Mg clay minerals are usually associated with carbonates in alkaline-saline environments, precipitated from solution and/or transformation from other minerals. The aim of this research is to identify the mineralogy and geochemistry of clay minerals in different alkaline lakes in the Nhecolândia region, the southernmost region of the Pantanal wetland (Brazil). Sediment samples were analyzed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and transmission electron microscopy. Water samples were analyzed, determining their main cations and anions, in order to understand their relationship with the clays. The analyses allowed classifying the water bodies as saline, oligosaline and freshwater lakes. The sediments are composed mainly of quartz and a fine-clay fraction, dominated by illite, kaolinite and smectite. The XRD results showed illite and smectite mixed-layered in the saline lakes at Barranco Alto farm, whereas at Nhumirim farm, trioctahedral smectite was only observed in one lake. The smectite minerals were normally identified coupled with calcite at the top of the sequences, associated with exopolymeric substances (EPS) in the lakes, suggesting that these minerals are precipitating due to the physical-chemical and biological conditions of the water bodies.
The aim of this paper is to discuss the integration of geological and geophysical data in the region between Tunas do Paraná e Adrianópolis, Ribeira Valley, State of Paraná. To generate the geological database, a Geographic Information System (GIS) was developed based on geological map in 1:25,000 scale, extracted from the 90's geological surveys. The area involves paleoproterozoic Tigre's Nuclei, mesoproterozoic metassedimentary and metavulcanossedimentary rocks from Perau and Votuverava formations, neoproterozoic Varginha Magmatic Suit and mesozoic basic dykes. The mineralization is hosted in calc-silicate rocks from Perau Formation, which was composed by Pb-Zn-Cu sulfides massive horizons. The airborne gamma-ray spectrometric and magnetic data were acquired by CPRM. The gamma spectrometry, utilizing K, eTh, eU and ternary maps, allowed making a litho-geophysical map. The magnetometry provided a magnetic-structural map, where it was possible to identify shear zones, minor expressive faults and metabasic rocks.
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