Brine chemistry and the spectrum of stratiform sediment-hosted Pb-Zn deposits

Brine compositions in Australian stratiform sediment-hosted Pb-Zn deposits are controlled by the nature of the basin fill and/or the flow path of the mineralising fluid, McArthur-type Paleoproterozic Pb-Zn deposits of Northern Australian (HYC, Mount Isa, etc.) formed when oxidised (SO₄²-predominant) basinal brines interacted with a major reductant. In contrast, base metal mineralisation in Broken Hill-type deposits (Broken Hill, Cannington) precipitated when hot, reduced brines of enigmatic origin entered a cool, oxidised environment. Selwyn-type deposits form when reduced metalliferous brines are quenched in a reducing environment. McArthur- and Broken Hill-type deposits contain the bulk of Australia's zinc resources, whereas Selwyn-type deposits are poorly represented in the Australian geological record.