Numerical simulation of Late Mesozoic accretion process along the continental margin of East China: A case study of the Nadanhada Terrane

Accretion of oceanic plateau is an important process of continental growth, and is exemplified by the presence of oceanic island basalts (OIB) and plume-type ophiolites in many modern orogens. Oceanic plateau can also subduct along convergent margins, as revealed by seismic tomography. The mechanism controlling accretion or subduction of oceanic plateau remain unclear. In this paper, we investigate the accretion of oceanic plateaus at continental margins using a thermo-mechanical-petrological model of an ocean-continent convergent zone. The results of the models show three major factors for the accretion of the oceanic plateaus onto the continental margin: (1) thinned continental margin for the overriding plate, (2) " weak” layers in oceanic lithosphere and (3) young oceanic plateau. The results of the model are further compared with the field structural analysis and geochemical characteristics of the Nadanhada Terrane in Northeast China. It is revealed that the intense compression of the seamount and the continental margin of Northeast Asia results in strain concentration in the subduction zone, forming high-angle thrust faults and back thrusts associated with the Alpine-type folds, and structural exhumation of low-metamorphic rocks through thrust faults.