Final-Stage Magmatic Record of Paleo-Asian Oceanic Subduction? Insights from Late Permian to Early Triassic Intrusive Rocks in the Yanbian Area, Easternmost Central Asian Orogenic Belt

Abstract

This paper reports new zircon LA–ICP–MS U–Pb and Hf isotope data, and whole-rock major and trace element data for Late Permian to Early Triassic intrusive rocks in the Yanbian area, NE China. These data provide new insights into the timing of the final subduction of the Paleo-Asian Ocean beneath the North China Craton. The zircon U–Pb age data indicate that a suite of Late Permian to Early Triassic intrusive rocks related to subduction is present within the Yanbian area. The Late Permian intrusive rocks consist of diorites while the Early Triassic granites and hornblende gabbros constitute a geochemically bimodal igneous rock association. Furthermore, the Early Triassic granites show the geochemical characteristics of shoshonitic rocks. All the rocks are characterized by enrichment in LILEs and LREEs, and depletion in HREEs and HFSEs, suggesting they formed in a subduction setting. Zircons from the Early Triassic gabbros have εHf(t) values and TDM2 ages of +7.6 to +10.7 and 735–1022 Ma, respectively, suggesting that they formed from a primary magma generated by the partial melting of lithospheric mantle material that had been previously modified by subduction-related fluids. The Late Permian diorites have εHf(t) values and TDM2 ages of +0.5 to +9.5 and 853 to 1669 Ma, respectively, while they have high contents of Al2O3, Fe2O3, and low contents of SiO2, Cr, and Ni, indicating Late Permian diorites should derive from the mantle and are influenced by some crustal material. Early Triassic granitic rocks have a wide range of εHf(t) values and TDM2 ages of −4.8 to +9.4 and 852 to 2136 Ma, respectively. Their zircons imply that the Early Triassic granites could be mainly derived from partial melting of the crust, with minor contribution of the crustal material of an ancient crust. The Early Triassic bimodal intrusive rocks in Yanbian area, combined with the regional geologic information; therefore, record a final post-subduction extensional environment due to the break-off of the previously subducted slab.

Can Targeted Source Information Be Extracted From Superimposed Magnetic Anomalies?

“…Let ‖ ‖ denote the Schatten‐p norm. The Schatten‐p norm satisfies $${\Vert}{\Vert}={\left(\sum {\sigma }_{j}^{p}\right)}^{\frac{1}{p}},\quad (0< p\le 1)$$ (Xie et al., 2016; C. Zhang et al., 2020; H. Zhang et al., 2020; M. Zhang et al., 2020). If p = 1, the Schatten‐1 norm is a nuclear norm; if p = 0, the Schatten‐0 norm is equal to the rank.…”

“…The rank of seismic data in the frequency‐space domain is equal to the number of recorded linear events (Oropeza & Sacchi, 2011), which demonstrates the low‐rank feature of the seismic data. A number of optimization schemes have been proposed to recover the low‐rank component when performing seismic data denoising and reconstruction according to the data and noise types (Gao et al., 2013; Ma, 2013; Oboué et al., 2021; C. Zhang et al., 2020; H. Zhang et al., 2020; M. Zhang et al., 2020). Within the separation of potential field data, low‐rank matrix decomposition methods based on the respective low‐rank and sparse trajectory matrices of magnetic anomalies generated by deep and shallow sources have been proposed (Zhu et al., 2020).…”

“…The magnetic information of target sources recovered from the observed magnetic anomaly field is often used in geological research and mineral exploration (Li et al., 2021; Paoletti et al., 2016, 2020; Wang et al., 2020). For example, igneous rocks usually contain a range of different lithologies and distributions in horizontal and vertical directions (C. Zhang et al., 2020; Feng & Zheng, 2021; H. Zhang et al., 2020; M. Zhang et al., 2020), and large‐scale magma chambers generally form at great depth, whereas smaller‐scale stocks and dikes typically occur at shallow depth. The magnetic susceptibility of a rock is determined by its mineral composition, and the natural remanent magnetic field reflects the geomagnetic information during rock formation (Liu et al., 2018).…”

Conversion of Natural Wetland to Farmland in the Tumen River Basin: Human and Environmental Factors

“…Since China and South Korea formally established diplomatic relations in 1992, Korean-Chinese farmers have increasingly sought nontraditional livelihoods. Diversified development means that many rural Korean-Chinese farmers have gradually abandoned rice cultivation, have gradually moved out of rural villages, and have migrated to South Korea to seek employment [39,40]. This decrease in the agricultural labor force of the TRB has led to a reduction in farmland cultivation.…”

The Late Triassic Molasse Deposits in Central Jilin Province, NE China: Constraints on the Paleo-Asian Ocean Closure

“…In one school of thought, the final closure occurred prior to the Permian, mainly including before the Late Devonian and between the Late Devonian [54][55][56] and Early Carboniferous [57][58][59]. In an alternative view, the closing of the PAO occurred during the Permian-Triassic, which can be reclassified as during the late Early Permian [60,61], during the Middle-Late Permian [62][63][64][65], during the Late Permian [4,34,48,66], during the Late Permian-Early Triassic [3,10,11,21,33,35,40,41,50,[67][68][69][70], during the Late Permian-Middle Triassic [5,22,25,26,28,32,42,71,72], and during the Middle-Late Triassic [20,24,37,49,73]. Therefore, substantial controversy remains regarding the closure time of the PAO along the CYS.…”