Mansfield granted title to Rio Grande

A court in Argentina has granted Mansfield Minerals (MDR-V) title to the 135-sq.-km Rio Grande copper-gold property.

The junior says it will seek a partner to explore the property, situated in the northwestern province of Salta. Teck (TEK-T) has right of first refusal under terms of a funding agreement signed in 1998.

Rio Grande hosts porphyry-style copper-gold mineralization that has been outlined over an area measuring 700 by 200 metres. Based on exposed topography, the zone extends at least 100 metres vertically, and the eastern portion remains open along strike. Assays from 36 grab samples returned an average of 1.3% copper and 1.25 grams gold per tonne.

Meanwhile, Teck has notified Mansfield that it will begin drilling the Cerro Samenta porphyry copper deposit, also in northwestern Argentina, in the upcoming months.

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.

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.

In a separate development, Mansfield has reached a tentative deal with an unnamed third party regarding the Aguas Calientes gold-silver property, 130 km west of the city of Salta. The unnamed party can earn a 60% interest in the property by spending US$2.5 million on exploration and paying US$1.2 million over four years.

Aguas Calientes hosts two northerly trending zones of silicified and clay-altered breccias in dacitic volcanic tuffs. The Ambrosia zone, in the northern portion of the property, has returned up to 3.3 grams gold from mineralized breccias. To the south, the North Boulder zone comprises angular boulders of silicified volcanic breccia assaying 2-5 grams gold.