Vancouver — Preliminary mapping and sampling by Chesapeake Gold (CKG-V, CHPGF-O) has resulted in the discovery of five zones of copper-silver-zinc mineralization at its wholly owned Rio Minas property in Oaxaca state, Mexico.
Only one of the zones, La Zapoteca, has been tested by a detailed mapping and sampling program to date. Continuous rock-channel samples taken across the 400-metre-long, 100-metre-wide outcrop exposure of the zone returned: 0.9% copper and 75 grams silver per tonne over 63 metres; 2.8% copper and 52 grams silver over 9 metres; 0.27% copper and 8 grams silver over 27 metres; 0.54% copper and 31 grams silver over 27 metres; 0.54% copper and 33 grams silver over 57 metres; and 0.51% copper and 18 grams silver over 21 metres.
Chesapeake holds a land package covering 3,650 sq. km in eastern Oaxaca state. On a regional scale, the Rio Minas property lies within a 100-km-long, northwest-trending structural belt that hosts several skarn prospects and other more advanced exploration projects.
The company says recent surface mapping and sampling “strongly indicate the presence of district-wide skarn mineralization” in the Rio Minas area. The five skarn zones are associated with a large circular feature (about 5 km in diameter) that is believed to represent the surface expression of a major intrusive stock underlying the calcareous rocks.
The five zones were found within a 6-km-long, northeast-trending corridor associated with a regional fault system that coincides with the eastern portion of the circular feature.
Mineralization is hosted in a series of altered limestones and calcareous sediments that are exposed in several small, eroded windows that outcrop where the rock sequence has been dissected to lower levels. Two types of mineralized settings were recognized, skarns replacing limestone beds, and structurally controlled skarn zones occurring within faults and fractures.
The La Zapoteca zone remains open along strike and laterally, and may be related to poorly exposed, sporadic showings of garnet skarn mineralization discovered 100 metres east and 120 metres west of the main zone at La Zapoteca. Sampling along the eastern flank returned encouraging results: notably 0.59% copper and 43 grams silver per tonne over 12 metres; 2.7% copper and 147 grams silver over 6 metres; and 0.46% copper and 30 grams silver over 18 metres. To the west, an initial channel section returned 24 metres of 0.3% copper, 23 grams silver and 0.57% zinc.
The other four prospective zones — known as El Camino, Rio Minas Creek, La Victoria and La Valentina — have yet to be fully sampled. El Camino hosts several manto-type occurrences of zinc-silver-copper skarn. Consecutive sampling of one outcrop at Rio Minas Creek returned a 9-metre section of 2.7% copper, 34 grams silver and 0.24% zinc, with other outcrops yet to be tested.
The areas of interest at La Valentina and La Victoria are dominated by zones of intensely altered calcareous rocks, which are believed to represent the mineralized external parts of the skarn system. Other targets to be tested include two new mineralized zones further north and southeast of Rio Minas.
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