The alteration history of Late Proterozoic Wooltana Volcanics, Mount Painter Province, S.A.

Abstract

The Wooltana Volcanics experienced a pervasive low grade hydrothermal alteration prior to the Delamerian. The timing of this event is poorly constrained. However the available evidence is consistent with the metasomatism occurring during the active stretching thought to have caused the uplift related refrigeration responsible for the formation of the Merinjina Tillite. This study confirms the proposals of previous workers that the Wooltana Volcanics, Beda Volcanics and Gairdner Dyke Swarm are temporal equivalents, although this study has shown the Gairdner Dyke Swann to be a systematically fractionated end member. The Wooltana Volcanics are very like the Parana low-Ti CFB of Brazil and also the dolerites from the Atlas Mountains of Morocco. Both are associated with magmatic events immediately preceding the first openings of the Atlantic Ocean. The occurrence of the Port Pirie Volcanics within Burra Group sediments suggests a reoccurrence of mantle decompression due to lithospheric stretching further to the south.