Abstract 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.

中文翻译：

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西澳大利亚 Lefroy 湖 Minotaur 金矿床残余风化层和输送覆盖层的金分布和岩石地球化学判别

摘要 西澳大利亚的伊尔加恩克拉通拥有许多新生代古河道，这些河道被切入下伏的古生代和前寒武纪岩石中，充满沉积物并随后风化。古河道在矿产勘探中特别受关注，因为它们不仅可能拥有砂矿型矿床，而且还覆盖在显着的表生和原生矿化上。古河道在勘探过程中也带来了特殊的挑战，因为它们掩盖了潜在的地球化学异常，包括金和探路者元素。本研究调查了一种利用现场和实验室技术相结合的方法，将运输的覆盖层与残留的风化层区分开来。在 Minotaur 矿床中，残留的风化层和输送的覆盖层在矿物学上是相似的，尽管存在黑云母、绿泥石和白云母是残留风化层的特征。在地球化学上，Zr、Ti、Co 和 Sc 的比率形成了不同的分组，从而可以更自信地从下伏的残余风化层单元中区分输送的覆盖层。在氧化还原前沿存在明显的金耗尽区也被确定为 Minotaur 矿床的一个特征，金富集发生在氧化还原前沿上方（在运输覆盖层内）和下方（在腐泥土内），类似于其他金矿床莱弗洛伊湖。Minotaur 的岩性、地层和 Au 富集特征也与区域研究进行了比较，并表明古河谷对 Lefroy 湖的沉积系统和 Au 分布的长期影响。