Late Mesoproterozoic to early Neoproterozoic metamorphic history of the North Wulan terrane, NW China: New constraints on the evolution of Rodinia

Abstract

Late Mesoproterozoic to early Neoproterozoic metamorphic and magmatic events related to the assembly of Rodinia are identified in microcontinents (such as North Wulan terrane, Qaidam block, Central Qilian terrane, Quanji Massif, and Hualong terrane) from the northeastern Tibet Plateau. However, the peak P–T conditions, P–T paths, and timing of the metamorphic events are still controversial. In this contribution, we integrate petrography, phase equilibrium modelling, mineral chemistry and zircon geochronology to develop a detailed metamorphic history of felsic paragneiss and garnet amphibolite from the North Wulan terrane. Zircon U–Pb geochronology reveals two stages of metamorphism at 1.2–1.0 Ga and ∼0.9 Ga. The earlier metamorphic event caused granulite-facies metamorphism with peak P–T conditions of 800–850 °C at 8–10 kbar. The second metamorphic event (∼0.9 Ga) reached amphibolite-facies conditions at 700–750 °C and 6–7 kbar. Granulite-facies metamorphism probably took place in an arc-related setting, whereas amphibolite-facies metamorphism was likely associated with tectonic extrusion during the collision between the North Wulan terrane and unknown continental fragments. The North Wulan terrane and surrounding continental blocks/fragments in the northeastern Tibet Plateau share a similar evolution that includes long-lived oceanic subduction from 1.2 to 1.0 Ga followed by continental collision at ∼0.9 Ga at the periphery of Rodinia. Our results improve the understanding of the tectonic processes responsible for microcontinent evolution in the northeastern Tibet Plateau during the assembly of Rodina, and provide important constraints on the reconstruction of Rodinia.