Geochemical specialization of the tin-bearing granitoid massifs of NW Bohemia

Abstract

The geochemistry of Hercynian tin-bearing granitoid massifs of the Krusne hory Mts. (Erzgebirge), Slavkovský les Forest (Kaiserwald) and Smrciny (eastern Fichtelgebirge) is compared by statistical processing of 270 analyses including a wide spectrum of major and trace elements. Seven different types of granites are distinguished. Out of these, five types represent the successive differentiation of the largest massif of NW Bohemia: the Karlovy Vary (Karlsbad) massif. This comprises strongly differentiated peraluminous granites evolving towards extreme Li-Rb-Cs-F-and Sn-enrichment in the youngest members, which are albite-topaz-zinwaldite “lithium” granites. The sixth and seventh types are different from the former by their location in the eastern Krusne hory and tectonic setting, and they display geochemical features of anorogenic granites: they are metaluminous albite-zinwaldite granites with marked enrichment of Nb, Y, and HREE in addition to Li, Rb, Cs, F and Sn, indicating contamination by sub-crustal material. Sn-W mineralizations, including flat peri-contact greisen bodies, steep greisen veins and tourmalinized phyllites, are all intimately associated with the most strongly differentiated granites — the Li-granite and the Cinovec-granite respectively.