BERILO DOS PEGMATITOS IPÊ, FERREIRINHA, JONAS LIMA E ESCONDIDO, GOVERNADOR VALADARES, MG: DADOS CRISTALOQUÍMICOS

Abstract

The Ipe, Ferreirinha, Jonas Lima and Escondido Pegmatites are situated in the Governador Valadares Pegmatitic District, Minas Gerais State, Brazil, and belongs to the Marilac Pegmatitic Field, hosted in the Rio Doce Group. This work shows the physicochemical and optical characteristics of 14 beryl samples from these pegmatites. The beryl type evolution from normal (N), to transition (NT), and tetrahedral (T) was obtained from c o /a o ratio determined from X-ray diffraction. Fourier Transform Infrared Spectroscopy (FTIR) data permited the characterization of the fluid components, as CO 2 , CH 4 and H 2 O types I and II. The mass loss variation (H 2 O and CO 2 ± alkaline elements) from 0,5 to 3,0%, showed by the Termogravimetric and Termodiferential Analyses (TGA/DTA) analysis, was indicated by three (Jonas Lima and Escondido) or two (Ipe and Ferreirinha) distinct ranges. The density (2,66 as 2,72) and the refractive index data (n ω from 1,574 to 1,585 and n e from 1,580 to 1,591) was given by physical tests. The beryl crystals contain a great number of two, three or multiphase fluid inclusions, primary, pseudosecondary and/or secondary in origin, with aqueous or aqueous carbonic solutions. The last ones show different CO 2 contents depending on the sample localization. The data represent a geochemical evolution from the less (Ipe/Ferreirinha) to the more differentiated (Jonas Lima/Escondido) alkaline elements and CO 2 enriched pegmatite bodies.