The continental subduction in the evolution of central qiangtang mélange belt and its tectonic significance

Abstract

ABSTRACT Models of in situ oceanic subduction and underthrusting is proposed to explain the formation and exhumation of the central Qiangtang mélange belt. Some studies have suggested that continental subduction occurred in central Qiangtang, but there is a lack of definitive evidence. Thus, the role of continental subduction in the formation and evolution of the central Qiangtang mélange belt has not been fully considered. We therefore studied the origin and structural evolution of the central Qiangtang mélange belt. Detrital zircon research indicates that the continental blocks in the Gangma Co mélange are part of the Carboniferous-Permian strata of the South Qiangtang terrane and have a Gondwanan affinity. Structural studies and geologic observations in the Gangma Co area show a change in the structural style and a pressure difference between the lower mélange and the upper Carboniferous-Permian strata. Structures in the Gangma Co mélange include D1 layer-parallel ductile structures, D2 horizontal contractional structures, D3 flattening structures, and D4 slightly horizontal contractional structures. According to our analysis, the newly proposed in situ continental subduction model best explain these findings.