Seamount subduction and accretion in West Junggar, NW China: A review

Seamounts are prominent seafloor features that make inhomogeneous oceanic crust, carried by some moving plates and eventually accreted or subducted at convergent margins. These seamounts contribute to subduction dynamics, continental crustal growth, and chemical mantle heterogeneities. We present a review of seamount subduction and accretion in the West Junggar based on available geological, geochronological, and geochemical data of the ophiolitic mélanges. Several ophiolitic mélanges with ages ranging from 572 Ma to 332 Ma developed in West Junggar, including the Mayile, Tangbale, Chagantaolegai, Barleik, Hebukesaier, Kujibai, Emin, Hongguleleng, Karamay, and Durbut ophiolitic mélanges, and displayed some typical block-in-matrix structures. The mafic rocks from these ophiolitic mélanges can be divided into MORB and OIB types. The MORB type likely to have formed in arc related setting were derived from a depleted mantle source that had been metasomatized by slab-derived fluids. However, the OIB type was formed in seamounts/oceanic plateaus related to mantle plume activities. Many seamounts with different ages developed in the Junggar Ocean as well as the Paleo-Asian Ocean, and had three different destinations: accretion in the accretionary prism, underplating to the overriding plate, and collision, resulting in different geological effects. The subducting and accreting seamounts in West Junggar are mainly involved in deformation of the overriding plate, magmatism of the volcanic arc and plate tectonics. Particularly, seamounts/oceanic plateaus accretion probably induced subduction initiation in West Junggar, namely subduction polarity-reversal and/or subduction transference. This will provide new insights into understanding the tectonic evolution of the West Junggar as well as the CAOB.