Eléments en traces dans les pyrites de la province de Huelva (Espagne)

Abstract

The following trace elements: Co, Ni, V, Cr, Mn, Pb, Zn, Cu and Sb were measured by atomic absorption spectrometry in 55 samples of selected pyrite from the volcanic sedimentary massive deposits of Huelva's province. Se was measured by colorimetry. These analyses were started after a geological and metallogenic study of the province's central area. This study has proved the sedimentary origin of the deposit and more or less close spatial relationship with the top of two acid volcanic sequences. The metallogenetic model is uncertain about the mineralizations origin: it could be concluded in favor of either a very close relationship with post-volcanic fluids (close feeder-pipes deposition) or the sedimentary sequence's predominance (massive deposits distant of the feeder-pipes). The answer is mainly given by the Co Ni and S Se ratios. The Co Ni ratio is very high in the massive sulphide deposits (about 19.2) and strongly decreases in the pyrite disseminated in the close massive deposit's host rocks ( Co Ni = 4.2 ). This ratio is much lower in the pyrite of metasedimentary rocks which are distant of any known massive deposits ( Co Ni = 0.8 ). The S Se ratio is very much lower in the massive deposits (mean = 3403) than in the disseminated pyrite (7852). The evolution of these two ratios' values proves the assumption of the direct relationship between the massive deposits and post-volcanic fluids.