GEOLOGY of POLYMETALLIC DEPOSIT WITH PRECIOUS METALS

The structure of this zone is similar to Cobriza mine. The sedimentary sequence takes layers that were developed initially during the Paleozoic era and others belong to the Jurassic period, and present a potence of 6,000 m.

The Carhuanco deposit consists of lutites with layers of limestone and quartzite. Mineralization follows direction N 45^o W and dip to the east. This litological environment is the host rock of veins and small layers of replacement ore.

VEINS.

The polymetallic deposit in the zone consists of fissures filled by minerals. The main veins are Maria Teresa, Maria I, Carmen, Maria II, Maritza e Icaro. The first five veins are the most important because present an interesting content of gold.

In general, veins are in average 0.20 m and fill fractures of Tarma group. The structures are in contact with dykes and replaced some contact material. Sometimes, fractures are filled by mineralized dykes where the ore is present at the top, at the bottom, or in both. Also fractures can be in stockwork. In this case, potence is superior and depends of the dyke width.

Due to the type of formation is difficult observe any outcrop. However, underground labors and surveys done by small miners indicate that veins have a big longitude. For example, Maria Teresa vein is the most important and has a longitude of 4 km.

The main texture in the zone is filling and replacement of primary sulphides. Oxidized material presents a substitution texture. Dykes offer a filling texture with weak dissemination.

The filling ore consists of oxides in the higher part, and mixed ore (oxides and sulphides) in the middle part. The lower zone of sulphides has not been studied enough, but it could be weathered.

Sequence of minerals formation is as follow: pyrite – arsenopyrite – pyrrhotite – quartz – sphalerite – marcasite – chalcopyrite – gold – tetrahedrite – electrum – galena – carbonates. The secondary minerals have de following formation: covellite – bornite – cerussite – limonite.

Gold and electrum are filling microporosities, cleavage and fractures on pyrite. This filling is the main gold occurrence and considering geological, economical, and metallurgical aspects, is the most important. Besides, there are pyrite-arsenopyrite contacts as inclusions on galena. Electrum is filling empty places and microfractures on quartz. In oxides from Maria Teresa vein, gold is filling empty places on limonite.

Silver is present as tetrahedrite in irregular forms filling porosities, cleavages and microfractures of pyrite, arsenopyrite, chalcopyrite, and sphalerite. Besides, it is possible observe small silver areas into galena, and also as microveins on sphalerite and chalcopyrite.

The mineralized veins and surrounded areas are formed in two concentric zones with particular mineralogical characteristics. The inner zone is located among Santa Rosa, Catarata, Perseverancia, Carhuancho, Cedruyoc and Fragua, contents minerals from medium to high temperature; and it is economically important due to the presence of metals such as lead, silver, gold. The gold can essay until 6 oz/t. The exterior zone surrounds the inner zone and has minerals from low temperature. The economical interest is due important contents of lead, silver, and zinc. The gold is present in contents less than 2 g/t.

Reserves are presented in the following table:

Subdivision of Channel in Vein Gallery Straight-Face Concaves Limestone Grinding Control Crusher Tables Stratabound Massive Sulphides Epithermal Veins Oxide Copper and Lead Ores Amphibole Occurrence and Uses Epidote Group – Zoisite and Epidote Composition Gold Mining Canada Using curves & charts to size crushers Single-Roll Crushers Blasthole Stoping Mining Method Smithsonite Composition, Crystallization & Structure Overflow Ball Mill Capacities Short Tons Per 24 Hr.