Abstract

MANRIQUE-CARRENO, John Luis  and  GUAMAN-JARAMILLO, Galo Alexander. Geochemical prospecting study in fluvial sediments of Chirimoyo and Guineo subbasins, Ecuador. Bol. geol. [online]. 2020, vol.42, n.1, pp.39-55.  Epub Jan 22, 2020. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v42n1-2020002.

A sampling of stream sediments was carried out in the Chirimoyo and Guineo microbasins, at the Puyango sector, Loja province, Ecuador, in order to perform a study of geochemical exploration, in which were determined anomalous values for CaO (>3.46wt%), MnO (>0.26wt%), P2O5 (>12.63wt%), V (>693 ppm), Zn (>709 ppm), Cu (>108 ppm) and, subanomalous values of U (>60 ppm) and, Ni (>232 ppm) for the subbasin Chirimoyo. As for the Guineo subbasin, the following anomalous values were determined: MnO (>0.47wt%), TiO2 (>1.16wt%), subanomalous values of CaO (>7.01wt%), P2O5 (>0,96wt%), V (>1903 ppm), U (>50 ppm), Ni (>451 ppm) and, Zn (>1306 ppm). According to the geochemical anomalies maps the highest values of vanadium (2520 ppm in Guineo), uranium (70 ppm in Chirimoyo), zinc (1445 ppm in Guineo) and nickel (629 ppm in Guineo) are associated with the northern part of both microbasins, specifically in the north of the Guineo microbasin close to the La Sota sector, where the sedimentary rocks of the Puyango Formation appear, which contain bituminous limestones and calcareous black shales, which may be hosting mineralizations of these elements, this is evidenced by the high values of Ca, which indicates a carbonate origin of the sediments. The sediments are composed mainly of silicates and aluminosilicates (clays and micas), in smaller proportion oxy-hydroxides of Fe-Ti: goethite, magnetite and anatase. Additionally, calcite and zircon were detected in two samples. There is the presence of vanadium minerals such as sherwoodite, rossite, ronneburgite and sincosite, which corroborates the vanadium geochemical anomalies determined by chemical analysis.

Keywords : Geochemical prospecting; stream sediments; Chirimoyo; Guineo; vanadium; uranium..

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