Tin deposits of the Sikhote-Alin and adjacent areas (Russian Far East) and their magmatic association

The Sikhote-Alin accretionary belt along the northwestern Pacific Plate hosts the most important tin province of Russia. Here, more than 500 ore deposits were formed between 105 and 55 Ma at transform and active subduction margins. Petrological models suggest an active role of the mantle in the mineralisation processes. The deposits can be divided into three groups according to their mineral content and associated magmatism. The first group, a cassiterite-quartz group is defined by tin-bearing greisens as well as quartz-cassiterite and quartz-cassiterite-feldspar veins and stockworks. The mineralisation shows distinct genetic relationships with S- and A-type granites. The deposits are located mainly in Jurassic accretionary prisms adjacent to the Bureya-Khanka Paleozoic continental terrane margin. The second group is represented by the economically important cassiterite-silicate-sulfide deposits, which produce about 80% of Russian tin. Mineralisation in this group is represented by metasomatic zones or veins related to I-type granitoids. The orebodies consist of cassiterite-tourmaline-quartz or cassiterite-chlorite-quartz associations and contain variable amounts of sulfides. The third group comprises tin deposits containing cassiterite and sulfides with the most complicated ore composition with abundant sulfides and sulfostannates accounting for 60-80% of the total ore mass. In some deposits, zinc, lead and silver dominate, whereas tin is sub-economic. The deposits of this group are generally associated with magmatic rocks of the Sikhote-Alin volcano-plutonic belt. The different associations are found together in the same districts and, locally, also in individual deposits. These are characterised by polychronous and polygenetic mineral systems, formed during long periods of time and in different tectonic settings. This testifies to changes in the many physico-chemical parameters of ore formation and, probably, of ore sources. We suggest that the complex mineral and element compositions of some of the ores were caused by the long-lasting composite tectono-magmatic processes.