El Valle-Boinás/Carlés Geology

Narcea Gold Belt is a 45 kilometres long, 4 kilometres wide northeast-trending zone located in Northern Spain. Gold deposits lie within the 15 kilometres long central part of the belt and the Carlés and El Valle deposits were mined by modern methods during the first part of this century.

The gold mineralization in the central part of the Rio Narcea Gold Belt is principally hosted by a series of Lower Cambrian to Devonian sedimentary rocks. This stratigraphic package was intruded by felsic magmas and thrusted and folded into a N20°E-trending, overturned anticline during the Hercynian Orogeny. Later extensional events resulted in the formation of three main sets of normal faults that strike NNE-SSW, NNW-SSE and EW.

The gold-copper-silver mineralization at the EVBC Mines is characterized by mesothermal magnesium and calcic-rich skarn deposits at the contacts of late Paleozoic intrusives as well as younger epithermal vein mineralization related to subvertical faults and quartz-feldspar porphyry dykes. The mineral assemblages are chalcopyrite, bornite, (arseno)pyrite, magnetite, and pyrhhotite in the skarns, and native gold, electrum, native copper, chalcopyrite, and chalcocite in the epithermal mineralization; the vein mineralization is characterized by hematitic jasperoids. Higher grades are encountered where the epithermal systems crosscut the skarns. Leaching and enrichment are common in the structural zones that host epithermal mineralization.

EVBC - General Geology

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El Valle-Boinás Cross-Sectionn

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