Anisian granodiorites and mafic microgranular enclaves in the eastern Kunlun Orogen, NW China: Insights into closure of the eastern Paleo–Tethys

Abstract

Granitoids and their mafic microgranular enclaves (MMEs) provide important insights into magmatic activity and tectonic evolution associated with accretionary orogens. Here we investigate the origin of Middle Triassic granodiorites and MMEs in the central segment of the eastern Kunlun Orogen (EKLO) in NW China, which is an important region to evaluate the history of closure of the Paleo–Tethys, through zircon U–Pb geochronology, major and trace element geochemistry, and Sr–Nd–Hf isotopes. Zircon U–Pb ages indicate the coeval formation of granodiorites and their MMEs during the Anisian (ca. 245 Ma). The granodiorites are calc‐alkaline and metaluminous with high SiO2 contents and Mg# values. They are characterized by enrichment of LREEs and LILEs, and depletion of Nb, Ta, and Ti. Their Sr–Nd –Hf isotopic compositions indicate that the magmas were derived from enriched mantle and Paleoproterozoic basement. The monzodioritic‐dioritic MMEs exhibit low SiO2 contents and high Al2O3 and MgO with high Mg# values, enrichment in LREEs and LILEs, and depletion in HFSEs with negative Nb, Ta, Ti, and P. In contrast, the gabbroic MMEs show higher Mg# values and Cr contents. Both types of MMEs have Sr–Nd–Hf isotopic compositions similar to the host granodiorites, and originated from mixing of lower crust‐ and enriched mantle‐derived magmas. The mantle‐derived sources were metasomatized by slab‐derived melts. The Middle Permian to Middle Triassic magmatism, metamorphism, sedimentation, and tectonics in the EKLO suggest northward subduction of the Paleo–Tethys Ocean as represented by the A'nyemaqen Ocean. The magma mixing that generated the Anisian granodiorites and MMEs was likely associated with slab break‐off of the Paleo–Tethys Ocean. The formation of the Anisian magmatic rocks in the EKLO suggest that the cessation of subduction of the Paleo–Tethys Ocean and onset of collision took place during the late stage of Middle Triassic.

Geochemistry, geochronology, and Hf isotope of diorites in the Marzheng area: Implications for the Early Palaeozoic tectonic evolution of the East Kunlun Orogenic Belt

“…Moreover, there are Early Palaeozoic (ca. 555–420 Ma) subduction‐related granodiorite and diorite, and a battery of Triassic post‐collisional plutons are widely exposed in the South Kunlun Belt (Chen et al, 2018; Dong, He, et al, 2018; Li et al, 2007, 2020; Li, Huang, Luo, Dong, & Mo, 2015; Song et al, 2020).…”

Petrogenesis and tectonic implications of the quartz diorites and mafic microgranular enclaves in the Asiha gold ore deposit in the East Kunlun orogenic belt: Evidence from zircon U–Pb dating, geochemistry, and Sr–Nd–Hf isotopes

“…W. Chen, Luo, Mo, Liu, & Ke, 2005; Y. J. Li et al, 2020;Shao et al, 2017;Xia et al, 2014Xia et al, , 2017Xin et al, 2019;Xiong et al, 2012;Yao et al, 2018;J. Y. Zhang, Yang, et al, 2017;Zhou et al, 2020).…”

“…Voluminous Permian to Late Triassic igneous rocks are widespread in the EKOB, which are interpreted to be associated with subduction and collision during the Palaeo‐Tethys evolution. The intermediate–acid rock types consist of granodiorite, quartz diorite, monzogranite, tonalite, and syenogranite (Y. P. Dong et al, 2018; Feng, Wang, Li, Ma, & Li, 2012; Huang et al, 2014; Yu et al, 2017), in which MMEs are abundant (G. C. Chen, Pei, Li, Li, Liu, Chen, et al, 2017; G. C. Chen, Pei, Li, Li, Liu, et al, 2018, G. C. Chen, Pei, Li, Li, Pei, et al, 2018; H. W. Chen, Luo, Mo, Liu, & Ke, 2005; Y. J. Li et al, 2020; R. B. Li, Pei, et al, 2018; Shao et al, 2017; Xia et al, 2014, 2017; Xia, Wang, Qing, Li, et al, 2015; Xin et al, 2019; Xiong et al, 2012; Yao et al, 2018; J. Y. Zhang, Yang, et al, 2017; Zhou et al, 2020). The EKOB is one of the most important Triassic polymetallic metallogenic belts in China (X. D. Chen, Li, et al, 2020; H. Wang, Feng, Li, & Li, 2018; Y.…”

“…Mafic microgranular enclaves (MMEs) in intermediate–acid rocks are very common and widely distributed in accretionary orogens (Y. P. Dong et al, 2018; Lemirre, Cochelin, Duchene, Blanquat, & Poujol, 2019), which could be formed during different stages of subduction (Y. J. Li et al, 2020; R. B. Li, Pei, et al, 2018; Xia, Wang, Qing, Li, et al, 2015; Xiong, Ma, Zhang, & Liu, 2012), collision (G. C. Chen, Pei, Li, Li, Liu, et al, 2018; Xin et al, 2019; J. Y. Zhang, Yang, et al, 2017), or post‐collision extension environment (Xia et al, 2014). The MMEs are ubiquitous within calc‐alkaline peraluminous and metaluminous I‐type granitoids (Xia et al, 2014; Xia, Wang, Qing, Li, et al, 2015) and may provide unique insights into deep magmatic processes (Özdamar, Zou, Billor, & Hames, 2021).…”

Tectonomagmatic Setting and Cu-Ni Mineralization Potential of the Gayahedonggou Complex, Northern Qinghai–Tibetan Plateau, China

“…The aforementioned features correspond to the I-type granite in the EKOB during the same period. Furthermore, a geological field investigation reveals that mafic microgranular enclaves (MMEs), which are considered to have originated from the mixing of lower-crust-and enriched mantle-derived magmas, exist in the quartz diorite samples [55,56]. The Rb/Sr values of quartz diorite are between 0.04 and 0.07, which are significantly lower than the crustal ratio (5.36~6.55) [40].…”