Análisis textural y paragenético de laveta sur del proyecto Cerro Norte, distrito minero Casposo, San Juan

Abstract

Textural and paragenetic analysis of the Sur vein of the Cerro Norte Project, Casposo Mining District, San Juan. The Casposo mining district is located in the province of San Juan (Argentina) in the eastern sector of the Cordillera Frontal. Within this district epithermal lowsulphidation deposits are hosted by Vega de los Machos Formation (Caballé 1986) of lower Permian age. Cerro Norte has a system of E-O veins with dip between 60 and 85° to the North and the South and form three main outcrops: Norte, Centro and Sur veins. The latter is the reason for the present study. The Sur vein extends more than 400 m and its thickness varies from 0.20 m. up to 3 m. It is characterized by a bifurcation pattern. It comprises 6 events. Event 1 is characterized by crustiform-colloform quartz 1 (Fig. 1a and b) with moss (Fig. 1a) and spherulitic texture (Fig. 1b). This event presents mosaic textures (Fig. 1c) and flaming extinction (Fig. 1d) typical of recrystallization. Recrystallization, although it constitutes another event, could not be temporarily limited. Event 2 is formed by massive microcrystalline quartz of anhedral habit (Fig. 1e). Event 3 is the crystallization of calcite in the form of "blades". Event 4 shows the pseudomorphic replacement of calcite by quartz that forms the lattice-bladed texture (Fig. 1f). Event 5 represents the crystallization of drustiform habit quartz with zoned texture (Fig. 1g). Event 6 constitutes the formation of a hydrothermal breccia that includes clasts from previous events and cement crustiform-colloform quartz 2 (Fig. 1h), calcite, chlorite, freibergite-argentotennantite 1 (?), freibergite-argentotennantite 2 (?), pearceite-polybasite (?), freieslebenite (?), sphalerite, chalcopyrite, pyrite and native silver.