CERRO DEL DIABLO AREA

These areas include properties belonging to Minera Cordillera del Viento S.A. with less information and geological antecedents than the previously mentioned ones. In the cases here described, it is considered necessary to generate new information in order to assess the potential of the deposits and mineral occurrences located in those properties.

n the first area the only property owned by Minera Cordillera del Viento S. A. is a copper mine called “María Aurelia”. In this case, to the limitations given by the size of the site and the fact that the test Expte Nº 4802-0003/2008 englobes them, the geological assessment done by JICA-SMN (2000) reports a low favorability of the zone for the development of disseminated copper mineralizations.

”The results of the chemical analysis of rock revealed the calc-alcaline property of granites, also showing higher content of light rare earth (La-Sm) in relation to the heavy rare earth (Gd-Lu), in comparison to the granitic rocks of Andacollo. This trend means that the granodiorite in this district is more differentiated than the one present in Andacollo, which is consistent with the fact that these rocks intrude in ground as small stocks. The mineralized zones with iron waste dumps are distributed in the area with linear continuity. However, the width of the hydrothermal alteration is not extensive and both pelites and granitic rocks do not show alterations beyond 20 or 30 meters on both sides of trenches and drifts. Therefore, the hydrothermal activity in the area is considered to be very little and it is not possible to expect bigger mineralizations.”

In spite of what is indicated in the report, the absence of geophysical studies and explorations limit the possibilities of definitive and conclusive assessments.

Antecedents

The mine “María Aurelia” is located about seven kilometers to the west of the spot called Trailathue, on the west slope of del Diablo hill. Up to 1975 a few tons of copper ores (mainly malachite) were extracted by means of two drifts linked by wells or extraction shafts. The area of del Diablo hill was prospected and explored by the General Management of Fabricaciones Militares in the decade of 1970 during the execution of the so called Plan Cordillerano (Andean Plan), when the main prospects and deposits of disseminated copper in the country were identified. Del Diablo hill would correspond to a model of copper / molybdenum porphyry, with satellite veins of lead sulfides, zinc, iron and copper in quartz and/or barite veinstone; María Aurelia is one of them.

The exploitation of the mine was suspended apparently due to the depletion of copper minerals in the front of each drift, the main ones being iron oxides (hematite and limonite) in dacite wall rock.

Other mineralizations in the district

The following mines, which also integrate the veins system surrounding Del Diablo hill, can be found nearby: “Octubre”, “La Esmeralda”, “Cacique Purrán” and “Alma Teresa”. All with mineralization of lead, copper, zinc, in barite veinstone. In some cases, the latter is dominant becoming the mineral with most commercial value. The area of prospective interest would cover a surface of 10 km2, and the mineralization and alteration would be controlled by the fracturing system due to the intrusion of dacitic and granodiaritic of late Cretaceous / Tertiary. The identified mineralization consists in chalcopyrite, tetrahedrite, pyrrhotite, pyrite, sphalerite galena and barite. Samples in charge of the Department of Mining reported geochemical anomalies of gold, silver and molybdenum (1993, in JICA, 2000).