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

ANA LAURA RAINOLDI; MARTA FRANCHINI; JOSEFINA PONS; ADOLFO GIUSIANO; CESARETTI NORA; ADRAIN BOYCE

Nancy

Congreso; The 13th SGA biennial meeting; 2015

CNRS, and a group of French, Belgian and German universities (Nancy, Liège, Aachen and Louvain

The Cu deposits of Neuquén Basin are an example of sediment-hosted deposits generated byinteraction of hydrocarbons with host red-beds and metalcharged basinal brines. After deposition and diagenesis of red beds, the incoming of hydrocarbons promoted thereduction 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 hydrocarbons migration, ii) calcite II, with lighter δ13CV-PDB values, precipitated during bleaching probably supplied by the organic acids that migrated together withhydrocarbons and, iii) calcite III precipitated with the mineralization, showing even more negative δ13CV-PDB values. Cu-sulfides have highly negative δ34SV-CDT values(-45.2? to -41.7?), indicating the involvement of bacterial sulfate reduction, which may also be linked to low δ13CV-PDB in calcite III. Fluid inclusions in calcite II and III fluoresce under UV light, present immiscibility and adherence phenomena and generates clathrates during cooling experiments suggesting the presence of organic fluids.