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Delamerian Glenelg tectonic zone, western Victoria: Geology and metamorphism of stratiform rocks

2002; Taylor & Francis; Volume: 49; Issue: 2 Linguagem: Inglês

10.1046/j.1440-0952.2002.00922.x

1440-0952

C. M. Gray, Anthony I.S. Kemp, J. Alton Anderson, D. J. Bushell, David Ferguson, J.A. Fitzherbert, Matthew Stevenson,

earthquake and tectonic studies

The Cambro‐Ordovician Glenelg tectonic zone of western Victoria is a distinctive metamorphic‐igneous segment of the Delamerian Orogenic Belt comprising two northwest‐striking regional metamorphic segments of andalusite‐sillimanite type prograding towards an axial granitic batholith. The second of five deformations (D2) was most significant, producing isoclinal folds, transposition and a pervasive regional foliation (S2). Southwest of the central batholith, biotite to migmatite zones contain mainly quartzo‐feldspathic rock (turbiditic metagreywacke, quartzo‐feldspathic schist and migmatite), plus less common metaquartzite and calc‐silicate rocks and minor metapelite. Metagabbro, metadolerite and amphibolite typically have the chemistry of mid‐ocean ridge basalts. Serpentinite pods and sheets were tectonically introduced to low‐grade areas. Northeast of the central batholith, quartzo‐feldspathic rock occupies the sillimanite and migmatite zones exclusively, with a regional concentration of pegmatites adjacent to the zone boundary. Gross interleaving of quartzo‐feldspathic schist, migmatite, pegmatite and muscovite‐bearing granitic rock is characteristic. Peak metamorphic conditions of 550 MPa at 640°C leading to migmatite formation were established by D2 time and accompanied by tonalite‐granodiorite and pegmatite emplacement. Subsequently, the thermal high contracted to the northeast culminating in the more extensive syn‐, post‐D4 to pre‐D5 granitic magmatism.