ABSTRACT
The Bushy Park Pb-Zn deposit is located in the Northern Cape Province of South Africa ca. 150 km west of Kimberley. It is hosted by virtually unmetamorphosed and undeformed Late Archean dolomites of the Transvaal Supergroup. The Bushy Park deposit displays many characteristic features of Phanerozoic MVT-style Pb-Zn deposits, but evidence is provided that mineralisation formed at unusually high temperatures several km of depth. The mineralisation is confined to a ring-shaped epigenetic solution collapse breccia body with host rock fragments cemented by several generations of sparitic dolomite, very coarse grained Fe-poor sphalerite, Ag-poor galena and minor chalcopyrite. Detailed fluid inclusions studies suggest that base metal mineralisation formed at temperatures ranging between 121°C and 239°C (average of 179°C) at a depth of 2.2-4.0 km by mixing of high-salinity metal-bearing brines with low-salinity meteoric water. The Sr-isotopic composition of hydrothermal dolomites indicate that the metal-bearing brine originated from a source outside the host rock dolomites.
