Drills turn at Cerro Samanta

Partners Mansfield Minerals (MDR-V) and Teck (TEK-T) have commenced a 1,200-to-1,500 metre diamond drill program on their Cerro Samenta copper property in northwestern Argentina.

The initial drill holes, to be collared in the South zone, will test a coincident induced-polarization geophysical and copper geochemical anomaly. Three holes will target a zone of supergene copper enrichment and primary copper beneath the leached cap zones.

Cerro Samenta is at the intersection of the Archibarca Transverse zone and a major north-southerly trending fault that defines the western edge of the Puna geological province. The property is 300 km northwest of the town of Salta and 125 km east of the Escondida copper porphyry deposit, which contains a resource of 2.1 billion tons averaging 1.6% copper. Cerro Samenta is structurally controlled by an east-west transverse fault that represents an important mineralizing control for four major Chilean copper porphyry deposits, including Escondida.

Mansfield discovered Cerro Samenta in 1994. In December 1995, it entered into an arrangement with Teck whereby the major can earn a half-interest in the property by paying US$1.6 million in cash and spending US$7.5 million on exploration over five years. Mansfield can dilute to a 40% interest if Teck arranges for all financing up to production.

In 1996, Teck initiated a 20-hole drill program, but, after only two holes, ownership disputes forced a suspension of all exploration work. The mining court of Salta ruled in favour of Jorge Daroca, a local claim-holder. However, the following year, the Salta court of appeal overturned the lower court’s judgment.

Daroca then filed a constitutional complaint with the supreme court of Salta, alleging that his constitutional rights had been violated by the government’s lack of due diligence in maintaining claim maps. The dispute focused on the location of claims in relation to the geographical point known as Cerro Samenta. Mansfield negotiated a US$70,000 deal with Daroca to buy a 100% interest in all his claims adjacent to Cerro Samenta. As a condition of the agreement, Daroca was required to remove his application to the supreme court and desist from any further court actions regarding the Samenta property.

Porphyry copper mineralization at Cerro Samenta has been traced over a 1.2-km strike length and a 400-metre width. Copper occurs as fracture fillings and disseminations in two areas of potassic and phyllic alteration at the North and South zones. A leached-cap assemblage overlies large portions of a phyllic zone, where weathering of hypogene pyrite and chalcopyrite has formed a chalcocite blanket at depth. A portion of this enrichment zone is exposed in trenches in the southern portion of the Samenta North zone. On the Jorge (or Central Samenta North) zone, trenching has exposed a 250-metre section grading 0.5% copper, including 1.4% copper over 75 metres. A zone 700 metres to the south assayed 0.96% copper over 200 metres.

During the 1996 program, 11 trenches were excavated, eight of which encountered well-developed, copper-depleted, leached-cap alteration. Two trenches revealed a strongly mineralized potassic core, and a third was found to host intermittent supergene copper mineralization, which coincided with the extreme southern tip of the 1-by-1.6-km-long induced-polarization anomaly of North Samenta. The supergene copper mineralization in the trench yielded grades of up to 1.6% copper.