Origin and Precambrian paleogeography of the North Wulan terrane, northwestern China: A coherent model of the Tarim–Qilian–Quanji continent during the Columbia–Rodinia supercontinent cycle

Abstract The occurrence of pre-existing crust in orogenic belts has important implications for constraining and testing models of orogenic processes and for making paleogeographic reconstructions. Asynchronous magmatic–metamorphic rocks provide an opportunity to reconstruct the positions and constituent blocks of certain Precambrian fragments. Here we report Neoarchean to Neoproterozoic crustal rocks preserved in the North Wulan Terrane (NWT), northwestern China. Our new zircon geochronological data reveal the ca. 2.57 Ga magmatic and 2.0–1.72 Ga metamorphic events in the NWT, implying its involvement in the formation of Columbia supercontinent. Meanwhile, the NWT also recorded the 1.5–1.3, 1.1, 0.9–0.8 and 0.51–0.48 Ga magmatic-metamorphic activities, corresponding to the involvement of regional Precambrian fragments in cyclic supercontinent-related processes from Columbia to Greater Gondwana. Most of the ca. 2.57 and 0.9–0.8 Ga granites are characterized by enriched zircon eHf(t) values of –5.7 to +0.9 and –5.2 to +7.1. Moreover, some of these granites show fractionated characteristics, with high silica contents (80.3–82.3 wt% and 73.9–75.2 wt%), indicating that these rocks were derived mainly from remelting of 3.6–2.7 Ga mature crustal materials and 1.6–2.0 Ga crustal materials without or with minor contribution of juvenile materials, respectively. On the basis of these new results, regional stratigraphy, and previously determined geochemical data and tectonic signatures, it is concluded that the Quanji Massif and the Central Qilian, Hualong and North Wulan terranes probably formed a coherent Qilian–Quanji block as the southeastern extension of the Tarim Craton initiated from the Neoarchean. We propose that from the Neoarchean to early Paleoproterozoic, the primal Qilian–Quanji block was formed by long-term arc-related magma emplacement and reworking of ancient mature crustal materials in southeastern Tarim Craton. Subsequently, the juvenile Tarim–Qilian–Quanji continent was involved in tectonic cycles during its involvement in the supercontinents of Columbia and Rodinia.