Geochronology and geochemistry of the Late Devonian–Early Carboniferous volcanic rocks in Aksu River area, western end of the East Kunlun Orogen

Abstract

We present LA‐ICP‐MS zircon U–Pb dating, geochemical data for the Late Devonian–Early Carboniferous volcanic rocks in the Aksu River area, western end of the East Kunlun Orogen, with an aim to constrain the ages, petrogenesis, and tectonic setting of volcanic rocks and to comprehend the Late Devonian–Early Carboniferous tectonic evolution of the north branch of the Paleo‐Tethys Ocean. The Late Devonian–Early Carboniferous volcanic rocks are mostly composed of andesite and rhyolite. The new U–Pb ages show that the volcanic rocks formed in the Late Devonian–Early Carboniferous with ages of ca. 364–343 Ma. The volcanic rocks are classified as calc‐alkaline series. All of the volcanic rocks are characterized by enrichment in large‐ion lithophile elements (e.g., Rb, Ba, U, Sr, and K) and light rare earth elements and depletion in some high‐field‐strength elements (e.g., Nb, Ta, P, and Ti). The andesite samples have relatively high La/Nb (1.66–3.63) but low La/Ba (0.05–0.23) ratios, indicating the mantle source could be depleted mantle, and it had been metasomatized before partial melting. The rhyolite samples have low Nb/Ta and Zr/Hf ratios and Cr, Ni, and Co contents, which indicate that the material source was mainly crust derived and has experienced fractional crystallization process. Combined with our zircon U–Pb dating, geochemical data and geological field investigation, the tectonic setting of the Late Devonian–Early Carboniferous volcanic rocks is possibly related to the subduction process. Furthermore, the Paleo‐Tethys oceanic crust between the Bayan Har and East Kunlun‐Qaidam terrane northward subducted beneath the East Kunlun‐Qaidam terrane in the Late Devonian–Early Carboniferous, and the north branch of the Paleo‐Tethys Ocean between the Bayan Har and East Kunlun‐Qaidam terrane opening event should be earlier than this time (~364 Ma).

Petrogenesis and tectonic significance of the late Devonian‐early Carboniferous Jianxiashan pluton in the western domain of the eastern Kunlun Orogen, northern Tibetan Plateau

“…The granites are part of a tripartite association consisting of inboard S‐type granite, outboard oceanic arc, and intervening, turbidite‐filled back‐arc basin (Collins & Richards, ). Xu et al () reported 344–362 Ma arc volcanic rocks from the western part of the EKO and suggested the onset of the northward subduction of a north branch of the Paleo‐Tethys oceanic crust occurred earlier than 362 Ma. Jia, Meng, and Feng () studied the Wenquan Carboniferous ophiolites and suggested the existed of Carboniferous oceanic basin in the Central East Kunlun Fault zone.…”

“…During the late Devonian–early Carboniferous, the northward subduction of the Kunlun oceanic crust led to the formation of the Tuokuzidaban Group arc volcanic rocks (e.g., Wu et al, ; Wu, Zuza, et al, ; Xu et al, ). The Jianxiashan S‐type granites herald the slab retreat phase because the initial burst of mantle‐derived arc magmatism weakens the lithosphere along the arc locus (Figure ), which becomes the site for crustal extension as rollback progresses (Collins & Richards, ).…”

“…The Kuhai Group (Pt; Figure ) includes amphibolite‐facies gneiss, marble, schist, and metavolcanite assemblages that are in contact with each other due to a fault. The Carboniferous Tuokuzidaban Group (C 1 ; Figure ) consists mainly of low–grade metamorphic clastic rocks and limestone with massive pillow lavas (Xu et al, ). The Upper Carboniferous rocks (C 2 ; Figure ) are dominated by basal limestone and cross‐bedded arkosic and quartz sandstone with minor calcareous siltstone.…”

“…Its east–west extent is nearly 90 km, and it has a width of 3–15 km (Figure ). The pluton intrudes the late Paleoproterozoic Kuhai Group amphibolite‐facies gneiss and the pillow lavas of the Carboniferous Tuokuzidaban Group (Wu, Liu, et al, ; Xu et al, ). The wall rock xenoliths are widespread in the pluton (Figure a) and are mainly composed of gneisses and schists.…”

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

“…The granite‐MME associations have been widely documented in many complexes from Middle Permian to Late Triassic: the Naomuhun granodiorites and their MMEs (Xiong et al, 2012), the Qianwadaqiao granodiorites and their MMEs (G. C. Chen, Pei, Li, Li, Pei, et al, 2018), the Qushi'ang granodiorites and their MMEs (G. C. Chen, Pei, Li, Li, Liu, Chen, et al, 2017), the Harizha granodiorites and their MMEs (Xin et al, 2019), the Saishitang granodiorites and their MMEs (J. Y. Zhang, Yang, et al, 2017), and the Xiangride porphyritic granodiorites and their MMEs (Xiong, Ma, Zhang, Liu, & Jiang, 2014). The EKOB in the Qinghai‐Tibetan Plateau is considered to undergo multi‐stages of tectonic‐magmatic evolution (Y. X. Chen, Pei, Li, Li, Liu, & Wang, 2017; Y. P. Dong et al, 2018; Du et al, 2017; J. J. Kong, Niu, He, Zhang, & Shao, 2020; Z. C. Li, Pei, et al, 2017; Y. G. Liu et al, 2018, 2019; X. Xu et al, 2020; Z. W. Zhang et al, 2018; M. J. Zhang et al, 2021). The evolutionary history of the Palaeo‐Tethys within the EKOB has attracted considerable attention over the past decades (Y. P. Dong et al, 2018; Gao & Sun, 2021; Hu et al, 2016; Huang et al, 2014; J. J. Kong et al, 2020; H. L. Kong et al, 2021; Y. Y. Liang, Xia, Ma, Zhao, & Guo, 2020; Richards, 2015; Shao et al, 2017; Song et al, 2020; Tian et al, 2021; J. Y. Zhang, Ma, Xiong, & Liu, 2012; Zhao et al, 2019).…”