A 2005–1970 Ma Andean-type batholith in the southern Gascoyne Complex, Western Australia

Abstract

Palaeoproterozoic granitic rocks of the Dalgaringa Supersuite dominate the Glenburgh Terrane, which forms the southern part of the Gascoyne Complex in the Capricorn Orogen, Western Australia. The Capricorn Orogen is a complex Proterozoic tectonic zone that is thought to reflect oblique collision of the Archaean Yilgarn and Pilbara Cratons at ca. 1800 Ma. Rocks of the Dalgaringa Supersuite do not intrude the adjacent Yilgarn Craton, and basement to the supersuite consists of ca. 2550 Ma granitic gneiss that has no equivalent in the Archaean Yilgarn and Pilbara Cratons on either side of the Capricorn Orogen. The supersuite comprises sheets, dykes and veins of 2005–1985 Ma foliated and gneissic I-type tonalite, granodiorite, quartz diorite and monzogranite, intruded by a large pluton of ca. 1975 Ma mesocratic and leucocratic I-type tonalite (Nardoo Granite). Initial ε Nd values of −1.3 to −6.0 for the supersuite are consistent with partial melting of ca. 2550 Ma granitic gneiss and variable proportions of basaltic rock, but petrogenesis of the granites probably involved a range of processes. At 1965–1945 Ma, silicic I-type granites of the Bertibubba Supersuite intruded the northwestern edge of the Yilgarn Craton and the southern margin of the Glenburgh Terrane, and are the first element common to both terranes. The Dalgaringa Supersuite represents an Andean-type batholith formed along the edge of the Glenburgh Terrane before collision with the passive margin of the Yilgarn Craton. In contrast to Phanerozoic batholiths in similar settings, generation of the Dalgaringa Supersuite involved a large degree of crustal recycling.