Zircon U–Pb dating, geochemical, and Sr–Nd isotopic characteristics of Duobagou trachyandesite from Dunhuang, NW China: Implications for crust–mantle interaction

Abstract

Comprehensive petrological, zircon U-Pb dating, whole-rock geochemical, and Sr-Nd isotopic data are reported for the Duobagou volcanic rocks, intercalated with terrigenous clastic sequence, composing former Jurassic strata located at southeastern Dunhuang region, NW China. Duobagou volcanic interlayer is mainly composed of trachyandesite. LA-ICP-MS zircon dating yields a weighted mean 206 Pb/ 238 U age of 201.4 ± 3.4 Ma, affirming the formation of Late Triassic. The trachyandesites are characterized by enrichment of LREE relative to HREE with negative Eu, Sr, and Ti anomalies. The ε Nd (t) values (−0.24-1.91) and ( 87 Sr/ 86 Sr) i (0.7037-0.7049) shows an affinity of OIB. The Duobagou trachyandesite and Lucaogou basalt were proposed to be produced via 1-5% and 10-20% partial melting of the spinel-garnet-bearing metasomatic enriched mantle and crystal fractionation coupled with slight extents of crustal contamination. Due to the delamination of thickened continental crust and asthenosphere upwelling, lower crustal material metasomatized and enriched the mantle source, leading to the eruption of trachyandesite. The Duobagou trachyandesite, Lucaogou sub-alkaline basalt and thick sedimentary strata revealed that the Dunhuang region remained in an extension setting accompanied by rifting from Late Triassic to Middle Jurassic.

Jurassic Evolution of the Dunhuang Basin and Its Implications for the Early History of the Altyn Tagh Fault, Northeast Tibet Plateau

“…The younger age group results are in high accordance with the zircon age spectrum for the granites and modern rivers in the Bei Shan area. Although several researchers have reported on the existence of Permian‐Triassic granites in the Sanwei Shan area (L. M. Feng et al., 2020; Y. X. Wang et al., 2019; Z. D. Wang et al., 2021; Q. W. L. Zhang et al., 2020, 2022), the long distance from the Daba Sag, small exposure of the granites and main granite age range of 350–430 Ma indicate that the Sanwei Shan is unlikely to provide detritus for the Daba Sag during the Late Jurassic.…”

“…274 Ma may have originated from Permian granites in nearby areas (Y. X. Wang et al., 2019; Z. D. Wang et al., 2021). However, a distinct peak age of 253 Ma ranging from 245 to 291 Ma in the lenticular sandstone samples is present in northern Duobagou, and this age group was likely derived from the Bei Shan and Permian‐Triassic granites in Sanwei Shan (L. M. Feng et al., 2020; W. T. Wang et al., 2016; Y. X. Wang et al., 2019; Z. D. Wang et al., 2021; Q. W. L. Zhang et al., 2020, 2022) (Figure 10g). The schists and marble in the gravels are the principal lithologic composition of the Dunhuang Group, which is exposed in the Sanwei Shan (Figure 2b), and the vein quartz and granite are the intrusions of the schist of the Dunhuang Group (Y. Zhao et al., 2016, 2017).…”

“…Zhao et al, 2017). Recently, studies have reported high-K calc-alkaline I-type granitoid intrusions in the Dongbatu and Duobagou regions during the early and Late , which are interpreted as arc/subduction-related and postcollisional extensional settings, respectively (L. M. Feng et al, 2020;Y. X. Wang et al, 2019;Q.…”

“…284–273 Ma) and Late Permian–Middle Triassic (ca. 255–238 Ma), which are interpreted as arc/subduction‐related and postcollisional extensional settings, respectively (L. M. Feng et al., 2020; Y. X. Wang et al., 2019; Z. D. Wang et al., 2021; Q. W. L. Zhang et al., 2020, 2022).…”

Origins of the meta‐mafic rocks in the southern Dunhuang Block (NW China): Implication for tectonic framework of the southernmost Central Asian Orogenic Belt

“…The Carboniferous granitoids are ascribed as the collisional intrusions formed by partial melting of the thickened lower crust (Bao et al, 2017; Wang et al, 2016a; Wang et al, 2016b; Zhang, Guo, Zou, Feng, & Li, 2009; Zhao, Sun, Diwu, et al, 2017; Zhu, Wang, Xu, Chen, & Li, 2014). Besides, the Early‐Mesozoic magmatic rocks are also distributed in different locations of the Dunhuang Block, which is suggested to be formed by the delamination of thickened continental crust and asthenosphere upwelling in the extension setting (Feng et al, 2018; Wang, Guo, Yu, & Zhang, 2020). The similar Palaeozoic–Mesozoic magmatic rocks are widely identified in the adjacent Beishan–Tianshan Orogen: 438–397 Ma granitoids in Beishan (Liu et al, 2011; Zhang & Guo, 2008; Zhao, Guo, & Wang, 2007), ~ 370 Ma volcanic rocks in the Dundunshan arc, south of Beishan (Guo et al, 2014, 2017), Silurian and Late Devonion granitoids in the central Tianshan (Shi et al, 2007), and Permian–Triassic magmatism in Beishan–Tianshan Orogen (Chen, Shu, & Santosh, 2011; Li et al, 2012; Li, Wang, Wilde, & Tong, 2013; Mao et al, 2014).…”