Thermochronological history of the northern Olympic Domain of the Gawler Craton; correlations between cooling ages and mineralising systems

Abstract

The Olympic Domain of the Gawler Craton is home to the world class Olympic Dam Iron Oxide Copper Gold (IOCG) mineral deposit in addition to numerous other IOCG mineral deposits. The Olympic Domain preserves a complex geological history that began in the Palaeoproterozoic. However, most published work conducted on these IOCG deposits have focused on their initial formation, with only a few studies investigating the post-formation thermal history of the Olympic Domain. This study uses multi-method thermochronology by combining apatite U/Pb, muscovite and potassium feldspar 40Ar/39Ar, zircon and apatite (U-Th-Sm)/He, and apatite fission track (AFT) dating to provide insights into the thermal history of the northern Olympic Domain between ~550°C and surface temperatures. Apatite U/Pb and muscovite 40Ar/39Ar record post magmatic cooling of the ~1850 Ma Donington Suite, and ~1590 Ma Hiltaba Suite. Potassium feldspar 40Ar/39Ar analyses record a cooling signal that is likely related to rifting in the Neoproterozoic Adelaide Rift Complex. A combination of AFT, and zircon and apatite (U-Th-Sm)/He dating preserves three thermal periods, at ~1000 Ma, ~430-400 Ma and ~200 Ma. The older two thermal periods are interpreted to be regional cooling. However, the youngest ages are preserved closest to known IOCG deposits suggesting that they reflect cooling of this elevated geothermal-gradient crust in the Mesozoic. These results have been modelled to produce a thermal history map of the northern Olympic Domain.