Hydrothermal tin Iodes typically have very high ore grades (half of the deposits grade> 1.3 % Sn, and a tenth ofthem > 2.3 %), and most ofthem contain in excess of 1,000 t Sn, with sorne hosting > 50,000 t Sn (Menzie et al., 1988; Singer et al., 1993). Compared to most tin Iodes, the Peruvian San Rafael Sn-Cu deposit, the subject of this thesis, is a giant member of this deposit clan. Hosting a total resource of ~ 1,000,000 t Sn (metal) and having an average grade of 4.7 wt.% Sn (Minsur, unpub. data, December 2002), it is responsible for ~13% of the annual global hard-rock tin production (J. Carlin, USGS, writlen comm. 2000) and is considered the world's richest hydrothermal tin Iode.
In the San Rafael deposit, the high-grade mineralization is of the cassiteritesulfide type, and the bulk of it is hosted by a large, vertically extensive, single complex vein, referred to as the San Rafael Iode. This Iode is part of a vein-breccia system, which is centered on a Late Oligocene granitoid stock, shallowly emplaced in Lower Paleozoic c1astic metasedimentary rocks. The tin ores form cassiterite-quartz-chlorite-bearing veins and breccias, hosted by several large fault jogs at depth in the Iode. By contrast, the copper ores, which contain disseminated acicular cassiterite, are localized in the upper part of the system. Both ore types are associated with a very distinctive strong chloritic alteration, which was preceded by intense sericitization, tourrnalinization and tourmal ........
