x 600m with the highest point 570m above sea
level. It is situated approximately 25 km ENE of Gravelotte (Fig. 2.2) and consists mostly of massive
serpentinite and ophicarbonate and, at the bottom of the hill, a few outcrops of mafic schists (Fig. 4.1).
2 FIELD RELATIONS
The massive serpentinite weathers to a reddish-brown colour and often contains brown spots indicating
the presence of partially weathered grains of carbonate minerals. The south-eastern portion of the hill
(Fig. 4.1) is highly weathered and carbonatized with outcrops of the ophicarbonate containing abundant
carbonate porphyroblasts. Veins filled with chrysotile cross-fibres are also present (Fig. 4.2). The fibres
in these veins can be up to 6cm long (Fig. 4.3). The massive serpentinite displays a weak planar fabric
mainly defined by the orientation of stringers of magnetite (Fig. 4.4). These stringers also display a
number of orientations which vary by 35 to 45° to one another. The poles to this fabric are plotted on the
stereogram in Fig. 4.5. It is uncertain whether these stringers are of tectonic origin or not. A narrow
shear zone approximately 0.7 to 1.5m wide, along which the serpentinite is strongly foliated, cuts across
the massive serpentinite (Fig. 4.6). The shear zone strikes in a WSW-ENE direction which is similar to
the trend of dominant regional foliation (D 1 ), which is also dominant at the Pioneer locality. Mafic schists
appear to surround the outcrops of serpentinite and ophicarbonate. At the bottom of the hill, the mafic
schists are covered by serpentinite and ophicarbonate rubble. An ESE-WNW striking shear zone with a
width of 3 - 4m is developed in the mafic schists. The shear zone could not be traced into the
serpentinite.
49
•
0 0 (7,
O
a 022
> to U
2
•
2
0
Folia
ted
ser
pe
n tln
ile
Mas
s ive
ser
pen
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e
•
40. •■ ...
/ ...
/ ... .
/ .4 - ....
I N.
I OD N. \ 4
k il •• y N.
\ 4. CI) \`
\ • S. • i, Oss
\ .■. 0 \ \ N.
\ • 4 CI) e ic \c 0.. ... ■
',.. •N. •• N
\ ■ \ * 0 0 \ \
N.. ...
▪
.-
\ \ \ ° °
\ 1 •
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ui cu
. 5) 0 5 _c
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7-n
a) ..c rn
_c co co 0
O o. co
_c a) to
75 U a) O
rn
_c
E'
LL
50
Figure 4.2. Veins filled with chrysotile cross-fibres in the massive serpentinite.
Figure 4.3. Sample showing the length of chrysotile cross-fibres in the serpentinite at Pike's Kop.
51
Figure 4.4. Sample showing the magnetite fabric on the weathered surface of massive serpentinite.
Figure 4.5. A stereonet plot of the poles to the magnetite fabric in the massive serpentinite.
52
3 PETROGRAPHY
3.1 Serpentinite and ophicarbonate
The massive serpentinite and ophicarbonate are characterized by the peak metamorphic assemblage;
antigorite + magnesite ± dolomite + opaque minerals (samples S4, S5, S6, S7, S10, S11, S14, S15, S17,
S18; Fig 4.1). The foliated serpentinite within a shear zone (sample S9) is characterized by the
assemblage; antigorite + talc + opaque minerals and also contains quartz veins.
Antigorite generally occurs in the form of non-pseudomorphic interpenetrating textures (Fig. 4.7) and
was identified by its bladed morphology and length-slow optical character (Wicks and Whittaker, 1977 ;
Wicks and O'Hanley, 1988) (Table 3.2). Transitional serpentine textures in the form of fine-grained
interlocking grains are also present (samples S11, S18, S14, S5, S7, S17, S10) and these are in some
cases surrounded by a rim of magnetite (Fig. 4.7). Wicks and Whittaker (1977), Wicks and O'Hanley
(1988) and O'Hanley et al. (1989) regard these interlocking textures as the result of prograde
recrystallization of a pre-existing serpentine. The intimate coexistence of non-pseudomorphic
interlocking and intepenetrating textures composed of antigorite, therefore, indicates that the serpentinite
at Pike's Kop locality was subjected to prograde metamorphism.
Thin sections of the foliated serpentinite indicate that the foliation is defined by the orientation of
antigorite blades (Fig. 4.8). The foliation consists of narrow zones, 0.5 to 2.0mm wide, surrounded by
randomly oriented antigorite blades from the interpenetrating texture. This relationship illustrates that
deformation occurred either during or after the prograde recrystallization of a serpentinite. Xenoblastic
grains of magnetite within the foliation are oriented in the same direction (Fig. 4.8). Minor talc occurs
intergrown with antigorite in the foliated serpentinite.
Quartz veins in the foliated serpentinite are composed of a finely granular mosaic of euhedral quart
grains and also contain traces of magnetite. Quart veins may be overgrown by antigorite blades in the
foliated serpentinite (Fig. 4.9). These cross-cutting relationships suggest that the formation of quart
veins predates deformation.
Magnesite is the dominant carbonate phase while dolomite was only identified in sample S11. Grains of
magnesite occur disseminated throughout the rock and is generally intergrown with antigorite (Fig. 4.7).
It is a known fact that carbonate phases in the serpentinites form as a result of the interaction with CO 2-
bearing fluids (Davies et al., 1990; van Schalkwyk, 1991). Magnesite and dolomite also occur in veins
53
Figure 4.6. A shear zone consisting of foliated serpentinite within the massive serpentinite.
..-1-
•
.
jOibl•-_,...1 _ Iirsz.V%:?.111, —la ;11::"RalilrAr-
Figure 4.7. Photomicrograph showing the interlocking textures rimmed by magnetite within the matrix of interpenetrating textures of antigorite(Atg). Note the presence of magnesite(Mst) within interpenetrating antigorite blades (sample S11; X Nicols).
54
Figure 4.8. Photomicrograph showing foliated antigorite(Atg) and elongated magnetite(Mt) grains in the foliated serpentinite in a shear zone (sample S9; X Nicols).
Figure 4.9. Photomicrograph showing the antigorite(Atg) blades cutting across the quartz(Q) vein (sample S9; X Nicols).
55
that cut through antigorite interpenetrating blades (Fig. 4.10). This suggests that CO2-bearing fluids that
resulted in the formation of carbonate-bearing assemblages were channeled by fractures.
Magnetite is the most common opaque mineral in the serpentinite and ophicarbonate. In the
undeformed serpentinite it occurs as subangular to subrounded 'pseudomorphic' outlines overgrown by
antigorite in samples S4 and S6 (Fig. 4.11). This could suggest that the magnetite was formed along
grain boundaries of the pre-existing igneous mineral, that had been pseudomorphed by the serpentinite.
Magnetite also commonly occurs as fine-grained granular grains in stringers. The stringers display a
number of orientations which vary by 35 to 45° between each other and have no effect on the
surrounding interpenetrating texture. They are generally overgrown by antigorite blades (Fig. 4.12)
which illustrates that recrystallization of a serpentinite which produced the non-pseudomorphic antigorite
texture postdates the formation of magnetite stringers. Other opaque phases present in the serpentinite
include chromite, hematite and ilmenite. Chromite occurs in subidioblastic to idioblastic grains that are
commonly surrounded by a magnetite rim. Hematite generally replaces magnetite along grain
boundaries and cleavage planes but also occurs disseminated throughout the rock. Exsolutions of
ilmenite are found in magnetite.
3.2 The origin of the fabric in the serpentinite
3.2.1 The magnetite fabric in the massive serpentinite
Stringers of magnetite define the fabric in the massive (unfoliated) serpentinite (Fig 4.13). These are
overgrown by undeformed interpenetrating blades of antigorite indicating that if the stringers were
produced during a tectonic event, this event occurred prior to the formation of antigorite. The
occurrence of 'pseudomorphic' outlines of magnetite (Fig. 4.11) could indicate that the orientation of
magnetite stringers is "inherited" from a pre-existing serpentinite. Although the origin of the magnetite
stringers is uncertain, a suggestion that the stringers are "inherited" from the precursor (pseudomorphic)
serpentinite is supported because a subsequent deformation should have obliterated the
'pseudomorphic' outlines.
3.2.2 The foliated serpentinite
The fabric is defined by strongly oriented antigorite and magnetite grains within narrow microshear
zones. These zones are enclosed within relatively undeformed antigorite interpenetrating textures.
Antigorite blades within the microshear zones are bent and display undulose extinction (Fig. 4.9) and
were probably rotated in the plane of deformation. The foliated serpentinite closely resembles features
56
Figure 4.10. Photomicrograph showing a carbonate(C) vein cutting through the antigorite(Atg) interpenetrating blades (sample S15; X Nicols).
Figure 4.11. Photomicrograph showing the magnetite(Mt) 'pseudomorphic' outlines that were probably concentrated along the grain boundaries of the pre-existing mineral (sample S6; X Nicols).
57
Figure 4.12. Photomicrograph showing a magnetite(Mt) stringer that is being overgrown by the antigorite(Atg) blades (sample S18; X nicols).
Figure 4.13. Photomicrograph showing the orientation of the magnetite stringers in the massive serpentinite (sample S7; X Nicols).
58
described by van Schalkwyk et al. (1992) as the result of ductile deformation. Similar interpretations
have been made by Raleight and Paterson (1965) who showed that although bulk deformation of
serpentinite is elastic, the microshear zones behave in a ductile manner.
3.5 The mafic schists
The two varieties of the mafic schists are briefly discussed.
3.5.1 Chlorite-Ca-amphibole schist
This rock is characterized by the assemblage; chlorite + Ca-amphibole + magnetite + chromite (sample
S16). The Ca-amphibole occurs as randomly orientated elongated grains. Chlorite is distinguished by its
green colour and occurs as massive aggregates. Both magnetite and chromite are fine-grained,
commonly subhedral and occur disseminated throughout the rock.
3.5.2. Epidote-bearinq schist
This rock type consists of chlorite + epidote + Ca-amphibole (samples S4X-1 and S4X-2). Chlorite
occurs as brown flakes that commonly defines the foliation and also as randomly oriented blades. Ca-
amphibole occurs as fine-grained elongated grains that, with chlorite, commonly defines the foliation.
Epidote commonly occurs as porphyroblastic grains in the matrix of chlorite and Ca-amphibole.
4 SUMMARY
The massive serpentinte is deformed in a shear zone which resulted in the formation of a strongly
foliated rock. The shear zone trends WSW-ENE and can be correlated with the regional foliation (D1),
which is the dominant foliation at the Pioneer locality. The presence of non-pseudomorphic interlocking
and interpenetrating textures indicate that Pike's Kop serpentinite represents a metamorphosed
serpentinite. The peak metamorphic assemblage of this serpentinite is progressively replaced by
carbonate-bearing assemblages as a result of the interaction with CO2-bearing fluids.
59
CHAPTER 5 : FIELD RELATIONS AND PETROGRAPHIC DESCRIPTIONS OF THE
MAJOR ROCK TYPES AT COUNTY DOWN
1 INTRODUCTION
County Down is situated approximately 32 km ENE of Gravelotte and about 2 km north-west of the
Pioneer locality (Fig. 2.2). Rock types at this locality include chlorite-carbonate schist, quartz-carbonate
rocks and mafic schists (Fig. 5.1).
2 FIELD RELATIONS
Exposure at County Down is poor and the contacts between various lithologies are not exposed.
Quartz-carbonate rocks, although schistose, are the most resistant lithologies due to the presence of
higher amounts of quartz relative to other lithologies. Outcrops of quartz-carbonate rocks are isolated
and are readily distinguished by a reddish-brown weathering colour. On the surface, outcrops
occasionally display ellipsoidal cavities which formed as a result of weathering of the grains of
carbonate minerals. Quartz-carbonate rocks have a fine-grained appearance with a planar fabric
defined by stringers of chlorite ± fuchsite (Fig. 5.2). In sample C7, planar fabrics are defined mainly by
strongly aligned quartz and / or carbonate lenses that give the rock a mylonitic appearance. Shear
movement indicators observed in outcrop indicate a right-lateral movement sense (Fig. 5.3).
Chlorite-carbonate schist appear to surround quartz-carbonate rocks (Fig. 5.1). It is green (Fig. 5.4) and
has a well-developed foliation which is frequently crenulated (Fig. 5.5).
Small isolated outcrops of mafic schists are only present in the southern portion of the study area
(Fig. 5.1).
3 PETROGRAPHY
3.1 Chlorite-carbonate schist
Chlorite-carbonate schist consists mainly of chlorite and carbonate minerals and is characterized by the
assemblage chlorite + dolomite + magnesite + quartz + opaque minerals (sample C4).
60
000
I= 0
Ma
c s
chi
st
Chlo
rite
-car
bona
te s
ch
ist
Quar t
z-c
arbona
te r
oc
ks
ui• E<
E
43
ca CL
-13 E C
a as = o N
'-' .o .,
3 -o c co -o" CU
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co o o. co ...Y -5 a 83 - >. C ca a. -o a) c) -c3c E o
co CO N N 2
cn cn ct3 CD C 73 CI
8 8 4 0 a) c :
•
-..-.; c ... 0
co = c o c. ED c13 .4) ' c7) cc 0 1- c7) a_ u_
The
geo
log
ica
l map
of C
oun
ty D
ow
n s
how
ing
the
dis
trib
utio
n o
f dif
fere
nt l
itho
log
ies
(Mo
difie
d a
fter
Mc
Cou
rt, 1
987).
61
Figure 5.2. Handspecimen of a fine-grained quartz-carbonate rock with stringers of chlorite defining the fabric (sample C5).
Figure 5.3. An oriented handspecimen of a quartz-carbonate rock displaying stringers of chlorite indicating a right-lateral shear movement as observed in outcrop (sample C5).
62
Figure 5.4. Handspecimen of a chlorite-carbonate schist.
Figure 5.5. Handspecimen showing crenulations in the chlorite-carbonate schist. Quartz veins along the foliation planes are also crenulated.
63
Chlorite generally occurs as stringers that define a planar fabric in these rocks and the nature of the
foliation is discussed below.
Carbonate minerals, including both dolomite and magnesite, commonly occur as fine- to medium-grained
grains which together with quartz constitutes the microlithons (quartz constitutes < 5% of the rock).
Dolomite is the dominant carbonate phase and it also occurs as coarse elongated grains of up to 2mm in
length that are oriented parallel to the chlorite fabric (Fig. 5.6).
The opaque phases in the rock include rutile, magnetite and pentlandite (iron-nickel sulphide). The
opaques form a minor constituent of the rock and occur as fine-grained granular grains disseminated
throughout the rock.
3.1.1 The nature of the foliation_ in chlorite-carbonate schist
The foliation developed in the chlorite-carbonate schist is mainly defined by the subparallel orientation of
chlorite stringers which can be up to 0.6mm thick. Foliation planes are closely spaced and are commonly
less than lmm apart. Grains of carbonate minerals and subordinate amounts of quartz that do not show
evidence of deformation constitute the microlithons. Elongated dolomite grains in the microlithons are
oriented subparallel to the foliation planes (Fig. 5.6) and these grains could possibly have developed
during formation of the fabric. The foliation is folded by a later deformation which produced a crenulation
cleavage at right angles to the pre-existing foliation (Fig. 5.7). The crenulation cleavage planes are up to
4mm apart and there appears to be a concentration of chlorite along these planes (Fig. 5.7). Elongated
grains of dolomite are also present along the crenulation cleavage planes (Fig. 5.6). The dolomite grains
are relatively undeformed and is probably the result of fracture-filling. The presence of fractures filled by
carbonate minerals along crenulation cleavage planes suggest that carbonatization accompanied
crenulation. The presence of crenulated quartz veins in chlorite-carbonate schist indicate that these
veins predate the development of the crenulation cleavage.
3.2 Quartz-carbonate rocks
Quartz-carbonate rocks are characterized by the assemblage : quartz ± dolomite ± magnesite ± chlorite
± fuchsite ± calcite ± talc + opaque minerals (samples C5, C6 and C7). Quartz-carbonate rocks
generally contain more quartz, less chlorite and, therefore, they are more massive than chlorite-
carbonate schist.
64
Figure 5.6. Photomicrograph showing a dolomite(Do) grain elongated parallel to the chlorite(Chl) fabric and an elongated dolomite(Do) grain along the crenulation cleavage plane (sample C4; X Nicols).
Figure 5.7. Photomicrograph showing crenulated chlorite(Chl) planes. The foliation planes are shown by a dashed line and the crenulation cleavage planes by a solid line (sample C4; X Nicols).
65
Chlorite ± fuchsite commonly define the foliation. Details of the fabric in these rocks are discussed in the
following section.
Quartz generally occurs as fine- to medium-grained aggregates intergrown with carbonates in the matrix.
In sample C7, quartz is also present as lenses consisting of medium- to coarse-grained grains
(Fig. 5.8). Carbonate minerals also form the main constituent of the lenses. These lenses commonly
contain elongated grains along their margins and represent the deformed quartz-carbonate matrix.
Sample C6 is also characterized by quartz veins that are both oriented parallel to and cross-cutting the
foliation. Quartz in the veins is commonly coarse-grained and contains small inclusions of dolomite.
Magnesite and dolomite are the most common carbonate phases present and both occur as fine- to
medium-grained grains that, together with quartz, constitute the matrix in samples C6 and C7. They also
occur in deformed lenses in sample C7. In sample C6, dolomite occurs as small idioblastic grains in
quartz veins and is also the dominant carbonate phase in veins that cut across the foliation. Calcite was
only identified in sample C5 where it occurs in variable grain sizes in the assemblage that comprises of
quartz, chlorite and talc.
Talc was identified only in sample C5 where it occurs as haloes surrounding the calcite grains (Fig. 5.9).
The opaque minerals identified include ilmenite, magnetite, rutile, hematite and sulphides. Rutile occurs
as fine-grained elongate grains and is also common in a stallate form. Hematite is intergrown with
ilmenite and also occurs as inclusions in ilmenite. Magnetite occurs as granular grains disseminated
through the rock. Pyrite appears to be the most common sulphide phase and is present as coarse-
grained subidioblastic grains that are commonly rimmed and appear to be replaced by magnetite. Most
of the opaque minerals are elongated parallel to and appear to be forming traces along the fabric.
3.2.1 The nature of the fabric in 1 quartz-carbonate rocks
The foliation samples C5 and C6 is defined by stringers of chlorite with minor fuchsite developed in
sample C6. Chlorite grains can be bent and commonly display undulose extinction. These deformational
features indicate that the foliation defined by chlorite is of tectonic origin. Stringers of chlorite are variably
intergrown and obliterated by quartz-dolomite-magnesite-bearing assemblage, in sample C6, and
quartz-calcite-bearing assemblage, in sample C5.
66
Figure 5.8. Photomicrograph showing a quartz(Q) lens containing carbonate minerals (sample C7; X Nicols).
Figure 5.9. Photomicrograph showing the occurrence of talc(Ta) around calcite(Ca) grains (sample C5; II Nicols)
67
0.1 Inni e
.$,
Figure 5.10. Photomicrograph showing elongate chlorite grain that possibly represent relics of chlorite fabric within quartz and carbonate minerals that display a mylonitic texture (sample C7; X Nicols).
Strongly deformed and oriented quartz-carbonate and quartz lenses define a mylonitic texture in sample
C7 (Fig. 5.10). Relics of chlorite stringers oriented parallel to the fabric are common within the quartz-
carbonates (Fig. 5.10).
The deformation of carbonate-bearing assemblages (in sample C7) might indicate that the
carbonatization event and deformation occurred coeval. The varying degrees of deformation, indicated
by the presence of relatively undeformed carbonates that overgrows the foliation, indicate the non-
penetrative nature of the deformation that affected the County Down study area.
3.3 Mafic schists
The two varieties of mafic schists present at this locality are briefly described:
68
3.3.1 Chlorite-Ca-amphibole schist
The schist is characterized by the assemblage: Ca-amphibole + chlorite + magnetite + ilmenite (samples
C8 and C1). The Ca-amphibole generally occurs as fine-grained elongated grains but is also present as
coarse-grained elongated and stubby grains that form clusters within the fine-grained matrix of Ca-
amphibole and chlorite. Chlorite is present as fine-grained flakes commonly intergrown with Ca-
amphibole. Fine-grained magnetite and ilmenite are disseminated throughout the rock.
3.3.2 Epidote-bearing schist
Epidote-bearing schists consist of the assemblage: chlorite + Ca-amphibole + plagioclase + epidote
(samples C2 and C9). Ca-amphibole is the dominant mineral and occurs as elongated and as stubby
grains displaying a random orientation. Epidote is present as subidioblastic grains scattered in the matrix
of Ca-amphibole and chlorite. Na-feldspar commonly occupies interstitial spaces between grains of
amphibole in the matrix.
4 SUMMARY
The foliation in chlorite-carbonate schist is folded by a later deformation that produced a crenulation
cleavage. The presence of fracture-filling grains of dolomite along the crenulation cleavage planes
suggest this deformation occurred while carbonatization was still active. The textural relationship in the
quart-carbonate rocks might, therefore, suggest that deformation and carbonatization were coeval. The
varying degrees of deformation indicate deformation within the County Down area was non-penetrative.
69
CJIAPT_ER 6 ; LIThLOLOGICAL DESCRIPTIONS OF THE MAJOR ROCK TYPES AND
MINERALIZATION AT THE MONARCH SHAFT
1 INTRODUCTION
The Monarch mine is located approximately 13 km north-east of Gravelotte (Fig. 2.2) and represents
one of the best known mineralized complexes along the Antimony line. Although antimony is the main
mined commodity, gold is also extracted from the antimony ores and from the sulphide-rich reefs
occurring almost entirely within quartz-carbonate lithologies.
The Antimony line itself consists of an intensely deformed suite of quartz-carbonate rocks. According to
the general characteristics of lode gold deposits hosted by ultramafic lithologies (Kerrich and Kishida,
1987; Colvine et al., 1988; Bohlke, 1989; de Ronde et al., 1992), supported by the distribution of
mineralization in the MGB, the Antimony line represents the final results of a combination of processes
dominated by alteration (metamorphism, carbonatization) and deformation.
Various incomplete stages of this process were described at the Pioneer, County Down and Pike's Kop
localities where the transition from the serpentinite to quartz-carbonate rocks was observed. Although
quartz-carbonate rocks were produced at Pioneer and County Down localities, no significant
mineralization accompanied the alteration process.
The investigation of the Free State ore body at the Monarch shaft is aimed at establishing the
relationship of the mineralization to the alteration and deformation processes. The ore body occurs in the
form of boudins of massive quartz-carbonate rock contained in a schistose quartz-carbonate rock that is
characterized by a low grade of mineralization. Quartz-carbonate schists are in turn surrounded by
talcose and chloritic schists. The two borehole cores, Monarch 2534 (21 st level) and 2458 (el level), that
intersected quartz-carbonate rocks and underground exposures of the contact between the massive and
schistose quartz-carbonate rocks were studied in detail. Borehole Monarch 2534 intersected quartz-
carbonate schists and chlorite quartz-carbonate schist. Borehole Monarch 2458 intersected quartz-
carbonate schists that contained mineralization in the form of quartz-carbonate veins. Sample locations
and some of the relationships (discussed in the following sections) from the underground exposures are
shown in figure 6.1.
70
0 411N...., — I • •
02 —• • •
03'
04 • 012
Quartz-carbonate schist
Massive quartz-carbonate rock
Siliceous quartz-carbonate rock
Quartz vein
Rock sample site and number
07
. 06
010
0.5 m 01
08
Figure 6.1. A sketch map showing the contact between the massive quartz-carbonate rock and quartz-carbonate schist in the crosscut no. 5, 9 u' level.
2 LITHOLOGICAL RELATIONS OF THE MAJOR ROCK TYPES FROM THE MONARCH SHAFT
The following major lithologies comprise the Free State ore body and the surrounding wall rock;
chlorite-quartz-carbonate schist
quartz-carbonate schist
massive quartz-carbonate rocks a ore body; mineralization in the form of quart-carbonate veins.
Chlorite-quartz-carbonate schist. The higher abundance of chlorite in chlorite-quartz-carbonate schist
results in the following characteristics which distinguishes it from the quartz-carbonate schists;
dark greenish-grey colour, and
well-developed and closely spaced foliation.
Quartz-carbonate schists are lighter in colour and have wider spaced foliation. The contact between
chlorite-quartz-carbonate schist and quartz-carbonate schists appears to be sharp and is basically
71
recognized by the striking change in colour. Narrow bands of chlorite-quartz-carbonate schist are
intercalated within quartz-carbonate schists in the vicinity of the contact.
On the basis of colour, quartz-carbonate schists can be subdivided into grey and green varieties. The
green quartz-carbonate schist is generally characterized by higher amounts of fuchsite which imparts a
green colour. There seem to be no systematic distribution of the two varieties as intercalated bands of
varying thicknesses are present in the borehole cores.
Massive quartz-carbonate rock From underground exposures, the massive quartz-carbonate rock is
surrounded by quartz-carbonate schist characterized by a light grey colour and prominent foliation. The
contact between the two lithologies is sharp and is generally parallel to the foliation (Fig. 6.2). The
massive quartz-carbonate rock is highly competent and is generally characterized by;
a dark grey colour,
the relative absence of prominent foliation and
the presence of extensive quartz and quartz-carbonate veining.
Locally the rock is deformed and displays a foliation (Fig. 6.3). Highly siliceous zones with a cherty
appearance (Fig. 6.3) are also developed within the massive quartz carbonate rock. This together with
the presence of abundant (quartz, quartz-carbonate and stibnite) veins contributes to the massive
appearance of the rock.
3 PETROGRAPHY
3.1 Chlorite-quartz-carbonate schist
The chlorite-quartz-carbonate schist is characterized by the assemblage: chlorite + quartz + dolomite +
magnesite ± albite + opaque minerals (samples M*1 and M3).
Chlorite generally occurs as stringers and elongated grains that define the foliation. Details of the
foliation are discussed in the following section.
Quartz and carbonate minerals mainly comprise the microlithons (Fig. 6.4). Quartz, dolomite and
magnesite (in the microlithons) are strongly oriented and often form "ribbons". They also occur in lenses
that are elongated parallel to the foliation. Carbonate minerals in lenses appear to be coarser grained
than the deformed carbonate minerals in the microlithons.
72
Figure 6.2. Underground exposure of the contact between the relatively massive quartz-carbonate rock(right) and quartz-carbonate schist(left). Crosscut no. 5, 9 th level.
Figure 6.3. The foliated zone within the massive quartz-carbonate rock. The top right corner (arrow) shows the siliceous zone with cherry appearance. Crosscut no. 5, 9 th level.
73
Albite occurs as elongate deformed grains, together with quartz and carbonate minerals, in the
microlithons.
The opaque phases in the rock include rutile and sulphide minerals (dominantly pyrite and arsenopyrite).
Sulphide minerals occur in two textural forms. Firstly, as porphyroblasts that are elongated parallel to the
foliation (Fig. 6.4) and, secondly, as relatively undeformed subidioblastic to idioblastic porphyroblasts.
3.1.1 The nature of the foliation in chlorite-quartz-carbonate schist
The foliation in these rocks is mainly defined by chlorite. The foliation planes are closely spaced and are
commonly 0.1 to 0.5 mm apart. The presence of separate individual microlithons, therefore, results in a
finely-banded appearance (with darker bands consisting of chlorite and lighter bands consisting of quartz
and carbonates) of the rock.
The occurrence of relatively undeformed quartz and carbonate minerals overprinting the foliation (Fig.
6.4) and the presence of deformed "ribbon" quartz and carbonate oriented parallel to the foliation
indicate that the carbonatization event occurred during deformation and also outlasted deformation.
3.2 Quartz-carbonate schists
Quartz-carbonate schists are characterized by the assemblage; quartz + magnesite + dolomite + chlorite
± fuchsite ± tourmaline ± albite ± talc ± biotite + opaque minerals.
The green quartz-carbonate schist (sample nos. M2, M5, M6, M7, M8, M9, M12, N4, N5, N6, N8) and
the grey quartz-carbonate schist (samples M4, M10, M11, M14, N1, N2, N3, N7, 01, 014, 019) have a
similar mineralogy except for the presence of higher amounts of fuchsite in the green quartz-carbonate
schist.
Chlorite occurs in two different textural forms;
as stubby randomly oriented grains in the microlithons (Fig. 6.5), and
as stringers and elongated grains that display a parallel orientation and, therefore, define the foliation.
Details of the foliation in these rocks is discussed in the following section.
Quartz generally occurs in three textural forms;
as grains of varying grain sizes in the microlithons,
as lenses that commonly contain elongated grains at the margins. These lenses consist of coarse-
grained quartz and carbonates (Fig. 6.6) and can, therefore, be interpreted as deformed quartz-
74
pr . — ...:. ti ',IV. .:: , ..- 111,,,,7, • VI To. •
ort - .._ ... .110 rt •
0.1 e
4.0 .
-
0.1 mm r
Figure 6.5. Photomicrograph showing coexisting randomly oriented stubby grains of chlorite(Chl) and talc(Ta) (sample N5; X Nicols).
Figure 6.4. Photomicrograph showing quartz(Q) and carbonate minerals(C) occupying the microlithons separated by a chlorite(Chl) foliation. Opaque minerals are also elongated along the foliation. The foliation is also overgrown and obliterated by quartz and carbonates (arrow) (sample N3; X Nicols).
75
carbonate assemblages. The lenses are commonly wrapped around by chlorite stringers (Fig. 6.6).
in lensoid bodies and veins (both composed of quartz and carbonates) that are developed parallel to
and also cut across the foliation. Quartz-carbonate veins in samples N4, N5 and N9 are characterized
by the presence of stibnite mineralization. Details of the mineralized veins are discussed in section 5.
Both dolomite and magnesite are associated with quartz in the quartz-carbonate schists. The phase
relations of the dolomite- and magnesite-bearing assemblages are discussed in chapter 9. The degree
of deformation (within the microlithons) varies with quartz and carbonate grains often displaying
"ribbons" (Fig. 6.7). These textures are commonly overprinted by relatively undeformed assemblages
comprising of quartz and magnesite (Fig. 6.8). Magnesite is also present as relatively undeformed
porphyroblasts that overgrow deformed quartz and carbonate minerals in the microlithons (Fig. 6.9).
Both dolomite and magnesite are also present in lenses (composed of both quartz and carbonate
minerals) that are oriented parallel to the foliation as well as in late mineralized quartz-carbonate veins
(Section 5).
Talc (present in samples N3, N5, N6, N7, N8, N9, M4, M9, and M12) occurs in two textural forms;
as stringers and elongate grains along the foliation (Fig. 6.10) and
as stubby grains with a random orientation in the microlithons (Fig. 6.5).
Talc is commonly associated with chlorite and appears to be replaced by chlorite (Figs 6.5 & 6.10), but
this relationship cannot be established unequivocally. Talc is also found in close association with and
appear to be replaced by magnesite and quartz (Fig. 6.10). This possibly represents reaction R21 on the
chemographic phase diagram (Chapter 9; Fig 9.1) where talc breaks down into quartz and magnesite.
Quartz and magnesite commonly occur overgrowing and overprinting deformed quartz-carbonate (both
dolomite and magnesite) assemblages that form °ribbons" in the microlithons (Fig. 6.8). This indicates
the production of quartz and magnesite from talc occurred whilst deformation was active and also
outlasted deformation.
Fuchsite commonly occurs as fine-grained aggregates associated with and appearing to be replacing
chlorite along the foliation (Fig. 6.9). Textural relationships between fuchsite and chlorite are discussed
in detail in section 4.
Albite is also a common constituent of the microlithons where it occurs as subidioblastic grains within
grains of quartz, dolomite and magnesite. It also occurs as deformed grains along the foliation. The
close association of albite with carbonate minerals and quartz indicates a close temporal relationship
between carbonate alteration and Na-metasomatism.
76
Figure 6.6. Photomicrograph showing a quartz-carbonate lens(arrow) wrapped around by chlorite(Chl) stringers (sample M7; X Nicols).
Figure 6.7. Photomicrograph of deformed quartz(0)and carbonate(C) grains displaying "ribbons" within the microlithons (sample N1; X Nicols).
77
Figure 6.8. Photomicrograph showing "ribbon" quartz(Q 1 ) and carbonate minerals overprinted and overgrown by relatively undeformed quartz(Q 2) and magnesite(Mst) (sample 019; X Nicols).
Figure 6.9. Photomicrograph showing deformed quartz and carbonate minerals in the microlithon overgrown by relatively undeformed magnesite(Mst) porphyroblast. Note the association of chlorite(Chl) and fuchsite(F) along the foliation (sample M6; X Nicols).
78
Biotite forms a minor constituent of the rocks and occurs as oriented stubby grains in the microlithons
and appears to be oriented parallel to the foliation.
Tourmaline occurs as elongate prismatic grains that are also oriented parallel to the foliation (Fig. 6.11).
It is often associated with, and appears to be, replacing chlorite, but the relationship cannot be
established without doubt.
The opaque phases present in the rock include rutile and sulphide minerals. The sulphide phases
include stibnite, berthierite, pyrite, chalcopyrite and arsenopyrite. The opaques are mostly concentrated
along the foliation where they commonly occur both as elongated and relatively undeformed
subidioblastic grains. Stibnite and berthierite occur mainly in mineralized quartz-carbonate veins. The
concentration of sulphide minerals along the foliation and in veins suggests that they were introduced
along planes of weakness and fractures within the rocks.
3.2.1 The nature ofthe foliationin quartz-carbonate schists
The foliation in quartz-carbonate schists is defined by chlorite ± fuchsite ± talc ± tourmaline. The spacing
between foliation planes varies and is commonly >1.5 mm. The foliation often appears to anastomoze
around quartz and carbonate lenses and individual grains. It separates individual microlithons which are
composed of quartz, dolomite and magnesite and minor amounts of tourmaline, talc, biotite, and chlorite.
The degree of deformation within the microlithons varies and is mainly indicated by the occurrence of
"ribbon" quartz and carbonate grains. The variation in the degree of deformation from one sample to
another indicates the heterogeneity of deformation within the study area. Deformed quartz and
carbonate grains are also present along the foliation. This suggests that carbonatization occurred before
or while deformation was active. Deformed quartz, dolomite and magnesite within the microlithons and
along the foliation are variably overgrown and obliterated by relatively undeformed assemblages
comprising mainly of quartz and magnesite (Fig. 6.12). This relationship, and the presence of relatively
undeformed porphyroblasts of magnesite that overprint deformed quartz and carbonate minerals in the
microlithons (Fig. 6.9), indicate that carbonatization occurred during deformation but also outlasted this
event.
3.3 Massive quartz-carbonate rock
The massive quartz-carbonate rock is characterized by the assemblage quartz + dolomite + magnesite +
chlorite ± fuchsite ± albite ± tourmaline + opaque minerals (sample nos 02, 03, 04, 05, 07, 08, 010;
Fig. 6.1).
79
Figure 6.10. Photomicrograph showing the occurrence of talc(Ta) defining the foliation together with chlorite(Chl). Talc also occurs associated with magnesite(Mst) and quartz(Q) (sample 019; X Nicols).
. .
Figure 6.11. Photomicrograph showing grains of tourmaline(T) elongated parallel to the foliation (sample M9: X Nicols).
80
Quartz and carbonate minerals form the major components of these rocks and, therefore, contributes to
its competency and massive nature relative to that of the quartz-carbonate schists. They commonly
occur in varying grain sizes that are frequently deformed, thus forming "ribbons". These deformed
quartz-carbonate assemblages, as was the case in the quartz-carbonate schists, are overprinted by
relatively undeformed quartz and magnesite. Quartz, dolomite and magnesite also occur as coarse
grains in lenses that often contain elongated grains at the margins. These lenses are oriented parallel to
elongate quartz and carbonate grains and can be interpreted to represent deformed quartz-carbonate
assemblages. Quartz, dolomite and magnesite are also present in mineralized quartz-carbonate veins
which also contribute to the competency and the massive nature of the massive quartz-carbonate rocks
and are discussed in detail in section 5. Massive quartz-carbonate rocks do not contain a prominent
foliation.
Chlorite, where present, occurs oriented parallel to the deformed carbonate and quartz "ribbons" thus
defining a weak foliation that is commonly obliterated and overprinted by grains of quartz and carbonate
minerals.
Sample 011 (Fig. 6.1) comprises of chlorite foliation planes that separate individual microlithons and,
therefore, represents a foliated variety within the massive quartz-carbonate rock. Where the foliation
planes are extensively overprinted by quartz and carbonate minerals, the rock display a massive
appearrance.
Samples 02, 03 and 07 (Fig. 6.1) represent a more siliceous competent variety and are characterized
by the presence of higher modal proportions of coarse-grained quartz and only minor amounts of
carbonates. There is no chlorite foliation observed in these rocks. Mineralized quartz-carbonate veins
which contain fibrous quartz and carbonate grains (section 5) are common within these rocks.
Albite, tourmaline and opaques form a minor constituent of the massive quartz-carbonate rocks and,
where present, display similar occurrences as in quartz-carbonate schists.
4 TEXTURAL RELATIONSHIP BETWEEN CHLORITE AND FUC_HSITE
Fuchsite (in quartz-carbonate rocks from Pioneer, County Down and Monarch shaft study areas)
commonly occurs as elongated grains and stringers along the foliation where it is closely associated with
chlorite. Fuchsite and chlorite may occur intergrown, with chlorite also occurring as inclusions in fuchsite,
81
and vice versa (Fig. 6.9). Similar textures have been described by van Schalkwyk (1991) and van
Schalkwyk et. aL (1992) in the carbonatized serpentinite from the Pietersburg Greenstone Belt.
Chlorite associated with fuchsite is characterized by Cr-content as high as 0.51 per formular unit (p.f.u.),
in sample P14. Chlorite not associated with fuchsite is generally characterized by low chromium-
content. The chemical compositions of chlorite and fuchsite are presented in table 6.1. Close pair
analyses of chlorite and fuchsite indicate that they have a comparable amount of Cr per formula unit.
Textural relationships suggest that fuchsite replaces chlorite as a result of K-metasomatism. This
replacement can be represented by the reaction (calculated from close pair chlorite-fuchsite analyses in
table 6.1): 4+ 3+ 2+ 2+
Chlorite + Na 0.08 + Si 0.91 + Al 0.15 + K 1.90 -* Fuchsite + Mg 7.62 + Fe 1 43 . 4+
Insignificant amounts of Na l" and Al were added while the main constituents added are Si and K . 2+ 2+
Mg and Fe are the main constituents released by the reaction.
The Cr-rich chlorite (associated with fuchsite in this case) could be produced by the breakdown of
chromite according to the following reactions:
chromite + olivine + I-1 20 = ferritchromit + magnetite + chlorite and
chromite + lizardite = antigorite + magnetite + chlorite.
The high Cr-content of the chlorite in the quartz-carbonate rocks could have been inherited from chlorite
produced in ultramafic lithologies that were subsequently carbonatized.
5 MINERALIZATION
Gold mineralization is generally restricted to massive quartz-carbonate rocks, although a few
occurrences are also described from the quartz-carbonate schists. Quartz-carbonate schists locally
contain quartz veins, quartz-carbonate veins and pods which contain stibnite mineralization.
Mineralization in massive quartz-carbonate rock can occur in the following forms;
as concentrations of sudidioblastic stibnite grains disseminated within coarse-grained quartz and
carbonate minerals ,
as elongate and subidioblastic grains (of stibnite and less commonly pyrite) in the foliation (Fig.
6.13),
as veinlets and small bodies of stibnite, and
dominantly associated with and occurring within quartz-carbonate veins (Fig. 6.14).
82
21 3 4 5 61 71 8 9
Na2O 01 0 0 0.4 0.27 0.27 0.31 0.02 0.28
Sf02 26.661 28.241 27.45 43.73 46.57 46.32 46.87 29.14 48.73
A1203 20.541 20.971 20.76 20.76 30.69 31.58 31.33 21.31 30.41
MgO 27.111 27.941 27.53 2.26 2.12 1.851 2.081 29.92 2.68
FeO 9.261 9.71 9.48 1.02 1.2 1.04 1.09 6.63 0.89
MnO 0.081 01 0.04 0.06 0 0 0.02 0.04 0.01
1102 01 0.13 0.06 0.78 0.3 0.061 0.381 0.09 0.27
K2O I 0.021 0.021 0.02 11.09 11.26 11.07 11.14 0.27 8.5
CaO 0.061 0.02 0.04 0 0 0.02 0.01 0.03 0.03
Cr203 1.881 1.7 1.79 1.67 2.3 3.17 2.38 1.65 2.93
NiO 1 0.031 0.011 0.02 0.06 0.16 0 0.07 0.62 0.4
#TOTAL 1 85.641 88.73 87.18 95.76 95.74 95.55 95.68 89.73 95.12
1 #Na+1 j 01 01 0 0.1 0.07 0.07 0.081 0.01 0.07
#Si+4 1 5.321 5.43i 5.38 6.38 6.25 6.23 6.291 5.48 6.46
#A1+3 4.841 4.751 4.79 4.83 4.99 5.031 4.941 4.72 4.75
#Mg+2 8.071 8.01: 8.04 0.451 0.42 0.371 0.421 8.38 0.53
#Fe+2 1.55i 1.561 1.55 0.11 0.13 0.12 0.121 1.04 0.1
#Mn+2 0.011 01 0.01 0.01 0 0 01 0.01 0
#11+4 1 01 0.021 0.01 0.08 0.03 0.01 0.04 0.01 0.03
#K 10.011 01 0.01 1.89 1.93 1.9 1.91 1.6 1.44
#Ca+2 1 0.011 01 0.01 0 0 0 0 0.01 0
#Cr+3 1 0.31 0.261 0.28 0.18 0.24 0.34 0.25 0.25 0.31
#Ni+2 01 01 0 0.11 0.02 . 0 0.01 0.09 0.04
#TOTAL 1 20.111 20.051 20.08 14.04 14.1 14.06 14.07 20.061 13.73
#0-2 I 281 281 28 22 22 221 221 28 22
Table 6.1. Chemical analyses of close pairs of chlorite and fuchsite. Columns 1 and 2 - chlorite analyses from sample M6 Column 3 - average of columns 1 and 2 Columns 4, 5 and 6 - fuchsite analyses from sample M6 Column 7 - average of columns 4, 5 and 6. Column 8 - average of eight chlorite analyses from samples P10 and P14 (from Pioneer locality) Column 9 - average of six fuchsite analyses from samples P10 and P14 (from Pioneer locality).
83
Figure 6.12. Photomicrograph showing the foliation overgrown and obliterated by quartz((J) and magnesite(Mst) (sample M6; X Nicols).
Figure 6.13. Photomicrograph showing the occurrence of stibnite(S) along the foliation (sample N2; X Nicols).
84
Quartz and quartz-carbonate veins
Quartz veins are commonly larger and barren, and are abundant in massive quartz-carbonate rock as
compared with quartz-carbonate schists. The veins display a number of orientations and may occur
parallel to or cut across the foliation. The relationship of these quartz veins to mineralized quartz-
carbonate veins in the massive quartz-carbonate rock could not be established equivocally.
Quartz-carbonate veins, like quartz veins, are restricted to the massive quartz-carbonate rocks and
occur both parallel to and cross-cutting the foliation. The occurrence of veins dominantly in the massive
quartz-carbonate rocks indicate that mineralization is controlled by the physical or mechanical properties
of these rocks relative to that of the surrounding quartz-carbonate schists. These veins generally occupy
brittle fractures which could have served as pathways through which mineralizing fluids were channelled.
Quartz-carbonate veins occur in various sizes but appear to be commonly smaller, and are more
pronounced in thin section. Stibnite and berthierite are the major sulphide phase in quartz-carbonate
veins. Gold was identified occurring as microinclusions (Fig. 6.15) and as free grains included in quartz.
The veins are relatively undeformed within deformed quartz-carbonate assemblages (Fig. 6.14) and are
characterized by the presence of coarser subidioblastic to idioblastic quartz and carbonates (Fig. 6.16).
Some veins contain only dolomite while others contain both dolomite and magnesite as carbonate
phases. The contact of the veins with the host rock is not well-defined and stibnite may occur intergrown
with the host rock assemblages (Fig. 6.14). Locally quartz-carbonate veins contain fibrous quartz, grains
of carbonate and stibnite (Fig. 6.17). These veins can be interpreted to have formed in an extensional
regime. The occurrence of elongate stibnite grains in veins and the occurrence of relatively undeformed
mineralized veins suggest that mineralization is syn- to post-deformation.
85
- r
Figure 6.14. Photomicrograph showing a relatively undeformed quartz-carbonate vein cutting across deformed quartz-carbonate assemblages (Sample N4; X Nicols).
S v Au
S
111i.
Figure 6.15. Photomicrograph showing the occurrence of gold(Au) as an inclusion in stibnite(S) (sample N4; reflected light, II Nicols).
86
Figure 6.16. Photomicrograph showing relatively undeformed quartz(Q) and carbonate minerals(C) within a quartz-carbonate veins (sample N4; II Nicols).
Figure 6.17. Photomicrograph showing fibrous quartz(Q). carbonates(C) and stibnite(S) in quartz-carbonate veins (sample 03, X Nicols).
87
6 SUMMARY
The degree of deformation within the study area varies. Deformed quartz-carbonate assemblages are
generally obliterated and overgrown by relatively undeformed quartz and magnesite, which indicate that
carbonatization occurred during and outlasted deformation. Similar relationships were also observed in
the quartz-carbonate rocks from the Pioneer and County Down localities.
Mineralization, commonly in the form of quartz-carbonate veins, is restricted to massive and competent
quartz-carbonate rocks. These quartz-carbonate veins occupy brittle fractures developed as a result of
later deformation. The occurrence of mineralized quartz-carbonate veins dominantly in the massive
quartz-carbonate rocks indicate that mineralization is largely controlled by the physical or mechanical
properties of the rocks. This can account for the relative absence of mineralization in surrounding
schistose and less competent lithologies (eg. quartz-carbonate and chlorite quartz-carbonate schists).
The mineralization is syn- to post- tectonic.
88
CHAPTER 7 : MINERAL CHEMISTRY
The mineral chemistry of assemblages from representative samples collected from the Pioneer, Pike's
Kop, County Down and the Monarch shaft localities are discussed in this section. A table of microprobe
analyses is presented in appendix I.
1 Serpentine minerals
All three forms of serpentine minerals (i.e. lizardite, chrysotile and antigorite) are present in the
serpentinite and ophicarbonate. Antigorite analyses are similar to analyses of prograde antigorite
reported by Wicks and Plant (1979) and Deer et al. (1992) and show up to 3.81 and 1.28 wt % FeO
(total iron as FeO) and A1203, respectively. Lizardite compositions are characterized by a higher amount
of FeO and A1203 which may be up to 6.23 and 5.5 wt %, respectively. A higher amount of FeO and
A1203 in lizardite than in antigorite is consistent with Wicks and Plant's (1979) and Wicks and O'Hanley's
(1988) interpretation that the antigorite structure can accommodate limited substitution. Chrysotile
occurs only in veins. Minor element substitution also occurs in serpentine minerals, with NiO and Cr203
reaching levels of 0.69 and 0.87 wt %, respectively.
2 Chromite
Chromite occurs in serpentinite, ophicarbonate lithologies and quartz-carbonate rocks as an accessory
mineral. The amount of minor elements, MnO and TiO, is low but may be up to 0.25 and 2.30 wt %,
respectively. NiO is lower than 0.05 wt %. The amount of A1203 is generally low and ranges from 9.16 to
12.74 wt %. The Cr, Al and Fe3+ composition of chromite is shown in fig 7.1.
3 Talc
Talc occurs in all ultramafic lithologies where it generally shows little systematic variation and is similar
in composition to that reported in other ultramafic bodies (eg. Deer et al., 1992; Trommsdorff and
Evans, 1972, Vance and Dungan, 1977; Sanford, 1982). The amount of FeO(total) ranges from 1.50 to
2.22 wt % in serpentinite and ophicarbonate lithologies. Talc in quartz-carbonate rocks is generally
characterized by an FeO(total) content that ranges from 2.52 to 3.05 wt % in sample N5 (from the
89
Fe3+
Cr
Al
Figure 7.1. Chromite composition with respect to Cr-Al- Fe 3+ content.
Monarch shaft) and may be up to 8.90 wt % in sample C5 (from County Down locality). Fe-rich talc
have also been reported from various types of hydrothermal deposits (Kagen and Oen, 1983; Lonsdale
et. al., 1980; Evans and Guggenheim, 1988). Talc in sample C5 is also characterised by minor Al
substitution with A1203 present in amounts of up to 2.40 wt %.
4 Chlorite
Chlorite occurs in all lithologies, but is more abundant in quartz-carbonate rocks. The composition of
chlorite was classified according to Hey's (1954) system (Fig. 7.2). Chlorite analyses in samples of
serpentinite and ophicarbonate lithologies are characterised by a penninite composition while those
from quartz-carbonate rocks have a wider range in Si content and can be classified as sheridanite and
clinochiore. Two compositions of chlorite distinguished on the basis of chrome content are present;
namely a high-chromium content associated with fuchsite and tourmaline, and a low-chromium content
not associated with fuchsite or tourmaline. Chlorite may contain up to 0.30 and 2.07 wt % MnO and NiO,
respectively.
90
cr?
Fe+2
+ Fe+3
Fe+2
+ Fe+3
+ Mg
P N3
9 .A.
9 01
9 C7)
J.
Curu dophilite Pseudoth ingite
= g.
CO 6
o = c) 3 0 cn
(TS'
a cp 5 cn cn .7c5.:
Sheridanite • .• .. •
.
Ripi lote Daphnite
'tt: .
Clinochlore • Pynochlorite Brunsvigite
to 0 00 Penninite Diabanite
03
Talc-chlorite
0 0
I A) !V 0 42,
I 42, O a
1 co b
1 9 C
-... f■3 O
Fe+2 + Fe+3
Figure 7.2. Classification diagram of chlorite compositions after Hey (1954). Open circles represent the composition of chlorite from the serpentinite and ophicarbonate lithologies. Closed circles represent chlorite analyses from quartz -carbonate rocks.
91
5 Carbonate minerals
Magnesite and dolomite, considered to be typical of ultramafic sequences (Phillips and Brown. 1987),
are the common carbonate phases in the ultramafic lithologies that were studied at the different
localities. Calcite was only identified in one sample of quartz-carbonate rock (iample C5, County Down)
which contains no magnesite. The composition of carbonate minerals from various localities are plotted
in fig. 7.3 which shows no variation in the compositions of carbonate minerals from various localities.
Magnesite is characterized by Fe2+ substituting for Mg t' and contains between 5.08 and 30.24 mot %
FeCO3. Magnesite in quartz-carbonate rocks is generally characterized by a higher amount of Fe 2+ as
compared to magnesite in serpentinites. There is only a minor substitution of Fe 2+ for Mg2+ in dolomite.
CaO
MgO
FeO
Table 7.3. Compositions of the carbonate minerals in an CaO-MgO-FeO compositional diagram. Field 1: dolomite from ophicarbonate and quartz-carbonate rocks (ophicarbonate rocks - n = 2; quartz-carbonate rocks - n = 30). Field 2: magnesite from ophicarbonate rocks - n = 12. Field 3: magnesite from quartz-carbonate rocks (n = 37).
92
CHAPTER 8 : BULK ROCK CHEMISTRY
1 INTRODUCTION
Quartz-carbonate rocks are important hosts to lode gold deposits in Archaean greenstone belts (eg.
Kishida & Kerrich, 1987; Colvine et al., 1988; Moritz & Crocket, 1991; Schandle & Wicks, 1991). Such
rocks along the Antimony line of the MGB have previously been interpreted to be either of a
sedimentary (Hall, 1912; Mendellsohn, 1938; van Eerden et aL; 1939) or submarine-volcanic exhalative
origin (Muff, 1976; Fripp, 1976). According to their similar bulk rock compositions, Pearton (1978,
1979a, 1980), however, suggested that these rocks were derived from peridotitic komatiites as a result
of interaction with CO2-bearing fluids. A komatiitic precursor, based on geochemical criteria, has also
been suggested for quartz-carbonate rocks associated with Archaean lode gold deposits from a number
of greenstone belts (eg. Fryer et aL, 1979; Roberts and Reading, 1981; Kishida and Kerrich, 1987;
Colvine et al., 1988; Moritz and Crocket, 1991; de Ronde et aL, 1992).
In this section, the bulk rock composition of quartz-carbonate rocks from the MGB is compared with
those of komatiites. The composition of quartz-carbonate rocks (from Pioneer, County Down and
Monarch shaft localities) is also compared with that of serpentinite and ophicarbonate rocks (from
Pioneer and Pike's Kop localities) with which they are associated. This data will be used to establish
whether other major elements (eg. Ca, K, Na, etc) were or were not introduced during carbonatization of
these ultramafic lithologies. The bulk rock compositions of serpentinite, ophicarbonate and quartz-
carbonate rocks are presented in appendix II.
2 QUARTZ-CARBONATE ROCKS
Quartz-carbonate rocks from the Pioneer, County Down and Monarch Mine localities generally have
similar mineralogical and overlapping bulk rock compositions. The overlapping bulk rock compositions
are clearly shown on Si02 variation diagrams (Fig. 8.1). The bulk rock composition of these rocks are
characterized by an (on a volatile-free basis; Appendix II, Table A) MgO content varying from 14.81 to
44.23 wt % and average TiO2 content < 0.44 wt %. The relatively high MgO, Cr and Ni contents
(Appendix II, Table B) and a low TiO2 content generally satisfy the geochemical criteria for a komatiitic
composition.
93
50
46
42
38
0
MgO 30
Nit % 26
22
0
0+
a
10 0 12 24 36 48 60
+ + 18 0 0
411. ++
14
10—
9
20
18
16
14
12
CaO (wt %) 10
8
6
2
a
41) 0 , .
10 20 30 40 50 60
O
20
1 8
16
14r
12 0 A1203
5 (wt
4
3r.
2
+
0 10 20 30 40 50 60
0 0 -4- J 0 0
of 0
+ .0 0
° 0 + 4.
10 22 34 46 58 70
Fei) 3(7) 10 (wt
8
6 0
co 0
a 0 0
° OL ° ao
, • e
+ 0
8
7
6 0
4
2
4.2 Si02 (Wt %) • 3.6
2.4
0
0
0 +
,• , 0
10 22 34 46 •••• 58 70
Si02 (WI %)
Figure 8.1. Si02 variation diagrams (on a volatile-bearing basis) of the major oxides. Serpentinite and ophicarbonate rocks: o - Pioneer locality; • - Pike's Kop locality. Quartz-carbonate rocks: + - Pioneer locality; A - County Down locality; 0- Monarch Shaft
3.0
Nal) + Kp 1.8 (Wt %)
1.2
0.6
94
3 SERPENTINITE AND OPHICARBONATE
Serpentinite and ophicarbonate rocks are generally characterized by a relatively low Si02, high MgO,
and high Cr and Ni contents typical of ultramafic rocks (Appendix II, Table C). Serpentinite and
ophicarbonate samples collected from the Pioneer locality are characterized by (on a volatile-free basis;
Appendix II, Table D) MgO contents that vary from 33.83 to 44.25 wt % and Si02 contents that vary from
43.80 to 56.19 wt %, while those from Pike's Kop are characterized by a higher MgO content of between
41.67 to 44.65 wt % and Si02 content that vary between 42.94 and 45.99 wt %. Serpentinite and
ophicarbonate rocks from the Pioneer locality also contain lower Fe203(total), higher A1203 , higher CO2
and lower H2O+ (Appendix II, Table C). The variations in Fe203(total) and A1203 contents are also
illustrated in Si02 variation diagrams (Fig. 8.1).
4 COMPARISONS BETWEEN QUARTZ-CARBONATE ROCKS. SERPENTINITE AND
OPHICARBONATE ROCKS
Although it is generally agreed that quartz-carbonate rocks represent intensely carbonatized equivalents
of ultramafic rocks, there appears to be differences with respect to the major oxide content of these
rocks when compared to the bulk rock compositions of serpentinite and ophicarbonate rocks. High CO2 /
(CaO + MgO + FeO) molar ratios of >0.8 in quartz-carbonate rocks reflect the intensity of
carbonatization (Moritz and Crocket, 1991; Davies et al., 1990; Kishida and Kerrich, 1987).
Compositions of quartz-carbonate rocks also reflect lqwer MgO, higher CaO, higher A1203 and higher
K20 and Na20 contents (Fig. 8.1).
Despite the differences that exist among the bulk rock compositions when comparing serpentinite and
ophicarbonate rocks with quartz-carbonate rocks, they all plot within the compositional field of peridotitic
komatiite on the appropriate classification diagram (Fig. .8.2).
5 DISCUSSION
Major oxide content of the serpentinite bodies from the Pioneer and Pike's Kop localities vary
considerably. This variation can either be attributed to the variation in the composition of the precursor
lithology or to changes as a result of the serpentinization process.
95
Fe203 + 1102
A1203 MgO
Figure 8.2. A1203-MgO-Fe203M+TiO2 classification diagram (Modified from Jensen, 1976). Field 1 -compositional field of serpentinite and ophicarbonate rocks; • - quartz-carbonate rocks.
The composition of quartz-carbonate rocks that plot within the compositional field of peridotitic
komatiite (Fig. 8.2) supports an earlier suggestion by Pearton (1978, 1979a, 1980) that quartz-
carbonate rocks along the Antimony Line represents carbonatized peridotitic komatiites. The
compositions of quartz-carbonate rocks, however, vary considerably with that of serpentinite and
ophicarbonate rocks which also plot within the compositional field of peridotitic komatiite. Lower
MgO and higher CaO and A1203 contents in quartz-carbonate rocks could suggest that these
lithologies represent more CaO-, A1203- and, to an extent, Si02-enriched precursors (possibly
harzburgitic, Iherzolitic or websteritic composition) relative to a dunitic composition of serpentinite
and ophicarbonate lithologies. This could possibly suggest that quartz-carbonate, serpentinite and
ophicarbonate lithologies represent different compositions within an ultramafic body that was
possibly fractionated and subsequently serpentinized and carbonatized.
Alternatively, the higher amounts of CaO, Na20 and K20 in quartz-carbonate rocks could suggest
that these elements were possibly introduced because they are considered to be highly mobile
during hyrothermal alteration (Kishida and Kerrich, 1987). This implies that the quartz-carbonate
rocks possibly represent metasomatised serpentinite.
96
CHAPTER 9: THE NATURE OF THE FLUID PHASE INVOLVED DURING
SERPENTINIZATION AND CARBONATE ALTERATION OF THE U RAMAFIC
LITHOLOGIES FROM THE MGB
1 INTRODUCTION
Evidence presented in the previous chapters suggests that the quartz-carbonate lithologies represent
the carbonatized equivalents of serpentinite. A prominent characteristic of lode gold deposits is that
quartz-carbonate rocks are invariably the host rocks for the mineralized quartz-carbonate veins. The
MGB is no exception. Carbonate alteration of serpentinite have been studied successfully in the past
with reference to an isobaric T-X co2 diagram that was calculated for pure phases in the CaO-Mg0-Si02-
H20-0O2 system (Trommsdorff and Evans, 1977; Trommsdorff and Connolly, 1990; Davies et. al., 1990;
Fig. 9.1). Based on information obtained from detailed mineralogical studies on lode gold deposits by a
number of workers, a constant pressure of 1Kbar was used to construct the isobaric T-X c02 phase
diagram of this study. At higher pressures the reaction curves shift to higher T at fixed X 02, or to lower
Xco2 at fixed T (Davies et al., 1990). All possible reactions that can occur in the specified system is
shown in table 9.1.
In this chapter, field relations and petrographic evidence are used to study the peak metamorphic
conditions and conditions of carbonatization of serpentinite in the MGB based on calculated isobaric
univariant curves. This approach explains the stability relations of the different assemblages as a
function of variation of the CO2 content of the coexisting fluid phase at specified pressure and
temperature conditions. The results will be used to determine whether carbonatization is the result of the
infiltration of an externally derived fluid, or that the fluid was derived internally through mineral reactions.
The mineralized quartz-carbonate veins are described in the same context.
2 THE NATURE OF THE FLUID PHASE ASSOCIATED WITH SERPENTINIZATION AND PEAK
METAMORPHIC CONDITIONS
2.1 Peak metamorphic assemblage of serpentinite
The peak metamorphic assemblage of a serpentinite (from the Pioneer and Pike's Kop localities) along
the MGB is characterized by the presence of antigorite ± talc, ± tremolite ± chlorite.
97
To ca O
a)
(7) cn O
O 0 0 0 CD 0 0 0 0 0 CNI 0 CO CO V CNI 0 CO CO
LO LC) V V V 4:1- Cr)
0 0.
(...) co
CO L
a.9..) ;6
0 cC -,- - °
co
-0 .0 .0 CO
.645 0 c 0 13 C) 2 a) M Lai .7) to
II O a,
c• al -c '2 o 1- (11
tvi cDE .— a) 7) 7)
>" 0>, 13
C U)
.c 0 CY
▪
F c 5 ..._ U) (D 0 C Q. a) o u) u) Ir.—) 0 co ..c co .c a. s2 c cn 2 ›...,_
O = -0 7 O. -0 0
8 a) 0 0 O c
-a a) 0
7- c , a)
co a) -6.3 N= -a .c
a z 0 (13 I.= cn
U c.._. o ca :rz
2 . (73- um co I > co
Sr. 'a 'I"' co za)
O cv cn ca c7) N a) co .c c ca. 4=a) o_
84 -o 7.. 0 CO -.'
X 1) 6 FL (1:1 'E
a a) cri co 2. 2 5) le., a a) co .., a) ii= i— IS
0
98
Table 9.1. A list of all possible reactions in the system CaO-MgO-Si0 2-H20-0O2 at a constant pressure of 1Kbar.
4 Ta + 18 Fo + 27 H20 = Atg
4 Tr + 18 Fo + 27 H20 = Atg + 8 Di
24 Fo + 5 Di + 31 H20 + 10 CO2 = Atg + 5 Do
Br + CO2 = Mst + H2O
Di + 2 CO2 = 2 Qtz + Do
Atg + 47 Di + 30 CO2 = 16 Tr + 15 Do + 15 H20.
2 Fo + Do + 2 CO2 = Di + 4 Mst
34 Fo + 31 H 2O + 20 CO2 = Atg + 20 Mst
5 Qtz + 3 Fo + 2 H 20 = 2 Ta
5 Qtz + 3 Fo + 4 Di + 2 H20 = 2 Tr
6 Fo + 13 Di + 4 H20 + 10 CO2 = 5 Do + 4 Tr
20 Tr + 282 Fo + 383 H 2O + 80 CO2 = 13 Atg + 40 Do
2 Atg + 45 CO2 = 45 Mst + 17 Ta + 45 H2O
3 Mst + 4 Di + H20 + CO2 = 2 Do + Tr
2 Atg + 15 Tr + 60 CO2 = 47 Ta + 30 Do + 30 H20
Fo + 2 CO2 = 2 Mst + Qtz
4 Fo + H20 + 5 CO2 = 5 Mst + Ta
8 Fo + 2 Do + H20 + 9 CO2 = 13 Mst + Tr
4 Fo + 2 Di + H 20 + 5 CO2 = 5 Mst + Tr
5 Tr + 12 Fo + 8 H 20 + 20 CO2 = 10 Do + 13 Ta
Ta + 3 CO2 = 3 Mst + 4 Qtz + H20
Tr + 7 CO2 = 8 Qtz + 3 Mst + 2 Do + H20
Tr + 3 Mst + H 2O + CO2 = 2 Do + 2 Ta
Tr + 4 CO2 = 2 Do + 4 Qtz + Ta.
99
Detailed petrographic studies of the serpentinite from the Pioneer locality revealed that the
pseudomorphic textures composed of lizardite are progressively replaced by non-pseudomorphic
hourglass and interlocking textures, and eventually by non-pseudomorphic interpenetrating textures
composed of antigorite (Chapter 3). This indicates that the serpentinite was subjected to prograde
metamorphism. The presence of non-pseudomorphic interlocking textures and interpenetrating textures
composed of antigorite in the serpentinite from Pike's Kop indicate that it represents a metamorphosed
serpentinite (Chapter 4).
Petrographic studies also established that the first generation of talc (coarse-grained talc) in the
serpentinite from the Pioneer locality could have been produced by the breakdown of pre-existing
enstatite (Chapter 3).
The bulk rock compositions of serpentinite and ophicarbonate lithologies from the Pioneer and Pike's
Kop localities are plotted on a CaO-MgO-Si02 chemographic phase diagram (Fig. 9.2a&b). The
samples are characterized by low bulk CaO content (0.02 to 1.21 wt %; Appendix II, Table C) and plot
on or very close to Atg-Ta tie-line inside the Tr-Ta-Atg subtriangle on the CaO-MgO-Si0 2 chemographic
diagrams (Fig. 9.2a&b). The composition of serpentinite from the Pike's Kop locality plot within the field
of antigorite, indicating that it is almost entirely composed of antigorite with minor amounts of dolomite
or magnesite and talc (Fig. 9.2b). CaO in serpentinite is normally contained either in diopside or
tremolite. The virtual absence of diopside or tremolite in the serpentinite from the MGB can be
explained by the presence of dolomite which could have resulted from the interaction with CO2-bearing
fluids. The sepentinite and ophicarbonate rocks from the MGB are characterized by MgO + FeO / (MgO
+ FeO + Si02) ratios <0.6 which suggest that tremolite was the stable CaO-bearing phase. According to
Evans (1977) diopside is considered to stabilize at MgO + FeO / (MgO + FeO + Si02) ratios >0.6 at low
grades of metamorphism. This verifies that the peak metamorphic assemblage of a serpentinite along
the MGB is characterized by the presence of antigorite ± talc1 ± tremolite ± chlorite.
2.2 Composition of the fluid phase during serpentinization and peak metamorphism
The peak metamorphic assemblage in combination with the chemographic phase relations (Fig. 9.2a&b)
and the calculated univariant reaction curves on the T-Xco2 phase diagram (Fig. 9.1) allows one to
constrain the maximum temperature conditions and the composition of the coexisting fluid phase.
The peak metamorphic assemblage of serpentinite from the MGB is characterized by antigorite t talc1 ±
tremolite ± chlorite. At high temperatures, antigorite breaks down to form forsterite according to the
100
S i02
A
S i02
S 102 S i02
i02 .
CaO to MgO
E
Figure 9.2. Chemographic diagrams showing the phase relations of various rock types from different localities; serpentinite and ophicarbonate : A - Pioneer locality and B - Pike's Kop locality; quartz-carbonate rocks: C - Pioneer locality, D - County Down locality and E - Monarch Mine.
101
reaction R1 (Fig 9.1)
R1: 4 Ta + 18 Fo + 27 H 2O = Atg.
The absence of forsterite from both the serpentinite and ophicarbonate samples (that plot inside the Tr-
Ta-Atg subtriangle in the CaO-MgO-Si0 2 chemographic phase diagram; Fig. 9.2a&b) indicates that the
stability field of forsterite was not reached during peak metamorphism in the MGB. Peak metamorphism
is, therefore, constrained to conditions below reaction R1 at low X c02 values.
The absence of tremolite and the presence of dolomite in the ophicarbonate (that plot inside the Tr-Ta-
Atg subtriangle within the CaO-MgO-Si02 chemographic phase diagrams; Fig. 9.2a&b) indicate that
reaction R15
R15: 2 Atg + 15 Tr + 60 CO 2 = 47 Ta + 30 Do + 30 H 2O
on the isobaric T-Xc02 phase diagram (Fig. 9.1) has been intersected. The absence of petrological
evidence in which tremolite is being replaced by dolomite means that the minimum temperature and the
fluid composition cannot be accurately constrained. Petrologically, magnesite (at the Pioneer and Pike's
Kop localities) occurs closely associated with and is replaced by antigorite (Figs 3.15, 3.23 and 4.7).
According to the T- Xc02 phase diagram, magnesite replaces antigorite according to reaction R13
R13: 2 Atg + 45 CO2 = 45 Mst + 17 Ta + 45 H2O.
The replacement of antigorite by magnesite according to reaction R13 can be accompanied by one of
the following possibilities (Fig. 9.1);
an increase in Xc02 and, to an extent, also a decrease in temperature, OR
an increase in temperature, i.e. it could have occurred during prograde metamorphism.
The absence of the isobaric univariant assemblages (at invariant point 1, ; Fig. 9.1), i.e. the absence of
coexisting forsterite + antigorite + magnesite + talc + dolomite, in the ophicarbonate samples, however,
does not favour the suggestion that the production of dolomite by reaction R13 has been accompanied
by an increase in temperature. This, therefore, suggests that the fluid phase has not been internally
buffered by mineral reactions and that the peak metamorphic assemblage of the serpentinite must have
been stable at Xc02 values below and temperature above those defined by reaction R13 (i.e. to the left of
reaction curve R13; Fig. 9.1).
Peak metamorphic conditions were, therefore, probably restricted to the divariant field enclosed by
reactions R13 and R1, indicating temperatures below 490°C and Xc02 values less than 0.3. The low X co2
content of the fluid phase indicates that the peak metamorphic assemblages equilibrated in the presence
of CO2-poor fluid phase that contained less than 30 mol 00 2. This suggest that the fluid phase
associated with serpentinization and prograde metamorphism of the serpentinite was H 20-rich.
102
3 THE COMPOSITION OF THE FLUID PHASE ASSOCIATED WITH THE CARBONATIZATION OF
THE SERPENTINITE
Petrographical evidence shows that the peak metamorphic assemblage of the serpentinite (antigorite ±
talc1 ± tremolite ± chlorite) is progressively replaced by magnesite±dolomite bearing assemblages as a
result of interaction with a CO2-bearing fluid (Chapters 3 and 4).
Since the peak metamorphic assemblage of the serpentinite equilibrated in the presence of an H 20-rich
fluid phase and since the fluid phase was not buffered internally, the different carbonate-bearing
assemblages produced from the serpentinite can be explained as the result of interaction with externally
derived CO2-bearing fluids. This suggestion is supported by petrological evidence, in which microshear
zones and fractures (Figs 3.23 and 4.10) occurring within the serpentinite and ophicarbonate rocks are
characterized by a high degree of carbonate alteration. This indicates that these structures possibly
served as pathways (and, therefore, zones of secondary permeability) through which the externally
derived fluids were transported.
It has been shown (Chapter 8) that quartz-carbonate rocks from the MGB represent the final alteration
stage of the ultramafic lithologies that were subsequently serpentinized and carbonatized as they have
similar bulk rock compositions. Petrographically, quartz-carbonate rocks (from all localities from the
MGB) consist mainly of quartz + magnesite + dolomite + chlorite ± talc ± fuchsite. Chlorite (in the
serpentinized metaperidotites) does not play an active role in the carbonatization reactions and is
preserved as 6 relic phase even in intensely carbonatized equivalents characterized by the assemblage;
quartz + magnesite + dolomite ± chlorite (Davies et al., 1990). Quartz-carbonate rocks from various
localities also have overlapping chemical compositions with samples plotting in the following fields in
the CaO-MgO-S102 chemographic phase diagrams (Fig. 9.2c to e);
Tr-Ta-Atg subtriangle (Pioneer and Monarch mine localities)
Tr-Di-Atg subtriangle (Pioneer, County Down and Monarch Mine localities)
Tr-Br-Atg (Monarch Mine).
Qtz-Tr-Ta subtriangle (Pioneer and County Down localities).
Atg-Do-Mst subtriangle (Pioneer locality).
According to the T-Xco2 diagram (Fig. 9.1), quartz + magnesite + dolomite-bearing assemblages are
stable to the right of reaction curve R21,
R21: Ta + 3 CO2 = 3 Mst + 4 Qtz + H20
103
i.e. stabilize at Xc02 > 0.7 at temperatures > 350°C, indicating that carbonate-bearing assemblages are
produced by various reactions as a result of interaction with externally-derived CO 2-bearing fluids. The
various alteration assemblages that resulted from the carbonatization of the serpentinite to produce
quartz-carbonate rocks in the MGB cannot be constrained by the T-X c02 diagram (Fig. 9.1) due to
variation in the bulk rock composition of the two lithologies (serpentinite and quartz-carbonate rocks).
This could have resulted from one or a combination of the following two scenarios (as outlined in the
previous chapter);
different precursor lithologies and/or
metasomatism.
The production of quartz-carbonate rocks from the serpentinite as a result of the internal buffering of the
fluid phase by mineral reactions is also possible. This could have occurred along either reaction curves
R17 or R20 on the T-Xc02 diagram (Fig. 9.1). This proccess of internal buffering could have been
accompanied by an increase in temperature, followed by a subsequent decrease in temperature to
stabilize quartz + dolomite + magnesite-bearing quartz-carbonate rocks. The absence of isobaric
univariant assemblages at invariant point 1 2 (Fig.9.1; i.e. coexisting tremolite + dolomite + quartz + talc +
forsterite + diopside) in the quartz-carbonate rocks from the MGB, however, does not support a process
of internal buffering of the fluid phase along reactions R17 or R20 during the carbonate alteration of the
serpentinite.
Petrographically, talc in quartz-carbonate samples from the Monarch Mine occurs associated with, and
appears to be replaced by, magnesite and quartz (Fig. 6.10). This suggests that quartz + magnesite in
the quartz-carbonate rocks from the MGB was produced by the breakdown of talc through reaction R21
(Fig. 9.1)
R21: Ta + 3 CO 2 = 3 Mst + 4 Qtz + H 2O.
This suggests that the carbonate alteration of the serpentinite as a result of interaction with CO 2-bearing
fluids can be constrained by the reaction path indicated on the T-X c02 diagram (Fig. 9.1).
4 THE FLUID PHASE ASSOCIATED WITH MINERALIZED VEINS FROM THE MONARCH MINE
Both dolomite-bearing and dolomite- and magnesite-bearing mineralized quartz-carbonate veins are
present in the massive quartz-carbonate rocks. The veins are relatively undeformed and overprint
quartz-carbonate assemblages (i.e. quartz + dolomite + magnesite), indicating that they are younger.
104
According to the calculated phase relations (Fig. 9.1), dolomite in the quartz-carbonate assemblages
forms by the breakdown of tremolite through reactions R15 and R24
R15: 2 Atg + 15 Tr + 60 CO2 = 47 Ta + 30 Do + 30 H 20
R24: Tr + 4 CO 2 = 2 Do + 4 Qtz + Ta.
It is important to note that all tremolite must have been used up (i.e. dolomite has been produced) by
reactions R15 and R24. Petrography has shown (Chapters 3, 5 and 6) that quartz + dolomite +
magnesite-bearing assemblages are overprinted by quartz + magnesite-bearing assemblages as the
intensity of carbonatization increases. Quartz and magnesite are produced by the breakdown of talc
through reaction R21
R21: Ta + 3 CO2 = 3 Mst + 4 Qtz + H 20.
The mineralized quartz-carbonate veins overprint and cut across various quartz-carbonate assemblages
including quartz + magnesite produced through reaction R21. The presence of dolomite in these quartz-
carbonate veins that overprint quartz + dolomite + magnesite assemblage can, therefore, not be
explained by the calculated phase relations demonstrated in Fig. 9.1.
5 SUMMARY
Peak metamorphic assemblages of serpentinite from the MGB equilibrated in the presence of H 20-rich
fluids with less than 30 mol % CO 2 at temperatures below 490°C.
Quartz-carbonate assemblages were produced from the serpentinite by various carbonatization
reactions as a result of interaction with externally-derived CO 2-bearing fluids. According to the T-X c02
diagram (Fig. 9.1), quartz-carbonate assemblages stabilize at Xco2 > 0.7 at temperatures > 350°C.
Fluids responsible for the carbonatization were derived externally and channeled through structural
features which include microshear zones and fractures.
The presence of dolomite in late mineralized veins that cut across the alteration quartz-carbonate
assemblages cannot be accounted for by carbonatization reactions.
105
CHAPTER 10 : FLUID INCLUSION AND STABLE ISOTOPE STUDIES
1 INTRODUCTION
Most previous studies related to Archaean lode gold deposits mainly concentrated on the mineralized
veins. The nature of the fluid phase associated with the mineralization was, therefore, only in a few
cases compared with that of the fluid phase associated with the wall rock alteration.
In this chapter, the results of the fluid inclusion and stable isotope studies of the wall rock assemblages
(serpentinite quartz-carbonate rocks) from the MGB are compared with those associated with the
mineralization that occurs in the form of quartz-carbonate veins hosted by quartz-carbonate rocks.
1.1 Sample selection for fluid_inclusion study
For the purpose of the fluid inclusion study, only primary inclusions (according to the criteria outlined by
Roedder, 1984) were considered in order to characterize the fluid phases associated with carbonate
alteration and with the mineralization. In order to characterize the fluid phase associated with the
carbonate alteration of the serpentinite, relatively less deformed samples from the Pioneer locality
(where the alteration zonation from the serpentinite to quartz-carbonate rocks is preserved) were
selected. An ophicarbonate rock (sample P20) and a quartz-carbonate rock (sample P14) were used for
this purpose.
Sample P20 consists of the metamorphic assemblage; lizardite + talc" + magnesite,. Fluid
characteristics were studied from the fluid inclusions trapped in the first generation of magnesite
produced by the breakdown of antigorite by reaction R13 (Fig. 9.1)
R13: 2 Atg + 45 CO 2 = 45 Mst + 17 Ta + 45 CO 2 .
Sample P14 is characterized by the alteration assemblage quartz + dolomite l . 2 + magnesite". Fluid
inclusions trapped in quartz and magnesite produced by the breakdown of talc by reaction R21 (Fig. 9.1)
R21 : Ta + 3 CO 2 = 3 Mst + 4 Qtz + CO 2
were studied.
Fluid inclusions associated with the wall rock alteration at the mineralized complex, the Monarch Shaft,
were not considered for fluid inclusion study for the following reasons;
(i) the complete alteration sequence from the serpentinite to the quartz-carbonate rocks is not preserved
106
the quartz-carbonate rocks from this locality are highly deformed and generally lack fluid inclusions
fluid inclusions, where present in these mineralized quartz-carbonate rocks, are also too small
(<3grn) for detailed analysis and are commonly represented by empty fluid cavities suggesting a
possible destruction of the inclusions (decrepitation).
Fluid inclusions associated with the mineralization (at the Monarch Shaft) were studied from inclusions
trapped in both quartz and magnesite from the mineralized quartz-carbonate veins occurring in
sample 05.
1.2 Fluid inclusion types
The different types of fluid inclusions observed from all localities are listed below;
Type 1 : two phase aqueous inclusions consisting of an aqueous liquid and a vapour bubble,
Type 2 : two phase CO2-rich inclusions consisting of liquid and gaseous CO 2
Type 3 : three phase mixed H 2O-0O2 inclusions consisting of an aqueous liquid, liquid CO 2
and gaseous CO2
The fouth type is represented by empty fluid inclusion cavities which are abundant in wall rock
assemblages from the Monarch Shaft. These inclusions do not show any reaction upon heating or
freezing.
It is important to note that not all fluid inclusion types are present at all the localities studied.
1.3 Sample selection for stable isotope studies
Stable isotope (8 13C and 8 180) studies were carried out on carbonate mineral separates and whole rock
powders from the various alteration assemblages as well as from mineralized quartz-carbonate veins.
Ophicarbonate samples (P1, P9, P17, P19, P20 and P30) from the Pioneer locality were used to
determine the stable isotope signature of the first generation of magnesite produced in the serpentinite.
Stable isotope signatures associated with magnesite veins that petrographically replace serpentine veins
were determined for samples P8 and P17 (Chapter 3). Stable isotope signatures associated with quartz-
carbonate alteration were determined for samples P10-1, P11, P14 and P59 from the Pioneer locality,
sample C7 from the County Down locality, and samples M4, M5, M6 and M7 from the Monarch Shaft.
Stable isotope signatures from mineralized quartz-carbonate veins were determined for samples 01
and 04.
107
2 PETROGRAPHY OF FLUID INCLUSIONS
2.1 Ophicarbonate rocks (Sample P20)
The first generation of magnesite was used for microthermomic measurements. Magnesite generally
occurs in the form of relatively undeformed porphyroblasts within a matrix consisting mainly of
serpentine minerals and talc (Fig. 3.14). It also occupies the interstitial spaces between individual
lizardite pseudomorphs in less altered samples (Fig. 10.1).
Only two phase aqueous inclusions (type 1) are present in magnesite. They occur either as type 1a
inclusions (small rounded, cubic or rectangular inclusions commonly <10grn in size) or as type 1 b
inclusions (larger rounded or irregular shaped inclusions 10 to 20gm in size) (Fig. 10.2). The vapour
bubble size in both types la and lb inclusions estimated at room temperature varies between 10 and
20% of the total area covered by the inclusion. This probably suggests that the inclusion types are
representative of one fluid generation. The inclusions commonly occur as single isolated inclusions
within the grains and can, therefore, be interpreted as primary. The occurrence of inclusions in clusters
is also not uncommon. Other occurrences include trails that are confined within the grains (interpreted as
pseudosecondary; Fig. 10.3), and trails occurring along cleavage planes (secondary inclusions;
Fig. 10.4).
2.2 Quartz-carbonate rocks (Sample P14)
Fluid inclusions were measured from fluids trapped in magnesite porphyroblasts and quartz. The
magnesite porphyroblasts are relatively undeformed and overprint the fabric in the rocks. Although
quartz grains may display evidence of deformation, the trapped fluid inclusions are stil well preserved.
Two inclusion types, namely typel (aqueous) and type 2 (CO 2-rich), are present in quartz. Only type 1
aqueous inclusions are present in magnesite. As is the case with magnesite in ophicarbonate,
magnesite in quartz-carbonate rocks also contains two distinct sizes of aqueous inclusions, namely the
smaller type la and the larger type 1 b, but type 1 b inclusions are not common. There is a minor variation
in the bubble size of the two inclusion types that ranges from 10 to 25% of the total area covered by the
inclusion at room temperature. Similar vapour / bubble ratios in these inclusions suggest that they
represent the same generation. The inclusions occur isolated or as clusters and can, therefore, be
108
Figure 10.1. Photomicrograph showing the occurrence of fluid inclusions in porphyroblastic and interstitial magnesite (Mst). Sample P20. II Nicols.
Figure 10.2. Photomicrograph showing types la and lb aqueous inclusions in a magnesite porphyroblast. Sample P20. II Nicols.
109
Figure 10.3. Photomicrograph showing a pseudosecondary fluid inclusion trail in a magnesite grain. Sample P20. II Nicols.
Figure 10.4. Photomicrograph showing secondary fluid inclusion trails along cleavage planes in magnesite. Sample P20. II Nicols.
110
interpreted as being primary (Fig. 10.5). Pseudosecondary and secondary trails or concentration of
inclusions along cleavage planes (possibly secondary) are also present in magnesite.
In quartz, the aqueous and CO 2 inclusions are difficult to distinguish because of their similar size (3 to
104m) and commonly rounded, oval or irregular morphology. However, the absence of a vapour bubble
in some CO 2 inclusions at room temperature makes the distinction easier. The vapour bubble ratio is
highly variable in aqueous inclusions and ranges from 10 to >50%, but generally clusters between 15
and 25%. Empty inclusion cavities are also present but are difficult to distinguish from CO 2 inclusions
with no vapour bubble at room temperature. Empty cavities can positively be distinguished from CO 2
inclusions during heating and freezing excercizes as they (cavities) do not show any phase changes.
Both type 1 aqueous and type 2 CO 2 inclusions occur randomly distributed and in clusters within quartz
grains and can, therefore, be interpreted as being primary (Fig. 10.6). Other occurrences of fluid
inclusions include pseudosecondary and secondary trails (Fig. 10.7).
2.3 Mineralized quartz-carbonate rocks (Sample 05)
Quartz and carbonate minerals (dolomite and magnesite) from the mineralized veins are relatively
undeformed and commonly occur as subidioblastic grains. Fluid inclusions occur in greater abundance
in quartz than in carbonate minerals.
Only type 1 aqueous inclusions were observed in carbonate minerals. The inclusions may be rounded,
oval or cubic in shape and are generally <10 i.m in size (Fig. 10.8). The inclusions may occur isolated or
in clusters within the grains and could, therefore, be interpreted as primary inclusions.
Both type 1 aqueous and type 2 CO 2 inclusions occur in quartz but the aqueous inclusions are the most
abundant. Aqueous inclusions occur as rounded to oval shaped inclusions either isolated or in clusters,
and can be interpreted as primary (Fig. 10.9). Two phase aqueous inclusions also occur as larger,
rounded to irregular shaped inclusions 10 to 20pm in size. These inclusions contain a miniscus between
the vapour bubble and the inclusion cavity (Fig. 10.10). They also occur as isolated or clustered primary
inclusions. The vapour bubble in aqueous inclusions commonly occupies 10 to >60% of the total area
covered by the inclusion at room temperature. CO 2 inclusions occur along trails which could be
interpreted as pseudosecondary or secondary and are, therefore, not considered for the microthermomic
measurements. These CO 2 inclusions may or may not contain a vapour bubble at room temperature.
111
Figure 10.5. Photomicrograph showing isolated aqueous inclusions in magnesite. Sample P14. II Nicols.
Figure 10.6. Photomicrograph showing a cluster of inclusions in quartz consisting dominantly of type 1 aqueous inclusions. Sample P14. II Nicols.
112
Figure 10.7. Photomicrograph showing a secondary H 2O fluid inclusion trail cutting through quartz (Qtr) and magnesite (Mst) grains. Sample P14. II Nicols.
Figure 10.8. Photomicrograph showing primary two phase aqueous inclusion (arrow) in magnesite from quartz carbonate veins. Sample 05. II Nicols.
113
Figure 10.9. Photomicrograph showing isolated two phase aqueous inclusions in quartz from quartz-carbonate veins. Sample 05. II Nicols.
Figure 10.10. Photomicrograph showing aqueous inclusions with a meniscus developed between the vapour bubble and the inclusion cavity. Sample 05. II Nicols.
114
Type 3, mixed H2O-0O2 inclusions are also present in quartz occurring in mineralized veins. These
inclusions contain an aqueous liquid, liquid CO 2 and gaseous CO2 (Fig. 10.11). In these inclusions,
gaseous CO2 is enclosed within liquid CO2 which is in turn enclosed within an aqueous liquid (Fig.
10.11), or the liquid CO2 and gaseous CO2 may form separate bubbles within an aqueous liquid (Fig.
10.12). The inclusions could be interpreted as H20-rich as the areal volume occupied by H2O was
estimated at >50 %. The inclusions are commonly >10 ).1.m in size and occur randomly distributed.
3 HEATING AND FREEZING RESULTS
Heating and freezing experiments were carried out on all fluid inclusion types trapped in magnesite and
quartz from various rock types and the data is presented in appendix 3. Heating and freezing
experiments were conducted on the same inclusions. The salinity, W = weight percent NaCI equivalent,
has been calculated either as a function of the liquidus temperature of ice:
W = -1.76958 x Tm(ice) - 4.2384 x 10 .2 x Tm(ice)2 - 5.2778 x 104 x Tm(ice) 3
or the melting temperature of the clathrate:
W = 0.5286 x (10 - Tm(clath) x (Tm(clath) + 29.261)
Haas (1976), Potter et al. (1978), Collins (1979), Hendel and Hollister (1981) and Coetzee (1993).
3.1 Ophicarbonate rocks
The small size of type la aqueous inclusions in magnesite generally makes observation difficult. Even
though only a limited number of type la inclusions as compared to type 1 b was used for heating and
freezing experiments, no variation in microthermomic measurements were observed between the two
inclusion types.
The freezing (Tf) of the type 1 inclusions occurs at temperatures between -60 and -50 °C. The initial
melting temperatures (Trn i) of the small type la inclusions were difficult to record but generally ranges
from -27.3 to -19.8 °C and clusters around -23 °C. The final melting (Tmf) occurred at temperatures
between -12.6 to +0.4 °C with a distinct peak between -10 and -7 °C (Fig 10.13). These final melting
temperatures correspond to the calculated salinity values between 0.03 to 16.62 wt % NaCI equivalent.
The majority of the inclusions are, however, characterized by the salinity values between 10.74 and
13.45 wt % NaCI equivalent. On further heating no clathrate melting phenomena was observed in any of
the inclusions. This suggests the relative absence of components such as CO 2 and CH4. The
temperatutes of homogenization (Th) of the inclusions range from 221.1 to 356.7 °C with most
temperatures clustering in the range of 290 to 320 °C (Fig. 10.14). All inclusions homogenised to a
liquid phase.
115
Figure 10.11. Photomicrograph showing mixed H 2O-0O2 inclusions with gaseous CO 2 enclosed within liquid CO2 which is in turn enclosed within an aqueous liquid. Sample 05. II Nicols.
Figure 10.12. Photomicrograph showing a mixed H 2O-0O2 inclusion with a liquid CO 2 bubble and a gaseous CO2 bubble within an aqueous liquid. Sample 05. II Nicols.
116
+1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13
Fre
qu
en
cy
11
10
12
13
14
2
3
4
1
6
5
7
8
9
c 0.. 3-0 ...
u_ 2—
Tm (*C)
Figure 10.13. Frequency histogram of Trn t of type 1 aqueous inclusions trapped in magnesite in ophicarbonate rock.
7 Magnesite in Ophicarbonate
6— n = 23
>. 5-o C
0 4—
014 220 225 230 235 240 245 250 255 260 265 270 275 2E30 285 290 295 300 305 31 0 315 320 325 330 335 340 345 350 355 360
1
Th (°C)
Figure 10.14. Frequency histogram of Th of type 1 aqueous inclusions trapped in magnesite in ophicarbonate rock.
117
3.2 Quartz-carbonate rocks
The type 1 aqueous inclusions trapped in both magnesite and quartz do not show much variation in
thermormetric measurements. The inclusions froze (T i) at temperatures in the range of -65 to -50 °C.
The initial melting temperatures (Trn i) of inclusions trapped in both magnesite and quartz were dificult to
record but occurred around -25 °C. The final melting (Tm f) of the aqueous inclusions trapped in
magnesite ranged from -6.7 to -2.0 °C with a distinct peak between -4 and -3 °C (Fig. 10.15), while those
trapped in quartz ranged from -11.5 to -2.0 °C, with most inclusions melting between -5 and -2 °C (Fig.
10.16). The Tmf corresponds to salinity values between 3.46 to 15.55 wt % NaCI equivalent. Most fluid
inclusions are, however, characterized by salinity values in the range 3.46 to 7.72 wt % NaCI equivalent.
As was the case with the ophicarbonate rocks, no clathrate melting occurred upon further heating
suggesting the relative absence of components such as CO 2 and CH4 in the fluid inclusions.
The aqueous inclusions trapped in both magnesite and quartz all homogenized (Th) to a liquid phase
over a wide range of temperatures; from 185.1 to 323.3 °C in magnesite (Fig. 10.17), and 236.8 to
388.6 °C in quartz (Fig. 10.18). A number of inclusions, however, homogenize within the range of 225.0
to 325.0 °C.
The type 2 CO 2-rich inclusions trapped in quartz froze (T f) at temperatures between -95.0 and -85.0 °C.
The initial melting (Tm i) in most type 2 inclusions occurred in the range of -66.0 to -63.0 °C. The final
melting temperatures (Tm f) of the type 2 inclusions ranged from -46.0 to -64.3 °C with a distinct peak
between -56.0 and -64.0 °C (Fig. 10.19). The Tm f range corresponds to a molar fraction of CH 4 (in most
inclusions) of between 0.00 to >0.30. The CO 2-rich inclusions homogenized (Th) within a very wide
temperature range of -34.9 to 15.0 °C with no distinct peak observed (Fig. 10.20).
3.3 Mineralized quartz-carbonate rocks
The two phase aqueous inclusions trapped in both carbonate minerals and in quartz froze (T i) at
temperatures in the range of -75 and -60 °C. The initial melting temperatures (Tal i) of inclusions trapped
in both carbonate minerals and quartz were dificult to record but took place between -42 and -31 °C. The
inclusions trapped in carbonate minerals and in quartz generally melted (Tm f) within the same
temperature range of -25.7 to -7.5 °C with a distinct peak between -25 and -22.3 °C (Fig. 10.21). The
final melting temperatures of the inclusions trapped in carbonate minerals are not plotted as no
homogenization temperatures (Th) could be determined. The Tm f of the aqueous inclusions corresponds
to salinity values ranging from 11.11 to 25.85 wt % NaCI equivalent with values clustering between 24.24
and 25.85 wt % NaCI equivalent.
118
24 —
22-
20-
18-
16-
14-
12-
10-
8-
6-
4 -
2—
0 -1 -2 -3 -4 -5 -6 -7 -8
Tm (•C)
Figure 10.15. Frequency histogram of Tm f of type 1 aqueous inclusions trapped in magnesite in quartz-carbonate rocks.
14 Quartz an Quartz-carbonate Rocks n - 35
0 - 6- U.
5—
4 —
3 —
2 —
1 —
-1 -2 4 -4 -5 -8 -7 -8 -9 -10 -11 -12 -13
Tm ('C) Figure 10.16. Frequency histogram of Tm f of type 1 aqueous inclusions trapped in quartz in quartz-carbonate rocks.
119
Fr
equ
en
cy
7
6— Magnesite in Quartz-Carbonate Rocks
n = 24 5-
0 4—
3-
u. 2—
0 I 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325
114 PI 1 P
Th (°C)
Figure 10.17. Frequency histogram of Th of type 1 aqueous inclusions trapped in magnesite in quartz-carbonate rocks.
8
7— Quartz in Quartz-Carbonate Rocks
n = 17 66 —
0 5-
C
4 0 ... 3
2—
rill 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 375 380 385
Th (°C)
Figure 10.18. Frequency histogram of Th of type 1 aqueous inclusions trapped in quartz in quartz-carbonate rocks.
120
45 -48 47 48 -49 -50 -51 42 -53 -54 -55 -56 -57 -58 -59 40 -61 -62 -63 -64 -65
Tmco2 ( 1C)
Figure 10.19. Frequency histogram of Trn, of type 2 CO 2-rich inclusions trapped in quartz in quartz-carbonate rocks.
7
14 !I NV 14
-8 -10 -12 -14 -16 -18 -20 -22 -24 -26 -28 -30
•
-32 -34 -36
Th (°C)
Quartz In Quartz-Carbonate Rocks 8 —
n st 23 5
• c 4 — o c 3— a-
2— u.
1— 1111 PR 14 +18 +14 +12 +10 +8 +8 +4 +2 0 -2 -4
Figure 10.20. Frequency histogram of Th of type 2 CO 2-rich inclusions trapped in quartz in quartz-carbonate rocks.
121
Th of inclusions trapped in carbonate minerals could not be measured as the minerals darkened at
temperatures above 400 °C. In quartz, aqueous inclusions homogenized within wide temperature ranges
above 350 °C with most inclusions homogenizing between 400 and 500 °C (Fig. 10.22). A number of
inclusions decrepitated at temperatures above 460 °C. Quartz grains also showed some darkening and
cracked at higher temperatures and as a result only a few close pair Tmf - Th measurements could be
determined from the inclusions.
On cooling, the aqueous liquid of the mixed H2O- CO2 inclusions appeared to freeze (Tf) at
temperatutes between -45 to -65 °C, while the CO2 component froze at teperatures between -110 and -
90 °C. On heating Tmf of CO2 was measured between -57.9 and -56.0 °C suggesting the presence of
other phases such as CH 4. Major phase changes within the inclusions were recorded at temperatures
between -28.2 to -23.8 °C. The final melting (Tmf) of ice was observed at temperatures between -8.3
and -7.0 °C.
Clathrate melting (Tcl) was recorded at temperatures between +9.3 to +12.4 °C. The homogenization
temperatures (Th) of the inclusions were difficult to record due to cracking of the grains at high
temperatures, but generally occured above 400 °C. Some inclusions decrepitated at temperatures
above 470 °C.
4 STABLE ISOTOPE DATA
Stable isotope data determined from magnesite and dolomite separated from various assemblages are
presented in appendix IV. In ophicarbonate rocks from the Pioneer locality, interstitial and
porphyroblastic magnesite is characterized by a 6 13C signature that range from -0.01 to 0.39 per mil,
while magnesite veins which replace serpentine veins have isotope signatures that vary from -0.08 to
0.90 (Fig. 10.23). Overlapping 6 13C values of magnesite from ophicarbonate assemblages and from
magnesite veins suggest that magnesite was produced by the break down of serpentine minerals
through reaction R13 (Fig. 9.1)
R13 : 2 Atg + 45 CO2 = 45 Mst + 17 Ta + 45 CO2 .
5 13C isotope signatures determined from magnesite and dolomite separated from quartz-carbonate
rocks from the Pioneer locality range from -4.49 to 0.47 per mil but dominantly fall within the range of
-1.64 to 0.47 per mil (Fig. 10.23). Magnesite and dolomite in quartz-carbonate rocks from the County
122
14—
13—
12—
11 —
1 0 —
5 —
4
3 —
2 —
0 111 1
-7 -8 -9 -10 -11 -12 -13 -14 -15 -18 -17 -18 -19 -20 -21 -22 -23 -24 -25 -28
Tm (°C)
Figure 10.21. Frequency histogram of Tm, of type 1 aqueous inclusions trapped in quartz in quartz-carbonate veins.
7 Quartz in Quartz-Carbonate Veins
6- n = 23
5—
4—
3— LL 2—
1-
0 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500 510 520 530 540 550 560 570
Th (°C)
Figure 10.22. Frequency histogram of Th of type 1 aqueous inclusions trapped in quartz in quartz-carbonate veins.
Quartz in Quartz-Carbonate Veins
n =19
1 1 I 1
1 1 1 I 1
123
-1 -2 -3 -4
313 C
Figure 10.23. Frequency histogram of 5 13C signatures of magnesite and dolomite from ophicarbonate samples (dark shaded area), quartz-carbonate rocks: Pioneer locality (dashed areas), County Down locality (circled areas), Monarch Shaft (plain areas) and mineralized quart-carbonate veins (light shaded area).
Down and Monarch Shaft localities have 8 130 values that range from -5.26 to -3.69 per mil with most
occurring within the range -4.08 to -5.26 per mil (Fig. 10.23).
The carbonate minerals in mineralized veins are characterised by 8 130 values that range from -6.83 to -
5.76 per mil (Fig. 10.23).
Magnesite occurring in ophicarbonate rocks is characterized by 8 180 signatures that range from 11.62
to 14.26 per mil with an average value of 12.49 per mil. Magnesite and dolomite in quartz-carbonate
rocks have 8 180 signatures that range between 10.49 and 12.61 per mil with an average value of 12.03
per mil, while those from mineralized quart-carbonate veins have 8 180 signatures in the range of 11.35
to 13.30 per mil with an average of 11.88 per mil.
124
5 DISCUSSION
Fluid inclusion and stable isotope data for the fluid phase associated with the wall rock alteration, i.e.
fluids trapped in the first generation of magnesite in the serpentinite and fluids trapped in quartz and
magnesite in the quartz-carbonate rocks are summarised in table 10.1.
The bulk rock compositions (Chapter 8) have shown that the quartz-carbonate rocks represent altered
(carbonatized) equivalents of the serpentinites. This suggestion is well supported by the overlapping
heavy 513C signatures in the range -1.64 to 0.90 per mil (Fig. 10.23) from magnesite occurring in
ophicarbonate and magnesite and dolomite from the quartz-carbonate rocks from Pioneer locality.
Heavy 5 13C signatures in the range -2 to +1 are compatible with the data of Golding et al. (1989) and
Veiser et al. (1989) who interpreted the carbonate minerals in the altered Archaean rocks with 5 13C
values in this range to be of marine (sea-floor) origin. This suggests that the carbonate alteration of
serpentinite from the MGB mainly resulted from interaction with percolating sea waters. The compatible
5 13C signatures of the serpentinite and quartz-carbonate rocks furthermore indicate that carbonatization
of the serpentinite resulted from a single alteration event. This suggestion is in contrast with earlier
suggestion by Pearton (1980) who interprested the alteration of the serpentinite to the quartz-carbonate
rocks in the MGB to be a result of at least two alteration events. De Ronde et aL (1992) also interpreted
a similar alteration phenomenon in the Barbeton greenstone belt as a result of two alteration events,
namely an early sea-floor event that resulted in talc-carbonate alteration and a later hydrothermal event
that resulted in quartz-carbonate rocks. A number of workers, however, have indicated that the
alteration of serpentinite to quartz-carbonate rocks associated with Archaean lode gold deposits is
related to a single hydrothermal event (eg. Kishida and Kerrich, 1987 - Kerr Addison deposits, Ontario;
Bohlke, 1989 - Alleghany deposits, California).
Quartz-carbonate rocks from the Pioneer, County Down and Monarch shaft localities also display lighter
5 13C signatures in the range -5.26 to -3.69 per mil (Fig. 10.23). This could possibly be the result of
overprinting of a later fluid phase associated with mineralized quartz-carbonate veins, as will be
discussed later.
Although primary fluid inclusions trapped in magnesite and quartz in ophicarbonate and quartz-
carbonate rocks (with heavier 5 13C signatures from the Pioneer locality) homogenized in a wide
temperature range (mostly between 255 and 235 °C), they show a considerable variation in the Tm f. A
shift in Tmf peaks from between -10 and -7 °C in ophicarbonate rocks to between -5 and -2 °C in quartz-
carbonate rocks was observed. This resulted in a decrease in salinity (peak) values from between 10.74
125
QU
AR
TZ
+ M
AG
NE
SIT
E +
DO
LO
MIT
E
_ _
___..... _
- 25.
7 to
-7.
5; d
isti
nct
pea
k be
twee
n
- 25.
0 an
d - 2
2.3
( in
qua
r tz)
gen
era
lly a
bove
350
; m
ost
ly
betw
een
40
0 a
nd
500
—
11.1
1 to
25.
85; c
lust
er b
e tw
een 2
4.24
an
d 25
. 85
( in
mag
nes
ite a
nd
dolo
mite
) -6
.83
to
- 5.7
6
I QU
AR
TZ-C
AR
BO
NA
TE
MA
GN
ES
ITE
-6
.7 t
o -
2.0;
dis
tinc
t pea
k be
twee
n -
4 a
nd
-3
- • 185.
1 to
323
. 3; c
lust
er
betw
een
225
. 0 a
nd
325.
0
3.46
to
15. 5
5; a
ver
age
= 4.
78
- 5.2
5 to
-0.
01
QU
AR
TZ
-11.
5 to
-2.
0; d
isti
nct p
eak
betw
een
-5
and
- 2
- 64.
3 to
-46
. 0; dis
tinc
t pea
k -
betw
een -
56 a
nd
-64
236
.8 t
o 38
8.6;
clu
ster
be
twee
n 2
25.
0 to
325
.0
-34.
9 to
15.
0; n
o d
isti
nct
pea
k
3.46
to
15.
55; av
erag
e =
4.7
8
IOP
HIC
AR
BO
NA
TE
W I— C5 W Z 0 < 2 - 1
2.6
to 0
.4; dis
tinc
t pea
k be
twee
n -
1 0 a
nd
- 7
221.
1 to
356
.7; c
lus t
er
betw
een
290
.0 a
nd
320.
0
0.03
to
16.
62; 1
0.4
7 to
13
. 45
-0.0
8 to
0.9
0
RO
CK
TY
PE
Tmf o
f aq
u eou
s in
clu
sio
ns (
°C)
Tmf o
f CO
2 in
clu
sion
s (°
C)
Th o
f aq
ueou
s in
clu
sion
s (°
C)
Th o
f CO
2 in
clus
ions
(°C
)
Sa l
inity
(wt
%
NaC
I eq
uiv
alen
t)
c O L.
co cr
C CO
CO C 0
0
O 0) cD
E a)
CO
U) C O
Co
E O w.
C U)
0 0 ca CO
0_ 0 0 U)
c Zi
> 11) 73 co C CO 0 C -f2
.0 F) 7
.0 (13
70 cr° 5 -c)
O .N Ta
UU E •c E
(f)
a) .c)
O
126
and 13.45 wt % NaCI equivalent in ophicarbonate rocks to between 3.46 to 7.72 wt % NaCI equivalent in
quartz-carbonate rocks. This relationship is clearly shown in a plot of Th vs salinity (Fig. 10.24). This
decrease in salinity with increasing carbonate alteration can be explained as follows;
the fluid inclusion represent two different fluid sources with varying salinities, or
the small sample size does not represent a good cross section of the fluid inclusion population.
The second suggestion is favoured because
there is no petrographic evidence in support of the first possibility, and
the carbonate phases in both alteration zones are characterized by 5 13C values in the same range
(-1.64 to 0.09 per mil).
A summary of fluid inclusion and stable isotope data of the mineralized quartz-carbonate veins from the
Monarch shaft is shown in table 10.1. The stable isotope data show that the fluid phase associated with
the stibnite-gold mineralization is characterized by light 5 13C values, ranging from -6.83 to -5.76 per mil.
These values are considered to be typical of either a deep-seated mantle or a magmatic source (Kyser,
1986; Ohmoto, 1986; Hoefs, 1987; Groves etal., 1988; Golding et al., 1989; Veiser et al., 1989). The
fluid is also characterized by salinity values dominantly falling between 24.24 and 25.85 wt% NaCI
equivalent.
The fluid associated with the mineralized veins vary considerably from the fluid phase associated with
the carbonate alteration of the serpentinite. High salinity and lighter 5 13C values clearly distinguish the
mineralizing fluid from the fluid that is responsible for the carbonatization of a serpentinite. This suggests
that the carbonate alteration assemblages of the precursor serpentinite and the mineralized veins
evolved as a result of interaction with fluids of different salinities and source, i.e. different fluids. This
possibility is furthermore supported by the presence of dolomite in the mineralized quartz-carbonate
veins (that overprinted and cut across quartz- and magnesite-bearing assemblages) that cannot be
explained by phase relations (Chapter 9). Lighter 6 13C values in the intermediate wall rock (quartz-
carbonate rocks) could have resulted from overprinting by this later mineralizing fluid.
The variation in the characteristics of the fluids associated with the carbonate alteration and with
mineralization (from the MGB) is in contrast with the data of some earlier workers who have shown that
the 5 13C signatures of the wall rock alteration and the mineralization associated with the Archaean lode
gold deposits are similar (eg. Kishida and Kerrich, 1987; de Ronde et al., 1992). The 6 130 signatures
are also in contrast with the data of some workers who have shown that the light 6 13C signatures are
associated with earlier CO 2 alteration while the heavier signatures are related to gold mineralization (eg.
Groves et al., 1988).
127
• so;
• • •
0
4
8
12 16 20
24
28
32
36
40
NaCI wt % equiv.
Figure 10.24. Th vs salinity plot of aqueous inclusions from magnesite in ophicarbonate rocks (open cubes), from quartz and magnesite in quartz-carbonate rocks (closed circles), and from quartz in mineralized quartz-carbonate veins (crosses).
The fluid associated with the gold-bearing veins from venous Archaean lode gold deposits are generally
characterized by a low salinity (5 to 6 wt % NaCI equivalent) and 5 13C values ranging from-4 to -2 per
mil. The fluids associated with the mineralized quartz-carbonate veins from the MGB are characterized
by high salinity (ranging from 11.11 to 25.85 and clustering between 24.24 and 25.85 wt% NaCI
equivalent) and lighter 5 13C values that range from -6.83 to -5.76 per mil. High salinity fluids of mantle or
magmatic origin associated with vein hosted gold mineralization are rarely documented in literature.
6 SUMMARY
Carbonate alteration of a serpentinite to produce quartz-carbonate rocks from the Pioneer locality was
induced by CO2-rich percolating sea waters as a result of a single alteration event. The carbonatizing
550
500
450
400
350
300
250
200
150
100
50
0
128
fluid is characterized by heavy 5 730 signatures in the range -1.64 to 0.90 per mil, typical of marine origin,
and by a salinity between 3.46 and 13.45 wt% NaCI equivalent.
Stibnite-gold mineralization in the form of quartz-carbonate veins hosted by quartz-carbonate rocks from
the Monarch Mine resulted from a later hydrothermal event. The fluids associated with the mineralization
have a high salinity (dominantly between 24.24 and 25.85 wt% NaCI equivalent) and 6 13C signatures of
mantle derivation (-6.83 to -5.76 per mil).
129
CHAPTER 11 : SUMMARY AND CONCLUSIONS
The occurrence of stibnite-gold mineralization along a shear zone, the Antimony line, in the MGB is similar to
other Archaean lode gold deposits hosted by ultramafic rocks world wide. These deposits are generally
characterized by extensive wall rock alteration and intense deformation. The metamorphic, stable isotope
and fluid inclusion studies were intergrated in an attempt to explain the relationship of the wall rock alteration
zonation (i.e. the transition of the serpentinite through talc-carbonate to quartz carbonate rocks) and
associated mineralization which occurs in the form of quartz-carbonate veins hosted exclusively by quartz-
carbonate rocks. The events that accompanied these processes at different study areas are summarized
below.
The pseudomorphic textures composed of lizardite in the serpentinite from the Pioneer locality are
progressively replaced by non-pseudomorphic hourglass and interlocking textures, and eventually by
non-pseudomorphic interpenetrating textures composed of antigorite. This indicates that the serpentinite
was subjected to prograde metamorphism. The presence of non-pseudomorphic interlocking textures
and interpenetrating textures composed of antigorite in the serpentinite from Pike's Kop indicate that it
represents a metamorphosed serpentinite.
The peak metamorphic assemblage of the serpentinite (from the Pioneer and Pike's Kop localities) is
characterized by the presence of antigorite ± talc, ± tremolite ± chlorite. This assemblage equilibrated in
the presence of an H 20-rich and CO 2-poor fluid containing less than 30 mol % CO 2 .
The peak metamorphic assemblage of the serpentinite is subsequently replaced by carbonate-bearinq
(magnesite ± dolomite) assemblages as a result of interaction with CO 2-bearing fluid. Quartz +
magnesite + dolomite-bearing assemblages stabilized at X co2 > 0.7 at temperatures > 350°C indicating
that carbonate-bearing assemblages are produced by various reactions as a result of interaction with
externally-derived CO 2-bearing fluids. Quartz-carbonate rocks, therefore, represent the final alteration
stage of the carbonatized serpentinite. This suggestion is also supported by the bulk rock compositions
of the quartz-carbonate rocks which are similar to that of peridotitic komatiite. This is consistent with a
suggestion by Pearton (1978, 1979a and 1980) that quartz-carbonate rocks represent peridotitic
komatiites that have been subsequently serpentinized and carbonatized. The depletion of MgO and the
enrichment of CaO, A1 203 and, to an extent, Si0 2 in quartz-carbonate rocks relative to serpentinite and
ophicarbonate could suggest that these lithologies represent an ultramafic body that was possibly
fractionated. Carbonatization of the serpentinite could have also been accompanied by the introduction
of Na20, K20 and possibly CaO.
130
The carbonatizing fluids are considered to have been channelled through microshear zones and
fractures. The microshear zones and fractures developed in the serpentinite and ophicarbonates are
characterised by intense carbonate alteration. In the quartz-carbonate rocks, deformed quartz, dolomite
and magnesite commonly occur along the foliation which is also obliterated and overgrown by relatively
undeformed quartz-magnesite assemblages and magnesite porphyroblasts. This indicates that
carbonatization occurred during deformation but also outlasted deformation. This foliation trends ENE
and has subvertical dips between 70°N and 80°S and can be correlated with Boocock's D 1 deformation.
Deformation was, however, not homogeneous along the Antimony line.
Carbonate alteration of a serpentinite to produce quartz-carbonate rocks from the Pioneer locality is
considered to be induced by cQrrich percolating sea waters as a result of a single alteration event. The
carbonatizing fluid is characterized by heavy 8 13C signatures in the range -1.64 to 0.90 per mil and by a
salinity between 3.46 and 13.45 wt% NaCI equivalent.
Mineralization, commonly in the form of quartz-carbonate veins, is restricted to massive and competent
quartz-carbonate rocks. These quartz-carbonate veins occupy brittle fractures developed as a result of
later deformation. The occurrence of mineralized quartz-carbonate veins dominantly in the massive
quartz-carbonate rocks indicate that mineralization is largely controlled by the physical or mechanical
properties of the rocks which are influenced by alteration. This can account for the relative absence of
mineralization in surrounding schistose and less competent lithologies (eg. quartz-carbonate and chlorite
quartz-carbonate schists).
The stable isotope data show that the fluid phase associated with the stibnite-gold mineralization is
characterized by light 8 13C values, ranging from -6.83 to -5.76 per mil. These values are considered to
be typical of either a deep-seated mantle or a magmatic source (Kyser, 1986; Ohmoto, 1986; Hoefs,
1987; Groves et. al., 1988; Golding et. al., 1989; Veiser et. al., 1989). The fluid is also characterized
by salinity values dominantly falling between 24.24 and 25.85 wt% NaCI equivalent.
The fluid associated with the mineralized veins differs considerably from the fluid phase associated
with the carbonate alteration of the serpentinite. High salinity and lighter 8 13C values clearly distinguish
the mineralizing fluid from the fluid that is responsible for the carbonatization of a serpentinite. This
suggests that the carbonate alteration assemblages of the precursor serpentinite and the mineralized
veins evolved as a result of-interaction with fluids of different salinities and source. i.e. different fluids.
This possibility is furthermore supported by the presence of dolomite in the mineralized quartz-
131
carbonate veins (that overprinted and cut across quartz- and magnesite-bearing assemblages) that
cannot be explained by phase relations (Chapter 9). Lighter 8 13C values in the intermediate wall rock
(quartz-carbonate rocks) could have resulted from overprinting by this later mineralizing fluid.
The variation in the characteristics of the fluids associated with the carbonate alteration and with
mineralization (from the MGB) is in contrast with the data of some of the workers who have shown that
the 5 13C signatures of the wall rock alteration and the mineralization associated with the Archaean
lode gold deposits are similar (eg. Kishida and Kerrich, 1987; de Ronde et. al., 1992). The 6 13C
signatures are also in contrast with the data of some workers who have shown that the light 8 13C
signatures are associated with earlier CO 2 alteration while the heavier signatures are related to gold
mineralization (eg. Groves et. al., 1988).
The fluid associated with the gold-bearing veins from various Archaean lode gold deposits are
generally characterized by a low salinity (5 to 6 wt % NaCI equivalent) and 6 13C values ranging from-4
to -2 per mil. The fluids associated with the mineralized quartz-carbonate veins from the MGB are
characterized by high salinity (ranging from 11.11 to 25.85 and clustering between 24.24 and 25.85
wt% NaCI equivalent) and lighter 5 13Cvalues that range from -6.83 to -5.76 per mil. High salinity fluids
of mantle or magmatic origin associated with vein hosted gold mineralization are rarely documented in
literature.
132
REFERENCES
Abbot, J.E., van Vuuren, C.J.J. and Viljoen, M.J., 1986. The Alpha-Gravelotte antimony ore body,
Murchison Greenstone Belt. In: C.R. Anhaeusser and S. Maske (Eds), Mineral deposits of Southern
Africa, 321-332.
Abu-Jaber, N.S. and Kimberly, M.M., 1992. Origin of ultramafic-hosted magnesite on Margarita Island,
Venezuela. Mineral. Deposita, 27, 234-241.
AM, A.M. and Essene, E.J., 1988. Minfile: A microcomputer program for storage and manipulation of
chemical data on minerals. Am. Mineral., 73, 446-448.
Anhaeusser, C.R., 1971. Cyclic volcanicity and sedimentation in the evolutionary development of
Archean greenstone belts of shield areas. Spec. Publ. Geol. Soc. Aust., 3, 57-70.
Ave Lallemant, H.G. and Carter, N.L., 1970. Syntectonic recrystallization of olivine and modes of flow in
the upper mantle. Geol. Soc. Am. Bull., 81, 2203-2220.
Beeson, M.H. and Jackson, E.D., 1969. Chemical composition of altered chromitites from the Stilwater
Complex, Montana. Am. Mineral., 54, 1084-1100.
Blais, S. and Auvray, B., 1990. Serpentinization in the Archean komatiitic rocks of the Kuhmo
greenstone belt, Eastern Finland. Can. Mineral., 28, 55-66.
Bohike, J.K., 1989. Comparisons of metasomatic reactions between a common CO2-rich vein fluid and
diverse wall rocks: variables, mass transfers, and Au mineralization at Alleghany, California. Econ.
Geol., 84, 291-327.
Boocock, C.N., 1984. Ore genesis along the Antimony line, Murchison Range, north-eastern Transvaal.
Unpubl. M.Sc. thesis, Univ. Witwatersrand, Johannesburg, 163pp.
Boocock, C.N., Cheshire, P.E. and Veamcombe, J.R., 1984. The structural geology of the Gravelotte
Shaft Quarry and Monarch Antimony Mine, Murchison greenstone belt, Transvaal. Trans. Geol. Soc. S.
Afr., 87, 315-325.
133
Boocock, C.N., Cheshire, P.E., Killick, A.M., Maiden, K.J. and Veamcombe, J.R., 1988. Antimony - gold
mineralization at Monarch mine, Murchinson schist belt, Kaapvaal craton. Univ. western Australia
Geology Dept. Univ. Ext. Pub., 12, 81 -97.
Cameron, E.M., 1988. Archean gold: relation to granulite formation and redox zoning in the crust. Geology, 16, 109-112.
Card, K.D., 1986. Tectonic setting and evolution of late Archean greenstone belts of Superior Province,
Canada. In: M.J. De Wit and L.D. Ashwal (Eds), Workshop on tectonic evolution of greenstone belts,
74-76. LPI Tech. Rpt. 86-10. Lunar and Planetary Institute, Houston.
Caruso, L.J. and Chemosky, J.V., Jr, 1979. The stability of lizardite. Can. Mineral., 17, 757-769.
Chemosky, J.V., Berman, R.G. and Bryndzia, L.T., 1988. Serpentine and chlorite equilibria. In: S.W. Bailey (Ed.), Rev. in Mineral., 19, 295-346.
Cheshire, P.E., 1986. Geology of the Pioneer Area (Old Rainbow Claims). JCI, Plan no. HAM 52, 1:2000.
Clark, M.E., Carmicheal, D.M., Hodgson, C.J. and Fu, M., 1988. Wall rock alteration, Victory gold mine,
Kambalda, Western Australia: Processes and P-T- Xco 2 conditions of metasomatism. In: R.R. Keays,
W.R.H. Ramsay and D.I. Groves (Eds), Econ. Geol., Monograph 6, 445-459.
Coetzee, D.S., 1993. Syn-tectonic quartz vein formation in relationship to metamorphism, fluid
inclusions and thrust tectonism on northern margin of the Witwatersrand basin. Unpubl. PhD thesis.
Rand Afrikaans Univ., Johannesburg, 395pp.
Cogulu, E. and Laurent, R., 1984. Mineralogical and chemical variation in chrysotile veins and peridotite
host-rocks from the asbestos belt of southern Quebec. Can. Mineral., 22, 173-183.
Collins, P.L.F., 1979. Gas hydrates in CO2-bearing fluid inclusions and the use of freezing data for estimation of salinity. Econ. Geol., 74, 1435-1444.
Colvine, A.C., 1983. The introduction to the geology of gold in Ontario. Ontario Geological Misc. Paper 110, 3-10.
134
Colvine, A.C., Fyon, A.J., Heather, K.B., Marmont, S., Smith, P.M and Troop, D.G., 1988. Archean lode
gold deposits in Ontario. Ontario Geological Survey Misc. Paper 139, 210pp.
Condie, K.C., 1980a. Origin and early development of the earth crust. Precamb. Res., 11, 183-197.
Condie, K.C., 1981. Archean greenstone belts. Elsevier, Amsterdam, 434pp.
Condie, K.C. and Harrison, N.M., 1976. Geochemistry of the Archean Bulawayan Group, Midlands
Greenstone Belt, Rhodesia. Precamb. Res., 3, 253-271.
Cox. S.F, Etheridge, M.A. and Wall. V.J., 1986. The role of fluids in syntectonic mass transport, and
the localization of metamorphic vein-type ore deposits. Ore Geol. Rev., 2, 65-86.
Crawford, M.L. and Hollister, L.S., 1986. Metamorphic Fluids: The evidence from fluid inclusion. In: J.V.
Walther and B.J. Wood (Eds), Fluid-Rock Interactions during Metamorphism. Springer, New York, 1-35.
Davies, J.F., Whitehead, R.E., Huang, J. and Nawarante, S., 1990. A comparision of progressive
hydrothermal carbonate alteration in Archean metabasalts and metaperidotites. Mineral. Dep., 25, 65-
72.
Deer, W.A., Howie, R.A. and Zussman, J., 1992. An introduction to the rock-forming minerals. 2nd Ed.
John Wiley and Sons. New York, 696pp.
De Ronde, C.E.J., Spooner, E.T.C., de Wit. M.J. and Bray, C.J., 1992. Shear zone-related, Au quartz
vein deposits in the Barbeton greenstone belt, South Africa: Field and petrographic characteristics, fluid
properties, and light stable isotope geochemistry. Econ. Geol., 87, 366-402.
DeSitter, L.U., 1954. Gravitational sliding tectonics - an essay on comparative structural geology. Am. J.
Sci., 254, 321-344.
De Wit, M.J., 1991. Archean greenstone belt tectonism and basin development: some insight from
Barberton and Pietersberg greenstone belts, Kaapvaal Craton, South Africa. J. Afr. Earth Sci., 13, 45-
63.
De Wit, M.J. and Ashwal, L.D., 1986. Workshop on tectonic evolution of greenstone belts. LPI Tech.
Rpt. 86-10. Lunar and Planetary Institute, Houston, 227pp.
135
De Wit, M.J., Van Reenen, D.D. and Roering, C., 1992. Geologic observations across a tectono-
metamorphic boundary, in the Babangu area, Giyani (Sutherland) Greenstone Belt, South Africa. In:
D.D. van Reenen, C. Roering, L.D. Ashwal and M.J. de Wit (Eds), The Archaean Limpopo Granulite
Belt: Tectonics and Deep Crustal Processes, Precambrian Res., 55, 111-122.
Dube, B., Guha, J. and Rocheleau, M., 1987. Alteration patterns related to gold mineralization and their
relation to CO2/H20 ratios. Mineral. Petrol., 37, 267-291.
Dymek, R.F., Brothers, S.0 and Cshiffries, C.M., 1988. Petrogenesis of ultramafic rocks from the 3800 Ma lsua Supracrustal Belt, West Greenland. Journal of petrology, 29, 1353-1397.
Eisenlorhr, B.N., Groves, D.I. and Partington, G.A., 1989. Crustal-scale shear zones and their
significance to Archean gold mineralization in Western Australia. Mineral. Deposit., 24, 1-8.
Evans, B.W., 1977. Metamorphism of alpine peridotite and serpentinite. Ann. Rev. Earth Planet. Sci., 5, 397-447.
Evans, B.W. and Frost. B.R., 1975. Chrome-spinel in progressive metamorphism - a preliminary analysis. Geochim. Cosmochim. Acta., 39, 959-972.
Evans, B.W. and Guggenheim, S., 1988. Talc, pyrophyllite and related minerals. In: S.W. Bailey (Ed.),
Hydrous phyllosilicates (exclusive of micas). Mineral. Soc. Am. Rev. in Mineral., 19, 225-294.
Francis, G.H., 1955. Zoned hydrothermal bodies in the serpentinite mass of Glen Urquhart (Inverness-shire). Geol. Mag., 92, 433-447.
Francis, G.H., 1956. The serpentinite mass in Glen Urquahart, Inverness-shire, Scotland. Am. J. Sci., 254, 201-226.
Fripp, R.E.P, van Nierop, D.A., Callow, M.J., Lilly, P.A. and du Plessis, L.U., 1980. Deformation in part
of the Archaean Kaapvaal Craton, South Africa. Precamb. Res., 13, 241-251.
Fryer, B.J., Kerrich, R, Hutchison, R.W., Peirce, M.G. and Rogers, D.S., 1979. Archean preceous-metal
hydrothermal systems, Dome mine, Abitibi greenstone belt. I. Patterns of alteration and metal
distribution. Can. J. Earth Sci., 16, 421-439.
136
Fyon, J.A. and Crocket, J.H., 1982. Gold exploration in in the Timmins district using field and
lithologeochemical characteristics of carbonate alteration zones. In: R.W. Hodder and W. Petruk (Eds),
Geology of Canadian ore deposits, Canadian Institute of Mining and Metallurgy, Spec. Vol., 24, 113-
129.
Gillery, G.H., 1959. X-ray study of synthetic Mg-Al serpentine and chlorite. Am. Mineral., 44, 143-152.
Glossary of geology and related sciences, 1962. The American Geological Institute, Washington,
Second Ed.
Golding, S.D. and Wilson, A.F., 1983. Geochemical and stable isotope studies of the No. 4 lode,
Kalgoorlie, Western Australia. Econ. Geol., 78, 438-450.
Golding, S.D., McNaughton, N.J., Barley, M.E., Groves, D.I., Ho. S.E, Rock, M.N.S. and Turner, J.V.,
1989. Archean carbon and oxygen reservoirs: The significance for fluid sources and circulation paths for
Archean mesothermal gold deposits of the Norseman-Wiluna belt, Western Australia. In: R.R. Keays,
W.R.H. Ramsay and D.I. Groves (Eds). Econ. Geol., Monograph 6, 376-388.
Gresens, R.L., 1967. Composition-volume relationship of metasomatism. Chem. Geol., 2, 47-65.
Groves, 1991. Structural setting and control of gold deposits. In: F. Robert, P.A. Shearhan and S.B.
Green (Eds), Nuna conference (1990; Val d'Or Quebec): Greenstone gold and crustal evolution, 79-85.
Groves, D.I., Barley, M.E. and Ho. S.E., 1989. Nature, genesis, and tectonic setting of mesothermal
gold mineralization in the Yilgam Block, Western Australia. In: R.R. Keays, W.R.H. Ramsay and D.I.
Groves (Eds), Econ. Geol., Monograph 6, 71-85.
Groves, D.I., Goldwin, S.D., Rock, N.M., Barley, M.E. and McNaughton, N.J, 1988. Archean carbon
reservoirs and their relevance to the fluid source for gold deposits. Nature 331, 254-257.
Groves, D.I. and Phillips, G.N., 1987. The genesis and tectonic control on Archean gold deposits of the
western Australian shield - a metamorphic replacement model. Ore Geol. Rev., 2, 286-322.
Groves, D.I., Phillips, G.N., Ho, S.E., Henderson, C.A., Clark, M.E. and Woad, G.M., 1984. Controls on
distribution of Archean hydrothermal gold deposits in western Australia. In: R.P. Foster (Ed.), Gold '82:
The geology, geochemistry and genesis of gold deposits. Rotterdam, A.A. Balkema Pub., 689-711.
137
Groves, D.I., Phillips, G.N., Ho, S.E., and Houstoun, S. M., 1985. The nature, genesis and regional
controls of gold mineralization in Archean greenstone belts of western Australian Shield: A brief review.
Trans. Geol. Soc. S. Afr., 88, 135-148.
Haas, J.L. Jr., 1976. Physical properties of the coexisting phases and thermochemical properties of the
H2O component in boiling NaCI solutions. U. S. Geol. Surv. Bull., 1421A, 73pp.
Hall, A.L., 1912. The Geology of Murchison Range and District. Mem. Geol. Surv. S. Afr., 6, 186pp.
Hedenquist, J.W. and Henley, R.W., 1985. The importance of CO2 on freezing point measurements of
fluid inclusions. Evidence from active geothermal systems and implications for epithermal ore
deposition. Econ. Geol., 80, 1379-1406.
Hendell, E.M. and Hollister, L.S., 1981. An impirical solvus for CO2 - H2O - 26 wt. % salt. Geochim.
Cosmochim. Acta., 45, 225-228.
Hey, H.M., 1954. A new review of the chlorites. Mineral. Mag., 30, 277-292.
Ho, S.E., Groves, D.I. and Phillips, G.N., 1985. Fluid inclusions as indicators of the nature and source of
ore fluids and ore depositional conditions for Archean gold depositsof the Yilgam Block, Western
Australia. Trans. Geol. Soc. S. Afr., 88, 149-158.
Hodgson, C.J. and Hamilton, J.V., 1989. Gold mineralization in the Abitibi greenstone belt: End-stage
results of Archean Collisional tectonics? In: R.R. Keays, W.R.H. Ramsay and D.I. Groves (Eds). Econ.
Geol., Monograph 6, 86-100.
Hoefs, J., 1987. Stable isotope geochemistry, Springer-Verlang, 241pp.
Hoffman, P.E., 1991. On accretion of granite-greenstone terranes. In: F. Robert, P.A. Shearhan and
S.B. Green (Eds), Nuna conference (1990; Val d'Or Quebec): Greenstone gold and crustal evolution,
32-45.
Hostetler, P.B., Coleman, R.G., Mumpton, F.A. and Evans, B.W., 1966. Brucite in alpine serpentinites.
Am. Mineral., 51, 75-98.
138
Huchison, R.W. and Burlington, J.L., 1984. Some broad characteristics of greenstone belt gold lodes. In:
R.P. Foster (Ed.), Gold '82: The geology, geochemistry and genesis of gold deposits. Rotterdam, A.A. Balkema Pub., 339-369.
Hunter, D.R., 1991. Crustal Processes during Archean evolution of the southeastern Kaapvaal province. J. Afr. Earth Sci., 13, 13-25.
Jensen, L.S., 1976. A new method of classifying subalkaline volcanic rocks. Ontario Division of Mines, Misc. Paper no. 66.
Johannes, W., 1969. An experimental investigation of the system MgO-Si02-H20-0O2. Am. J. Sci., 267, 1083-1104.
Kagen, P.C.A. and Oen, I.S., 1983. Iron-rich talc-opal-minnesotaite spherulites and crystallochemical
relations relations of talc and minnesotaite. Mineral. Mag., 47, 229-231.
Keenan, J.H., Keyes, F.G., Hill. P.G. and Moore, J.G., 1969. Steam table. Thermodynamic properties of
water including vapour, liquid and solid phases. John Wiley & Sons, Inc., New York, 156pp.
Kerrich, R., 1983. Geochemistry of gold deposits in the Abitibi greenstone belt. Canadian Institute of Mining and Metallurgy, Spec. Vol., 27, 75pp.
Kerrich, R. and Allison, I., 1978. Vein geometry and hydrostatics during during Yellowknife
mineralization; Can. J. Earth Sci., 15, 1653-1660.
Kerrich, R. and Fyfe, W.S., 1981. The gold-carbonate association: source of CO2, and CO 2 fixation
reactions in Archean lode deposits. Chem. Geol., 33, 265-294.
Kerrich, R., Kishida, A. and Willmore, L.M., 1984. Timing of Abitibi beltlode gold deposits: Evidence from 39Ar/40Ar and 87Rb-86Sr (Abs.), Geol. Assoc. Canada, Program with Abs., 9, 78.
Kishida, A. and Kerrich, R., 1987. Hydrothermal alteration zoning and gold deposit, Kirkland lake,
Ontario. Econ Geol., 82, 649-690.
Kyser, T.K., 1986. Stable isotope variations in the mantle. In: J.W. Valley, H.P. Taylor and J.R. O'Neil
(Eds), Stable isotopes in high temperature geological processes. Am. Mineral. Soc. Rev. Mineral., 16, 141-164.
139
Lappin, M.A., 1971. The petrofabric orientation of olivine and seismic anisotropy of the mantle. J. Geol.,
79, 730-740.
Le Grange, J.M., 1929. The Barbara beryls: A study of an occurrence of emeralds in the north-eastern
Transvaal with some observations on metallogenic zoning in the Murchison Range. Trans. Geol. Soc. S.
Afr., 32, 1-25.
Loferski, P.J., 1986. Petrology of metamorphosed chromite-bearing ultramafic rocks from the Red
Lodge District, Montana. U.S.G.S., Bull., 1626-B, 34pp.
Lonsdale, P.F., Bischoff, J.L., Bums, V.M., Kastner, M. and Sweeney, R.E., 1980. A high temperature
hydrothermal depositon the seabed at a Gulf of California spreading center. Earth Planet. Sci. Letters,
49, 8-20.
Lowe, D.R. and Byerly, 1986. The rock components and structure of Archean greenstone belts: An
overview. In: M.J. De Wit and L.D. Ashwal (Eds), Workshop on tectonic evolution of greenstone belts,
142-146. LPI Tech. Rpt. 86-10. Lunar and Planetary Institute, Houston.
McCourt, S. and Van Reenen, D.D., 1992. Structural geology and tectonic setting of the Sutherland
Greenstone Belt, Kaapvaal Craton South Africa. In: D.D. van Reenen, C. Roering, L.D. Ashwal and M.J.
de Wit (Eds), The Archean Limpopo Granulite Belt: Tectonics and Deep Crustal Processes,
Precambrian Res., 55., 93-110.
McCourt, S., 1987. Geology of the County Down Mine area. JCI, Plan no. HAM 53, 1:1000.
Mendelssohn, E., 1938. Gold deposits of the central Murchison Range, Transvaal. Trans. Geol. Soc. S.
Afr., 41, 249-272.
Mercier, J.C.C. and Nocolas, A., 1975. Textures and fabrics of upper-mantle peridotites as illustrated by
xenoliths from basalt. J. Petrol., 16, 454-487.
Minnit, R.C.A., 1975. The geology of eastern portion of the Murchison Range between Quagga camp
area and the Kruger National Park. Unpubl. M.Sc. thesis. Univ. Witwatersrand, Johannesburg, 171pp.
Moritz, R.P. and Crocket, J.H., 1991. Hydrothermal wall rock alteration and formation of the gold-
bearing quartz-fuchsite vein at the dome mine, Timmins Area, Ontario, Canada. Econ. Geol., 86, 620-
643.
140
Muff, R., 1976. Geological, metallogenic and geostatistical investigation at the United Jack and Weigel
mines, Murchison Range. Unpubl. Ph.D. thesis. Univ. Heidelberg, West Germany, 262pp.
Muff, R. and Saager, R., 1979. Metallogenic interpretations from a mineragraphic and geostatistic study
of study of the Murchison greenstone belt, South Africa. Spec. Publ. Geol. Soc. S. Afr., 5, 167-180.
Neall, F.B. and Phillips, G.N.,1987. Fluid-wall rock interaction in an Archean hydrothermal gold deposit:
a thermodynamic model for the Hunt Mine, Kambalda. Econ. Geol., 82, 1679-1694.
Nelson, B.W. and Roy, R., Synthesis of chlorites and their structural and chemical composition. Am.
Mineral., 43, 707-725.
Nesbitt, B.E., Murowchich, J.B. and Muehlenbachs, K., 1986. Dual origins of lode gold deposits in the
Canadian Cordillera. Geol., 14, 501-509.
Nicolas, A., Bouchez, J.L., Boudier, F. and Mercier, J.C., 1971. Textures, structures and fabrics due to
solid state flow in some european lherzolites. Tectonophys., 12, 55-86.
Nicolas, A., Boudier, F. and Boullier, A.M., 1973. Mechanism of flow in naturally and experimentally
deformed peridotites. Am. J. Sci., 273, 853-876.
Nisbet. E.G., Bickle, M.J. and Martin, A., 1977. The mafic and ultramafic lavas of the Belingwe
greenstone belt, Rhodesia. J. Petrol., 18, 521-566.
O'Hanley, D.S., 1987. A chemographic analysis of magnesian serpentinites using dual networks. Can. Mineral., 25, 121-133.
O'Hanley, D.S., 1991. Fault-related phenomena associated with hydration and serpentine
recrystallization during serpentinization. Can. Mineral., 29, 21-35.
O'Hanley, D.S., 1991. Metamorphism in greenstone belts: serpentinites. Unpubl.
O'Hanley, D.S., 1992. Solution to the volume problem in serpentinization. Geol., 20, 705-708.
O'Hanley, D.S., Chemosky,. J.V. Jr., and Wicks, F.J., 1989a. The stability of lizardite and chrysotile.
Can. Mineral., 27, 483-394.
141
Ohmoto, H, 1986. Stable isotope geochemistry of ore deposits. In: J.W. Valley, H.P. Taylor Jr. and J.R.
O'Neil (Eds), Am. Mineral. Soc. Rev. Mineral., 16, 491-560.
Page, N., 1967a. Serpentinization at Burro Mountain, Carlifomia. Contrib. Mineral. Petrol., 14, 321-342.
Page, N., 1967b. Serpentinization considered as a constant volume metasomatic process - a
discussion. Am. Mineral., 52, 545-549.
Pearton, T.N., 1978. The geology and geochemistry of the Monarch ore body and environs, Murchison
Range, North-eastern Transvaal. Spec. Publ. Geol. Soc. S. Afr., 4, 77-86.
Pearton, T.N., 1979. A geochemical investigation of the carbonate and associated rocks of the Monarch
Antimony Line, Murchison Range, north-eastern Transvaal. Spec. Publ. Geol. Soc. S. Afr., 5, 159-166.
Pearton, T.N., 1980. The geochemistry of the carbonate and related rocks of the Antimony line,
Murchison Greenstone Belt, with particular reference to their genesis and to the origin of stibnite
mineralization. Unpubl. Ph.D. thesis, Univ. Witwatersrand, Johannesburg, South Africa, 347pp.
Pearton, T.N. and Viljoen, M.J., 1986. Antimony mineralization in the Murchison greenstone belt - An
Overview. In: C.R. Anhaeusser and S. Maske (Eds), Mineral Dep. S. Afr., 293-320.
Percival, J.A. and Card, K.D., 1986. Greenstone belts: Their boundaries, surrounding rock terrains, and
interrelationships. In: M.J. De Wit and L.D. Ashwal (Eds), Workshop on tectonic evolution of greenstone
belts, 170-174. LPI Tech. Rpt. 86-10. Lunar and Planetary Institute, Houston.
Perkins, E.H., Brown, T.H. and Berman, R.G., 1986. PTX-system: Three programs for calculation of
pressure-temperature-composition phase diagrams. Computers and Geosc., 12, 749-755.
Phillips, G.N., 1990. Wall rock alteration and P-T environments of gold deposition. In: F. Robert, P.A.
Shearhan and S.B. Green (Eds), Nuna conference (1990; Val d'Or Quebec): Greenstone gold and
crustal evolution, 98-99.
Phillips, G.N. and Brown, I.J., 1987. Host rock and fluid control on carbonate assemblages in the
Golden Mile Dolerite, Kalgoorlie gold deposit, Australia. Can. Mineral., 23, 265-273.
Phillips, G.N. and Groves, D.I., 1983. The nature of Archean gold-bearing fluids as deduced from gold
deposits of Western Australia. Geol. Soc. Australia Jour., 30, 25-39.
142
Pinsent, R.H. and Hirst, D.M., 1977. The metamorphism of Blue River ultramafic body, Cassiar, British
Columbia, Canada. J. Petrol., 18, 567-594.
Potter, R.W., Clynne, M.A. and Brown, D.L., 1978. Freezing point depression of aqueous sodium
chlorine solutions. Econ. Geol., 73, 284-285.
Ragan, D.M., 1967. The Twin Sister dunite, Washington. In: P.J. Wyllie (Ed.), Ultramafic and related rocks. New York, John Wiley & Sons, 160-167.
Raleight, C.B. and Paterson, M.S., 1965. Experimental deformation of serpentinite and its tectonic
implications. J. Geophys. Res., 70, 3965-3985.
Robert, F. and Brown, A.C., 1986b. Archean gold-bearing quartz-veins at the Sigma mine, Abitibi
greenstone belt, Quebec: Part 2, vein paragenesis and hydrothermal alteration. Econ. Geol., 81, 593-616.
Robert, F., Phillips, G.N. and Kesler, S.E., 1991. Greenstone gold and crustal evolution: Scope and
results of the conference. In: F. Robert, P.A. Shearhan and S.B. Green (Eds), Nuna conference (1990;
Val d'Or Quebec): Greenstone gold and crustal evolution, 2-7.
Roberts, R.G., 1987. Ore deposit models-II: Archean lode gold deposits. Geosci. Can., 14, 37-52.
Roberts, R.G. and Reading, D.J., 1981. Volcanic tectonic setting of gold deposits in the Timmins District
- carbonate-bearing rocks at the Dome mine, Ontario Geol. Surv. Misc. Paper, 98, 222-232.
Roedder, E. 1984. Fluid inclusions. Rev. Mineral., 12, 643pp.
Roedder, E. 1984. Fluid inclusion evidence bearing on enviroments of gold deposition. In: R.P. Foster
(Ed.), Gold '82: The geology, geochemistry and genesis of gold deposits. Rotterdam, A.A. Balkema Pub., 129-163.
Sanford, R.F., 1982. Growth of ultramafic reaction zones in greenschist to amphibolite facies
metamorphism. Am. J. Sci., 282, 543-616.
Schandl, E.S. and Wicks, F.J., 1991. Two stages of CO2 metasomatism at the Munro mine, Munro
Township, Ontario: evidence from fluid inclusion, stable isotope, and mineralogical studies. Can. J. Earth Sci., 28, 721-728.
143
Sheperd, T.J., Rankin, A.H. and Alderton, D.H.M., 1985. A practical guide to fluid inclusions. Blackie.
New York. 239pp.
Smith, H.S., 1986. Evidence for 13C and 180 isotopes in carbonate minerals for the origin of fluids in
Archean greenstone belt metamorphic and mineralization processes (Abs.), Geocongress '86, Geol.
Soc. S. Afr., Johannesburg. Univ. Witwatersrand., July 7-11, Ext. Abs., 341-344.
Tankard, A.J., Jackson, M.P.A., Eriksson, K.A., Hobday, D.K., Hunter, D.R. and Minter, W.E.L., 1982.
Crustal evolution of southern Africa, 3.8 bilion years of earth history. Springer-Verlag, Berlin, 523pp.
Tamey, J., Dalziel, I.D.W. and de Wit, M.J., 1976. Marginal basin "Rocas Verdes" complex from S.
Chile: A model for Archean greenstone belt formation. In: B.F. Windley (Ed), The early history of the
earth. J. Wiley & Sons, New York, 131-146.
Thayer, T.P., 1967. Serpentinization considered as a constant-volume metasomatic process: A reply.
Am. Mineral., 51, 685-710.
Trommsdorff, V. and Connolly, J.A., 1990. Constrains on phase diagram topology for the system CaO-
Mg0-Si02-0O2-H20. Contrib. Mineral. Petrol., 104, 1-7.
Trommsdorff, V. and Evans, B.W., 1972. Progressive metamorphism of antigorite schist in the Bergell
tonalite aureole (Italy). Am. J. Sci., 272, 523-437.
Trommsdorff, V. and Evans, B.W., 1977. Antigorite-ophicarbonates: Phase relations in the portion of the
system CaO-MgO-SiO2-H20-0O2. Contrib. Mineral. Petrol., 60, 39-56.
Ulmer, G.C., 1974. Alteration of chromite during serpentinization in the Pennsylvania-Maryland District.
Am. Mineral., 59, 1236-1241.
Vance, J.A. and Dungan, M.A., 1977. Formation of peridotites by deserpentinization in the Darrington
and Sultan areas, Cascade Mountains, Washington. Geol. Soc. Am. Bull., 88, 1497-1508.
Van Eeden, O.R., Partridge, F.C., Kent, L.R., and Brandt, J.W., 1939. The mineral deposits of the
Murchison Range east of Leydsdorp. Mem. Geol. Soc. S. Afr., 36, 172pp.
Van Schalkwyk, J.F. 1991. Metamorphism of ultramafic rocks during the Limpopo orogeny: evidence for
the timing and significance of CO2-rich fluids. Unpubl. Ph.D. thesis. Rand Afrikaans University,
Johannesburg, 268pp.
144
Van Schalkwyk, J.F., De Wit, M.J., Roering, C and Van Reenen, D.D., 1992. Tectono-metamorphic
evolution of simatic basement of the Pietersberg greenstone belt relative to the Limpopo Orogeny:
evidence from serpentinite. Precamb. Res., 61, 67-88.
Veamcombe, J.R., 1988. Structure and metamorphism of the Archean Murchison Belt, Kaapvaal
Craton, South Africa. Tectonics, 7, 761-774.
Veamcombe, J.R., 1991. A possible island arc in the Murchison Belt, Kaapvaal Craton, South Africa. J. Afr. Earth Sci., 13, 200-304.
Veamcombe, J.R., 1992. The Murchison Belt, Kaapvaal Craton: A possible source for Witwatersrand
gold? In: J.E. Glover and S.E. Ho (Eds), The Archean: Terrains, Processes and metallogeny, 409-420.
Geology Department and University Extension, University of Western Australia.
Veamcombe, J . R., Barley, M. E., Eisenlohr, B. N., Groves, D. I., Houston, S. M., Skwamecki, M . S.,
Grigson, M. W. and Partington, G . A., 1988. Structural controls on mesothermal gold mineralization:
Examples from Archean terranes of Southern Africa and Western Australis. In Reid R. Keays, W. R. H.
Ramsay and David I. Groves (Eds). Econ. Geol. Monograph 6. 124 - 134.
Veamcombe, J.R., Barton, J.M. and van Reenen. D.D., 1986. Greenstone belts: Their components and
structure. In: M.J. De Wit and L.D. Ashwal (Eds). Workshop on tectonic evolution of greenstone belts,
214-220. LPI Tech. Rpt. 86-10. Lunar and Planetary Institute, Houston.
Veamcombe, J.R., Barton, J.M. and Walsh, K.L., 1987. The Rooiwater Complex and associated rocks,
Murchison granitoid-greenstone terrane, Kaapvaal Craton. S. Afr. J. Geol., 90, 361-377.
Veamcombe, J.R., Cheshire, P.E., De Beer, J.H., Killick, A., Mallinson, W.S., McCourt, S. and Stettler,
E.H., 1988. Structures related to the Antimony line, Murchison shist belt, Kaapvaal craton South Africa.
Tectonophys., 154, 285-305.
Veiser, J., Hoefs, J., Lowe, D.R. and Thurston, P.C., 1989. Geochemistry of Precambrian carbonates: II.
Archean greenstone belts and Archean sea water. Geochim. Cosmochim. Acta, 53, 859-871.
Veiser, J., Hoefs, J., Riddler, R.H., Jensen, L.S. and Lowe, D.R., 1989. Geochemistry of Precambrian
carbonates: I. Archean hydrothermal systems. Geochim. Cosmochim. Acta, 53, 845-857.
Viljoen, M.J., 1979. Geology and Geochemistry of the "Antimony line" in the United Jack Complex,
Murchison Range. Spec. Publ. Geol. Soc. Surv. S. Afr., 5, 133-158.
145
Viljoen, M.J., Van Vuuren, C.J.J., Pearton, T.N., Minnit, R, Muff, R. and Cilliers, P., 1978. The regional
geological setting of mineralization in the Murchison Range with particular reference to antimony. Spec.
Publ. Geol. Soc. S. Afr., 4, 55-76.
Wicks, F.J., 1984. Deformational histories as recorded by serpentinites. I. Deformation prior to
serpentinization. Can. Mineral., 22, 185-195.
Wicks, F.J., 1984. Deformational histories as recorded by serpentinites. III. Fracture patterns developed
prior to serpentinization. Can. Mineral., 22, 205-209.
Wicks, F.J. and O'Hanley, D.S., 1988. Serpentine minerals, structures, and petrology. In: S.W. Bailey,
(Ed.), Hydrous Phylosilicates. Rev. in Mineral., 19, 91-167.
Wicks, F.J. and Plant, A.G., 1979. Electron microprobe and X-ray microbeam studies of serpentine
textures. Can. Mineral., 17, 785-830.
Wicks, F.J. and Whittaker, E.W.J., 1977. Serpentine textures and serpentinization. Can. Mineral., 15,
459-488.
Wicks, F.J., Whittaker, E.W.J. and Zussman, J., 1977. An idealized model for serpentine textures after
olivine. Can. Mineral., 15, 446-458.
Willemse, J., 1935. On the ore-minerals of the Murchison Range, the Cam and Motor Mine (Gatooma)
and the Globe and Phenix Mine (Que Que). Trans. Geol. Soc. S. Afr., 38, 41-54.
Williams, A.J., 1979. Foliation development in serpentinites, Glenrock, New South Wales.
Tectonophys., 58, 81-95.
Windley, B.F., 1977. The evolving continents. J. Wiley & Sons, New York, 385pp.
146
APPENDIX I : MICROPROBE DATA
Some of the microprobe analyses from the serpentinite, ophicarbonate and quartz-carbonate rocks that
were used in this study are presented in tables 1 to 5.
Mineral analyses were carried out with a Cameca Camebax 355 electron microprobe located in the
Geology Department at RAU. Operating conditions were 15KeV accelerating potential used with a
absorbed 10 nAmp beam current on brass and a beam diameter of approximately 3pm. A set of both
natural and synthetic oxide and silicate standards were used and element concentrations were
calculated using ZAF correction program.
The structural formulae were calculated using the program MINFILE (Afifi and Essene, 1988). Oxygen
basis for the calculation of the cation abundances were use as follows;
Serpentine minerals (lizardite and antigorite) = 7
Chromite = 32
Talc = 22
Chlorite = 28
Carbonate minerals (dolomite an magnesite) = 6
The samples are labelled in the following way;
P = Pioneer locality
S = Pike's Kop locality
C = County Down locality
M and N = Monarch Mine
eg. P11105
P = Pioneer locality
First two numbers (11) = sample number
Last three numbers (105) = number of analysis.
147
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APPENDIX II : BULK ROCK ANALYSES
Bulk rock analyses of serpentinite, ophicarbonate and quartz-carbonate rocks used in the study are
presented in tables A to D.
Bulk rock analyses of major and minor elements were done by the Council for Geosciences. Some of
the analyses were done by the analytical company, Rocklabs, in Pretoria. XRF methods were used in
both instances. Sample preparation was done at RAU. Samples were crushed using a hammer and
were milled in a steel shatterbox to a fine powder size. All equipment was cleaned thoroughly between
successive samples to avoid any contamination.
167
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.cr v 6
el ..-. 6
a:I vr oi el
al .-
0
0 .-
0
•••• 0
a
N. .- ci
N -• 6
al 0
)
0 V 6
0 0 0
CO V 46 0 —
4045
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1
2744
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.
7 CO
N C1) al 0
v. .- 6
co CV 6 8.
43
1
— -•
46
in N. co el
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tf.r0
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1
01 .- .—
0 0
0
0 V' o 0
3983
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0 -..
CO
N
cci r.)
N.
a
CO 0) ci
V* CO d
C') - a
C) el cci C')
0) 0 6
0 .- ... 0 6 6
CO 0 a
C') -• 6
0 el 6
v CO 6
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0 0 d
C0 D N
til U, 38
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1
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If) to 6
CV ..- a
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ai a)
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01
2521
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[60'0
CO ..- N. C')
N
6 O—
0.
10
0.0
1
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CO cv 6
CD .- d
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t... V*
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01
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CO
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151 CO 0
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1
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1
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01
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N CD r...: el
0.15
1 N. CO (7 CV a N
.-
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r 3
6.52
1
v sr 0
0 ..- V .-- 46 o 0 6 a
ul r .-
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c0 0 .-
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0 0 6 N. N. .41*
0 0 a co .cr V'
ttcl I
CO ..- cri
N. ..- 6
Q CI cv ..- .- cci
1 0.
04
c0 CO tti C')
LI:rio
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10
0.02
0.02
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1 8.
331 el
c0 44-
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N 0
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0 0 9 9
N .- a)
cu
0.) a_ O) 141•-)
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CO 0) v el ..-- N.:
1••• ..- 46
CO N to el
0 u.) 6
0 .- .cr .4- o O 6
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6 5.40
1
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4
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cv V
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31
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14
7.23
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el 0 a
al N. ri el
v 0 6 0.
10
0.01
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4.0 cv) CO
c0 0 0) 0 N 6
N. co 6 01
1675
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221
2.00
CIO 44.4
01
0.50
1 N. c.") CV V* .-- CO
N 0 0
N. N. ri c.)
al
6
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CV cv 0
01 rs. .4-
c0 0 CT) 0 a 0
V N. ai a)
3044
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co.)
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o a
au
)
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2 O CO
O 2.26
6.55
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6
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6 6
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2184
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el 4.14
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CO C') N oi r-:
V. 0 ci 35
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cv a
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CV ai a)
771
3.00
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N. el o Tt - N.
go.o
34.0
5.1
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0.00
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1675
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61
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co co In. co .- CO
190'0 1
35
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10
0.01
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a) 4-4. Lc)
co o o 0
r.. 6
el ap cri a)
1572
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2369
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C•I 0 05
CV 0 i= d
r120
3
Fe2O
3To
t.
o c M Im
g 0
o 3
o e. 0 On I Y.4 CC'
'o E
a 14
CSI 8 to
ra 1-9
a_ = .c.
170
2 O
cTst
3
a GM
C))
O fA a,
01
O
O
a
21 to
r ei I ci - sr ) 1
c7,3
a
ts
(N
v.
a
ccz,
oi Tr
.- ci
a3 o a
cn CO
) CO ) .3.
to -•
Ci
a LO 6
N- 00 C:i .-•
LCI ..- C=i
0 0 C1i V
CO -• a
C4 .-•• a 0.
20
S4 I
LO CO si
i Nr
I (0 I .- I ci 1
0 VI a
.- Vs oi
V) .... ci
01 (C) 4 Nr
CLI 0 ci
CNI ...- ci
- 0 ci
LO 0 ci
co 0) Vi 4
10) ..- a
1 co . o .-
o in o ..- tsi a .--
0) CV tsi 4
o .- c:i 0.
11
0.01
60'0
43.
621
1.11 .- ci
,- V- a
in el - .-
.-: ci
el 0 4 V
v) 0 ci
..•••
.-O a O
03 0 a
01 crs isi V
Vs .- a
Ill -•
ci
Csi 0 r-- .-
..- a
ft. fp s- 4
0 a
Ctl CO .- o o ci ci a
S
18
r. CO .0• 4
C. i .- ci
0 sr 6
V .- 03 •-• 0) a
CO Cs,F 4 4
190'0
.- .-- in L-• 0 0 ci 46 ci
.tr o NV
rs. .- a
L 0
.42 co el
to ,- ri a
00 co ..- ta.
0 to 0
••-• .- to ,- o o 0 ci a
1 td
ot a, CO 4
01 ,- a
Is. 61 .-
0 0 0) a
V) 0) el
CLI g 0 a
.- 0 0 a (6 ci
6d
O
vi 4
ces
a
.-
.-
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0) ci 44. 2
5
O
VLI .- - 0 0 a c:i a
0 c■I 51
. 321
O) 1 el r- I V ctsi
s- (s) 0) 0 n: a
.- 0) ci cn
0.04
0.11
0.01
0.04
CO 0.
co •
II- Lc,
co 1 co
to .1. •
0 •-•
..-
ZO'0
101
in CO CO r)
L0'0
ZL'O
LZ 0
0) CL •.-
O CO CNI If)
to o to rs. di VI
VI tNi Cs/ 0 ts: ci
el tO tri el
0.15
0.08
0.02
0.02
to ...- cs-
0) .- 6 in
0.53
2.38
069 33
.83
C•I .-- 0 ' ci a ci
IN (13 a.
48.6
51
1.... Cr) q- tf)
ci oi 8.75
0.04
CO t)
6 vl
lN 4-• m- CO .-• .- 0 0
smi ci ci
1 -7
.1.71
co Ncs.: V
.••• co NCV 01 .-
Ps 0 e0 .-- 00 ci
Ul c10 0 v
sr CNI s•-• 'V scr .- 0 0 .- 6 ci 0
I0£d
n cr) co sr
tO 6
CD Ps Ps 0
ci
O• cl ..- st
S0'0
LO*0
ZL
0
60'0
6s
en 6, oz I-7 < I Fe
2 03T
ot.
Mn0
co'd
ozm
OzeN
0e
0
o6vg
171
APPENDIX III - FLUID INCLUSION DATA
Heating and freezing experiments on fluid inclusions were conducted on doubly polished thin
sections of an average 0.5mm thickness prepared in the RAU geology laboratory. The
experiments were carried out using a modified U.S. Geological Survey gas flow heating-freezing
stage. A calibration standard with a composition of 25 mol % CO2 + 75 mol % H2O was used for
calibration at a temperature of -56.6°C which represents the tripple point of pure CO 2 . The
calibration at the tripple point of water (0.0°C) was done with a calibration sample sample
containing pure water with density of 0.317 g.cre which is equal to the critical density of pure
water (Keenan et al., 1969). Both heating and freezing experiments were conducted on the same
inclusions, with the low temperature experiments done first so as to avoid possible decrepitation
or leakage.
Only primary inclusions, according to the criteria outlined by Roedder (1984), were used for the
study.
1 Ophicarbonate rocks
a Maanesite
Aqueous inclusions
Tmf_ (°C) Th (°C) -7.7 222.1 -2.2 -7.8 327.9 -7.8 -8.7 -7.6 -7.3 -8.5 -8.5 326.5 -8.5 329.2 +0.4 293.4 -7.2 356.7 -7.6 340.8 -9.6 283.7 -7.8 -7.6 306.7 -8.8 -7.3 309.1 -8.9 290.8 -9.7 316.3 -9.5 282.4 -4.5 303.7 -7.2
172
Aqueous inclusions (continued)
1.fn_ (°C) Th (°C) -8.4 299.4 -10.8 311.9 -6.2 305.3 -9.6 -8.2 340.2 -12.0 -12.6 303.8 -8.9 296.8 -8.9 299.4 -8.9 297.1 -8.9 300.0
2 Quartz-carbonate rocks
a Magnesite
Aqueous inclusions
Tmf (°C) Th (°C) -3.3 -6.7 -3.4 -2.4 -2.6 245.0 -5.4 243.4 -3.8 270.0 -4.4 213.7 -3.9 185.1 -4.5 -3.4 275.6 -4.9 236.1 -4.2 243.4 -5.6 227.1 -4.9 -2.0 269.7 -3.2 284.0 -3.2 283.0 -4.3 255.0 -3.8 -2.9 314.6 -3.3 -2.9 281.2 -3.2 -3.2 249.7 -3.2 -3.2 317.2 -3.2 -3.2 279.8 -3.2 -3.6 324.8
173
Aqueous inclusions (continued)
Tmf (°C) Th (°C) -3.3
-3.0 288.3 -3.1 -3.1 -3.2 302.9 -3.4 -3.4
-2.8 241.1
-3.7 -
-4.1 228.5 -4.3
-3.2 267.6 -4.7
b Quartz
Aqueous inclusions
Tmf (°C) Th (°C)
-3.8 384.6 -4.2 -4.2
-4.3 315.5
-3.4 257.6
-3.6 260.3
-3.8 258.2
-3.8 258.2
-6.2 262.7
-4.6 340.1
-2.8 384.6
-2.9 322.5
-3.4 299.4
-4.5 320.6
-3.0 315.3
-2.6 -
-3.9 332.7 -4.2 -4.2 -2.7
-2.6 256.0
-2.9 236.8
-4.8 249.0 -2.8
-3.1 283.4
-3.6 292.7
-2.0 283.2 -3.0 -5.1 -2.5 -2.0 -2.8
174
Aqueous inclusions
Dm_ (°C) Th (°C) -2.9 -11.5 -8.2 -4.4
CO inclusions
lain_ (°C) Th (°C)
-61.4 -26.2
-61.3 -23.1
-64.8 -34.9
-59.8 -16.0
-63.2 -14.1 -57.8
-56.4 2.0
-55.8 6.6
-57.0 7.6
-62.9 -15.0 -59.9 -63.4
-61.1 -12.8
-57.8 -9.9
-60.8 -16.7
-59.4 -5.4
-58.9 -14.8
-59.5 -27.8
-58.3 9.4
-59.6 12.8
-59.8 13.2
-60.0 12.6
-61.3 14.0
-60.0 13.0
-60.6 14.2 -59.4 -61.0 -62.5 -46.9 -46.2 -56.6 -63.1
3 Quartz-carbonate veins
a Quartz
Aqueous inclusions
(°C) Th (°C)
-24.3 423.8
-24.3 - -24.1
175
Aqueous inclusions (continued)
_Tint_ (°C) Th (°C) -24.1 -7.5 >600 -24.2 -20.9 479.5 -24.0 -25.3 -22.9 -23.6 516.2 -22.9 455.5 -25.7
Mixed Hp-CO inclusions
Tcl (°C) Th (°C) +11.2 +10.8 535.0 +12.4 430.7 +10.0 470 (decrepitated) +9.3
176
APPENDIX IV : STABLE ISOTOPE DATA
Carbonate phases from various assemblages were extracted. Various phases were identified by
microprobe analyses. CO 2 was extracted from carbonate minerals and was analysed for 5 13C
isotopes. The analyses were done by Dr. Chris Harris at the University of Cape Town.
1 Ophicarbonate rocks
Magnesite Sample number 513C 8180
P1 0.15 12.23 P9 -0.01 12.21 P17 0.26 12.61 P19 0.09 12.07 P20 0.01 12.35 P30 0.39 14.26
Magnesite veins Sample number 513C 5180
P8 -0.08 12.03 P17 0.90 11.62
2 Quartz-carbonate rocks
Magnesite Sample number 513C 5180
P10-1 -1.63 12.27 P11 -4.49 11.97 P14 0.29 11.78 P59 -0.09 12.39 C7 -4.99 11.93 01 -4.83 11.77 M4 -4.86 11.18 M5 -4.08 12.05 M6 -4.96 12.05 M7 -4.83 12.23
Dolomite Sample number 513C 5180
P10-1 -1.64 11.48 P11 -4.28 10.74 P14 0.47 11.08 P59 0.11 11.69 C7 -5.26 10.49 01 -5.31 11.00 M4 -5.09 10.46 M5 -3.69 10.84 M6 -5.19 10.94 M7 -4.37 11.37
177
3 Quartz-carbonate veins
Magnesite Sample number 513c 5180 01 -6.89 11.45 04 -5.76 13.30
Dolomite Sample number 513C 5180 01 -6.83 11.29 04 -6.43 11.59
178