Rio Grande shows growth potential for Antares, Mansfield (June 16, 2008)

VANCOUVER — Three stepout holes at the Rio Grande coppergold project in northwestern Argentina returned strong intercepts for joint-venture partners Antares Minerals (ANM-V, ANMFF-O) and Mansfield Minerals (MDR-V, MFMNF-O).

The holes stepped out from the Sofia zone to the northeast, each placed 75 metres away from hole 34. A few months ago, hole 34 returned 189 metres grading 0.7% copper, 0.67 gram gold per tonne and 11.1 grams silver.

Hole 65, the stepout farthest to the north, cut the longest mineralized intercept: 146 metres grading 0.6% copper, 0.57 gram gold and 7.2 grams silver from 196 metres depth, including 46 metres of 1.16% copper, 1.18 grams gold and 10.4 grams silver. Hole 63 returned 65 metres grading 0.49% copper, 0.35 gram gold and 6 grams silver from 394 metres down-hole, and hole 64 to the south cut 114 metres of 0.56% copper, 0.58 gram gold and 10.6 grams silver.

In shallower holes 64 and 65, the copper-gold mineralization is predominately oxidized, with only minor traces of chalcopyrite. Hole 63, which hit deeper mineralization, is only weakly oxidized and consists mostly of chalcopyrite with pyrite and magnetite.

The mineralized zone at Sofia is a tabular body that strikes due north and dips at 70 to the west. True thicknesses are estimated to be roughly 60% of down-hole intercept lengths.

The zone has a high-grade core with grades exceeding 1% copper, 1 gram gold, and 10 grams silver, on average, that is surrounded by a halo of lower-grade material. Exploration has traced Sofia’s strike length for 450 metres; the zone has an average true thickness around 90 metres and extends some 500 metres downdip.

Interestingly, some holes at Sofia have encountered molybdenum mineralization in a distinctly separate zone below the copper-gold mineralization. Hole 63 hit 48.5 metres grading 0.064% molybdenum and hole 65 returned 31 metres grading 0.027% molybdenum. The new zone is not yet well understood.

Sofia is only one of five zones at Rio Grande. Mineralization at Rio Grande occurs within a distinct 2-km-diameter ring-shaped fracture zone clearly defined by induced polarization-chargeability and geochemical anomalies. Clockwise from the north, the zones around the ring are North, Sofia, Discovery, Southwest, and No. 7. To date, exploration has focused on the betterexposed Discovery and Sofia zones but recent drilling on the North and No. 7 zones has produced significant well-mineralized intercepts.

In January, hole 56 returned 0.42% copper, 0.5 gram gold and 7.1 grams silver over 215 metres, essentially from surface, in zone No. 7. Mansfield director John Leask described the hit as a “blind shot — no geochem, no geophysics, no trenching, nothing — a 700-metre stepout right in mineralization, right off the collar.”

Rio Grande is located along the prominent northwest-trending Archibarca Lineament, which also hosts BHP Billiton’s (BHP-N, BLT-L) Escondida copper porphyry deposit, 150 km northwest in Chile.

Antares is currently advancing a 15,000-metre drill campaign, of which these first three holes represent some 1,900 metres. Antares has remained as project operator after completing its 50% earn-in in mid-2007. Around the same time, Mansfield completed a $5.25-million financing in Antares to hold almost 10% of its partner.

The drill results boosted Mansfield 15 to close at $3.15. The company has a 52-week trading range of $2.13-5.10 and has 44 million shares issued. Antares gained 13 on the news to close at $3.88; it has a 52-week trading range of $1.56-5.14 and has 42 million shares issued.