The role of magmatism in hydrocarbon generation in sedimented rifts: A Nd isotope perspective from mid-Cretaceous methane-seep deposits of the Basque-Cantabrian Basin, Spain

Studies on the involvement of intrusive magmatism in hydrocarbon generation within sedimentary basins have gained momentum owing to increasing appraisal role that such processes may play controlling global carbon cycle perturbations, and exploration potential volcanic basins. Nevertheless, for many areas causal link between intrusions surrounding systems remains disputed, encouraging a search methods could aid identifying different sources. Here, we performed multi-proxy geochemical study middle Cretaceous methane-seep deposits Basque-Cantabrian Basin, an early-stage, peri-cratonic rift marking Mesozoic opening Bay Biscay. Infilled by thick succession intruded shallow-level igneous bodies, basin shares analogies with modern young, sedimented rifts sustain seepage. We applied novel approach uses Nd isotope composition seep constrain relationship seepage activity, explore general isotopes trace magmatic-influenced fluids The data been combined rare earth element analyses oxygen measurements, providing broad insight into former seeping fluids. For three out four investigated seeps, ratios observed authigenic carbonates include signatures markedly more radiogenic than reconstructed background seawater-derived pore waters. level this 143Nd-enrichment varies both individual deposits, reflecting spatial temporal differences fluid typical seep-related environments. signals provide evidence subseafloor interactions mafic materials, supporting model control mid-Cretaceous methane expulsion Basin. thermogenic origin is accord moderately negative δ13C values paragenetic successions studied carbonates. single deposit, its relatively unradiogenic can be attributed smallest size shallowest emplacement depth underlying intrusion, likely resulting short-lived character limited hydrocarbon-generation associated contact metamorphism. demonstrates offer tool disentangling fluxes from organic matter alteration pathways numerous, fossil which various sources insufficiently understood.