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A detailed petrographical, mineralogical, morphological, geochemical and physicochemical characterization of talc from an Argentinean ore is presented. This deposit is located in the San Juan province at the foothills of the Andes. Characterization was performed on rock and milled talc using different techniques including polarized light microscopy, transmission electron and scanning microscopy with energy dispersive spectroscopy (SEM/EDX), chemical analyses, X-ray diffraction (XRD), X-ray fluorescence, Fourier transform infrared spectroscopy (FTIR), particle size determination by laser diffraction, thermogravimetry analysis, and colorimetry. A mineral sample contains approximately 80 wt% talc. Associated minerals such as carbonates as veins and chlorite interlaminated with talc were detected. Carbonates are calcite, dolomite and magnesite, as was corroborated by FTIR. Morphology and crystallinity were assessed by XRD data, obtaining a morphological index of 0.79 which indicates the macrocrystalline character. Crystalline habits of associated minerals were recognized by SEM, detecting their constitutive elements by EDX. Talc color parameters are L* = 82.76, a* = −1.50, and b* = 5.38. The slight yellowing could be attributed to chlorite or traces of Fe oxides. Although the whiteness index (62.12) impedes its commercialization as a high-priced mineral, this kind of talc can be used as an additive for polymers, since it would offer a high reinforcing effect (improvement of mechanical properties). [ABSTRACT FROM AUTHOR]

This paper presents a detailed geological map at the 1:20,000 scale of the Tocomar basin in the Central Puna (north-western Argentina), which extends over an area of about 80 km2 and displays the spatial distribution of the Quaternary deposits and the structures that cover the Ordovician basement and the Tertiary sedimentary and volcanic units. The new dataset includes litho-facies descriptions, stratigraphic and structural data and new 234U/230Th ages for travertine rocks. The new reconstructed stratigraphic framework, along with the structural analysis, has revealed the complex evolution of a small extensional basin including a period of prolonged volcanic activity with different eruptive centres and styles. The geological map improves the knowledge of the geology of the Tocomar basin and the local interplay between orogen-parallel thrusts and orogen-oblique fault systems. This contribution represents a fundamental support for in depth research and also for encouraging geothermal exploration and exploitation in the Puna Plateau region. [ABSTRACT FROM AUTHOR]