Metamorphic evolution and geochronology of the Dunhuang orogenic belt in the Hongliuxia area, northwestern China

Wang, Hao; Wang, Juan; Wang, Guo-Dong; Lu, Jun‐Sheng; Chen, Hong‐Xu; Peng, Tao; Zhang, Hui C.G.; Zhang, Qian W.L.; Xiao, Wenjiao; Hou, Quanlin; Yan, Quanren; Zhang, Qing; Wu, Chun‐Ming

doi:10.1016/j.jseaes.2016.12.014

Cited by 46 publications

(41 citation statements)

References 79 publications

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“…Recent research indicates that the Hongliuxia block to the south and the Qingshigou block to the southwest of the Dunhuang orogenic belt underwent high-pressure metamorphism during the Paleozoic; the Paleozoic high-pressure mafic granulites and amphibolites enclosed by metasediments all record clockwise pressure-temperature-time (P-T-t) paths, typical of orogenic metamorphism (H.Y.C. Wang et al, 2016Wang et al, , 2017aWang et al, , 2017b. The Dunhuang orogenic belt was previously considered to be a tectonic mélange belt formed in a subduction zone, and to possibly represent the southernmost Central Asian orogenic belt (H.Y.C.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The Dunhuang orogenic belt was previously considered to be a tectonic mélange belt formed in a subduction zone, and to possibly represent the southernmost Central Asian orogenic belt (H.Y.C. Wang et al, 2016Wang et al, , 2017aWang et al, , 2017b. Nevertheless, most of the other blocks (Dahongshan, Mingshashan, Mogutai, and Dongbatu) remain poorly explored, which in turn limits our understanding of the tectonic evolution of the Dunhuang orogenic belt in the Paleozoic.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…As outlined by H.Y.C. Wang et al (2017a), tectonic mélange can be identified by interruption of metamorphic strata, chaotic gathering of metamorphic lenses of discontinuous metamorphic facies, sharp contacts of schistosity and/or gneissosity between different metamorphic rocks, or a high angle of schistosity and/or gneissosity between the metamorphic lenses and the matrix. One of the most prominent features of tectonic mélange is the huge diversity of metamorphic peak pressure-temperature (P-T) conditions or metamorphic ages of the metamorphic rocks possibly amalgamated during tectonic exhumation.…”

Section: Introductionmentioning

confidence: 99%

“…One such typical tectonic mélange is exposed in the Hongliuxia block, southern Dunhuang orogenic belt, southernmost Central Asian orogenic belt, northwest China (H.Y.C. Wang et al, 2017a).…”

Section: Introductionmentioning

confidence: 99%

“…One is the tectonic mélange exposed in the Hongliuxia block (H.Y.C. Wang et al, 2017a), and the other is exposed in the Dongbatu and Mogutai blocks. In this paper, we report the metamorphic P-T paths and geochronology of the tectonic mélange exposed in the Dongbatu and Mogutai blocks, middle Dunhuang orogenic belt.…”

Section: Introductionmentioning

confidence: 99%

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Metamorphic evolution and geochronology of the tectonic mélange of the Dongbatu and Mogutai blocks, middle Dunhuang orogenic belt, northwestern China

Wang

Zhang

et al. 2018

Geosphere

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Mafic granulite and amphibolite in the Dongbatu and Mogutai blocks, middle Dunhuang orogenic belt, northwest China, southernmost Central Asian orogenic belt, occur as lenses within the matrix of metapelite and marble, exhibiting typical block-in-matrix fabrics of tectonic mélange. Three stages of metamorphic mineral assemblages were identified in these lenses. Clockwise metamorphic pressure-temperature (P-T) paths were obtained through geothermobarometry and thermodynamic pseudosection modeling, passing from 656 °C and 10.9 kbar through 830 °C and 16.5 kbar to 657 °C and 4.9 kbar for the mafic granulite, and from 564-645 °C and 3.2-9.6 kbar through 634-727 °C and 6.1-14.2 kbar to 615-664 °C and 3.2-4.2 kbar for the amphibolites, respectively. Metamorphic peak P-T conditions in the metapelitic country rocks were estimated to be 635-675 °C and 6.0-6.9 kbar. The metamorphic peak of the mafic granulite approaches the high P-T facies series, indicative of a subduction zone. Secondary-ion mass spectrometry and laser ablationinductively coupled plasma-mass spectrometry U-Pb dating of metamorphic zircons suggests that the metamorphic event occurred between ca. 420 and 372 Ma. These data further certify that the subduction of the continental margin and subsequent uplift of the Dunhuang orogenic belt represent a longlived tectono-metamorphic event in the Paleozoic.

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Section: Geological Backgroundmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Metamorphic evolution and geochronology of the tectonic mélange of the Dongbatu and Mogutai blocks, middle Dunhuang orogenic belt, northwestern China

Wang

Zhang

et al. 2018

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Palaeozoic diorites from the south‐western Dunhuang terrane, NW China: Constraints on tectonic evolution of southernmost CAOB

et al. 2019

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The petrology, geochemistry, zircon U-Pb geochronology, and Hf isotopes of Duobagou diorite and Karatashtage diorite were studied to establish the evolution of Palaeozoic orogeny in the Dunhuang area in Western China. The weighted mean 206 Pb/ 238 U age of 448 ± 2 Ma in zircon grains from Duobagou diorite indicated an origin in the late Ordovician Period; age-corrected ε Hf (t) values of −0.98 to +4.46 correspond to a two-stage zircon Hf model age (T DM2 ) of 1,145 Ma to 1,477 Ma. Karatashtage diorite has a weighted mean 206 Pb/ 238 U age of 436 ± 3 Ma, indicating an origin in the early Silurian Period; age-corrected ε Hf (t) values of −1.13 to +7.96 correspond to a two-stage zircon Hf model age (T DM2 ) of 718 Ma to 1,301 Ma. These findings indicate that Duobagou and Karatashtage diorites were derived from ancient crust. Duobagou diorite has high levels of Al 2 O 3 (15.76%~17.64%), MgO (2.18%~5.44%), Mg # (40~51), Na 2 O (2.78%~4.19%), Sr (466~1,160 ppm), and Ba (523~892 ppm), low levels of K 2 O (1.29%~3.13%) and TiO 2 (0.64%~1.0%), variable levels of Cr (73.4~253 ppm) and Ni (42.2~98.8 ppm), and depleted HREEs. Karatashtage diorite is characterized by high levels of Al 2 O 3 (16.33%~17.59%), MgO (4.15%~7.10%), Mg # (50~59), Na 2 O (3.39%~4.41%), Cr (73.4~253 ppm), Ni (42.2~98.8 ppm), Sr (466~1,160 ppm), and Ba (523~892 ppm), low levels of K 2 O (1.29%~3.13%) and TiO 2 (0.64%~1.0%), and depleted HREEs. The Duobagou pluton and the Karatashtage pluton display arc signa-tures, suggesting that they were formed by the partial melting of a subducted slab under garnet-amphibolite facies in an active continental margin, and an interaction between melt and mantle materials during emplacement. Subduction of the oceanic plate in the Dunhuang terrane occurred during the Early Silurian Period (435-430 Ma), which is close to that of the Beishan orogenesis but later than the formation of the Hongliugou-Lapeiquan ophiolitic belt. We suggest that the Dunhuang terrane underwent an orogenic process related to the Palaeo-Asian Ocean during the Early Palaeozoic Era, and that it belongs to the Central Asian Orogenic Belt (CAOB).

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

Wang

Guo

et al. 2019

Geological Journal

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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.

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Metamorphic evolution and geochronology of the Dunhuang orogenic belt in the Hongliuxia area, northwestern China

Cited by 46 publications

References 79 publications

Metamorphic evolution and geochronology of the tectonic mélange of the Dongbatu and Mogutai blocks, middle Dunhuang orogenic belt, northwestern China

Metamorphic evolution and geochronology of the tectonic mélange of the Dongbatu and Mogutai blocks, middle Dunhuang orogenic belt, northwestern China

Palaeozoic diorites from the south‐western Dunhuang terrane, NW China: Constraints on tectonic evolution of southernmost CAOB

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

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