Gold distribution and lithogeochemical discrimination of residual regolith and transported overburden, Minotaur gold deposit, Lake Lefroy, Western Australia

The Yilgarn Craton of Western Australia hosts a number of Cenozoic paleochannels, which have been incised into the underlying Paleozoic and Precambrian rocks, filled with sediments and subsequently weathered. The paleochannels are of particular interest in mineral exploration as they may not only ho...

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Bibliographic Details
Published in:Australian journal of earth sciences 2019-11, Vol.66 (8), p.1113-1128
Main Authors: McHarg, S., Aspandiar, M. F.
Format: Article
Language:English
Subjects:
Anomalies
Biotite
Cenozoic
Chlorite
Cratons
Depletion
Discrimination
Distribution
Enrichment
Gold
Kambalda
Lake Lefroy
Lakes
Lithology
Mica
Mineral exploration
Mineralization
Minotaur gold deposit
Muscovite
Overburden
Oxidoreductions
Paleozoic
Precambrian
Ratios
Regolith
Sediments
Stratigraphy
supergene gold
Zirconium
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Summary:The Yilgarn Craton of Western Australia hosts a number of Cenozoic paleochannels, which have been incised into the underlying Paleozoic and Precambrian rocks, filled with sediments and subsequently weathered. The paleochannels are of particular interest in mineral exploration as they may not only host placer-type deposits but also overlie significant supergene and primary mineralisation. Paleochannels also pose particular challenges during exploration as they mask underlying geochemical anomalies, including gold and pathfinder elements. This study investigates a method of distinguishing transported overburden from residual regolith utilising a combination of field and laboratory-based techniques. At the Minotaur deposit, the residual regolith and transported overburden are mineralogically similar, although the presence of biotite, chlorite and muscovite is more characteristic of the residual regolith. Geochemically, Zr, Ti, Co and Sc ratios form distinct groupings allowing more confident discrimination of transported overburden from the underlying residual regolith units. The presence of a distinct gold depletion zone at the redox front was also identified to be a feature of the Minotaur deposit, with Au enrichment occurring above (within transported overburden) and below (within saprolite) the redox front, similar to other gold deposits on Lake Lefroy. The lithological, stratigraphic and Au-enrichment characteristics at Minotaur have also been compared with regional studies and suggest the long-lived impact of paleovalleys on the depositional systems and Au distribution of Lake Lefroy. This work provides a basis for future studies of the region in particular the variation of depositional sequences within regional paleochannel networks.
ISSN:0812-0099
1440-0952
DOI:10.1080/08120099.2019.1611663