Geological relationships and ⁴⁰Ar/³⁹Ar age constraints on gold mineralisation at Tarcoola, central Gawler gold province, South Australia

The Tarcoola Goldfield is one of several districts included in the recently proposed central Gawler gold province. Understanding of the genesis of the deposits in this metallogenic province is in its infancy, and dating the age of alteration, mineralisation and microdiorite dyke intrusions has been carried out at Tarcoola as a first step towards developing mineral-systems models for the province. At Tarcoola, four samples of sericite from alteration as well as one sample of hornblende from a microdiorite dyke yield ⁴⁰Ar/³⁹Ar ages of ca 1580 Ma. Geological and petrological relationships suggest that this age represents the time of fracture-controlled Au mineralisation. These data provide evidence for coeval Au mineralisation, microdiorite dyke intrusion and local deformation. This mineralisation age is indistinguishable from U-Pb ages for the regional Gawler Range - Hiltaba volcano-plutonic complex, and is more than 100 million years younger than the Paxton Granite, which is part-host to the minerallsation. Possible temporal and genetic relationships with other deposits in the central Gawler gold province remain to be tested.