Permian back‐arc extension in central Inner Mongolia, NE China: Elemental and Sr–Nd–Pb–Hf–O isotopic constraints from the Linxi high‐MgO diabase dikes

Abstract

Early Permian (272 ± 2 Ma) diabase dikes from the Linxi area in central Inner Mongolia of NE China have high .2 -6.0 ‰ with an average of 5.7 ‰) than normal mantle. The combined geochemical data indicate their derivation from a depleted mantle metasomatized by recycled crustal component. Elemental and isotopic modeling results suggest that the primary magma was produced through 5 % to 10 % melting of a depleted mantle, which contained approximately 1 % sediment fluid released from the subducted paleo-Asian Ocean. Considering the widespread distribution of contemporaneous mafic rocks across the central Inner Mongolia, which show REE patterns from E-MORBs to normal MORBs, we propose a petrogenetic link between the Early Permian mafic magmatism and a back-arc extension in response to northward subduction of the paleo-Asian Ocean. The Permian mafic magmatism and the new age constraints from the metamorphic and sedimentary records in this area tend to indicate the ultimate closure of the paleo-Asian Ocean by the end of Paleozoic.

Geochemical evolution of the Late Carboniferous to Early Permian igneous rocks from the Baolidao magmatic belt, eastern Central Asian Orogenic Belt

“…This tectonic model is different from the “back‐arc extension model” proposed for the end Early Permian diabase dykes from Linxi by Li, Guo, Li, Zhao, & Huang (2015) and for the Late Palaeozoic A‐type granite belt by Zhang et al (2013). In fact, a back‐arc magma suite should be associated with an arc volcanic front system.…”

Variable sediment flux in generation of Permian subduction-related mafic intrusions from the Yanbian region, NE China

“…Several hypotheses, including the middle Devonian (e.g., Xu et al, 2013a), between the late Devonian and early Carboniferous (e.g., Tang, 1990), or even in the late Permian to Triassic (e.g., Zhou and Wilde, 2013;Eizenhöfer et al, 2014;Wilde, 2015), have been proposed. In NE China, especially in the central Mongolia, the Permian mafic rocks show geochemical and isotopic features of N-MORBs and E-MORBs, reflecting the existence of oceanic basin at that time (Chen et al, 2012;Li et al, 2015). Permian arc magmatism along the northern margin of the North China Craton suggested a Cordillera-type active continental margin related to subduction of the paleo-Asian Ocean (Zhang et al, 2009).…”

Early Permian back‐arc extension in the southeastern Central Asian Orogenic Belt: Evidence from the gabbro–granite complex, Xilinhot, Inner Mongolia, China

“…Some scholars have proposed that PAO evolution terminated in the Middle or Late Devonian to Early Carboniferous, followed by a continental rift or post‐orogenic extension during the Late Palaeozoic (Shao, Tian, Tang, & Wang, 2015; Xu, Charvet, Chen, Zhao, & Shi, 2013; Zhang, Zhang, Tang, Wilde, & Hu, 2008; Zhao, Xu, Tong, Chen, & Faure, 2016). In contrast, it has also been suggested that the PAO experienced sustained bidirectional dipping‐subduction during the Late Palaeozoic, and finally terminated in the Late Permian to Early–Middle Triassic (Eizenhöfer et al, 2015; Li, Guo, Li, Zhao, & Huang, 2015; Liu, Li, et al, 2017; Xiao et al, 2003; Zhang et al, 2020). Therefore, the southeastern CAOB tectonic attributed in the Late Palaeozoic (in particular, the Early Permian) is a key to decipher the PAO evolution and identify these different models.…”