Rio Grande Property -- Drillhole Map Click to enlarge map
The Rio Grande property is a porphyry copper-gold prospect located 250 kilometres west of the City of Salta, Salta Province, northwestern Argentina. Access is by all-weather road from the City of Salta to the Village of Tolar Grande and then by traveling 60 kilometres southward across the Solar de Arizaro.
In June 2004, Mansfield executed a binding Letter of Understanding with Antares Minerals Inc., whereby Antares was granted an option to earn a 50% interest in the project by completing work expenditures, issuing shares and making payments over a four-year period. In September 2007, Antares vested a 50% interest and is operator of the project. Mansfield's 50% interest in the property was transferred to Pachamama in 2008 when Mansfield was restructured.
The Rio Grande property is hosted in a thick pile of young (less than 10Ma) porphyritic andesites and dacites that are cut by post mineral andesite dikes and several andesite to diorite plugs. These volcanics and plugs represent at least two dissected strato volcanic centres. The mineralizing system consists of a large zone of hydrothermal alteration covering an area of 2.2 kilometres (E-W) by 2.0 kilometres (N-S) and may extend under cover. Alteration styles include a central core area typified by potassic alteration (K-feldspar and biotite) and albite-diopside surrounded by sericite-argillic alteration that grades outwards into propylitic alteration. Copper-gold mineralization appears to be largely restricted to the potassic zone. Hypogene mineralization appears to consist of fine-grained disseminated chalcopyrite in association with disseminated to aggregated magnetite. Gold grades appear to have a linear relationship to copper grade at a proportion of 1 gram gold to 1% copper.
Work to date has included geological, geophysical (I.P. and Mag), soil geochemical, trenching and diamond drilling. Drilling at Rio Grande is outlining a significant body of copper-gold mineralization. The Discovery-Sophia zone represents a body of continuous mineralization over a 1.5 km strike length with width ranging from 100 metres to a maximum of 250 metres and depth of up to 500 metres. Recent drilling has intersected high grade copper-gold mineralization at the north end of the Sofia Zone in RGA-07-34 which assayed 189 metres of 0.7% Cu and 0.67 g/t Au, and under the Discovery Zone in RGA-07-040 which returned 102.8 metres grading 0.58% Cu and 0.75 g/t Au. Drilling has also established that the North Zone extends to depth with strong grade-width values.
Over 60 drill holes have been completed to date at Rio Grande. Grades in excess of 0.7 g/t gold and 0.7% copper have been encountered over significant widths in what appears to be one contiguous ring of mineralization measuring in excess of 2 km in diameter with true thickness greater than 200 metres. The deposit demonstrates a very large metal budget and requires further extensive drilling to establish its economic potential.
Rio Grande Property Trenching Results
Rio Grande Property Drilling Results
Rio Grande Technical Report - 2008
