Physico-chemical processes in seawater-saturated subduction zone sediments - an experimental approach

Abstract

End members of the incoming sedimentary sequence at the Nankai margin subduction zone were subjected to effective stresses of ~70 MPa at temperatures of 20 C, 100 C and 150 C. The main result is the positive correlation of increasing temperature and pore space reduction under drained, normal consolidated conditions. The new findings shed light on the complex consolidation pattern along the Nankai prism toe where in-situ temperatures reach up to 110 C. The data suggests that decollement formation along the central portion of the Nankai Trough is determined by excess pore pressure generation and low intrinsically shear strength of the sediment. The geochemical analysis of expelled pore water reveal that water-rock interaction is largely governed by desorption-adsorption processes during the heated consolidation tests. The released solutes may facilitate cementation of underthrust sediments.