Geochronology and geochemistry of the Triassic volcanic rocks at the eastern margin of the Xing’an Massif, NE China: constraints on the spatial–temporal extent of the influence of the Mongol–Okhotsk tectonic regime

Abstract:

The Mongol–Okhotsk suture belt is located between the Siberian and the North China cratons and played an important role in the formation and tectonic evolution of the eastern part of the Eurasian continent during the Mesozoic. It was previously thought that subduction of the Mongol–Okhotsk oceanic plate beneath the Siberian Craton was north-directed throughout the entire period of subduction, but recent research has provided evidence of southward subduction beneath the Central Mongolia and Erguna massifs during the late Permian and early Mesozoic. However, the spatial and temporal extent of the influence of the Mongol–Okhotsk tectonic regime on NE China remains unclear. In this paper, we present new zircon U–Pb and geochemical data for Triassic volcanic rocks that crop out on the eastern margin of the Xing’an Massif to address the above-mentioned question.

Zircon U–Pb dating indicates that the Triassic volcanism in the Xing’an Massif occurred in two stages during the Middle (~240 Ma) and Late (~224 Ma) Triassic. Triassic volcanism consists of a suite of calc-alkaline trachybasalt and andesite, and are enriched in light rare earth elements (LREE) and depleted in high field strength elements (HFSE; e.g., Nb, Ta, Zr, and Hf), indicating an affinity to arc-type volcanic rocks. The Triassic volcanic rocks formed in an active continental margin setting associated with southward subduction of the Mongol–Okhotsk oceanic plate. Combined with the spatial and temporal variations of late Mesozoic igneous rocks in NE China, we conclude that the spatial extent of the influence of the Mongol–Okhotsk tectonic regime reached at least the eastern margin of the Xing’an Massif, and the temporal influence of this tectonism spanned from the late Permian to the early Early Cretaceous.

This research was financially supported by the National Natural Science Foundation of China (Grant 41330206) and Graduate Innovation Fund of Jilin University (Project 2015038).