CORÍNDON NO BRASIL: QUÍMICA, INCLUSÕES, ESPECTROSCOPIA E ASPECTOS GENÉTICOS

Abstract

Investigation of mineralogical and chemical characteristics of corundum from eleven deposits in Brazil aimed to contribute to the understanding of genesis and to obtain a set of data to be used as a finger print to elucidate provenience of unknown samples. In most deposits corundum is recovered from recent sediments except in two cases where it is found in the host rock. Trace-elements were analyzed by INAA and ICP-OES, solid inclusions by SEM-EDS and absorption spectra were obtained in the range of UV - visible. The most important trace-elements considered in the discussion of cause of color and/or genesis are REE, Th, Ga, Fe, Ti, Cr, W, Sb, La, and Ta. Formation by high-grade metamorphismin aluminous metasedimentary rocks is suggested for corundum from most deposits (Catingal and Lajedinho - BA, Palmeiras, Sapucaia, lndaiá and Caputira - MG) as indicated by geological context, mineral inclusions and/or chemistry. In Peixe (TO), corundum hosted in pegmatite is magmatic. In the secondary deposits of Malacacheta and Campo Belo (MG), Coxim (MS), and Barra Velha (SC) the genesis of corundum is unclear or possibly due to the interaction of metamorphic and metassomatic processes.