Geochemistry and petrogenesis of mafic–ultramafic suites of the Irindina Province, Northern Territory, Australia: Implications for the Neoproterozoic to Devonian evolution of central Australia

Abstract

Petrological and geochemical data for magmatic mafic–ultramafic suites of the Irindina and Aileron provinces of the Eastern Arunta region, Northern Territory, Australia constrain the petrogenesis and tectonic setting of magmatic events covering ~500millionyears. Six geochemically distinct magmatic suites, here named A–F, have been identified and provide evidence of the tectonic history of this region and also are linked to two mineralisation-related magmatic events: the Lloyd Gabbro (Ni–Cu–PGE mineralisation) and the Riddoch Amphibolite (Cyprus-style Cu–Co volcanogenic massive sulphide mineralisation).The whole-rock geochemistry of Suites A and F is indicative of melts derived from a range of mantle depths (garnet to spinel lherzolite) and source enrichment. Suite D is likely related to the ~1070Ma Warakurna/Giles event of central Australia, including the Alcurra (Musgrave) and Stuart (Arunta) dyke swarms, and likely formed through either: a) melting of subduction modified, sub-continental lithospheric mantle (SCLM) by an upwelling mantle plume; or b) a combination of intra-plate tectonic processes involving a long-lived thermal anomaly, lithospheric-scale architecture that focussed magmatism, and large-scale tectonism. Suite F represents more alkaline magmas, derived from a deeper source, but most likely formed during the same Warakurna LIP event (possibly contemporaneously) as Suite D. Suite E (the Riddoch Amphibolite) was most likely emplaced in a back-arc basin (BAB) setting at ~600Ma, coincident with Delamerian subduction and BAB formation along the eastern Proterozoic margin of Australia from Queensland to the eastern Arunta and possibly further south. Subsequent destabilisation of the SCLM underneath the North Australian Craton generated the ~510Ma Kalkarindji LIP in the form of Suite B intrusions that assimilated some of the older Suite E (Riddoch) material. This event is locally known as the ~506Ma Stanovos Igneous Suite and represents the most voluminous magmatic event within the study area. Suite A samples are more alkaline and cannot be correlated with any known magmatic events; however, they probably represent an unidentified alkaline phase of the Kalkarindji LIP event derived from a deep mantle source region. This suite is similar to the more widespread Kalkarindji and Suite B/Stanovos magmas in that these magmas assimilated arc material (i.e., Suite D) prior to emplacement. The last magmatic event occurred during the exhumation and inversion of the Irindina basin during the 450–300Ma Alice Springs Orogeny, resulting in the formation of melts derived from a deep mantle source. These melts subsequently became contaminated en route to emplacement as the ~409Ma Suite C Lloyd Gabbro.