Genesis of some calcretes in the southern Yilgarn Craton, Western Australia: Implications for mineral exploration

Abstract

Calcrete is extensively distributed in the semi‐arid and arid regions of the southern Yilgarn Craton of Western Australia. Two general types are recognised, groundwater and pedogenic calcretes; a model for the genesis of the latter is proposed, based on detailed studies in two regions (Mt Gibson and Kalgoorlie) in the southern Yilgarn Craton. At Mt Gibson, calcrete is largely restricted to erosional regimes on greenstones and is absent or present in minor amounts in relict and depositional regimes. In granitic terrain, calcrete is absent in relict and erosional regimes, but it is present in minor amounts in depositional regimes. By contrast, it is present in all the geomorphic regimes in the Kalgoorlie region although it is more abundant in erosional regimes on mafic bedrock. In soils over Ca‐poor ultramafic rocks, calcrete abundance is highly variable. Calcium and Mg in calcretes comes from two sources, in situ from weathering and from external sources (such as laterally moving soil water and erosion and...