Geoquímica de la casiterita de los filones de estaño del granito especializado de Logrosán (Cáceres, España)

Abstract

The granitic cupola of Logrosán (Cáceres, España) shows petrographic and geochemical characteristics which make it possible to define it as a highly evolved stanniferous granite. This stock can be classified as a S-type, peraluminious, volatile-rich granite enriched in incompatible elements, mainly tin. The tin mineralization represents a late hydrothermal stage and it is concentrated in greisen alteration zones and in extensional quartz-cassiterite veins that cut the granite with a N35 trend. The main mineral ore in the deposit is the cassiterite (SnO2). The cassiterite of Logrosán displays a compositional zoning related to the increase for tin substitution in favor of other cations (Ti, Nb, Ta and Fe). The cassiterite frequently contains inclusions of rutile and columbite which are mainly distributed in the more transparent areas of the host mineral. The cationic substitution mechanisms for the cassiterite, rutile and columbite follow the trend defined by the ideal substitution: 2(Nb,Ta)5+(Fe,Mn)2+ ↔ 3(Ti,Sn)4+.