Linking thermochronological data to transient geodynamic regimes; new insights from kinematic modeling and Monte Carlo sampling of thermal boundary conditions

摘要

It is common practice to assume values for basal heat flow or basal temperatures as a lower boundary condition for thermo-kinematic models of crustal tectonics. Here, we infer spatial and temporal variations of the paleobasal temperature from integrated modelling of thermochronological ages, to relate the inferred variations to the geodynamic setting. To this end, we consider the Argentine Precordillera as a natural laboratory, given that its kinematic evolution is relatively well constrained and therefore, the focus can be placed on the variations of its basal thermal state. By means of a simple Monte Carlo sampling approach with thermochronological data as constraints, we infer the paleo-basal temperature history. This is compared to estimates posed by models existing in the literature concerning flat-slab subduction. Our results imply that, given the kinematic models used to date in the area, extremely low temperature gradients (15 degrees C/km) are required to adequately predict the observed thermochronological ages. Substantial cooling of the lithosphere around 10 Ma is also required in order to fit measured values. This agrees with previous thermal simulations carried out in the region. Furthermore, major controls of the thermal architecture on the Argentine Precordillera are implied, thus reigniting the debate on thermal driving mechanisms in the evolution of mountainous settings and their relationship with deeper processes within the Earth, such as on the effects of the flat-slab subduction.