gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1997.061.406.03 Mineralogy Geochemistry and EPR of Cassiterites from the Iberian Hercynian Massif Murciego A. Area de Cristalografía y Mineralogía, Universidad de Extremadura, Badajoz, Spain Garcia Sanchez A. IRNA-CSIC, Aptdo. 257, Salamanca, Spain Dusausoy Y. Laboratoire de Mineralogie et Cristallographie, Université de Nancy I, Vandoeuvre-lès-Nancy, France Martin Pozas J. M. Departamento de Geología, Universidad de Salamanca, Spain Ruck R. CREGU, B.P. 23, 54501, Vandoeuvre-lès-Nancy, France 6 1997 61 406 357 365 8 12 1995 9 9 1996 Copyright © 1997, The Mineralogical Society 1997 Abstract

This paper is based on microprobe analysis (Ta, Nb, Fe, Mn, Ti, W, Sn) and Fe3+ 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 Fe3+ EPR spectra reveal that the coupled substitution: 3Sn4+ = (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: 2Sn4+ = Fe3+ + (Nb,Ta)5+ and Sn4+ + O2− = Fe3+ + OH− are dominant in those from medium-low temperature quartz veins and in the light zones of cassiterites.

 Keywords cassiterite trace elements Fe3+ EPR spectra coupled substitutions