Geology and geochemistry of the emerald mines of Gachalá, Cundinamarca
DOI:
https://doi.org/10.32685/0120-1425/bolgeol22.3.1979.317Keywords:
Colombia, Mesozoic, sedimentary rocks, structural characteristics, lithological characteristics, leaching
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Copyright (c) 1979 Servicio Geológico Colombiano
This work is licensed under a Creative Commons Attribution 4.0 International License.
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Abstract
Emerald mineralization. in the Gachalá region is emplaced in breccias, veins, and in fault walls, these faults having an N-NE strike and affecting lower Mesozoic strata. Sedimentary rocks of the Paleozoic age are also present in the area.
Mineralization is intimately related to the black shales, showing a high degree of metasomatic alteration. This alteration consists of replacing the host rock and cavity filling with oligoclase, dolomite, pyrite, some calcite, and traces of rutile and fluorite. Mineralizing solutions could have been originated by meteoric and/or connate water from sediments, this water leaching the necessary ions on their way through the host rocks. Many features suggest a loose relationship between evaporitic sequences and emerald mineralization, the former contributing, by solution, some of the ions required to the formation of the latter.
Some emerald exploration guides are proposed based on the knowledge of structural, lithologic, and geochemical characteristics. Different methods are applicable in all exploration steps, from a regional scale to the orientation of mining works.
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