Summary of results. In situ Lu-Hf apatite geochronology from the Rover field, Warramunga Province

Abstract

The Rover field is an undercover Paleoproterozoic terrane in Central Australia that hosts gold–copper–bismuth mineralisation (Rover 1, Explorer 142) and base metal mineralisation (Explorer 108 and Curiosity). The mineralisation in Rover 1 is similar in style to the ca 1.85 Ga gold–copper mineralisation of the Tennant Creek mineral field (Fraser et al 2008, Huston et al 2020, Farias et al 2022b) 80 km to the northeast, but the absolute age of Rover 1 mineralisation remains elusive. Similarities in mineralisation styles suggest that Rover 1 could be contemporaneous with the ca 1.85 Ga Tennant Creek mineral field. However, minor mineralising episodes recorded in the Tennant Creek mineral field (eg ca 1.72–1.71 Ga gold–copper–tungsten mineralisation and ca 1.66 Ga gold–copper mineralisation) could have imprinted mineralisation in Rover 1.

Previous geochronological and drill core logging suggest that the host rocks of Rover 1 are dominated by volcanic andvolcaniclastic sequences of the 1.85-1.84 Ga Yungkulungu Formation of the Ooradidgee Group (Huston et al 2020, Valenta et al 2020, Cross et al 2021, Cross et al 2022, Farias et al 2022b). New Rb-Sr data presented by Farias et al (2022c) raises the possibility that the host rock could be as young as 1.73 Ga, which would indicate the host rocks (and associated mineralisation) are younger than previously thought. Understanding the timing of mineralisation in the Rover field requires resolving the timing of deposition of the host rocks.

Apatite from a mineralised sample from Rover 1 (BW20PGF127A) was dated for this study via in situ Lu-Hf geochronology in an attempt to resolve an age for Rover 1 mineralisation. The large uncertainty in the resulting Lu-Hf isochron age of 1828 ± 147 Ma (2s at the 95% confidence level) is considered too great to enable the resolution of either the timing of deposition of the host rocks or the timing of mineralisation in Rover 1, ie the range encompasses the timing of all known mineralising events recorded in the Rover field and the Tennant Creek mineral field.