Abstract
This thesis is divided into eight chapters excluding the Introduction (Chapter 1):-
Literature Review: Chapter 2 provides a detailed overview of the historical mining activities
within the East Pilbara Superterrain. Details such gold production, grades and mining techniques
are described, together with size and orientation of the orebodies. The alteration zone is described
in
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detaiL At the end of Chapter 2, a comparison between the different gold deposits is made, and
according to their importance, specific gold deposits are selected for detailed studies.
Structural and Kinematic Setting of Greenstone-Hosted Gold Deposits and Structural and
Kinematic Setting of Turbidite-Hosted Gold Deposits: Chapters 3 and 4 describe the kinematic and
tectonic history of the main research areas in the Marble Bar and Nullagine Domains. The reason
for classifying the gold deposits in two separate domains is the fact that gold deposits in the Marble
Bar Domain are mainly hosted by greenstones wrapping the Mount Edgar Batholith, while in the
Nullagine Domain the gold mineralisation is hosted by turbidites. Furthermore, the area around
each gold deposit has been studied in terms of kinematic and structural setting. Later, the
kinematics of structures at the gold deposits is correlated with the regional tectonic studies of
previous works (e.g. Kloppenberg et aL, 2001; Huston et aL, 2002; Zegers et al., 2002). The timing
of the gold deposition, in relation to the tectonothermal events, is constructed.
Mineral Associations. Paragenetic Sequences and Alte~ation Associated with the
Greenstone-Hosted Gold Deposits and Alteration. Paragenetic Sequences, Mineral AssociationsTurbidite-
Hosted Gold Deposits: - Chapters 5 and 6 describe the petrogenetic characteristics of
several deposits in each domain, as well as alteration zones and mineral assemblages. The paragenetic sequence of each mineral phase in relation to other mineral phases is constructed, and
tables containing paragenetic relations between the mineral phases are presented. This work was
undertaken using reflected light microscopy and qualitative analysis using Jeol JXA8600
Superprobe. The evolution of the gold bearing fluid is discussed for some deposits.
Microstructural and Fabric Studies of Chert Leaders. and Au Mineralisation within the
Warrawoona Greenstone Belt: Microstructural Fabric and Geochemical Studies:- Chapter 7
Illite Crystallinity: - Chapter 8:
Geochronology: - Chapter 9 deals with the geochronological dating of some gold deposits, to
establish the relationship between the gold deposition event and the tectonothermal events that
occurred in the Pilbara Craton. This chapter presents a different dating technique from the Pb
isotope model ages extensively used for the gold deposits of the Pilbara Craton. The Pb isotope
technique offers many disadvantages as even within a single deposit, an age variation due to
mixing of Pb isotopes is observed (Huston eta!., 2002). A compilation of the Pb isotope ages using
galena has been completed by Huston et a!. (2002) and is presented at the beginning of Chapter 9.
In addition to the compilation of the ages of the gold deposits in the Pilbara Craton, a summary of
geochronological dating of tectonic events is also provided. This summary has been presented by
Hickman (1984), Collins et a!. (1998), Zegers et a!. (1998) and Van Kranendonk et a!. (2002). In
addition to the compilations of the age dating, as well the compilation of the tectonothermal events
that took place in the Pilbara Craton, the relation between both compilations is made.
In order to precisely date the gold deposits of the Warrawoona Mining Centre and later
compare those data with Pb isotope age dating using galena samples from the same area, two felsic
dykes with well-constrained kinematics, were collected (Samples KL00/04 and KL00/05). The
felsic dyke KL00/05 display similar kinematics and has stretching lineation with similar orientation
as the stretched gold-bearing pyrites from Klondyke Queen Mine. This sample is interpreted as
syn-tectonic to the gold deposition event. Sample KL00/04 on the other hand, displays no notable
deformation and is interpreted to be younger than the felsic dyke sample (KL00/05). This sample is
interpreted as post-tectonic to the gold deposition event. Dating of these two felsic dykes gave a
best constrain for the gold deposition event in the Warrawoona Mining Centre.
The gold deposits of the Sharks Well Mining Centre were also selected for dating. Within
this mining centre, the Sample SG00/01 had been collected. Sample SG00/01 consists of felsic
volcanic rock that crosscuts the gold-bearing quartz vein at Mount Ada Mine. Dating of this sample
provided a minimum age constraint for the age of the gold depositionat Sharks Well Mining
Centre.
Both the gold deposits from the Warrawoona Mining Centre and Sharks Well Mining Centre
were dated using Pb-Pb and U/Pb simultaneous solution nebulisation and Laser Ablation
Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) at the University of Utrecht,
Netherlands. The LA-ICP-MS uses a short wavelength _Lambda Physik Complex Argon Fluoride 193 nm Excimer Laser, associated with a Micromass Platform ICP single collector quadrupole
mass spectrometer.
In addition to the two mining centres, one attempt to date the gold deposits from the
Mosquito Creek 'Block was conducted. In order to date the deposits from the Mosquito Creek
Block, chemical Th-U-Pb dating of monazite was undertaken using the Jeol JXA8600 Superprobe
at the University of Utrecht, Netherlands. However, the technique could not be applied to monazite
crystals from the Mosquito Creek Mining Centre as they have small sizes and contain .little Th.
Conclusions: - Chapter 9 summarises the strata-tectonic history of the Marble Bar and
Nullagine domains with respect to the genesis of gold mineralisation.
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