SAN GREGORIO MINE GEOLOGY AND DEPOSITS

print page

San Gregorio

Summary: the San Gregorio deposit is the central lode along the San Gregorio Shear Zone (SGSZ) and was the focus of historic mining activities in the Minas Corrales District. The San Gregorio deposit has historically produced in excess of 400,000 ounces of gold from two open pit deposits down to approximately 200 meters vertical depth. Recent mining activities by OMI (F2009) include a cut back of the east pit (East Extension). The remaining in-situ resource of 8 million tonnes at 1.04 g/t for 270,000 ounces gold lies mainly along strike to the west and at depth between the two pits. A cut back is planned for the west pit during F2010 and is expected to produce 55,000 - 57,500 ounces. On the exploration front OMI has completed several drilling programs on and around the SGSZ that highlight potential for additional mineralization down dip along the shear. OMI believes there is significant potential to define additional underground reserves at the historic San Gregorio deposit.

Geology: Gold mineralization at San Gregorio is distributed along and adjacent to a moderate to steep, south dipping thrust fault that collectively forms a shear zone. The host rocks are Proterozoic age granite, monzonite and diorite rocks that have been metamorphosed to amphibolite facies. Gold mineralization is localized along a central quartz-carbonate-pyrite lode with variable amounts of silica-pyrite stock-work veining immediately adjacent in the footwall and hanging wall. The altered shear zone is up to 100 meters wide and is generally composed of silica-sericite-carbonate-pyrite alteration and strongly deformed rocks including abundant breccias in the footwall

Click here for larger version

Resource: A resource estimate for San Gregorio including the Rieles zone was completed by Golders and Associates in August, 2007 resulting in 0.72Mt @ 1.24g/t for 29,578oz Au of measured resource and 8.07Mt @ 1.04g/t for 270Koz Au of indicated resource using a 0.5g/t Au cut-off.

Exploration & Development plans (H2 F2009): Drilling is currently underway at San Gregorio with the goal of converting the higher grade part of the indicated resource into an underground reserve and also test for additional underground resources along and down dip of the main structure which has over 1km of strike and has indicated significant potential in a recent drill hole; SGDD003 intersected 3.65m @ 3.92g/t from 656.75m (about 400m down-dip of the base of the San Gregorio pit)