Geochemistry and EPR of cassiterites from the Iberian Hercynian Massif

Abstract

Abstract This paper is based on microprobe analysis (Ta, Nb, Fe, Mn, Ti, W, Sn) and Fe 3+ EPR spectra of cassiterite samples from 14 tin deposits from the Iberian Hercynian Massif. The interpretation of microprobe data, atomic ratios (Fe+Mn)/(Nb+Ta), and Fe 3+ EPR spectra reveal that the coupled substitution: 3Sn 4+ = (Fe,Mn) 2+ + 2(Nb,Ta) 5+ is dominant in cassiterites from pegmatites, and high-temperature quartz veins and in the dark zones of cassiterites. The mechanisms: 2Sn 4+ = Fe 3+ + (Nb,Ta) 5+ and Sn 4+ + O 2− = Fe 3+ + OH − are dominant in those from medium-low temperature quartz veins and in the light zones of cassiterites.