Summary:
The gold-silver deposits of the Deseado Massif are hosted in silicic volcanic and volcano-sedimentary Jurassic rocks related to arc or back-arc settings in Andean or extra-Andean settings. The ore geology, textures, mineralogy, restricted alteration, and geochemistry of these mineralised occurrences indicate that they belong to the epithermal class of precious metal deposits. The deposits are mainly associated with quartz +/- calcite +/- adularia +/- illite alteration assemblages interpreted to represent low and intermediate sulphidation epithermal type deposits.
At La Paloma, the Sulfuro-Rocio vein system comprises narrow, arcuate, steeply dipping quartz- breccia veins. Drilling has defined four areas of interest:
• The Sulfuro vein, the principal deposit of economic interest, is represented by a single, well developed quartz vein typically 2 m to 4 m in thickness and has a primarily northwest-south southeast orientation with a steep southwestwardly dip. Associated sulphide minerals include pyrite and minor galena and sphalerite.
• The Ramal Sulfuro vein occurs at the northern end of the main Sulfuro vein and is strongly curved from a north-south orientation to east-west and is typically 2 m to 4 m in thickness.
• The Rocio vein occurs to the west of the main Sulfuro vein. The Rocio vein is typically 2 m to 5 m in thickness and dips steeply to the east. It is also arcuate in shape and sub-parallels the Sulfuro vein.
• The Esperanza vein system dips 75 degrees toward Sulfuro and has an average thickness of 0.3 m to 6 m.
A near-surface oxidised resource has been estimated for the Arco Iris vein, located towards the north of the Sulfuro vein system. It is represented by a series of narrow, structurally displaced, sub- parallel aligned, sheared quartz veins hosting erratic precious metal mineralisation.
The La Paloma veins remain open-ended at depth. Geological interpretation of the results of recent geophysical studies strongly suggests that the main Sulfuro vein is additionally open-ended towards the south.
At Martinetas, multiple mineralised structures occurring as “vein swarms” with minor intervening stockwork development occur. Five resource areas have been delineated. The main resource is at the Coyote and Cerro Oro deposits comprising a series of narrow, sub-parallel, anastomosing quartz veins varying in width from tens of centimetres to several metres, and typically averaging 1 m or less in thickness. Au/Ag mineralisation is variable within the veins with some minor stockwork mineralisation extending into the host volcanic lithology. Conceptually, near-surface oxidised stockwork precious metal mineralisation might provide a low grade, conventional, heap- leachable resource.
Other resource areas at Martinetas include the Lucia, Calafate and Armadillo deposits. Precious metal mineralisation associated with these deposits is also hosted by narrow to moderately thick, steep dipping quartz veins of variable tenor.