Geochronology and Hf isotopes of the bimodal mafic-felsic high heat producing igneous suite from Mt Painter Province, South Australia

摘要

The Mt Painter Province of northern South Australia is a site of exceptional suite of Mesoproterozoic high heat producing (HHP) granites and felsic volcanics. These rocks have very high heat production values of >5μWm~(-3). The HHP granites, including the Mt Neill, Box Bore, Terrapinna, Wattleowie and Yerila granites, form part of a broadly coeval association of mafic and felsic volcanic rocks that also include the Pepegoona Volcanics, lamprophyres and mafic-intermediate dykes. U-Pb LA-ICPMS zircon dating and Hf-in-zircon isotopic data are used to constrain both the timing and source of these magmatic rocks. U-Pb zircon LA-ICPMS crystallization ages range from ~1596 to 1521Ma and imply a protracted sequence of magmatic events. Initial Hf isotopic compositions of these zircons from both dykes and felsic rocks have overlapping compositional ranges, with ε_(Hf) values mainly from +4 to -2. These Hf values are significantly higher than contemporary crustal values which are likely to have been in the range -4 to -20. These data imply that the magmatic suite has both mantle and crustal sources.