The Role of Hydrocarbons in the Genesis of the Sediment-Hosted Stratiform Copper Deposits, Neuquén Basin (Argentina)

RAINOLDI A. L.; FRANCHINI M.; PONS M. J.; GIUSIANO A.; CECARETTI N.; BOYCE A.

Nancy

Otro; 2015 SGA biennial meeting; 2015

Society for Geology Applied to Mineral Deposits

The Cu deposits of Neuquén Basin are an example of sediment-hosted deposits generated by interaction of hydrocarbons with host red-beds and metal charged basinalbrines. After deposition and diagenesis of redbeds, the incoming of hydrocarbons promoted the reduction of hematite to Fe2+ resulting in bleaching of the sandstones. The presence of bitumen is evidence that hydrocarbons were the reducing agents. Three calcite events are: i) calcite I, with heaviest δ13CV-PDB values, precipitated from evolved  meteoric waters before hydrocarbonsmigration, ii) calcite II, with lighter δ13CV-PDB values, precipitated during bleaching probably supplied by the organic acids that migrated together with hydrocarbons and, iii) calcite III precipitated with the mineralization, showing even more negative δ13CV-PDB values.Cu-sulfides have highly negative δ34SV-CDTvalues (-45.2? to -41.7?), indicating the involvement of bacterial sulfate reduction, which may also be linked to low δ13CV-PDBin calcite III. Fluid inclusions incalcite II and III fluoresce under UV light, present immiscibility and adherence phenomena and generates clathrates during cooling experiments suggesting thepresence of organic fluids.