GEOLOGICAL AFFINITIES OF THE GLENELG RIVER COMPLEX, WESTERN VICTORIA

A detailed comparison between the Glenelg River Complex in the Wando V ale district of western Victoria and the South Australian Kanmantoo Gr oup of the Mt Lofty Ranges reveals many common elements. As the basis of comparison the geology of Wando Vale is described concisely with em phasis on its magmatic and structural history. Both have similar metas edimentary rocks, which are siliciclastically dominated with a substan tial calcareous component. Geochemically, these rocks are relatively r ich in CaO and Na2O, and compositionally distinct from the mature turb idites of the Lachlan Orogenic Belt. Four deformational episodes are i dentified in the Glenelg River Complex and are comparable to the histo ry of the Kanmantoo Group in the Tungkillo-Palmer region. The regional metamorphic zonation of both units extends into the amphibolite facie s and is of the andalusite-sillimanite type with similar mineral cryst allization sequences. Tholeiitic dykes with comparable timing, the geo chemical affinities of mid-ocean ridge basalts, and distinctive high-a lumina compositions are common to both areas. Six syntectonic granitic bodies (one tonalite and five granodiorites) intrude the metasediment ary rocks of Wando Vale; high Na2O and Sr contents indicate links with the Cambro-Ordovician syntectonic granitic rocks of South Australia. The isotopic ages of granites in the Glenelg River Complex constrain t he timing of regional metamorphism, deformation and magmatism as compa rable to that of the Delamerian Orogeny. The Glenelg River Complex is a distal equivalent of the Kanmantoo Group and thus the easternmost ex posure of the Adelaide Orogenic Belt.