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% of the total exposed area of the Lachlan fold belt and comprise subequal proportions of I and S types. 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 ore element ratios (Sn/W/Cu/Mo, etc.) of granite-related mineralization in the Lachlan fold belt is a straightforward function of the relative oxidation state and degree of fractionation within the associated granite suites. The progression from Cu-Au, and W to Mo mineralization related to progressively more fractionated, oxidized I-type magmas can be traced within single supersuites. Such a systematic relationship between magma composition, redox state, and ore element ratios is good evidence for the magmatic source of ore elements in granite-related mineral deposits and for the production of the observed ore element ratios dominantly through magmatic processes. -from Authors