Geochemistry and EPR of Cassiterites from the Iberian Hercynian Massif

A. Murciego, A. Garcia Sanchez, Y. Dusausoy, J. M. Martin Pozas and R. Ruck
Area de Cristalografía y Mineralogía, Universidad de Extremadura, Badajoz, Spain
IRNA-CSIC, Aptdo. 257, Salamanca, Spain
Laboratoire de Mineralogie et Cristallographie, Université de Nancy I, Vandoeuvre-lès-Nancy, France
Departamento de Geología, Universidad de Salamanca, Spain
CREGU, B.P. 23, 54501, Vandoeuvre-lès-Nancy, France

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

Mineralogical Magazine; June 1997 v. 61; no. 406; p. 357-365; DOI: 10.1180/minmag.1997.061.406.03
© 1997, The Mineralogical Society
Mineralogical Society (www.minersoc.org)