Geochemical study in the Pantanos - Pegadorcito area, municipalities of Frontino and Dabeiba, Antioquia
DOI:
https://doi.org/10.32685/0120-1425/bolgeol22.2.1979.400Keywords:
Colombia, Western Cordillera, volcanic Sequence, Cretaceous, sericitic alteration
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Copyright (c) 1979 Servicio Geológico Colombiano
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Abstract
As a result of the geochemical reconnaissance program of the Western Cordillera, initiated by Ingeominas in 1970, several areas of interest for their anomalous contents of copper and associated elements were located.
Subsequently, it was agreed to carry out detailed work in these areas, starting in the Pantanos-Pegadorcito region. This type of work included geochemical sampling over approximately 140 km2, in which 981 rock samples, 1199 soil samples, 1502 sediment samples, 1 502 sediment samples, and 934 samples of pan concentrates were collected and analyzed.
In addition, 13 km were geologically mapped at a scale of 1:10,000, and 556-meter s were drilled in 9 holes.
The known geological relationships in the northern part of the Western Cordillera indicate that a Cretaceous-age sedimentary-volcanic sequence has been intruded by the Mandé Batholith, of quartz diorite-diorite composition, and minor plutons considered to be of middle Tertiary age.
In the Pantanos-Pegadorcito area, the quartz diorite, which has been tentatively considered part of the Mandé Batholith, has been cut by quartz diorite porphyry bodies that were grouped into three types, with minor differences from each other. In addition to these rocks, several intrusive breccia bodies were partially mapped.
Sericitic alteration and, to a lesser extent, argillic alteration and silicification are observed preferentially in the porphyries; the quartz diorite generally shows propylitic alteration. The potassic alteration was only observed very locally and poorly developed.
Pyrite, chalcopyrite, and bornite in disseminated form and in veinlets occur preferentially in the A-type porphyry and in the quartz diorite near the porphyry contact; of the rocks mapped, the intrusive breccia is the least mineralized.
Detailed geochemical prospecting allowed the delineation of two anomalous zones for copper and molybdenum. The larger zone is approximately 5.0 km long and 500 m wide on average and is related to Cerro Pantanos; the second zone is located 1.5 km northwest of the first zone and is 1 km long and 500 m wide on average.
Drilling indicated the presence of copper mineralization in the anomalous zones detected by geochemistry and the absence of significant copper values in holes drilled away from these zones.
From the lithological, structural, mineralization, alteration, and geochemical anomalies recognized at Pantanos-Pegadorcito, it can be concluded that the area presents very favorable characteristics for the development of a porphyry copper deposit whose true economic potential is yet to be determined.
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