Mineralogical and petrographical characterization of the Vizcaya, Octubrina and Gabi veins from the Zaruma-Portovelo gold epithermal ore deposit (Ecuador)

Abstract

Ore petrography through optical microscopy and electron microprobe analysis (EMPA) can be applied to the characterization of ore deposits, allowing accurate and representative information on the evolutionary sequences of mineral phases (paragenesis). In this studywork mineralogical and petrographical characteristics of three veins (Vizcaya, Octubrina and Gabi) of the Zaruma-Portovelo hydrothermal deposit (Ecuador) have been studied. The main objective of this research was to identify and quantify the ore minerals present in the polished section studied by optical microscopy and EPM, and to correlate the data obtained with the previously defined paragenetic evolution. In addition, the systematics we describe is revealed as an appropriate method for the characterization and basic knowledge of the mineralized areas. The mineralogical characterization was completed by scanning electron microscopy, optical image analysis and X-ray diffraction. The results have provided us with allowed: i) the identification and quantification of gold, sphalerite, chalcopyrite, galena, pyrite, hematite, chalcocite, covellite and tetrahedrite in the polished sections of the veins studied; ii) the characterization of the mineral associations as a complement to the previous studies of the mineral paragenesis of the deposit and indicative in the geometallurgy of the deposit. The mineralogical and ore petrographical characterization of the ores represent the basis of knowledge to understand the characterization of the mineral deposit and, in addition, improve the processing of the mineral of interest.