Magmatic segregation mineralizations in the Sabanalarga batholite
DOI:
https://doi.org/10.32685/0120-1425/bolgeol35.2-3.1995.284Keywords:
Colombia, Valdivia Group, sulfides, pyrrhotin, chalcopyrite, pyrite
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Abstract
Associated with the Sabanalarga batholith in the Ituango area, there are sulfide mineralizations. The area of interest is in the geological boundary between continental and oceanic affinity rocks, marked by the Cauca-Romeral fault system.
The Sabanalarga batholith, with radiometric ages of 97±10 and 98.2±3.5 m.y. (Coniacian Albian), is a composite Pluton, with mafic-ultramafic facies associated with sulfides, and another of intermediate composition. It includes metamorphic rocks of the Valdivia Group of Paleozoic age and is in faulted contact with the volcano -sedimentary rocks of the Barroso Formation; to the east, there are ultramafic rocks not associated with the batholith and to the west Quaternary deposits.
Mineralization occurs in the El Encanto, Chontaduro, and El Tinto creeks. The sulfides are massive and disseminated in bands and pockets with thicknesses between 0.4 and 3 m. They are constituted by pyrrhotite and in smaller proportion chalcopyrite, magnetite, and pyrite, with small amounts of gold and silver. The gangue minerals are olivine, pyroxenes, and uralitic amphibole.
The sulfide/silicate ratio varies from 1/9 in disseminated mineralization to 4/6 and 7 /3 in massive ores. The samples were analyzed by atomic absorption and showed copper values ranging from 200 ppm to 2.38%, zinc between 44 and 146 ppm, nickel (280-710 ppm), and cobalt (29-552 ppm). The analyses for gold and silver were also carried out by correlation, obtaining results between 0.28 and 2.13 g/ton of gold and 3.31-20.5 g/ton of silver.
By mineralogical and lithological association and textures, these manifestations of sulfides are of magmatic segregation formed by differentiation processes of immiscible sulfurous liquids in the magmatic chamber.
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