Análise de espectros de lepidolites obtidos por fluorescência de raios x usando a radiação do sincrotrão

Abstract

The present work is part of the attempt to establish the composition of the micas of Mozambique, as component minerals of pegmatites, underway at the Department of Chemistry of the Faculty of Sciences, funded by the “Swedish Agency for Research Cooperation with Developing Countries” (SAREC), result of the high economic interest of the mineralizations that occur in the region of Zambézia, province of north-central Mozambique, origin of the samples studied here. The present work presents the analysis of lepidolite spectra from Zambézia pegmatites. The analysis is done with the computer program Wapi, which applies the principle of non-linear least squares to calculate the areas of the Ka and La fluorescence stripes after complex stripe deconvolution and continuous background reduction due to diffuse and braking radiation in the sample . This calculation is done by comparing a real spectrum of the sample, the registered one, and the computer simulated through the imposition of elements. In this program, the accuracy of the fit between the recorded and simulated spectrum is given by criterion x2. The identification of subtrace elements such as Ir, Pt and Hf is also described by analyzing the spectra obtained by X-ray fluorescence, using synchrotron radiation (SXRF) for the excitation of the samples. The interferences to take into account when detecting Pt elements using the L linha2 line are indicated, taking into account the interferences from Ta, Ir and W; Go using the Lß2 line with interferences from Hf, Ge, W, Ta, TI and Pt; and Hf using the line Lo4, from which multiple interferences from Cu, Os, Ir and Gd are marked. It is also determined, by atomic absorption spectrophotometry (AAS*), the contents of Li,Na,Al,Si,K,Ca,Mn,Fe,Rb and Cs, destined for computer processing. The samples were solubilized by acid etching with HF-HNO3-HC1O4 acids and the solutions obtained in 4N HNO3 medium. (TRADUÇÃO NOSSA)