Nueva exploración arrojó resultados alentadores en el Valle de Chita
https://sisanjuan.gob.ar/mineria/2021-03-22/30614-nueva-exploracion-arrojo-resultados-alentadores-en-el-valle-de-chita
Exploration activities at the Chita Valley Project began in 1968, starting with geological mapping, geophysical surveys, and initial drilling focused on Cu-Mo porphyry mineralization in Chita South. Over the years, exploration efforts expanded to include detailed surface mapping, geochemical sampling of soil and rock, petrographic studies, and geophysical surveys (IP, resistivity, and magnetometry). Since 1969, a total of 257 drill holes has been completed, covering 112,857 meters, primarily using diamond drilling, with some reverse circulation drilling.
Between 2014 and 2017, systematic diamond drilling at Chita South identified Cu-Mo porphyry mineralization, characterized by copper oxides at the surface, a supergene enrichment zone with chalcocite/digenite at depth, transitioning to primary chalcopyrite-dominant (+ substantial molybdenite) copper sulfides. Drilling efforts targeted the supergene-enriched zone, while the deeper primary sulfide zone remains largely underexplored with the few deeper drillholes (750m) intersected coherent >200 ppm Mo zones.
Under the Minsud and South32 Earn-In Agreement (2019–2025), exploration expanded, with a total of 154 drillholes, encompassing 102, 219m conducted under this agreement. Exploration has been hugely successful with the discovery of the largely blind Chinchillones polymetallic (Cu-Zn-Mo-Ag-Au-Pb) porphyry-epithermal deposit. The discovery was borne from: i) the recognition of porphyry-related veins (i.e., B-, D- type porphyry veinlets) traversing the silicified and brecciated sandstone country rocks occupying prominent EW-and NE-trending ridges; ii) interpretation that the late-mineral dome complex was not vertical in geometry but thought to assume a flat-moderate geometry (vented farther to the SE) and underlain by high-grade, polymetallic IS (intermediate sulfidation)-style, breccia-hosted mineralisation; and iii) the core review of the fourth scout drillhole (CHDH20-04) identified that the bottom 15m indicated under-recognised but compelling chalcopyrite-bornite-molybdenite mineralisation hosted in secondary quartz-white mica (phengitic with chalcopyrite>>pyrite ratios) flooding which was interpreted as precursor characteristics to more productive porphyry centre at depth; re-entry to this drillhole to machine capacity of 740m proved this hypothesis correct with 104m@ 0.70% CuEq from 634m to EOH.
Chinchillones has been the most intensively drilled area. Drill spacing ranged from 150 m x 150 m to 80–100 m in denser zones, with an average drill depth of 640 m and a maximum depth of 1,380 m. These efforts contributed to the maiden Mineral Resource estimate filed in February 2025 and an updated Mineral Resource filed in early April 2026. The April 2026 Mineral Resource Estimate reported 1.3 Mt (Indicated) and 3.33 Mt (Inferred) contained copper equivalent resource base.
Additional exploratory activities included: i) detailed mapping (in conjunction with surface geochemistry) over the principal prospects; ii) geophysical IP and magnetics surveys over Brechas Vacas, Link Zone, Placetas prospects; iii) UAV drone-based topographic survey at Brechas Vacas and Minas de Pinto properties; iv) hyperspectral analyses of high-resolution Worldview imageries of the tenement areas; and iv) and detailed soil grid surveys over the Placetas prospects.
The Chinchillones polymetallic deposit is characterised as a substantial Cu-Mo (Au) porphyry system with overlapping polymetallic mineralization. The upper polymetallic zone, found between 200 m and 850 m depth, contains significant lead and zinc (>1%), along with notable gold and silver grades (above 0.1 g/t Au and 10 g/t Ag) up to 1,050 m vertical interval, primarily associated with hydrothermal breccias. The porphyry zone hosts continuous copper mineralization (>0.1% Cu) from 125 m to over 1,200 m, with the highest copper grades (>1% Cu) concentrated between 250 m and 1,000 m. Molybdenum grades exceed 500 ppm at depths beyond 750 m, indicating further potential at depth. Both copper and molybdenum mineralization remain open for expansion at deeper levels, supported by convincing coherent IP conductivity anomalies and alteration-mineralization zonation established from drilling.
Future exploration efforts will focus on assessing: i) high-grade hydrothermal breccias at Chinchillones, increasing its grade profile; ii) investigate the open deeper extensions of the porphyry Cu-Mo system at Chinchillones and Chita South Porphyry (PSU), leading to an effective deep drilling program; and iii) more detailed systematic work, leading to a scout drilling program over the identified prospective targets.
Thus, exploration at the Chita Valley prospect area has been successful, increasing the historical resource base at less than 0.2 Mt to 4.3 Mt contained copper equivalent, making it one of the largest new discoveries in the Andes during the last decade.