Chemistry, origin, and evolution of mineralized granites in the Lachlan fold belt, Australia; the metallogeny of I- and S-type granites

Granites crop out over 20 percent of the total exposed area of the Lachlan fold belt and comprise subequal proportions of I and S types. Despite the volume of granite present, economic mineralization is sporadic. Major Sn mineralization is related to S- and I-type granites that are both reduced and have undergone extended feldspar-dominated crystal fractionation. Mo showings are common but, as for Cu, large deposits are absent. Scheelite skarn mineralization is represented by the major King Island deposits; however, granite-related W mineralization of a similar scale is not found elsewhere within the belt. The I-type granites of the belt represent the products of partial melting of older tonalitic-granodioritic source rocks in the deep crust which were themselves ultimately derived through fusion of mantle materials (M types). This evolution is also mirrored in the nature of related mineralization which changes from Cu dominated atthe chemically primitive nd of this series through to lithophile dominated inthe more evolved I types. Most of the Lachlan fold belt I types have not undergone significant crystal fractionation and are neither strongly oxidized nor reduced. Two prominent mineralized I-type suites, the Boggy Plain Supersuite of the central Lachlan fold belt and the Grassy Suite of King Island, are anomalously mineralized relative to other Lachlan I types. Both are chemically distinct from other I types in the belt by being enriched in the