Processes related to the rift-to-collision transition in the eastern Betics as revealed by low-temperature thermochronology on magmatic, U-Pb dating and clumped isotopes on calcite-filled veins

The Alboran margin in the Betics formed as a result of backarc crustal thinning oblique to the direction of the slab retreat. The history of sediment infill, subsidence and faulting reveals extension at upper crustal levels operated from the Serravallian-early Tortonian to the late Tortonian (14-8 Ma) synchronously with Ca-K magmatism. Only recently, around 8 Ma, the retreating slab detached resulting in the onset of the tectonic inversion of the margin. Here we report new apatite (U-Th)/He thermochronological analyses from Cabo de Gata magmatic province, and new U-Pb dating, Oxygen (O) and carbon (C) stable isotopic analyses of calcite-filled veins from the Tabernas basin combined with fluid temperatures determined by clumped isotope D47 analyses. U-Pb ages from 8.56 ± 0.21 to 4.88 ± 0.45 Ma are remarkably synchronous with late alkaline Tortonian-Messinian magmatic events and post-Messinian uplift. Low-temperature thermochronology confirms that magmatic edifices cooled below sea-level at around 8-7 Ma, and then slowly exhumed onshore during shortening along the Carboneras fault and regional kinematic reorganisation associated with slab detachment. C and O isotopic compositions (-17.23‰ to -9.08‰ for O and -15.77‰ to -1.60‰ for C, in V-PDB) of calcite veins are close to carbonates endmember of the Alpujárride basement. The O and C isotopes trend highlights a burial where all δ18O and δ13C calcite have depleted values compared with host rocks indicating a higher temperature of calcite precipitation (estimated at 83.7°C) and an increasing organic matter degradation with depth. The concordance on ages suggests that deep processes including mantle delamination and hot mantle triggered CaCO3 fluid precipitation and uplift during the transition from extension to onset of tectonic inversion. The deep mantle processes related to the 8 Ma event impacted not only the uplift of the Alboran basin that caused the Messinian Salinity Crisis that is well recorded in the Betics, but also the recent uplift of Iberia and Western Europe.