EVIDENCE FOR EARLY MESOPROTEROZOIC ARC MAGMATISM IN THE MUSGRAVE BLOCK, CENTRAL AUSTRALIA: IMPLICATIONS FOR PROTEROZOIC CRUSTAL GROWTH AND TECTONIC RECONSTRUCTIONS OF AUSTRALIA

Abstract

The Musgrave Block in central southern Australia separates the dominantly Paleoproterozoic North Australian Craton from the Late Archean to early Mesoproterozoic Gawler Craton in southern Australia. Geochemical and Nd isotopic data from ~1.59-1.55-Ga felsic rocks in the Mann Ranges suggest that the early history of the Musgrave Block was linked to the development of subduction along the northern margin of the Gawler Craton. Characteristic geochemical patterns of these felsic rocks include negative anomalies in Nb, Ti, and Y and are accompanied by steep light rare earth element patterns and comparatively juvenile Nd isotopic compositions (εNd(1550) values from -1.2 to 0.9). The geochemical and isotopic signatures of these early Mesoproterozoic felsic rocks have similarities with island arc systems involving residual Ti-bearing minerals and garnet. We propose that the 1.59-1.55-Ga arclike rocks in the Musgrave Block indicate the presence of an active margin between the North Australian Craton and the South Australian Craton, with subsequent suturing of the Australian continent during the early Mesoproterozoic. The existence of arclike magmatism. in the Musgrave Block during the early Mesoproterozoic suggests a period of major crustal growth in the Australian Proterozoic that has important implications for current Proterozoic reconstructions of Australia and Australia's fit within the supercontinent Rodinia. © 2006 by The University of Chicago. All rights reserved.