Consequently, these medium-P high-T parageneses are early formed, prior to pervasive regional metamorphic events.
This is substantiated by overprinting of medium-P rocks within shear zones by lower grade shear assemblages and the formation of these rocks in thermal regimes entirely distinct from all younger events (i.e. regional metamorphism and low grade shear events), all of which are characterized by high average thermal gradients (G ≥40 ºC/km).
These high-T, high-G conditions in the upper-crust are most possibly formed in a high heat flow magmatic arc environment (Ma).
Unlike stress fields, thermal event switching involves slow rates, conductive delays and a history less punctuated than the structural evolution; necessitating broad thermal events and continuums between them, particularly from M2 to M3a and M3b (see below).In contrast, formation in either an extensional or plume setting would result in widespread distribution.600 ºC) and uniquely low average thermal gradient (G ≤20 ºC/km) metamorphic parageneses are found almost exclusively associated with high-strain shear zones (e.g. The East Yilgarn Craton is a major gold mineralization province, it is also a complex mosaic of different tectono-metamorphic domains and terranes.The thermal and barometric evolution, timing of different metamorphic parageneses and connection between thermal evolution and Au-mineralization has not previously been adequately addressed.
These granulites are statically metamorphosed gabbros, preserving ghosted ophitic textures, recrystallised to granoblastic two pyroxene assemblages.