IDENTIFICATION OF ZEOLITE GROUP OF MINERALS BY REFLECTANCE SPECTROSCOPY
The use of zeolites to improve the quality of the soil for agriculture gains space around the world. The high cation exchange capacity of zeolites favors the retention of nutrients in the soil and the high capacity of these minerals to retain water in their crystal lattices makes them excellent soil conditioner. The absence of zeolite deposits in exploration in Brazil points to the basalts of the Serra Geral Formation of the Parana Basin as a target with great potential for the exploration of natural zeolites. Researches done by CPRM (Geological Survey of Brazil) highlight the significant presence of zeolites at the contact between the lower flows of the Serra Geral Formation and eolian sandstones of the Botucatu Formation in Rio Grande do Sul. Reflectance spectroscopy is a tool that can contribute to the identification of zeolites in the field or laboratory, using rapid analysis and low cost. Prior knowledge of the spectral behavior of zeolites is of great use in the exploration of potential targets in the Serra Geral Formation (piles of lobes and breccias from top of basalt flows).In these ambiences were recognized macroscopically heulandite, scolecite, stilbite, laumontite and mordenite. This paper presents the results of analysis in representative samples of the paragenesis characterizing the different blocks determined by Project Agrominerals from Parana Basin in Rio Grande do Sul (RS) – CPRM, using the spectroradiometer FieldSpec Hi-Res 3 © – ASD, with spectral resolution between 0.35 and 2.5 micrometers. Spectral curves stilbite, heulandite, laumontite, mordenite and possibly analcime and clinoptilolite were identified, locally associated with calcite. Through spectral signatures may be constructed standards for zeolites, useful to the classification of satellite images, considering the relationship between the size of the targets and the spatial and spectral resolutions of satellite and aerial sensors available for imaging the research area.
