Devil in the detail; The 1150-1000Ma magmatic and structural evolution of the Ngaanyatjarra Rift, west Musgrave Province, Central Australia

Abstract

Mafic and felsic rocks units of the Musgrave Province originally attributed to the c. 1075. Ma Giles Event of the greater Warakurna Large Igneous Province (LIP) are shown to be part of a complex sequence of magmatic and tectonic events punctuated over a span of at least 50. m.y. New geochronology and mapping resolve a sequence of at least 10 magmatic pulses with hiati of up to 10. m.y. consistent with a long-lived intracontinental rift setting. This rift, here named the Ngaanyatjarra Rift, features giant layered mafic-ultramafic Giles intrusions cut by a 10. km wide mafic-felsic magmatic shear zone. The latter is temporally related to the Warakurna LIP, however it is not clear that the Giles intrusions actually form part of the Warakurna LIP. Macroscopic folding and the formation of the large synmagmatic transpressional shear zone attest to synmagmatic basin inversion in the early stages of the rift. The extensive mafic to felsic volcanic rocks of the Tollu Group (traditionally grouped with the Giles Event) were emplaced 25-50. m.y. later than the c. 1075. Ma Warakurna LIP. © 2010.