Invicta

Overview

The 28,200 ha Invicta gold-silver property is located in the Western Pre-Cordillera of the Peruvian Andes in the Huaura Province, Department of Lima, Central Coast of Peru in the Districts of Paccho and Leoncio Prado. The property is approximately 250 km north of Lima, and approximately 29 km east of the town of Sayan. 

Mining activities date back from 1968 to 1969, time during which two adits were developed. Barrick acquired the property in 2000. In September 2005, Andean American signed an option agreement with Barrick to acquire a 100% interest in the property. 

Invicta is a gold-silver-copper hydrothermal mineral deposit. The probable mineral reserve of 7.8 million tonnes have an average grade of 2.14 g/t Au, 16.08 g/t Ag, 0.43% Cu, 0.32% Pb and 0.30% Zn. 

The deposit is envisioned to be mostly mined through specific underground mining methods; and an estimated 8% of the ore would be mined through a small open pit. 

Mine life is estimated at 8 years and the workforce at 140 persons. 

Processing consists of crushing, grinding, gravity recovery, and scavenger and differential floatation. The plant is supposed to process 5,000 tpd. 

Average annual production was estimated at 97,931 oz gold and average annual gold equivalent production of 160,857 oz.

Location

Invicta mineral property is located in the Western Pre-Cordillera of the Peruvian Andes in theHuauraProvince, Department of Lima, Central Coast of Peru in the Districts of Paccho and Leoncio Prado. The property is approximately 250 km north ofLima, and approximately 29 km east of the town of Sayan. 

Peru (Quechua language:Peru, Aymara language; Piruw) is a South American republic inhabited by about 30 million Spanish speaking people. Local currency is Nuevo Sol. 

The average elevation in the project area is 3,600 m asl. The rainy season runs from December to March, with annual rainfall of 250 to 530 mm. 

Temperatures in the summer months reach up to 34 deg Celsius and during winter 5 deg Celsius. The climate is semi-arid most of the year with little vegetation, mainly small plants and cacti. The topography is rugged with deep V shaped valleys cutting through.

Geology and Mineralization

The coastal batholith is the main lithological feature along the coast of Peru. It lies parallel to the continental margin. The batholith is divided into several complexes, one of which is the Huaura plutonic complex. These plutons are mainly composed of tonalite, diorite and granodiorite. The age of the Batholith is Lower Cretaceous to Middle Upper Cretaceous. 

Sediments, quartzite, sandstone and limestone of the Goyllarisquizga Family were deposited in the Lower Cretaceous. These rocks are severely faulted and folded and are host to base metal vein and replacement deposits in central Peru. 

The Calipuy volcanics were deposited during the Tertiary mainly composed of andesites and tuffs of intermediate to felsic composition. Calipuy Family is crosscut by dioritic and andesitic porphyries that have introduced the mineralization to the volcanic dominion along elongated structures that show lengths of 2.7 km, striking N10ËšW to EW, with widths between 0.8 m and 45 m, averaging 7.0 m. 

Observation and data suggest multiple phases of mineralization. Two phases of gold-silver plus base metal mesothermal type mineralization exist with a late-phase of gold-silver plus copper vein type epithermal mineralization. The mesothermal association is composed of pyrite, chalcopyrite and alteration minerals, such as epidote. This was followed by a transitional and mostly epithermal mineral association composed by pyrite, chalcopyrite, sphalerite, galena and alteration minerals as quartz, pervasive chalcedonic silica, specularite and additional chlorite and epidote. A third association, and final paragenetic stage, was introduced to the structures as additional native gold, electrum, native silver, native copper, euhedral quartz and calcite filling veinlets and microveinlets cross cutting the families deposited before. 

Measured and indicated resource of 7,903,000 tonnes grading 2.11 g/t Au, 19.1 g/t Ag, 0.52% Cu and inferred resources of 11,695,000 million tonnes grading 1.22 g/t Au, 10.1 g/t Ag and 0.27% Cu, 0.24% Pb, and 0.23% Zn. 

The probable mineral reserve of 7.8 million tonnes have an average grade of 2.14 g/t Au, 16.08 g/t Ag, 0.43% Cu, 0.32% Pb and 0.30% Zn.

The project life may extend with increased reserves when additional drilling is completed.

Mining & Operation

The underground mining methods that are going to be used are sublevel stoping, cut and fill, and shrinkage, respectively. The remaining 8% will be mined by open pit. 

Mining equipment:two 200 HP Scooptram LHD Atlas Copco ST1020;two 140 HP Scooptram LHD Atlas Copco ST710; one 14 t Dumper Tamrock EJC 416; one 68 HP Simba Atlas Copco; two 68 HP Jumbo Boomer H104 Atlas Copco; two 100 HP service trucks; two 80 HP service trucks.

Processing

Process flow includes crushing, grinding, gravity recovery, and scavenger and differential floatation. 

The final products are gold, containing copper concentrate, lead, and zinc concentrate. Silver is contained in the lead concentrate. 

The delivery of the concentrates from the mine to the CORMIN warehouse located in El Callao seaport, in Lima. Procesadora Sudamericana offered the best contract for smelting and refining Invicta’s high-grade concentrate. 

This plant is designed for production of 5,100-t/d. The plant includes areas for crushers, pre-concentrators, grinders, flotation, thickeners, filters, and tailings disposal for poly-metallic ore, which contains gold, silver, copper, lead and zinc. The crushing area includes primary, secondary and tertiary crushing with ample storage between the crushing stages and between the crushing and pre-concentrator area. There is a 20,000-tonne capacity stockpile ahead of the crushing area. 

The pre-concentrator area contains continuous Knelson gravimetric concentrators. The grinding circuit includes rod and ball mills. There are two flotation circuits. The bulk flotation of lead/copper and rougher scavenger zinc will be in cylindrical flotation cells, while the cleaning and separation stages will also be in cylindrical cells, but of lower capacity. 

The ore will be transported from the primary crusher inside the mine to the concentrator plant via an underground mine conveyor system. 

The project will draw power from the national grids through the Huacho substation. 

The concentrator plant water supply is a combination of reclaimed water from the processing plant and fresh water, which will be taken from a well that has been drilled adjacent the Huaura River. 

There are two new roads planned for the project. 

The schedule for the project will cover fourteen months. The project includes construction of the plant and development of the mine, water and power lines, camps, and roads.

Environment & Community

Environmental Impact Assessment (EIA) has been submitted to the Ministry in June 2008. Official approval was received in December 2009.

Surface rights agreements have been reached with the native communities in the area. Most of the areas are too rocky to serve for agricultural purposes.