Abstract

Geochemical and Nd isotopic studies of two postorogenic, Late Proterozoic (1083 ±23 Ma), high-Mg tholeiitec dike swarms in central Australia indicate that the dike swarms were derived by partial melting of the continental lithospheric mantle, which was modified by subduction processes during major crust-formation events in the region. Both dike swarms (Stuart and Kulgera, which intrude the Arunta and Musgrave inliers, respectively) resemble island-arc tholeiites in terms of geochemical features. They yield whole-rock Sm-Nd ages of 1853 ±189 Ma with ϵNd = -4.2 ±4.2 (Stuart) and 1589 ±165 Ma with ϵNd = +1.7 ±3.6 (Kulgera). The two whole-rock ages and initial ϵNd values are remarkably similar to the oldest U-Pb zircon ages and initial ϵNd values obtained from the corresponding basement blocks. These isotopic data are interpreted as recording Sm-Nd fractionation events in the continental lithospheric mantle associated with major episodes of crust formation in the Early Proterozoic.

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