The prospect is located in the high Andes of Region I, the Tarapacá Region, 20 km to the west of the settlement of Huara, in the Lagarto mining district, Huara District. It lies at an average elevation of 1200 meters above sea level. The central reference UTM coordinates are 7 791 200 N, 405 800 E. Mining rights
It comprises 812 mining rights units that cover 6787 hectares located in the Huara District, Tamarugal Province, Tarapacá Region. Companies that hold mining rights in the surroundings of the prospect include Sociedad Minera Contractual Minera Lagarto.
The Lagarto Fe-Cu-Au deposit is a poly-metallic zone dating back to the Lower Cretaceous-Jurassic period. This mineral zone forms part of the Ore Province of the Coastal Range, and mainly comprises Jurassic and Cretaceous intrusive, sedimentary, and volcanic rocks. Its deposits are mainly veins, strata-bound, and filled fissures, with copper, gold, silver, and to a lesser extent iron mineralization. Known deposits in this ore zone are: Camarones, Carolina de Michilla, and Mantos Blancos.
The principal iron-copper-gold mineralization and alteration areas in the Lower Cretaceous-Jurassic poly-metallic zone are spatially linked to intrusive diorite and granodiorite rocks. Structural interpretations of regional geological mapping and Landsat imagery show fault systems that cut through Jurassic and Lower Cretaceous-Upper Jurassic units.
The district features a sequence of volcanic and sedimentary surface rock types, with at least two diorite and granodiorite intrusives. The Oficina Viz Formation (Middle Bajocian) has been defined, comprising andesitic volcanic rocks, as well as a sequence of sedimentary rocks assigned to the Huantajaya Formation, from the Upper Bajocian-Lower Oxfordian. In general, a metamorphic effect is observed in both volcanic and sedimentary rocks, forming a band 1.0 to 1.5 km in width (EW) along the boundary with the Huara intrusive.
The prospect area extends for almost 22 km long the western contact with the Huara Plutonic Formation, featuring Jurassic volcanic and sedimentary rocks. Quaternary alluvium and colluvium deposits cover almost 50 percent of the area. The northern and northwestern areas feature normal morphology, with valleys 2 to 4 km in width, filled with conglomerates, breccia, and sand.
The area’s mineralization is related to an IOCG system that developed in the Upper Jurassic-Lower Cretaceous, and in particular, gold mineralization appears to be associated and co-located with multiple intrusive diorite and granodiorite phases associated with the Huara plutonic complex, which is also responsible for the development of extensive areas of contact metamorphism. These processes are believed to have given rise to the development of strips of marbled calcium carbonate rock, creating mineralized bodies of metasomatic origin similar to a Skarn formation model.
Most of the zone’s economically viable Cu-Au mineralization is located in different levels of calcium carbonate rock, between these rocks and andesites, and in higher andesite levels. The mineralized bodies are mainly thin layers, measuring no more than 3 meters, and with relatively short continuous extension, mainly at the edges of structures. The Cu-Au mineralization observed in the area’s andesites is clearly associated with biotite – actinolite – magnetite, meaning that magnetic anomalies are attractive targets for exploration. The depth of the oxidation zone varies between 70 and 100 meters.
The mineralization is irregular and strata-bound, associated with stockwork and narrow veins of quartz-magnetite, magnetite (martite), specularite, sulfides, and copper oxide minerals, formed in metasediments. The mineralization is formed in layers concordant with stratification, with partial brecciation, with significant occurrence of copper oxide minerals filling fissures and small veins, associated with quartz, sulphide residues (bornite-chalcocite poor chalcopyrite-pyrite), gold, magnetite (martite), specularite, and minerals associated with contact metamorphism. The mineralized area runs some 2.5 km in length NE and 1.2 km in width EW, with notable structures running NS to NE and NW that break the continuity of the mineralized structures.
Lagarto is an Fe-Cu-Au deposit mainly associated with the Ore Province of the Coastal Range on the western edge of the Pacific watershed. It is spatially and formatively related to intrusions of Fe ore and/or felsic to intermediate intrusions. In general terms, mineralized bodies are distributed in areas of structural weakness and conditions of structural permeability in volcanic and sedimentary rocks. The area’s copper and gold mineralization is associated with the formation of iron ore and/or diorite and granodiorite intrusions from the Upper Jurassic-Lower Cretaceous period. In this case, mineralization appears to be more closely linked with strong potassium-rich and sodium-rich copper alteration during late hydrothermal phases, linked to the formation of iron ore and/or felsic to intermediate intrusions.
In structural terms, this area features structured aligned NNE, creating normal movements with major block displacement; this primary system is cut through with another NWW-oriented system, which produces displacements along that bearing. It is the intersection of these systems that has allowed Fe-Au-Cu bodies to form.
Exploration at the Lagarto Prospect began in the 1980s and continued through to 2001. Between 1980 –1993, work comprised preliminary geology, sampling, and air reverse and diamond drilling. Later, between 1993 – 1996, magnetotelluric and magnetometric geophysical studies were conducted. Finally, in 2000 geological studies, geochemical sampling, petrographic, chalcographic, aero-magnetic, radiometric, and diamond drilling studies were performed. A total of 5037 meters of drilling was completed.
Over 80% of this prospect’s surface area abuts mineral rights areas held by other companies, which are: SOQUIMICH with 16 exploitation concessions, Merck Química Chile with 6 concessions, SCM Virginia, and Cominor. The Lagarto Prospect mineral rights unit is surrounded by areas with mineral rights held by third parties, mostly belonging to SOQUIMICH.
The work programs implemented between 1987 and 2012 have found that gold and copper mineralization in the Lagarto deposit may support the development of new phases of exploration. Past exploration campaigns and geological resources reported for the Lagarto Prospect cover 5.0% of the usable mining area, which is estimated to contain potential of the order of 5.0 million tons of geological resources for such exploration campaigns.
Specifically, resources were estimated with a threshold ore grade of 0.2 g/t, reporting 1 142 983 tons with a grade of 1.002 g/t Au, 0.32% Cu and equivalent to 1.480 g/t AuEq, or 54,382 Oz AuEq. Total geological resources, including inferred resources, amount to 5 497 120 tons with a grade of 0.742 g/t Au, 0.31% Cu and 1.202 AuEq (g/t), or 212 442 Oz AuEq.
Furthermore, evidence of mineralization is observed in at least eight mines in the Lagarto district. From North to South, these include San Marcos, Fabián, Lagarto, and the Cerrito del Frente sector. The San Marcos Mine and adjacent mines cover the largest deposit, known as the Lagarto Prospect, where the ore bodies are lenticular metasomatic deposits scattered throughout the limestone-intrusive contact area, with past ore grades averaging 3.0 g/t Au and 1.4% Cu.