Search

The Capricorn Orogen in Western Australia is a major zone of Proterozoic deformation, metamorphism and magmatism between the Archaean Yilgarn and Pilbara cratons and contains a number of small Au-bearing hydrothermal veins in various geological settings, including low-grade Palaeoproterozoic pelitic, psammitic and mafic schist of the Padbury Group at the Egerton mining centre, Mesoproterozoic dolerite and Edmund Group sedimentary rocks at the Bangemall mining centre and veins and stratabound Au mineralisation associated with variscite in the Edmund Group at Low Hill. Bedrock-hosted and alluvial Au at Egerton have similar chemistry and are characterised by low Ag concentrations, high Cu/Au ratios and low Hg/Pb ratios. Bedrock-hosted and alluvial Au at Bangemall differ from Egerton in having a higher Ag content, higher Ag/Cu ratios and higher Hg and Sb levels, and a single source for the alluvial Au is suggested. In contrast to Egerton and Bangemall, the Au at Low Hill has a distinctive spongy morphology and is very high purity. The data indicate that the Capricorn Orogen underwent at least two periods of hydrothermal Au mineralisation during the Proterozoic and at least one period of secondary Au formation, probably during the Phanerozoic., The Capricorn Orogen in Western Australia is a major zone of Proterozoic deformation, metamorphism and magmatism between the Archaean Yilgarn and Pilbara cratons and contains a number of small Au-bearing hydrothermal veins in various geological settings, including low-grade Palaeoproterozoic pelitic, psammitic and mafic schist of the Padbury Group at the Egerton mining centre, Mesoproterozoic dolerite and Edmund Group sedimentary rocks at the Bangemall mining centre and veins and stratabound Au mineralisation associated with variscite in the Edmund Group at Low Hill. Bedrock-hosted and alluvial Au at Egerton have similar chemistry and are characterised by low Ag concentrations, high Cu/Au ratios and low Hg/Pb ratios. Bedrock-hosted and alluvial Au at Bangemall differ from Egerton in having a higher Ag content, higher Ag/Cu ratios and higher Hg and Sb levels, and a single source for the alluvial Au is suggested. In contrast to Egerton and Bangemall, the Au at Low Hill has a distinctive spongy morphology and is very high purity. The data indicate that the Capricorn Orogen underwent at least two periods of hydrothermal Au mineralisation during the Proterozoic and at least one period of secondary Au formation, probably during the Phanerozoic.

The deposit is a blind, stratabound sedimentary-rock hosted Fe-Pb-Zn- Ba-Cu(-Au-Ag-Bi-W) deposit located within the easterly trending Jillawarra rift sub-basin of the Mesoproterozoic Edmund Basin in Western Australia. The deposit is in the exploration stage and is estimated to contain 93 000 000 t of ore grading 4% Pb and 10 g/t Ag and 14 000 000 t at 0.62% Cu and 0.5 g/t Ag. The mineral system is characterised by several overprinting phases of hydrothermal activity from several stages of brecciation and fluidisation, barite and sulphide veining to barren low-temperature chalcedonic veining. Hydrothermal alteration minerals include multi-stage quartz, chlorite, prehnite, Fe-rich carbonate and albite. A preliminary genetic model is presented which indicates that there may be several hydrothermal breccia pipes each of which may be associated with distal haematite-barite chemical sediments and enhancing the prospectivity of the basin., The deposit is a blind, stratabound sedimentary-rock hosted Fe-Pb-Zn- Ba-Cu(-Au-Ag-Bi-W) deposit located within the easterly trending Jillawarra rift sub-basin of the Mesoproterozoic Edmund Basin in Western Australia. The deposit is in the exploration stage and is estimated to contain 93 000 000 t of ore grading 4% Pb and 10 g/t Ag and 14 000 000 t at 0.62% Cu and 0.5 g/t Ag. The mineral system is characterised by several overprinting phases of hydrothermal activity from several stages of brecciation and fluidisation, barite and sulphide veining to barren low-temperature chalcedonic veining. Hydrothermal alteration minerals include multi-stage quartz, chlorite, prehnite, Fe-rich carbonate and albite. A preliminary genetic model is presented which indicates that there may be several hydrothermal breccia pipes each of which may be associated with distal haematite-barite chemical sediments and enhancing the prospectivity of the basin.