From hydroplastic to brittle deformation: controls on fluid flow in fold and thrust belts. Insights from the Lower Pedraforca thrust sheet (SE Pyrenees)

We present a multidisciplinary study to decipher the controls of deformation on fluid flow regime in fold and thrust belts using the Lower Pedraforca thrust sheet in the SE Pyrenees as an example. We integrate field-based and petrographic observations and geochemical and geochronological data to differentiate seven types of fractures, eight types of calcite cement (Cc1 to Cc8) and two sets of stylolites during the deformation stretching the studied thrust sheet. During syn-sedimentary hydroplastic normal faulting affecting poorly consolidated Upper Cretaceous and Eocene syn-orogenic sediments, calcite cement did not precipitate. During burial, bed-parallel stylolites formed and Cc1 and Cc2 precipitated from formation waters in a closed palaeohydrological system. During the layer-parallel shortening, Cc3 precipitated from formation waters (~+5.4‰ VSMOW) with 87Sr/86Sr ratios of 0.707922 and at ~70 °C. Cc4 …