PALEOFLUID HISTORY OF THE SANT CORNELI ANTICLINE, SOUTH-CENTRAL SPANISH PYRENEES

Multiple systematic fracture (joint and vein) sets have been observed within the Sant Corneli anticline area in the south-central Spanish Pyrenees. However, syntectonic strata and cross-cutting relationships do not fully constrain the timing of these fracture sets and little is known about the paleo-fluid and deformation conditions. For simplicity, the naming conventions set by Shackleton et al (2011) will be used for description of the fracture sets. Detailed petrography and fluid inclusion microthermometry of syn-tectonic vein minerals provides information on the type and degree of mineralization, composition, fluid history, including trapping conditions (PT), and changes over time. This data, in turn, could provide insight into the conditions present during deformation and paleo-hydrologic structure. Calcite veins were sampled from multiple fracture sets in the Sant Corneli anticline in the south-central Spanish Pyrenees.

Vein mineral petrography was conducted for all veins sampled. The type of vein mineralization is consistently calcite with rare quartz, and vein thicknesses range from one millimeter to several centimeters. The calcite ranges from white to colorless. The J2 fracture set is characterized by drusy calcite fill followed by fibrous to elongate blocky calcite fill and very little iron oxide staining. The J1/J3 fracture set appears to be characterized by isopachous small blocky calcite followed by isopachous large blocky calcite cement, as well as by what appears to be a later generation of fibrous calcite cement. This fracture set does not appear to have any associated iron oxide staining. J4/J5 fracture set is characterized by isopachous small blocky calcite followed by isopachous large blocky calcite vein fill and iron oxide staining. Fluid inclusion analyses will provide pressure and temperature conditions at the time of vein formation, and potentially salinity of the fluids as well, which may distinguish these fracture sets from each other even further.