Palaeoproterozoic Fe-rich tholeiites in Eastern Australia: A geochemical link between inliers?

Palaeoproterozoic sedimentary basins of north-eastern and central-eastern Australia are host to large amounts of variably deformed and metamorphosed Fe-rich tholeiitic rocks. Emplacement and/or extrusion of the mafic rocks occurred during one or more episodes of crustal thinning relating to a period of regional extension and sedimentation across Palaeoproterozoic northeastern Australia (ca. 1730-1650 Ma; [1, 2, 3]). The widespread occurrence of Fe-rich tholeiites of similar age, coupled with other geochronological and tectonic evidence, has led some authors to suggest a shared evolution for these terranes [3, 4]. With the addition of new geochemical and isotopic data from the Curnamona Province of western NSW [5, 6] and the Georgetown Inlier of north Queensland, the geochemical characterisitcs of the mafic rocks can be compared. The most primitive tholeiites from the Curnamona Province and Georgetown Inlier were both derived from a depleted mantle parent (avg. εNd(t) ~ +3 to +4), and have strong Fe-enrichment trends (up to ~ 25 wt % Fe2O3(total)) consistent with simple closed-system crystal fractionation. Both suites also experienced low degrees of crustal contamination (LaN/SmN ~ 0.5-1.3). Despite pervasive metamorphism and recrystallization, the suites also appear geochemically similar to Fe-rich tholeiites of the Mt Isa Eastern Succession (western Queensland). However, at present there are no significant isotopic datasets available for this suite. The geochemical similarities between the Fe-rich tholeiites is of regional significance, as it may point to a tectonic relationship between the Palaeoproterozoic terranes of eastern Australia between ca. 1700 Ma and 1650 Ma.