Geochronological studies of selected Australian mineral deposits, 2003 – 2020

Geoscience Australia, in collaboration with State and Territory Geological Surveys, began a geochronology program in the mid-2000’s to determine the age of mineralising events in Australia. It began with the Paterson Project in the mid-2000’s and continued with the Onshore Energy Security program and the current Exploring for the Future program. Some of the results were published, either as formal publications or in abstracts, however, much of the analytical data collected have never been formally published. This report aims to formally publish all the data from these past projects and programs. Geochronology analyses for this program have been carried out by Geoscience Australia, the Australian National University, the University of Alberta, the University of Melbourne, the University of Queensland and the United States Geological Survey. The first part of this report summarises the analytical procedures and uncertainties of all laboratories used. The second part presents the results of the analyses along with brief descriptions of the deposit studied and an interpretation of the significance of the results. Molybdenite Re–Os results from 22 deposits that are considered to have geological significance include: Strelley greisen – ca 3230 Ma, Jupiter – ca 2683 Ma, Mulgine Hill – ca 2740 Ma and Katanning – ca 2617 Ma (Western Australia); Molyhil – ca 1720 Ma (Northern Territory); Kaiser Bill – ca 1524 Ma, Greenback – ca 426 Ma, Gromac – ca 426 Ma, Chloe – ca 413 Ma, Mount Specimen – ca 318 Ma, Anthony – ca 310 Ma, Black Mountain – ca 301 Ma and Whitewash – ca 244 Ma (Queensland); Cowal Central – ca 451 Ma and Whipstick – ca 389 Ma (New South Wales); Unicorn – ca 412 Ma, Everton – ca 380 Ma, Monkey Gully – ca 371 Ma, and Myrtle Creek – Scorpion Hill – 370 Ma (Victoria); and Mount Stronach – ca 393 Ma, Squib – ca 383 Ma, and King Island – ca 358 Ma (Tasmania). In each case, the age is placed in context with the geological history of the deposit and compared with other relevant ages (e.g. the age(s) of spatially associated granites). We report apparent ages from two other deposits (Mount Moliagul, Victoria and Mount Killiecrankie, Tasmania) that are geologically implausible. At Molyhil, the molybdenite Re–Os age agrees within error of previously reported xenotime U–Pb (Cross, 2009) and muscovite 40Ar–39Ar age (Reno and Fraser, 2021; using new (Kwon, 2002) K-Ar decay constants) ages, and all three ages agree within uncertainty with a SHRIMP U–Pb zircon age of the spatially associated Marshall Granite (Kositcin et al., 2018). 40Ar–39Ar ages reported include ages of muscovite intergrown with Zn-Cu-Sn veins at the Wallabadah prospect (Queensland: ca 285 Ma) and ages of various minerals from the Magnum Au-Cu prospect (Western Australia: ca 637 Ma). The Magnum age agrees within error with the age previously reported (Maidment et al., 2010) for the Telfer Au-Cu deposit, indicating a widespread granite-related Au-Cu event in the Paterson Province.