Rift and salt-related multi-phase dolomitization: example from the northwestern Pyrenees

The Meillon (Callovo-Oxfordian) and Mano (Tithonian) Formations are dolomitized carbonate reservoirs that actively produce oil gas (Aquitaine Basin, France). In this study, the dolomitization conditions of their counterparts exhumed in northwestern Pyrenees detailed using a combination field observations, petrography, fluid inclusion microthermometry, elemental isotopic geochemistry, U–Pb geochronology. Dolomitization occurred several stages spanning from Neocomian (pre-rift) to Albian (syn-rift, associated with mantle exhumation active salt tectonics). Both formations were first massively near-surface shallow burial during Berriasian-Valanginian, likely triggered by influx marine-derived waters. Between Barremian Albian, Early Cretaceous rifting caused upward hot fluids partial complete recrystallization initial dolomites. During subsequent dolomites precipitated both as high-temperature (T > 160 °C) vein- pore-filling cement. Distinct chlorinities rare earth element patterns between point compartmentalization stage. Whereas dolomite cements indicate involvement evaporite-derived brines Formation, precipitation was related clay-derived water Formation. Lastly, final episode cementation only vicinity faults volcanic intrusions when highest temperatures recorded 250 °C). These saddle hydrothermal mixture mantle-, crustal-, waters channeled diapirs. Subsequent quartz calcite cement reveals temperature decrease post-rift inversion setting (post-Cenomanian) indicates formations. This study highlights major control exerted rifting, combined presence diapiric salt, on dolomitization, making platforms modern salt-rich passive margins potential targets for exploration.