Abstract
Plate tectonic reconstructions place Laurentia and eastern Australia together during the Mesoproterozoic. Specifically, the Belt-Purcell Basin in the USA and Canada has been linked to the Rocky Cape Group in northwest Tasmania based on detrital zircon studies. The Belt-Purcell Basin is highly endowed in economic deposits of Cu, Pb, Zn, Ag and critical metals such as Co, formed during the Mesoproterozoic. The Rocky Cape Group of northwest Tasmania hosts several sediment-hosted Cu-Pb-Zn ± Co prospects, however they were previously thought to be Devonian in age. New laser ablation inductively-couple plasma mass spectroscopy (LA-ICP-MS) in situ U-Pb monazite, xenotime and apatite data, sensitive high resolution ion microprobe (SHRIMP) in-situ U-Pb monazite data, and LA-ICP-MS galena Pb isotope data were collected from these prospects. By using multiple minerals with different U–Pb closure temperatures, we have unravelled a complex and protracted history of thermal pulses in the Rocky Cape region associated with Cu-Pb-Zn ± Co mineralisation. These data indicate that primary sulphide mineralisation formed at c. 1350 Ma, with several resetting or remobilisation events recorded at c. 1250 Ma, c. 1100 Ma and c. 950 Ma. These ages are contemporaneous with previously published authigenic monazite and metamorphic monazite ages from the Rocky Cape Group. This suggests that mineralisation is broadly syn-sedimentary and related to the development of the basin into which the Rocky Cape Group was deposited. These new ages are similar to those of sediment-hosted ore deposits in the Belt-Purcell Basin in the USA and Canada, further supporting the proposed link between northwest Tasmania and North America during the Mesoproterozoic. The high metal endowment of age-equivalent rocks in the Belt-Purcell Basin, highlight the potential for new discoveries of base and critical metals in southeastern Australia.
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