The implications to exploration of chalcophile corridors in the Archaean Yilgarn Block, Western Australia, as revealed by laterite geochemistry

Abstract The regional distribution of the chalcophile and associated elements As, Sb, Bi, Mo, Ag, Sn and W in laterite over the Archaean Yilgarn Block of Western Australia is dominated by elongated trends within which chalcophile abundances are relatively high compared with general backgrounds. As seen from orientation studies, laterite geochemistry in Western Australia generally provides an imprint of geochemical patterns observed in bedrock, albeit with some degree of dispersion. These chalcophile trends in the lateritic duricrust materials imply the existence of chalcophile geochemical provinces in bedrock and mark out the spatial distribution of such provinces across the Precambrian craton. The chalcophile trends revealed by regional multi-element laterite geochemistry are typically 15–30 km wide and 50–100 km long, some extending to 150 km. There appears to be a broadly coincident spatial relationship between the chalcophile trends and the distribution of a variety of ore types, including gold and base-metal sulphide deposits. The name “chalcophile corridor” is herein proposed because the trends appear to be the geochemical expression of the gold exploration corridors recognized some years ago. Some of the chalcophile corridors appear to spatially link with major faults and regional shear zones. Whether the chalcophile associations in laterite are reflecting hydrothermal processes of rock alteration and mineralization along shear zones, or hydrothermal activity at Archaean volcanic centres or intrusions is presently an open question. Much more research needs to be directed at identifying in bedrock the specific rock types/structural associations that give rise to the anomalous chalcophile elements. The concept of chalcophile corridors appears to have important implications in mineral exploration because of the possibility of delineating the most prospective terrain at the reconnaissance stage of the exploration operations.