Figure 1. Cobremani historical workings
MAP
UTM:
345,000 E
8,220,000 S
Size: 6,000 Ha
Elevation Range: 4000m-4400m
The Picha copper-silver project is located within the Tertiary Volcanic Arc of Southern Peru, host to various epithermal gold-silver deposits and copper porphyry-skarn deposits. Picha is found within the NW part of the Pichacane quadrangle (33‐v), near to the Jesus Maria settlement in the San Antonio de Esquilache district, Sanchez Cerro province and Moquegua department.
The access from Lima is by commercial flight to Juliaca city with stopover in Arequipa (about 2 hours). Then, Juliaca to Puno, through a paved road of 44 km (50 min) and from Puno to Jesus Maria in a gravelled road with 89 km (3.5 hours). Access from Arequipa is via a paved road to Juliaca and Puno and then by graveled road to Jesus Maria.
Elevations range from 3,900 m in the valley of Rio San Antonio to 4,450 m on Cerro Mojapunta and there is relatively moderate relief. The property is above the timberline and there are no trees. Rio San Antonio is a small, but permanent river, which passes through the center of the concessions and would supply sufficient water for exploration programs.
Climate is fairly moderate and dry with cool nights and small amounts of snow in winter. While most exploration does not continue into January and February because of the annual rains, development work could probably be undertaken on a year-round basis.
Nearby Mining/EXPLORATION ActivityNearby Producers:
Cerro Verde (134km W): Copper/Moly producer
Cuajone (104km SW): Copper producer
Mines de Toquepala (125km SW): Copper producer
Nearby Discoveries:
Chucapaca: Picha is adjacent to the properties of Gold Fields Limited and Compañía de Minas Buenaventura S.A. with reported mineral resources of 7.5 million gold equivalent ounces.
Figure 4: Chucapaca viewed from Picha
EXPLORATION
Previous exploration completed by Lara consisted of two reconnaissance field campaigns. A total of 419 rock samples were collected, with 11 reporting values over 3% copper; 37 reporting values over 1% copper; 53 reporting values over 0.5% copper; 69 reporting values over 0.1% copper; 85 reporting values over 500 parts per million (“ppm”) copper; and 174 reporting over 100 ppm copper. Molybdenum values were generally low, with anomalous values where present correlating with anomalous copper values. Silver values were also mostly low, but a total of 58 samples (or 19%) reported anomalous values, with good correlation with copper. Barium values were found to be high, with lead, zinc and arsenic also related with copper anomalism. These samples revealed seven distinct zones of mineralization.
Cobremani
The Cobremani Cu-Ag mineralization occurs in porphyritic andesites of the Tacaza Group and has approximate dimensions of about 100 m by 80 m. In part the mineralization is similar to that at Maricate with a set of steeply dipping quartz (chalcedony) veinlets striking about 060o. In addition the mineralization at Cobremani is associated with some flat veinlets and with relatively small, poorly defined breccia bodies which are interpreted to be hydrothermal in origin. Some of the Cu-Ag mineralization is related to the matrix of the breccia unit which is a poorly sorted unit containing a few small exotic clasts. Minerals observed are malachite, azurite, chrysocolla, tenorite and iron oxides within zones of clay and chlorite alteration. The depths of several small shafts and declines within the zone are unknown, but these are assumed not to be more than a few metres deep. Historical assays are:
• 1.95% Cu, 4.5 ppm Ag over 3.5 m
• 2.64% Cu, 16.0 ppm Ag over 3.5 m
• 12.0% Cu, 75.0 ppm Ag over 3.5 m
• 1.36% Cu, 7.5 ppm Ag over 3.5 m
Maricate
Located about 1 km from the Cobremani occurences, the main occurrence at Maricate consists of a weak stockwork of quartz (chalcedony) veinlets normally 1 cm to 5 cm thick with weak clay alteration haloes. A prominent set of veinlets strikes 050o with steep south-easterly dips. Host rocks are porphyritic andesites of the Tacaza Group. An area of about 50 m by 50 m contains the mineralization which consists of malachite, azurite, chalcocite, chrysocolla, galena and iron oxides. Otherwise the surrounding volcanic host rocks are essentially unaltered. Best assays recorded are:
•
2.13% Cu, 47 ppm Ag, over 2.7 m and 2.14% Cu, 43 ppm Ag over 5.0 m.
Cumbre Coya
The Cumbre Coya Ag, Pb, Cu mineralization occurs within clayey sandstone of the Maure Group. Although described as a stratabound mineralized zone striking 120o azimuth and dipping 20o to the SW the occurrence is probably controlled by faulting. Chalcedony veinlets reach up to 2 cm wide and are surrounded by an alteration zone consisting of clays, chlorite and calcite. Mineralization consists of malachite, chrysocolla, chalcocite, galena and iron oxides. Assays reported by Lovang, G., Carrasco, J., Yauri Velasquez, L.E. (1996) are:
• 1.20% Cu, 295 ppm Ag, 18.1 % Pb over 2 m.
• 0.65% Cu, 178 ppm Ag, 0.83% Pb over 3 m.
• 8.23% Cu, 880 ppm Ag, 13.8% Pb over 0.1 m.
The mineralization has been followed for about 40 m.
Huancune
A quartz-carbonate vein about 0.15 m wide occurs in essentially unaltered Tacaza porphyritic andesites. The structure strikes at 215o azimuth, dips 86o to the NW and has no significant continuity. Minerals encountered are malachite, chrysocolla and iron oxides.
Timillo
The Timillo prospect consists of quartz veinlets within a steeply dipping shear zone striking 030o
azimuth. Spanish workings consist of six inclined shafts, now inaccessible, over a distance of
about 200 m. Minerals encountered on the surface are malachite, chrysocolla, tetrahedrite,
galena, sphalerite and iron oxides. Host rocks are clay and propylitic altered porphyritic
andesites of the Tacaza Volcanics. The depth or continuity of the mineralization is not known. A
grab sample from dump material assayed:
•
365 g/t Ag, 21.5% Cu, 2.1% Zn, 0.35% Pb, 3.6% As.
Fundicion
The Fundicion prospect consists of sub vertical quartz veins up to 0.4 m wide trending 042o
azimuth. Most of the veining is from 1 cm to 5 cm wide and appear to have lengths of from 5 to
10 m. Six small Spanish colonial adits were driven in altered porphyritic andesites of the Tacaza
Volcanics near to the contact with overlying siltstones of the Maure Group. Visible
mineralization consists of malachite, chrysocolla, chalcocite and iron oxides. The best assay
recorded in the historical data is:
•
88 g/t Ag, 2.79%Cu, 5.23%Zn, 4.44% Pb over 0.38 m.
Ventilla
Narrow sub vertical quartz veinlets from 1 cm to 8 cm thick strike 300o azimuth. These veinlets which occur in porphyritic andesites of the Tacaza Group are not continuous for significant distances. Galena has been noted in the veinlets.
MINERALIZATION
Except for the Cumbre Coya mineralization, which occurs in Maure Group sediments, all mineralization is found within porphyritic andesites of the Tacaza Group volcanics. Geological controls consist of epigenetic quartz stockworks and veinlet arrays within clay altered and propylitic alteration zones. Most of the structures are steeply dipping. At Cobremani the mineralization may also be controlled by hydrothermal breccia zones.
GEOPHYSICS
Lara Exploration recently completed geophysical surveys outlining six chargeability anomalies indicative of sulphide mineralization in a wider area of moderate chargeability and higher magnetic response interpreted as volcanic or intrusive rocks.
The geophysical program comprised 158.22 line kilometres of Magnetic (“Mag”) surveys and 65.5 line kilometres of Induced Polarization (“IP”) surveys, targeting disseminated and semi-massive copper sulphide mineralization down to maximum depth of approximately 300 metres.
The Mag results indicate the presence of magnetic rocks at shallow depths forming a semicircular shape in the center of the survey grid, with the strongest magnetic responses generally corresponding to volcanic and intrusive rocks. Structures and geological contacts can be inferred from the magnetic profiles and form a complex pattern with a strike direction generally NE.
The IP survey shows a large area of relatively high background chargeability in the center and eastern part of the grid, within which six weak-moderate chargeability anomalies have been outlined, interpreted as corresponding to the presence of sulphides. values were found to be high, with lead, zinc and arsenic also related with copper anomalism.
IP Interpretation:
Trent Pezzot's Report
Copyright © 2012, Network Exploration Ltd.