ESTUDIO PRELIMINAR DE LOS CONTENIDOS DE ELEMENTOS DE TIERRAS RARAS E INCLUSIONES FLUIDAS EN FLUORITAS HIDROTERMALES DE LA SIERRA DE ANCASTI, CATAMARCA, ARGENTINA

MONTENEGRO TERESITA; IRIARTE MATIAS; ALTENBERGER UWE; FERNANDO SARDI

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Lugar: Buenos Aires; Año: 2021 vol. 78 p. 423 - 432

1853-7138

Preliminary study of the REE-composition and fluid inclusions in hydrothermal fluorites of the Ancasti range, Catamarca, Argentina. This paper is a preliminary contribution of the REE-composition, petrography and microthermometry of fluid inclusions of hydrothermal fluorite veins of the El Portezuelo - Los Mudaderos fluoritic district, northwestern of Ancasti range, Sierras Pampeanas, Catamarca province. The veins are located in Sauce Guacho (333.9 Ma) and Los Mudaderos (369.8 Ma) granites and in the metamorphic basement (Ancasti Formation). The granites have equigranular and porphyric textures, with monzo-syenogranitic compositions. Fluorite is mainly violet in color and it is usually accompanied by quartz and chalcedony. The microthermometric data of fluid inclusions were obtained from granular violet fluorite exfoliation plates from Dal mine, while the REE composition was carried out by ICP-OES in fluorite from three different veins. The REE content varies from 6.70 to 64.33 ppm. LREE/HREE > 1, high Lan/Ybn values and distribution patterns indicate enrichment in LREE, suggesting mineralization from early and weakly-fractionated hydrothermal fluids. Negative anomalies of europium and cerium indicate low oxygen fugacity during fluorite formation. The geochemical data of Tb and La indicates a hydrothermal origin, consistent with the geological and textural-mineralogical features that, in addition, show more than one mineralizing pulse and low formation temperatures. The fluid inclusions vary in size and shape, are predominantly biphasic and show average homogenization temperature of 126 °C. The eutectic was registered between -21 °C and -24 °C and final ice melting was metastable and always ≥0 °C.