Geochronology of the DeGrussa volcanic-hosted massive sulphide deposit and associated mineralisation of the Yerrida, Bryah and Padbury Basins, Western Australia

•Yerrida, Bryah and Padbury Groups on margin of Yilgarn Craton host diverse mineral deposits.•The age of DeGrussa VHMS mineralisation is 2027 ± 7 Ma.•The age of the stratigraphically younger Narracoota Formation mafic rocks is 1991 ± 7 Ma to 2018 ± 9 Ma.•Correlation of Capricorn Orogen tectonic and mineralising events occurred over near a billion years.•Correlation of tectonic events and mineralisation indicates events occurred over near a billion years of time in the Capricorn Orogen.

The Palaeoproterozoic Yerrida, Bryah and Padbury Group sedimentary rocks are located on the northern margin of the Archaean Yilgarn Craton and are host to epigenetic gold (Peak Hill, Fortnum and Horseshoe), volcanic-hosted massive sulphide (VHMS; Horseshoe Lights, Red Bore and DeGrussa) and epithermal copper deposits (Thaduna). The DeGrussa Cu–Au–Ag VHMS deposit (12.4 Mt @ 4.7% Cu and 1.8 g/t Au) comprises four lenses and is hosted in turbiditic sedimentary rocks and basalts of the DeGrussa host sediments/Karalundi Formation, the lowest mafic volcano-sedimentary unit of the Bryah Group and crosscut by intrusive dolerite of Narracoota Formation age. Immediate wall rocks to the ore lenses are commonly altered to chlorite and talc-carbonate.A number of geochronological techniques were employed to date mineralisation in the DeGrussa deposit. These include rhenium–osmium (Re–Os) of molybdenite, Pb isotopes of galena and pyrite, and U–Pb on zircon. Re–Os geochronology of molybdenite resulted in ages of 2027 ± 7 Ma and 2011 ± 7 Ma and 2013 ± 7 Ma for mineralisation, similar to Pb–Pb model ages for galena of 2060 ± 50 Ma and 2075 ± 50 Ma. U–Pb for magmatic zircons from intrusive dolerite within the mine sequence provided ages of 1991 ± 7 Ma, 1999 ± 7 Ma and 2003 ± 7 Ma with granodiorite rocks providing ages of 2014 ± 7 Ma and 2018 ± 9 Ma. Remobilisation of DeGrussa sulphides occurred at approximately 1980 Ma given Re–Os ages of pyrrhotite (1982 ± 7 Ma and 1984 ± 8 Ma) and Pb–Pb pyrite ages of 1980 ± 30 Ma.Re-examination of the Pb isotopic evolution models for this area and the Capricorn Orogen suggests that the model of Stacey and Kramers (1975) is more appropriate than Cumming and Richards (1975); using the former model leads to revised model ages as follows: Horseshoe Lights VHMS 2000 ± 35 Ma; Nathans 1820 ± 30 Ma, Peak Hill (Main pit: 1610 Ma, 1620 Ma, 1705 Ma, and 2070 ± 30 Ma; Fiveways: 1955 Ma; Mt. Pleasant: 1770 Ma), Horseshoe/Cassidy 1940 ± 30 Ma, Mikhaburra 1915 ± 30 Ma, and Labouchere 1800 ± 30 Ma. These new ages coincide with major regional orogenic events – the Glenburgh from 2005 to 1960 Ma, the Capricorn from 1830 to 1780 Ma, the Mangaroon from 1690 to 1620 Ma, and the Edmundian from 920 to 850 Ma. Although orogenic events are compressional, the Yerrida/Bryah Group sedimentary rocks, along with mineralisation at the DeGrussa and Horseshoe Lights deposits, were formed in an extensional basin setting during the Glenburgh Orogeny.These new ages assist in constraining stratigraphic and mineralising events of the Palaeoproterozoic Yerrida, Bryah and Padbury Group with regional orogenic events and may provide guidance for exploration for significant gold and base metal mineralisation, not only in the Bryah, but also throughout the larger Capricorn Orogen.