Caracterización petrográfica de los materiales procesados en pequeña minería en la zona de Zaruma – Portovelo, provincia de el Oro, Ecuador

Abstract

Zaruma - Portovelo mining district has been of great interest to the economy of Ecuador for more than 500 years, remaining in continuous exploration and exploitation. It has generated mineral treatment processes without previous studies, generating tailings with high levels of heavy metals, becoming pollutants for the environment and with repercussions on health. Therefore, this research aimed to carry out a petrographic characterization of the materials processed in small-scale mining in the Zaruma - Portovelo area, El Oro province, Ecuador. The methodology implemented had a qualitative approach, carried out a sampling of the Sorochoza vein, elaborating polished sections for microscopic and macroscopic analysis, a codification of results in cards, an atomic absorption assay, and analyzed its implications in mineral processing (gravimetry, flotation, and leaching). In this study, the analysis focused on the mineralogy of the area, which is characterized by mineralization in lava with andesitic and basaltic-andesitic compositions. Delimited to the north by Palestina fault - Buza bridge and to the south by Piñas – Portovelo fault. Besides identifying minerals such as gold (Au), pyrite (Py), chalcopyrite (Ccp), hematite (Hem), galena (Gn), tennantite - tetrahedrite (Tnt - Ttr), quartz (Qz) and plagioclase (Pl), an average size of the gold grains found (78.05 micrometers = 0.07805 mm) and the paragenetic sequence is defined in three stages; the first one with Qz and Pl massively and homogeneously, stage two with the enrichment of Py, Ccp, Gn and Tnt - Ttr minerals and the third one continues with the enrichment. In conclusion, comparing the data from the mineral processing implications indicates that the flotation process is likely the most profitable method for application in this study area.