Magmatism, orogeny and the origin of high-heat-producing granites in Australian Proterozoic terranes

Abstract

Temperature-dependent processes such as magmatism and orogeny provide key insights into the Earth’s thermal state. We propose an integrated model for the origin of voluminous Proterozoic-aged granitic rocks in northern Australia, suggesting that the observed large range of concentrations of incompatible elements (particularly U, Th and K) was established progressively as a consequence of a hot-plate orogenic style involving little crustal thickening, combined with ‘normal’ juvenile magma additions. Progressive extraction of the heat-producing elements into the mid- to upper crust, where they remain below the erosional base level, resulted in anomalous thermal conditions that modulated the continuing orogenic history. This may represent an important style in post-Archaean lithospheric behaviour. Supplementary materials: Age and calculated heat production data for all Australian Proterozoic granitic rocks (calculated for the time of intrusion and for the present day) and for individual Proterozoic terranes of the North Australian craton, comparison of the range and distribution of calculated heat production of granitic rocks with the North Australian Craton and within the Mount Isa Inlier, and Zr and SiO 2 data for granites of the Lachlan Fold Belt and for the Mount Isa Inlier are available at www.geolsoc.org.uk/SUP18721.