Tectonic facies along the Nujiang-Lancangjiang-Jinshajiang orogenic belt in southwestern China

The Nujiang-Lancangjiang-Jinshajiang orogenic belt in southwestern China displays the mosaic tectonic framework of alternating suture zones and continental masses.The tectonic attributes and division of the orogenic belt have long been much debated.In this study,eleven first-order tectonic facies and several second-order tectonic facies are recognized for this orogenic belt.The first-order tectonic facies include subduction,subduction complex and obduction tectonic faces,and associated post-orogenic and strike-slip tectonic facies.The subduction tectonic facies may be subdivided into mass metamorphic facies,foreland fold-thrust facies,foreland basin facies;the subduction complex tectonic facies into oceanic crust relicts facies,continental crust relicts facies,accretionary metamorphic complex facies,activiated basement facies,intrusive facies and superimposed molasse facies,and obduction tectonic faces into fore-arc basin facies,island-arc facies,back-arc basin facies and inter-arc basin facies.The northward subduction of the Tethyan Ocean led to the collage of the Pan-Cathysian continental masses,and following back-arc spreading,closure and mountain building,thus resulting in the formation of the tectonic features of "multiple suture zones" and "multiple continental masses".