Statistical classification of tin deposits from cassiterite compositions: application to Russian Far East tin region

A range of large polymineral tin deposits is localized within the accretion fold system of Sikhote-Alln (Far East, Russia), in the Asian margin of the Pacific Ocean. A new ore formation model has been proposed recently, according to which these deposits are formed under two different geodynamic environments of an active continental paleomargin, with a shifting between Californian-type-transform and Andian-type-subduction. The present study concerns some of the tin deposits of Komsomol'sk and Kavalerovo regions, which were previously classified according to their tectogenetic and metamorphic conditions. This classification is validated with trace element composition of cassiterites: the statistical methods used take into special account the relative nature of compositions. This allows us to reproduce almost exactly the existing groups, and to characterize them using mainly log-ratios between In, Fe, Sc, V, Nb and Zr. In contrast, the performance of classical statistical analysis is worse. Concluding, the proposed approach reveals essential differences between groups of deposits corresponding to different geodynamic settings, thus confirming the validity of the new ore formation model.