Caracterización petrográfica y mineralógica del depósito vms “la plata” en el cantón Sigchos, provincia de Cotopaxi.

Abstract

The VMS "La Plata" project is divided into two main ore bodies economically "La Mina Norte" and "La Mina Sur", the latter in turn is subdivided into "Cuerpo Norte" and "Cuerpo Sur". New exploratory data of mineralization in the "South Body" is obtained, and with it the need to establish and correlate the mineral paragenesis of the orebody arises. The mineralization is found as small lenses of massive sulphides, stockwork, and disseminated. Drill core samples were taken from the "Cuerpo Sur" of La Plata Mining Company where 20 polished sections and 3 thin sections were analyzed under the petrographic microscope with reflected and transmitted light, respectively. Selected samples were analyzed under the scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (SEM-EDS). The petrographic, mineralogical and textural study of "La Plata-South Body" allowed determining the paragenetic sequence defining 6 stages of mineralization; Stage 1: framboidal pyrite which is syngenetic with the sediments (mudstones) is classified as early mineralization. The main mineralization is represented by; Stage 2: Zn-Pb enrichment which presents a replacement of stage 1, the mineralization suggests low temperatures (~150 - 250ºC); Stage 3: Zn-Cu-Au enrichment, textures indicate a replacement of the previous stages and an increase in temperature (~250 - 300ºC); Stage 4: Cu enrichment, represented by ore of chalcopyrite, mineralization and textures observed suggest a temperature increase (~300 - 350ºC); Stage 5: Brt enrichment, represents a stage of system closure and cooling, barite stability is low temperature (˂ 250ºC). Finally, Stage 6: presents covellite that replaces the previous stages and suggests a supergene enrichment stage.