THE YILGARN CRATON, A FOCUS FOR EXPLORATION
The Yilgarn Craton is one of the world’s principal mineral provinces, with considerable resources of primary (hypogene) and supergene gold, sulphide-hosted and lateritic nickel, and bauxite, as well as lesser amounts of a wide range of other commodities. As such, it remains a major target for exploration. Despite variations in total expenditure in exploration for mineral resources (other than coal and petroleum) over the past 5 years, including a sharp decline from $1077m in 1996–1997 to $670m in 1999–2000, the proportion of Australian exploration expenditure spent in Western Australia has remained constant at about 62%. Most of this is for exploration on the Yilgarn Craton, with nearly 70% targeting gold and 18% targeting base metals, dominantly nickel (⇓ABARE 2000; ⇓ABS 2000; ⇓WA-DME 2000). The dominance of gold over nickel exploration is reflected in the relative numbers of papers in this compilation.
The majority of exploration expenditure is on geological, geochemical and geophysical observations of the regolith and regolith materials, by both direct and remote means. Quantification is difficult, although drilling statistics indicate one possible measure of the importance of direct observations of the regolith. Assuming that most non-core drilling (i.e. by reverse circulation (RC) and open hole percussion, rotary air blast (RAB), air-core, vacuum and auger) targets the regolith, then this accounts for about 90% of the total metres, and 70% of the cost, of exploration drilling in Western Australia from 1993 to 2000. (J. Gregory, Department of Minerals & Energy, Western Australia, pers. comm. 2000.)
The presence of a thick regolith has great significance in providing both impediments to, and opportunities for, exploration throughout Australia and in other deeply weathered, continental landmasses (⇓Butt & Zeegers 1992). The regolith of the Yilgarn Craton represents the most intensely investigated of these terrains and can thus serve as …