Coupled heat and fluid transport at the Peruvian convergent margin at 12??S was studied with finite element modelling. Structural information was available from two seismic reflection lines. Heat production in the oceanic plate, the metamorphic basement, and sediments was estimated from literature. Porosity, permeability, and thermal conductivity for the models were partly available from Ocean Drilling Program (ODP) Leg 112; otherwise we used empirical relations. Our models accounted for a possible permeability anisotropy. The decollement was best modelled as a highly permeable zone (10-13 m2). Permeabilities of the Peruvian accretionary wedge adopted from the model calculations fall within the range of 2 to 7 x 10-16 m2 at the ocean bottom to a few 10-18 m2 at the base and need to be anisotropic. Fluid expulsion at the sea floor decreases gradually with distance from the deformation front and is structure controlled. Small scale variations of heat flux reflected by fluctuations of BSR depths across major faults could be modelled assuming high permeability in the faults which allow for efficient advective transport along those faults. The models were constrained by the thermal gradient obtained from the depth of bottom simulating reflectors (BSRs) at the lower slope and some conventional measurements. We found that significant frictional heating is required to explain the observed strong landward increase of heat flux. This is consistent with results from sandbox modelling which predict strong basal friction at this margin. A significantly higher heat source is needed to match the observed thermal gradient in the southern line.
Additional Publication Details
Thermo-hydraulics of the Peruvian accretionary complex at 12??S