REE and Sm-Nd Clues of High-temperature Fluid-rock Interaction in the Riópar Dolomitization (SE Spain)

Abstract

REE geochemistry and Sm-Nd isotope data of Mesozoic stratabound and patchy dolostones of the Riópar area (Prebetic Zone, SE Spain) are presented. The results, combined with previously published data, suggest the dolomitizing fluid was a warm brine that interacted with siliciclastic rocks of Triassic age and with the host carbonates at low fluid-rock ratios. The positive Eu anomaly, negative ɛNd values and MREE patterns confirm that the dolostones were formed by interaction with warm acidic crustal fluids. C-O isotopic interaction models indicate that these fluids were characterized by δ18O-enriched and δ13C-depleted compositions, pointing to low ratios of fluid to rock volumes. The studied dolostones show two Sr sources: one Sr signature is close to the host carbonate values and the other one is more radiogenic, indicating that fluids became enriched in 87Sr after interacting with siliciclastic rocks. Furthermore, the Sr-Nd isotope data systematic depicts a positive correlation, thus probably the same rock sources are shared for both elements. Moreover, the warm fluids interacted with regional limestones achieving a negative Ce and positive La anomalies, low δ18O compositions and similar δ13C values than the host carbonates.