This prospect is located in Region III , the Atacama Region, in the Sierra Los Leones Mountains, Tierra Amarilla District, some 70 km southeast of the city of Copiapó, going through the settlements of Tierra Amarilla and Los Loros, to the Lautaro reservoir. The reference UTM coordinates are the area bounded by 6 910 000 N – 6 925 000 N and 400 000 E – 430 000 E.
The prospect comprises 390 mining rights units that cover 3900 hectares located in Tierra Amarilla District, Sierra Los Leones Mountains, Atacama Region.
The region features lithologically diverse geology, covering a wide range of periods (Paleozoic to Upper Tertiary), with a high concentration of superimposed tectonic events that cut through and/or deform underlying stratigraphy. The Blanco mining concessions feature plutonic La Estancilla and El Gato lithology, together with sequences of sedimentary and volcanic rock, limestone, and gravel, as well as other formations. Three mines have been recognized in the region’s history: Zapallar, Placetones and Calquis. The latter, located to the south of the Blanco mining concessions and closest to the area of interest for this study, features veins of copper and silver ore running through andesitic and basalt lava from the La Ternera formation.
The Calquis district consists of at least eight mines built on vein ore lodes, with copper and silver mineralization, mainly running N-S to N-W with sub-vertical emplacement and thickness varying between 0.6 and 3 meters. It is worth highlighting that the Las Tórtolas and La Buitrera Mines are located outside the study area but close to it to the east and west, respectively.
The study area contains poorly stratified andesitic volcanic rocks and volcanic breccia, assigned to the Sierra Los Leones strata (Upper Cretacious). Limestone and calcareous rocks assigned to the Lautaro formation (Jurassic) are also found. These two lithological units have a close spatial relationship with the El Gato plutonic formation (Eocene) that intrudes into them, creating significant zones of hydrothermal alteration. Varied tectonic activity has been recognized in the area, with extensive fault systems generally running N-S, which may have formed conduits for the ascension of hydrothermal fluids rich in metal content from the El Gato plutonic formation. This hydrothermal alteration can be broken down into three types: Silicate, Silicate – Argillic, and Argillic; these are present in different combinations and levels.
The metal content of the study area’s lithology and the region’s mineralization structures were estimated by sampling, and correspond to spoil heaps from former mines and/or mineralized structures located outside the Blanco concessions. Sampling has detected high grades of copper (mean 4.89% total copper) in the Calquis mining district (veins of copper and silver), located between 10 and 15 km south of the prospect. High grade silver ore has also been detected (up to 1902 gr. / Ton, at the Las Tórtolas mine) in lateral vein structures close to the Blanco prospect.
The area’s geology features silica plugs intricately linked with and formed from the El Gato plutonic formation and an extensive fault system, including the significant El Molle Fault. The surroundings comprise volcanic rocks (breccia of strata from the Sierra Los Leones strata) and sedimentary limestone rocks (Lautaro formation). The model is based on background information indicating that many precious metal deposits are associated with silica-rich geological environments, in particular with the type of plugs discovered here, which are located very close to intrusive bodies that provide heat through the emission of consecutive hydrothermal pulses.
No exhaustive studies have been conducted on the prospect, with geological sampling of spoil from former mines and mineralized structures. A total of 45 samples were taken at the prospect, 15 of which are spoil or mineralized structures.
The Calquis mining district is located to the south of the Blanco concessions, and comprises at least 8 mines, all now abandoned, that exploited rich veins of copper and gold. Two abandoned mines are located to the sides of the concessions (Las Tórtolas and La Buitrera), which exploited veins with very high grades of silver, and to the NW and NE there are two known significant volcanic calderas (El Durazno and Jorquera, respectively).
Prospection studies and background information indicate that this area features major hydrothermal alteration associated with the El Gato plutonic formation, an Eocene structure that extends from the eastern edge of the concessions north-eastwards, to the Jorquera River. The concessions feature a system of 4 silica plugs associated with the extensive El Gato plutonic formation, limited by major faults that run north-south.
The conceptual geological model for the exploration targets associated with the silica plugs leaves room for similar expectations for the prospect’s ore deposits. Therefore, the geological potential of the mineral resources to be found in the Blanco area is considered to be prospective interest. In addition to the silica plugs, a copper-bearing layer has been discovered, with unknown but presumably high thickness and grade, which was the target of a mining project that has since been abandoned. Notable color anomalies have also been observed, measuring 0.5 and 1 km2 at the surface, forming attractive areas for exploration.