Geodynamic framework for Mount Isa and contemporaneous Proterozoic terranes in the Curnamona and southern NAC (Arunta-Tanami)

George M. Gibson
Geoscience Australia

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Introduction

Strikingly similar geological histories and metal endowments support the view that the Broken Hill (Curnamona craton) and Mt Isa regions were once contiguous, or at least formed part of a single continuous Zn-Pb and/or IOCG mineral province, during the late Palaeoproterozoic-early Mesoproterozoic (Giles et al., 2004). Pb model ages for major Zn-Pb deposits like Broken Hill and Cannington (1675 Ma and 1665 Ma respectively) are comparable (Carr et al., 2004) and high grade metasedimentary rocks hosting these deposits are thought to have been deposited at about the same time (ca 1690-1670 Ma) in either an intra-continental rift or a back–arc extensional environment (e.g., Blake, 1987; Walters & Bailey 1998; Betts et al., 2003). High grade deformation and metamorphism at 1580-1600 Ma (e.g., Page & Sweet, 1998; Page et al. 2004) preclude unequivocal identification of the original ore-forming environment in both cases, although clues to the tectonic setting and kinematic framework are still preserved in less intensely metamorphosed rocks of equivalent age in the Mount Isa Western Succession. The Western Succession rocks developed over a 200-Myr period from 1.8 Ga to 1.6 Ga (Blake, 1987) and, thus, overlap in age with five major tectonothermal events (Claoué-Long, 2003; Scrimgeour, 2005) recognised in the Arunta-Tanami region of the NAC. Major events identified at 1810 Ma and 1770 Ma (Stafford and Yambah), 1730-1700 Ma (Strangways), ~ 1640 Ma (Leibig) and 1560-1590 Ma (Chewings) in the NAC also find expression in the Mount Isa and Broken Hill regions (Page et al., 2000; Neumann et al., 2006), inviting speculation that the crustal processes and geodynamic framework inferred for these two regions are equally pertinent to the mineral provinces in the southern and eastern NAC.

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Evolution and metallogenesis of the North Australian Craton Conference Abstracts