Summary:
The deposits identified within the Casposo Property are characteristic of Epithermal Low Sulfidation (LS) systems.
The Casposo deposits are on the eastern border of the Cordillera Frontal. In the mine area, Cordillera Frontal is exposed and underlain by marine metasediments of Carboniferouslower Permian of the La Puerta Formation, which include shales, sandstones, and conglomerates. Overlain is a thick intrusive and volcanic sequence assigned to the Permian-Triassic Choiyoi Group, which bears the main Low Sulfidation deposits in the Casposo property.
Four main deposits have been geologically modelled. These structures are Manantiales, Mercado, Julieta, and B-Vein.
The mineralization frame occurs along a 10 km long WNW-ESE structural corridor. All the structures are the continuity of the main and previously exploited deposits called Kamila, and from south to north are B-Vein, Mercado, Julieta, and Manantiales.
The Casposo Mine is a prolific district with mineralized bodies that remain open.
The Casposo gold–silver mineralization occurs in both the rhyolite and underlying andesite, where it is associated with banded quartz–chalcedony veins, typical of Low Sulfidation Epithermal environments. Adularia in the main veins gives an age date of 280 ± 0.8 Ma (K/Ar), very close to the published age dates for the andesite unit. Post-mineralization dykes, of rhyolitic, aphanitic-felsic, and trachytic compositions, affect all the deposits. These dykes, sometimes reaching up to 30 m thickness, are usually steeply dipping and north–south oriented.
Mineralisation
Epithermal Low Sulfidation deposits typically host gold and silver minerals, and other minerals. They are characterized by structurally controlled mineralization styles such as veins, breccias, stockworks, and veinlets.
Structurally, the Casposo deposit exhibits well-developed structural systems featured by primary and secondary faults occurring in jogs or bends, settings that serve as the main controls for mineral deposition. The spatial distribution of the deposits and their relationship to previously exploited zones. Main faults have played a long-term, secular role in the formation of these deposits.
The Manantiales Vein represents the northwestern extension of mineralization within the Manantiales Property, located approximately 5 km northwest of the main facilities.
The Julieta Vein situated south-east of Manantiales, is expressed as a quartz-carbonate vein breccia with several tensional structures along the main ore body.
The Mercado Vein is the northern extension of the Kamila system, (the main system), and was partially exploited via open pit mining in the past.
The B-Vein, a sub-parallel mineralized structure to the Inca vein system, has been evaluated, and its resources estimated. It was previously mined to a limited extent using underground mining methods.
Accordingly, geological modeling of the ore shoots reveals discontinuities primarily caused by successive deformation events dating from the Paleozoic era to the present. These events are physically manifested through strike-slip displacements, undulations, and the development of parallel ore shoots.