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Cornerstone's two most recent acquisitions, made through its wholly-owned subsidiary Minera Cornerstone Chile Limitada ("MCCL"), are the Miocene and La Fortuna projects in Chile. The Miocene project is located in the Regions of Atacama and Antofagasta of northern Chile, and is targeting epithermal gold-silver and porphyry gold-copper deposits along the interpreted northern extension of the Maricunga magmatic belt which hosts several world-class gold deposits. The La Fortuna project is located in the Valparaíso Region of central Chile, and is targeting manto-type copper-silver and epithermal gold-silver deposits similar to those at the Cerro Negro copper-silver mine and El Bronce epithermal gold-silver district respectively. These projects were selected after two years of careful research and evaluation, and Cornerstone feels both offer tremendous potential for discovery. Chile consistently ranks among the world's top mining jurisdictions, and we are extremely excited to have added these projects to our international portfolio.
Available for Option:
100% Cornerstone Properties
La Fortuna
Miocene
La Fortuna
Primary Target
Copper-Silver
Location
The La Fortuna property is located in the Valparaíso Region of central Chile, approximately 100 km north of Santiago.
Underlying Agreements and Interests
Cornerstone, through its wholly-owned subsidiary, Minera Cornerstone Chile Limitada (MCCL), has signed an option agreement with a Chilean individual which gives Cornerstone the right to acquire an undivided 100% interest in the La Fortuna property by incurring exploration expenditures of C$3.0 million and making cash payments totalling C$600,000 over a 4-year period. Requirements to maintain the agreement through the first year include a cash payment of C$100,000 and exploration expenditures of C$500,000. The acquisition is subject to a 1.5% Net Smelter Royalty ("NSR"), and to advance payments of the NSR on each anniversary following the date the option is exercised. Cornerstone has a right of first refusal to purchase the NSR if the holder decides to sell it.
Property Information
The La Fortuna property covers an area of approximately 2,900 hectares, measuring 10 km north-south by 3 km east-west. The project is favourably located in an established mining district at relatively low elevations (1,200 to 1,800 m above sea level), and is easily accessed by existing roads. The property is partly contiguous with the Cerro Negro copper-silver mine, a manto-type deposit immediately to the west which combines open pit and underground operations and produces copper cathodes via heap leach SX-EW and copper-silver concentrates via flotation. The El Bronce epithermal gold-silver district is located 30 km to the north. The region is sparsely populated, and has a hot and dry climate which is well-suited for leaching operations. Many surface mineral occurrences have been worked by small scale miners in the past, but no drilling has ever been carried out at La Fortuna.
The La Fortuna area is underlain by a sequence of Cretaceous age volcano-sedimentary rocks composed of (from bottom to top) greywacke, lithic tuff and conglomerate with intercalations of limestone, ignimbrite and volcanic breccias. In the north, the volcano-sedimentary rocks are intruded by andesitic porphyry dykes and sub-volcanic rocks and the southern part of the property is underlain by a diorite plug showing a fine grained (sub-volcanic?) phase in the contact zone with the volcano-sedimentary units. Chloritization and hematization are widespread throughout the entire area. The intrusive rocks are interpreted as the possible heat source for the development of the hydrothermal processes that led to the deposition of base and precious metals.
At La Fortuna, structurally and lithologically controlled copper-silver mineralization is hosted by volcanic breccias and interbedded sediments and at the contact zone between intrusive and volcano-sedimentary rocks. Disseminations also occur in permeable and brecciated geological units. Mineralized structures are preferentially oriented NE and NW to NNW. At the neighbouring Cerro Negro mine, similar veins and mineralized structures are believed to have acted as conduits for hydrothermal fluids to circulate and precipitate copper and silver mineralization. It is postulated that manto-type mineralization occurs at the intersection of these mineralized conduits and reactive geological units.
Cornerstone began field exploration programs in April 2011 with reconnaissance geological mapping, prospecting and rock sampling. During this initial work phase, geological units were defined, a structural study performed, and altered and mineralized zones were mapped and sampled. Seven prospective mineralized zones which are distributed over a large area (18 km2) have been identified to date. From north to south these are:
1) Guayacan: NW trending vein, within andesitic porphyry, 0.5 m wide and 0.9 km long. Quartz vein, comb textures, disseminated copper carbonates and sulfates.
2) Loma Verde Norte: ENE trending structure, emplaced at the contact with a porphyry dyke. Halos of disseminated malachite.
3) Loma Verde: ENE trending structure, traced from artisanal miner workings to the west (third party exploitation concession), reaches a total length of 1.2 km along strike with 0.5 km mapped on La Fortuna property. Sheared volcano-sedimentary rocks with a stockwork of malachite, copper sulfates and minor chalcopyrite. Mineralized width is at least 19.5 m in trench TH1 to the east (see below).
4) Loma Verde Sur: NE trending structure, parallel to the Loma Verde structure to the north, 50 m wide and 0.4 km long. Brecciated zone and porphyry dykes. Silicification and quartz veinlets with chalcocite and copper sulfates.
5) Quebrada Honda: NNW to NNE trending vein, > 1 km length, located at contact zone between the subvolcanic and the volcano-sedimentary rocks. Sheared contact with quartz veinlets, hematite and copper sulfates and oxides.
6) Vizcachas: NNW trending vein, > 1 km long, 2-5 m wide. Outside of the property to the north artisanal miners exploit the vein, as well as stratabound mineralization. The vein was traced from this mineral occurrence for another 1.0 km along strike, within the property. Quartz vein with comb textures and disseminated copper sulfates in the host rocks.
7) Enjalmao: ENE trending vein, 2-4 m wide and 0.7 km long, hosted by black shale and limestone near the contact with a diorite intrusive. Mineralization is present as disseminations and fracture fillings of malachite and copper sulfates.
A total of 163 rock samples (representative chip samples) were collected and assayed during the reconnaissance geological mapping and prospecting work. Of these, 63 samples returned > 0.1% Cu, including 34 samples which returned > 0.5% Cu and 24 samples which returned > 1% Cu. Eighteen (18) samples returned > 30 g/t Ag, including 5 samples which returned > 100 g/t Ag.
Follow-up work on the most prospective mineralized zones is ongoing, and includes detailed geological mapping, hand-trenching and channel sampling. Thus far, the best mineralization encountered is at the Loma Verde prospect, where channel samples in trench TH1 returned 19.5 m (apparent thickness) at 1.34% Cu and 58.0 g/t Ag. Re-assaying of samples (prospecting rock chip samples and trench channel samples) which returned > 0.5% Cu, indicates that 78% of the copper is soluble.
A 200 line km ground magnetic survey has been completed in the northern 2/3 portion of the property, and will assist in identifying structures and the most prospective areas for planned induced polarization (IP) surveys.
Related News
12-09 - Cornerstone Announces Final Trenching Results and Proposed Phase 1 Drilling Program at La Fortuna Copper-Silver Project, Chile
12-04 - Cornerstone Reports Further Trenching Results at La Fortuna Copper-Silver Project, Chile
11-28 - Cornerstone Reports 1.34% Copper and 58.0 g/t Silver over 19.5 m in trenching at La Fortuna Copper-Silver Project, Chile
Maps
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Property
Location Map |
Phase 1 DDH Targets |
Ag Sample Location Map |
Cu Sample Location Map |
Photos
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View of Cerro
La Muela |
Intense albite-epidote
alteration |
Epithermal Qtz Veins |
Small Scale
Surface Workings |
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| Stockwork Veins |
Small-scale
Exploitation Adit |
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Miocene
Primary Target
Gold-Silver-Copper
Location
The project covers a large area of 14,770km2 in northern Chile.
Property Information
In February 2011 Cornerstone acquired the Miocene gold--silver--copper project located north and along strike of the Maricunga belt, which hosts a number of world class epithermal gold-silver and porphyry gold-copper deposits. Although post-mineralization sediments and volcanics largely cover the Miocene project area, geological and geochemical data suggest that prospective Maricunga rocks underlie the area. Cornerstone is utilizing a proprietary geological and geochemical database to acquire mineral concessions within the project area, and has already filed mineral concession applications covering 46.5 km2 of prospective ground. Planned exploration programs include soil and stream sediment geochemistry surveys designed to identify targets for follow-up work.
Related News
11-08 - Cornerstone acquires new Gold-Silver-Copper project in Chile
Photos
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| Temporary Camp |
Hydrothermal Alteration
Zone |
Oxidized Rocks |
Soil Sampling |
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Breccia With Argillic
Alteration |
Vuggy Silica |
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