A guide for mineral exploration through the regolith in the Yilgarn Craton, Western Australia

Abstract

The Yilgarn Craton is one of the world's principal mineral provinces, with considerable resources of gold, nickel, bauxite and iron ore, as well as lesser amounts of a wide range of other commodities. As such, it is a major target for exploration. However, as most of the Craton has been exposed to sub-aerial conditions since at least the Late Proterozoic, it has had a long history of weathering and erosion under a wide variety of climatic conditions, resulting in a widespread and complex regolith cover. This diverse and extensive regolith poses considerable difficulties for exploration—as well as opportunities in terms of different sample media and the formation of resources within the regolith itself. The development of appropriate geochemical exploration procedures has been the subject of considerable research by government, university and industry for nearly 50 years. This guide is intended to summarise the results of this research in a single, stand-alone document to assist mineral explorers. It provides a synthesis of the characteristics and evolution of the Yilgarn landscape and advice on appropriate strategies and techniques for exploring through different types of cover, based on current knowledge and best practice. Because broadly similar deeply weathered regolith-dominated terrains occur elsewhere in Australia and, indeed, in other continents, many of the principles discussed here can be more widely applied. The guide develops exploration strategies for gold, base metals, nickel and surficial uranium deposits within the context of the evolution of the landscape and regolith of the Yilgarn Craton. The guide commences with a brief introduction to the geology and principal ore deposits of the Craton, followed by a description of the development and characteristics of the regolith, and the relationship between regolith type and landforms. The distribution, characteristics and use of the principal sample media are described. The regolith and landforms provide a framework for empirical models that describe the processes of geochemical dispersion, based on numerous case histories and other investigations, grouped according to the principal commodities. The models anticipate and summarise the surface expression of mineralisation and include recommendations on exploration procedures, such as sample selection, sampling interval and analytical approach. A comprehensive reference list provides a source for further information.