Sr–Nd isotope decoupling at Cretaceous hydrocarbon seeps of the Basque-Cantabrian Basin (Spain): Implications for tracing volcanic-influenced fluids in sedimented rifts

• DOI: 10.1016/j.marpetgeo.2021.105430
• Publication Date: 2021-11-10T01:58:30Z
• Authors: M. Jakubowicz; L.M. Agirrezabala; Z. Belka; M. Siepak; J. Dopieralska
• Keywords: Petroleum seep; Isotopes of strontium; Isotopic signature; Radiogenic nuclide; Mud volcano; Cold seep

Strontium isotopes have seen common use as a tracer of volcanic-influenced fluids at hydrothermal vents and cold seeps hosted by sedimented rifts. However, for some fluid emissions, no apparent contribution volcanogenic Sr has been observed, despite geological or seismic evidence suggesting magmatic involvement in the expulsion. Here, we explore behaviour during fluid-rock interactions rift based on isotope elemental composition Albian hydrocarbon-seep carbonates Basque-Cantabrian Basin, Pyrenees. The basin represents peri-cratonic formed opening Bay Biscay infilled with organic-rich siliciclastics affected subvolcanic intrusions. intrusions stimulated thermogenic hydrocarbon generation sediments resulted enrichment associated seep volcanic-derived, radiogenic Nd. In contrast, none 87Sr/86Srcarbonate ratios observed this study provide subseafloor between seeping igneous materials. Instead, all four studied deposits show various degrees 87Sr-enrichment, bearing fingerprint rift-filling siliciclastics, rather than signature. Furthermore, three deposits, unusual, positive correlation Nd attests to presence an evolved, deep-seated end-member enriched both 87Sr 143Nd. This decoupling can be explained different responses fluid-volcanic interactions, moderate degree exchange able modify signal, but insufficient affect shows that many vents, especially low-temperature, hydrocarbon-dominated more reliably traced using system, whereas cannot standalone their absence.