Neoproterozoic amalgamation of the Northern Qinling terrain to the North China Craton: Constraints from geochronology and geochemistry of the Kuanping ophiolite

• Kuanping ophiolite indicates an ocean between North Qinling and North China Blocks.
• Zircon U–Pb age of 1445 ± 60 Ma for N-MORB constrains the age of Kuanping ophiolite.
• Southward subduction of Kuanping Ocean beneath North Qinling island-arc terrain.
• North Qinling amalgamated to North China Block in Neoproterozoic due to subduction.

The Proterozoic tectonic evolution of the Qinling Orogenic Belt is a key to understanding the convergent processes between the North China and South China Blocks. The widely exposed Kuanping ophiolite melange between the North Qinling Terrain and the North China Block provides important constraints on the Meso-Neoproterozoic tectonic evolutionary processes between the North Qinling Terrain and North China Block. Detailed geological mapping reveal that the Kuanping ophiolite melange consists of an ophiolite and a meta-sedimentary unit. According to our new geochemical investigations, the ophiolite unit can be briefly divided into two groups: (1) N-MORB and (2) E-MORB. The former is characterized by depletion in light rare earth elements, large-ion lithophile elements, and non-differentiation in high field strength elements. The latter shows slight enrichment in light rare earth elements, large-ion lithophile elements, and minor differentiation in high field strength elements. Accordingly, it is inferred that the Kuanping ophiolite likely represents remnants of an oceanic crust (named as Kuanping Ocean) between the North Qinling Terrain and the North China Block. One metamorphosed N-MORB sample from the Kuanping ophiolite was selected for LA-ICPMS zircon U–Pb dating, which displays an age of 1445 ± 60 Ma, probably represents the formation time of the Kuanping Ocean. Integrated with the regional geological, geochemical and geochronological data, we propose that the North Qinling Terrain amalgamated to the North China Block after a southward subduction of a Mesoproterozoic ocean represented by the Kuanping ophiolite.

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