WMo-Skarn From the Mraconia Valley, Romania
Résumé
The skarn from the Mraconia was formed at the contact between crystalline limestone of the Neamtu Series and a porphyritic ranodiorite. The main metallic minerals in the Mraconia Valley are scheelite and molybdenite. The skarn mainly consists of garnet (andradite), ferroactinolite, magnetite, epidote, apatite, vesuvianite and wollastonite. Four stages of mineralization overprint the primary skarn: (a) a high temperature stage, consists of the deposition of scheelite as impregnations in the mass of andraditic skarn and a simultaneous deposition of the classical "quartzmolybdenum" ore along the cracks in granodiorite mass; (b) the hydrothermal stage which overprinted the first event, conducing to the deposition of pyrite, chalcopyrite and calcite along the cracks and leading to the impregnation of the skarn mass by pyrite and chalcopyrite; (c) the second hydrothermal stage conduced to the deposition of massive mineralization of chalcopyrite, pyrite, sphalerite and galena, while scarce pyrrhotite and tertahedrite mineralization formed veins and lenses in the skarn mass; (d) a low temperature hydrothermal stage yielded the depositions of bornite and covellite on chalcopyrite and hematite (specularite) on magnetite. The endoskarns are characterized by the presence of sulfides of Mo, Pb, Cu, Zn and the exoskarns are much richer in scheelite.
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