Delamerian Glenelg tectonic zone, western Victoria: Characterisation and synthesis of igneous rocks

• DOI: 10.1046/j.1440-0952.2002.00920.x
• Publication Date: 2003-03-10T10:44:15Z
• Authors: A. I. S. Kemp; C. M. Gray; D. J. Ellis; J. A. C. Anderson; D. J. Ferguson
• Keywords: Felsic; Diorite; Hornblende; Batholith; Anatexis; Migmatite; Fractional crystallization (geology); Underplating

Cambro‐Ordovician plutonic rocks of the Glenelg River Complex (western Victoria) are grouped into three structural associations based on intrusion timing relative to Delamerian deformational episodes. Early syn‐compressional plutons contain regional S2 foliation and comprise Wando, Wennicott Deep Creek granitic types, which have low K affinity confined southwestern corner complex. Wando types include hornblende diorite gneissic tonalite numerous mafic igneous enclaves; high Al2O3 increasing K2O with silica characteristic. Hornblende tonalites type less deformed by contrast evolve towards lower K2O, whereas geochemistry granodiorites suggests plagioclase accumulation. The nearby Caupaul Igneous also developed at this time encompasses through diorite, gabbronorite pyroxenite. Tonalitic dioritic geochemically equivalent exhibit a steep increase in silica, implying compositional control fractional crystallisation, though relationships cumulate obscure. Crystallisation foliated is estimated ∼460–660 MPa from hornblende‐plagioclase geobarometry. These were supplanted late Tuloona, Harrow Loftus magma post‐date D2, but weakly D5. Tuloona predominantly tonalitic elongate central batholith. Mafic enclaves ubiquitous, although more felsic varieties magmatic muscovite complexly interleaved migmatites. northeast abundant muscovite, metasedimentary transitional migmatitic envelopes, consistent derivation situ anatexis host sequence. subsequent transition higher magmatism marked granodiorite, biotite phenocrysts Sr signature diagnostic. Considerably shallower emplacement levels (∼200–360 MPa) require exhumation up 11 km crust after formation types. Following cessation compressional deformation, final activity involved distinctive K‐rich adamellite granite far west. This coherent sequence elaborate than documented eastern Mt Lofty Ranges South Australia conveys dynamic impression within trans‐Gondwana Orogen has hitherto been appreciated.