Résumé
At the giant tin deposit of San Rafael, Peru, the early hydrothermal stages, preceding the economic tin mineralization, include successively: 1) potassic alteration represented by hydrothermal K-feldspar altering magmatic plagioclase; 2) sericite replacing magmatic plagioclase in the ground mass and hydrothermal K-feldspar, with greisen formation in the apical part of the intrusion; 3) widespread albitic alteration, both disseminated and as intense replacement along fractures, overprinting and obliterating the previous stages; 4) quartz-tourmaline veins rimmed by albitic alteration halos. In this contribution, the greisen-style alteration and sodic alteration, are studied in depth. Trace element analysis of hydrothermal albite reveals a marked enrichment in incompatible elements (B, Rb, Cs) compared to magmatic plagioclase, suggesting albitization was triggered by magmatic fluids exsolved from an evolved silicate melt.