Gammon Lake Resources (GAM-T) has a new gold-silver resource estimate at its Ocampo project in Chihuahua state, Mexico.
In total the Ocampo project contains about 1.85 million oz. gold and 76.7 million oz. silver (3.03 million gold-equivalent oz.) in the measured and indicated categories and 2.55 million oz. gold and 127.8 million oz. silver (4.53 million gold-equivalent oz.) in the inferred category.
The total resource for the Ocampo project comprises the Northeast area underground and surface mineralization, and the Open pit area with its low grade and high grade (below the open pit) resource.
The Northeast underground resource is estimated to be a measured and indicated 4.06 million tonnes grading 4.8 grams gold per tonne and 227 grams silver per tonne, for a total of 628,000 oz. gold and 29.7 million oz. silver (or 1.08 million contained gold-equivalent oz.) This was calculated using a 3 grams gold-equivalent per tonne cutoff.
The Northeast underground resource estimate is based on five vein-deposits namely: Aventurero, San Juan, Las Animas-San Amado, Rosario and Esperanza. The underground resource was calculated using a 3 grams gold-equivalent per tonne cutoff and the open-pit used a 0.4 gram gold-equivalent. The resource used a US$375 per oz. gold price and a silver price of US$5.77.
About 70% of the drilling in the Northeast has been done from underground. About three km of underground ramps and tunnels have been developed. The veins occur within a 1.7 km by 2.8 km area. Based on statistical analyses assays from different veins were cut to different values.
The Northeast surface resource contains a measured and indicated 2.3 million tonnes grading 1.11 grams gold and 55 grams silver per tonne, using a 0.4-gram gold-equivalent cutoff and a 65:1 silver to gold ratio. The surface resource is estimated using data from the Brenda and San Juan deposits.
The Ocampo Open-pit area contains a measured and indicated 32.2 million tonnes grading 1.03 grams gold and 37 grams silver per tonne. The area contains a high grade core with a measured and indicated 4.7 million tonnes grading 3.46 grams gold and 146 grams silver per tonne (or 870,000 gold-equivalent oz.). The cutoff of the high grade was set at 3.0 grams gold-equivalent per tonne, whereas the low grade area used a 0.3 gram per tonne cutoff. The lower grade mineralization may be treated as a heap-leach deposit.
The Open pit area is within a 3.7 km by 1.6 km zone that was tested along known structures to a depth of 200-250 metres.
The resource was calculated by mining engineering consultant MINTEC, of Tucson, Ariz. The gold grade is slightly lower than the June 2003 estimate, however the tonnage has increased so the number of oz. is similar.
The revised resource will be incorporated into a feasibility study that is due for completion before year-end.
There are two major hosts to the mineralization; gold, silver, electrum, argentite and pyrite are present in low-sulphide quartz stockworks and breccias, and secondly, high-sulphide, enargite-bearing, vuggy breccias with sulphide-replacement in rhyolite and dacite.
The 35-sq.-km-Ocampo project comprises 44 mining concessions, held by Gammon Lake’s Mexican subsidiary, Gammon Lake de Mexico.
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