Fracture-Seal Diagenesis and Geochemistry as Markers of Fluid Evolution in Anticline Structures: Zagros Fold and Thrust Belt and Analogues in the Pyrenees

Conxita Taberner¹, Jaume Vergés², Paul Gillespie³, Silvayn Grelaud¹, Ian Sharp⁴, Ridvan Karpuz⁵, Nils Bang⁶, Marta Rejas⁷, Davoud Morselnezhad⁸, and Hassan Guadarzi⁹. (1) Geologia Ambiental, Institute of Earth Sciences "Jaume Almera", CSIC, Lluis Solé Sabaris s/n, Barcelona, 08028, Spain, phone: +34 93 4095410, fax: +34 93 4110012, ctaberner@ija.csic.es, (2) Geofisica i Geologia Estructural, Institute of Earth Sciences "Jaume Almera", Lluis solé i Sabaris s/n, Barcelona, 08028, (3) Norsk Hydro Research Center, Sandsliveien 90, N-5020, Norway, (4) Norsk Hydro Research Center, Sandsliveien 90, Bergen, N-5020, Norway, (5) Norsk Hydro Zagros Petroleum, Tehran, 15137, Iran, (6) Norsk Hydro ASA, Oslo, N-0246, Norway, (7) Institute of Earth Sciences "Jaume Almera", Lluis Solé i Sabaris s/n, Barcelona, 08028, Spain, (8) National Iranian Oil Company, Tehran, Iran, (9) National Iranian Oil Company, Tehran, 11394, Iran

Fracture-seals provide information on the kynematic evolution of structures and thus have been a main focuss of structural studies. However, few studies integrate the results of structural analyses and diagenetic and geochemical investigations of the actual precipitates in the fracture-seal. This approach has been used for the study of one of the frontal anticlines from the Zagros fold and thrust belt and the Sant Corneli anticline located at the frontal zone of the southern Pyrenees. These studies are addressed to better understand the fracture-seal systems from the oil and gas reservoirs in the Zagros province (Iran).

Field mapping provides the framework of fracture development and relative timing during anticline evolution. Cathodoluminiscence petrography unravels the successive stage of fracture reopening, hydraulic brecciation, dissolution and crack-seal in calcite /dolomite cements. Isotopic composition (d¹³C, d¹⁸O) and ⁸⁷Sr/⁸⁶Sr ratios of carbonate cements combined to fluid inclusion studies enables the reconstruction of fluid evolution along with fracture-sealing and the relationship of the different stages to oil migration.

Fault Seals
2004 AAPG International Conference and Exhibition Technical Program