Les gisements d'émeraude de la Cordillère Orientale de la Colombie: Nouvelles données métallogéniques |
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| Authors: | G Giuliani C T Rodriguez F Rueda |
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| Institution: | (1) ORSTOM. Universidade de Brasilia, Institute de Geociências, 70140 Brasilia, Brasil;(2) Centre de Recherches Pétrographiques et Géochimiques, 15 Rue N.D. des Pauvres, BP 20, 54501 Vandoeuvre, France;(3) Empresa Colombiana de Minas, calle 32, n 1307, Bogotà, Colombia |
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| Abstract: | Emerald deposits of Colombia are confined to lower Cretaceous shales of the Eastern Cordillera. The tectonic pattern of the deposits is related to deep reverse and large regional fault systems. Hydrofracturing is the main factor controlling emerald mineralization. It permitted to the hydrothermal solutions to permeate through fractures but also along stratification planes forming in this case stratabound mineralizations. Emerald occurs in calcite veins, veinlets, pockets and brecciated zones associated mainly with pyrite, quartz, parisite, codazzite and fluorite. Emerald mineralization belongs to an epigenetic hydrothermal process. The alternance of arenite-shale formations in the Cretaceous probably played an important role in the accumulation of solutions and in the propagation of the hydrothermal channels. The origin of emerald involves chemical elements mobilized by the fluids in the Cr-V-Fe-Al-Si-bearing black shales. The source of beryllium remains a problem and is discussed in the paper. |
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