Long history of a Grenville orogen relic – The North Qinling terrane: Evolution of the Qinling orogenic belt from Rodinia to Gondwana

Abstract

The North Qinling terrane (NQT) is considered to be a relic of the Grenvillian orogeny and is related to the formation of Rodinia because of the extensive magmatism and typical amphibolite-facies metamorphism that occurred in the NQT at ∼1.0Ga. It was also involved in the Qinling orogen in the early Paleozoic during the amalgamation of Gondwana, as indicated by a phase of ultra-high pressure metamorphism at ∼500Ma. We provide a synthesis of the tectono-magmatism, metamorphism, detrital zircon age spectra and the evolution of oceanic basins of the NQT and its adjacent areas to determine the evolutionary history of the NQT from Rodinia to Gondwana. We reconstruct the tectonic history of the NQT from the Neoproterozoic to Paleozoic and identify three key events in the geological history of the NQT. Firstly, the NQT initialized as an intra-oceanic arc probably during the Paleoproterozoic around the South China blocks. It accreted onto the supercontinent Rodinia at ∼1.0Ga, resulting in the closure of the Songshugou Ocean, where it likely formed a Grenvillian-aged orogen with the Cathaysia Block. Subsequently, it rifted from Rodinia by post-collision extension during Rodinia breakup at ∼750Ma, and finally, the NQT was accreted to the present day southern edge of the North China Block (NCB) during the late Silurian to Early Devonian, likely as part of the amalgamation of Gondwana. A number of distinct oceanic terranes were also identified. The Kuanping Ocean was a Precambrian ocean located in the southern NCB, its meta-mafic unit, the Kuanping ophiolite belt, is likely the remnant of the preliminary Panthalassa oceanic crust. The Erlangping ophiolite belt records two Wilson Cycles, with the Proto-Erlangping Ocean initially opening as a back-arc basin at ∼1.0Ga due to the subduction of the preliminary Panthalassic Ocean, and was then closed by the arc-arc collision between the NQT and the Proto-Erlangping arc at ∼500Ma. With the onset of subduction of the Shangdan Ocean, the Erlangping Ocean re-opened as a back-arc basin at ∼475–460Ma. The Kuanping and Erlangping oceans closed during ∼440–400Ma when the NQT collided with the NCB. Our model also suggests that the Shangdan Ocean was an oceanic region along the northern margin of Eastern Gondwana.