Geophysical delineation and mineral potential of mafic-ultramafic intrusions in the Arunta Region

Tony Meixner; Dean Hoatson; Yanis Miezitis; Subhash Jaireth; and Jon Claoué-Long,
Geoscience Australia.

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Introduction

The Arunta Region of central Australia is a geologically complex and tectonically longlived terrane which has been subjected to several periods of magmatism. SHRIMP U-Pb dating of zircons by Claoué-Long & Hoatson (2005) constrain the major mafic magmatic events to the dominantly tholeiitic ~1810-1800 Ma Stafford Event, the ~1790-1770 Ma Yambah Event, ~1690 Ma Strangways Event, ~1635 Ma Liebig Event, and a much younger event of probable early Palaeozoic age. A further event (Teapot) at ~1135 Ma has alkaline-ultramafic affinities.

Field-relationships and mineralisation-features of the intrusions are described by Hoatson & Stewart (2001) and Hoatson et al. (2005). The intrusions form large homogeneous mafic granulite and gabbroic bodies, stacked sequences of high-level sills, small pods, laterally extensive amphibolite sheets, and relatively undeformed ultramafic plugs. The intrusions occur in proximity to major province-wide faults where differential movements have resulted in the exposure of the intrusions from crustal depths ranging from ~5 km to ~25 km. Metamorphic grades range from granulite to sub-amphibolite facies. Chilled and contaminated margins and net-vein complexes resulting from the commingling of mafic and felsic magmas indicate that most intrusions crystallised in situ and were not tectonically emplaced.

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Evolution and metallogenesis of the North Australian Craton Conference Abstracts