| Summary: | La Bodega (LB) and La Mascota (LM) deposits (inferred resources in 2010 of 3.47 Moz Au, 19.2 Moz Ag and 84.4 Mlbs Cu at 2 g/t Au cut off) are located in the California-Vetas Mining District, 35 km NE of Bucaramanga, in the Eastern Cordillera of Colombia within the Santander Massif.
Mineralization exhibits NE-trending, NW-dipping structural control associated with the right lateral strike-slip La Baja fault. Mineralization at LB is composed of veins networks and tectonic-hydrothermal breccias while LM mineralization is largely contained in hydrothermal breccias with adjacent narrow veining zones. Mineralization is hosted in Proterozoic Bucaramanga (gneiss) Complex and Triassic-Jurassic leucogranites.
Hydrothermal alteration and mineralization occur in six stages. An early porphyry-style phase comprises stages 1 and 2. Stage 1 is characterized by propylitic alteration with epidote, chlorite, calcite, specularite veins, minor pyrite and chalcopyrite, probably associated in time with Mo-Cu mineralization (Re/Os on molybdenite ~10 Ma) and porphyritic granodiorites (U/Pb in zircon ~10-8.4 Ma) cropping out in the district. Stage 2 (⁴⁰Ar/³⁹Ar on muscovite ~3.4 Ma) is characterized by phyllic alteration (muscovite/sericite – illite, quartz, pyrite) associated with quartz+pyrite veins. Epithermal phase (stages 3-6) is related to multi-phase hydrothermal breccia development and advanced argillic (quartz-alunite) alteration which based on alunite ⁴⁰Ar/³⁹Ar geochronology took place between ~2.6 and ~1.3 Ma. Stage 3 is characterized by copper sulfide deposition. Stage 4 is characterized by wolframite deposition in veins/breccias. Stage 5 is characterized by enargite deposition. Stage 6 is characterized by minor porous quartz deposition followed by sphalerite with alunite+quartz. Pyrite is common to all these stages. Gold-silver mineralization took place in stages 2-5 associated with sulfides, sulfosalts, tellurides, as electrum and native gold. Hydrothermal events were by followed by near surface supergene alteration and fault reactivation that created intensely fractured/gouge-rich fault zones.
At LM, stages 4-5 quartz primary fluid inclusions assemblages indicate boiling and they have homogenization temperatures of ~143-238°C and salinities of 0.5-5.6 wt% NaCl equiv. LM and LB pyrite exhibit light δ³⁴S signatures: -16.9‰ to –11.3‰ at LM and -8.3‰ and –6.1‰ at LB. Alunite δ¹⁸O and δD data indicate that it was precipitated largely from magmatic fluids. === Science, Faculty of === Earth, Ocean and Atmospheric Sciences, Department of === Replacement PDF uploaded by cIRcle staff at the request of the Faculty of Graduate and Postdoctoral Studies on March 12, 2014. === Graduate
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