Porphyry Cu fertility of the Loch Lilly-Kars Belt, Western New South Wales, Australia

Abstract

This study investigates the prospectivity for porphyry Cu mineralisation of the early Paleozoic Loch Lilly-Kars Belt, which follows the southern margin of the Paleoproterozoic Broken Hill (Willyama) Inlier in western New South Wales, Australia. The belt is thought to have resulted from the 515–510 Ma collision of a volcanic passive margin and an intra-oceanic island arc above a west-dipping subduction zone, with subsequent post-collisional magmatism. To identify fertility signals of selected magmatic intrusive rocks, we combined whole-rock analyses with in-situ zircon trace-element and isotopic measurements. Data reveal that both Cambrian (ca 496 Ma) and Devonian (ca 393 Ma) intrusive suites are present in the Loch Lilly-Kars Belt. Cambrian dioritic rocks are largely non-fertile for porphyry Cu mineralisation, whereas Devonian monzodiorites and monzonitic porphyries carry strong fertility signals that include high whole-rock Sr/Y (>35) and V/Sc (>10) values, associated with the occurrence of equant, stubby zircons showing relatively constant Eu/Eu* values without any significant Eu anomalies. Although only few samples were analysed and more intensive exploration is required, the results of this study indicate significant potential for porphyry Cu mineralisation in this poorly known belt.

Keywords:

• zircon trace elements
• U–Pb geochronology
• O isotopes
• porphyry Cu mineralisation
• Loch Lilly-Kars Belt
• New South Wales

Acknowledgements

We acknowledge the facilities, and scientific and technical assistance of the Australian Microscopy and Microanalysis Research Facility at the Centre for Microscopy, Characterisation and Analysis at UWA. We also thank the Key Centre for the Geochemical Evolution and Metallogeny of Continents (GEMOC) for analytical data. Baatar thanks his wife and children for their undying patience, moral and emotional support. This is contribution 1358 from the ARC Centre of Excellence for Core to Crust Fluid Systems (http://www.ccfs.mq.edu.au).

Additional information

Funding

The Australian Microscopy and Microanalysis Research Facility at the Centre for Microscopy, Characterisation and Analysis at UWA is funded by the University, State and Commonwealth Governments. The Key Centre for the Geochemical Evolution and Metallogeny of Continents (GEMOC) instrumentation was funded by DEST Systemic Infrastructure Grants, ARC LIEF, NCRIS/Auscope industry partners and Macquarie University. Fiorentini acknowledges the ARC grant schemes FT110100241 and CE110001017.