Diagenetic minerals and paleothermal constraints in Maestrat Basin, Iberian Range: relation to rift stage and other regional thermal events

In the Lower Cretaceous sandstones of the Maestrat Basin are present several diagenetic minerals that provide information about their temperature of precipitation. Quartz cement (homogenisation temperatures with a mode of 145ºC), fibrous illite replacing feldspars (70-130ºC), the complete transformation of kaolinite to dickite (90-130ºC), the complete albitization of detrital feldspars (>105ºC) and barite and saddle dolomite cements (associated to hydrothermal fluids). Vitrinite reflectance of the organic matter in the intercalated marls revealed burial temperatures from 119 to 134ºC. However, these temperatures are not consistent with the thermal modelling of Penyagolosa sub-basin (Maestrat Basin). In the Penyagolosa Sub-basin model, the Lower Cretaceous sediments reached a maximum burial temperature of 65ºC, based on a thermal gradient of 30ºC/km, which was estimated by subsidence analysis, vitrinite reflectance and the stretching factor and thermal conductivities during syn-rift stage 2. Thus, in the Maestrat Basin existed conditions of relative higher temperature than predicted in a typical rift basin. These thermal anomaly is consistent with the existence other high-temperature events, such as alkali basaltic volcanism, metamorphism, thermal heating associated with high thermal gradients, and Hg-Sb bearing deposits have been reported in the Basque-Cantabrian Chain, the Pyrenean Mountains and the Iberian Chain