Origin of the North Qinling Microcontinent and Proterozoic geotectonic evolution of the Kuanping Ocean, Central China

Abstract

The high Pb isotopic ratios among the North Qinling Microcontinent (NQM), the western margin of the Yangtze Craton (WYC) and the western part of South Qinling (WSQ) indicate an identical or very similar origin of their basement. In addition, the analogical peak values of Paleoproterozoic detrital zircons also agree that the NQM originated from the WYC. The evolution of the NQM and the Kuanping Ocean is closely related to the aggregation and break-up of the Columbia supercontinent. According to the formation of the Supercontinent Columbia in the Paleoproterozoic (ca. 2.0–1.8Ga), the debris from the WYC accreted vertically to form the NQM. Then the Kuanping Ocean began its subduction when the Supercontinent Columbia was rifted after the Paleoproterozoic (ca. 1.8Ga). As a result, the passive continental margin of the North China Craton (NCC) and the Yangtze Craton (YZC) turned into an active continental margin. The continental arc (the Xiong’er Group) at the southern margin of the North China Craton (SNCC) and separation of the Qinling Group from the WYC in the Paleoproterozoic to Mesoproterozoic (ca. 1.8–1.0Ga) are also the consequence of this subduction. In the context of the amalgamation of the Neoproterozoic (ca. 1.0–0.9Ga) Supercontinent Rodinia, the NQM and the YZC collided with each other, thereby generating the closure of the Songshugou back-arc basin. Moreover, the terrigenous clastic sediments from some cratons of the Rodinia Supercontinent and the remnant oceanic crust of the Kuanping Ocean constituted the protolith of the present-day Kuanping Group.