Análise qualitativa da composição química de espeleotemas precipitados em cavidades em rochas siliciclásticas na região sudeste de Diamantina/mg

Abstract

This paper aims to present the qualitative chemical composition of chemical deposits present in caves developed in siliciclastic rocks in the southeastern region of Diamantina/ MG. The methodological procedures included a literature review, field work, sampling and decal of chemical deposits, preparation of polished thin sections, plating the samples with carbon (C) and EDX line analysis and Scanning Electron Microscope (SEM). The results show that the chemical deposits are presents in all studied caves and they occur, especially in the form of coralóides, crusts, pending, dikes silica and bleeding. Six samples were collected for chemical deposits in the caves Extração, Sempre Vivas and Salitre. Qualitative studies using SEM and EDX line indicate varieties of chemical elements, especially Ca, Si and Na. Microscopic images of the samples show variations in mineral concentration and the macroscopic interpretation indicates different thickness layers of chemical deposition. These obtained data associated with the literature review allow discussion of paleoclimatic processes and point initially the occurrence of wetter conditions and subsequently reducing humidity. Paleoclimatic variations probably interfered with chemical deposits and generally resulted in a reduction in the thickness of the layers at the edges of these deposits.