Thermal impact of the break-up of Pangea on the Iberian Peninsula, assessed by thermochronological dating and numerical modelling

Thermochronological studies of Variscan basement in Iberia yield cooling ages typically younger than ~ 200 Ma. In this paper, we explore the regional implications of this recurrent age maximum by examination of low and high temperature thermochronological datasets from all over Iberia. Based on these results, we show that in general the lack of cooling ages older than 200 Ma is the result of several important regional periods of thermal resetting. Resetting took place in areas of extension and burial during the Mesozoic break-up of Pangea. Evidence for large scale magmatism and mineralisation is found in Iberia during the Mesozoic, since at that time Iberia formed part of the Central Atlantic Magmatic Province and a large mineralization province extending from North Africa to Western Europe. Numerical modelling allows us to assess the conditions under which rocks in the upper crust may have been thermally reset and the mechanisms likely involved. Results show that active rifting combined with shallow magmatism, and to a lesser extent deep sedimentary burial, could have led to an increase of the geothermal gradient up to ~ 73 °C/km and the reset of thermochronometers with closure temperatures up to 200 °C. Yet, we suggest that also hydrothermal activity, associated to extensional basins, played an important role to the increase of temperatures of some basement rocks above 300 °C.