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Woodcutters Goldfield - Federal |
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Western Australia, WA, Australia |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Woodcutters goldfield (previously known as Golden Cities) is located some 50 km north of Kalgoorlie in Western Australia. It is one of the largest granite hosted Archaean gold systems in Australia, and is unusual in being so distant laterally from the nearest greenstone belt.
At the Federal zone, one of the deposits that makes up the Woodcutters goldfield, gold is hosted by hornblende-biotite granodiorite, 6 km from the nearest mapped contact with greenstones. The granodiorite in the Federal open pit is coarse-grained in the northern half, and fine-grained in the south. Both varieties host gold and are quite similar in mineralogy and geochemistry. There is also a subordinate fine-grained monzodiorite
The Federal gold deposit is within a northwest striking (315°) and 60° northeast-dipping shear zone in the Scotia granite. The grain size variation of the host rocks may have influenced the style of deformation with more brittle fabrics in the coarse-grained phase and a more ductile response in the fine-grained granodiorite.
Hydrothermal alteration is extensively developed around the Federal deposit and is a useful vector pointing to gold mineralisation. Distal epidote surrounds a proximal muscovite-biotite alteration zone which contains quartz-sulphide veins. The alteration shares some of the common characteristics of Archaean greenstone-hosted gold, but differs in that carbonate-chlorite alteration is only weakly developed, explained by the difference in host-rock composition and lower concentrations of Fe, Mg and Ca in the granite compared to the greenstone.
Fluid inclusion studies provide no evidence of a granite-derived fluid having been responsible for gold mineralisation. The granodiorite host rock had cooled, crystallised and had at least started to undergo deformation prior to gold introduction. The distribution of gold mineralisation in the Woodcutters goldfield has the same style, shape and orientation as greenstone-hosted gold deposits in the same region. The northwest trend, the quartz veining and simple pyrite mineralogy are all features common to other greenstone-hosted gold deposits near Kalgoorlie such as Mt Pleasant. The alteration fluid appears to have penetrated the granite on the scale of many hundreds of metres, causing large-scale alteration. The Woodcutters gold mineralisation resulted from the same metamorphic fluid processes that led to formation of greenstone gold deposits.
The goldfield contains 43 t (1.4 Moz) of gold at an average grade of 1.5 g/t Au
This goldfield was previously known as the Golden Cities cluster of deposits - see the separate database record.
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2003.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Mason D R 2004 - Thermodynamic modelling of lode-gold deposits in Archaean granitoids: Woodcutters and Lady Bountiful mines, Kalgoorlie region, Western Australia: in Australian J. of Earth Sciences v51 pp 431-438
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Zhou T, Phillips G N, Denn S, Burke S 2003 - Woodcutters goldfield: gold in an Archaean granite, Kalgoorlie, Western Australia: in Australian J. of Earth Sciences v50 pp 553-569
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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