Back-thrusting response of continental collision: Early Cretaceous NW-directed thrusting in the Changle-Nan'ao belt (Southeast China)

摘要

The SE coastal area of the South China Block (SCB) is generally interpreted as a Cretaceous active continental margin due to subduction of the Paleo-Pacific plate beneath the Eurasian plate. There, the NE SW striking Changle-Nan'ao belt was previously considered as a major strike-slip fault zone with a large displacement accommodating the northward subduction of the Paleo-Pacific plate. Our new field and laboratory investigations document a NW-directed ductile thrust zone that placed gneiss upon Early Cretaceous foliated volcanic rocks. Structural analyses and Anisotropy of Magnetic Susceptibility results indicate that the ductile fabrics in both units are represented by a NE SW striking foliation and a NW SE stretching lineation with top-to-the-NW shear sense. This deformation occurred at ca. 130-105 Ma, before the deposition of undeformed (ca. 104 Ma) volcanic rocks, and the intrusion of ca. 90 Ma isotropic plutons. This continent-ward structure is tentatively interpreted as a back-thrust resulting of the collision of the West Philippines microcontinent with the SCB rather than an effect of a simple oceanic subduction. (C) 2015 Elsevier Ltd. All rights reserved.