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  • 1. Meng, Qingpeng
    et al.
    He, Yuankai
    Zhang, Wen
    Stockholm University, Faculty of Science, Department of Geological Sciences. Peking University.
    Zheng, Rongguo
    Xu, Cao
    Zhang, Zhaoyu
    Wu, Tairan
    Time constraints on the inversion of the tectonic regime in the northern margin of the North China Craton: Evidence from the Daqingshan granites2014In: Journal of Asian Earth Sciences, ISSN 1367-9120, E-ISSN 1878-5786, Vol. 79, p. 246-259Article in journal (Refereed)
    Abstract [en]

    The Daqingshan granites are located in a late Mesozoic tectono-magmatic belt at the northern margin of the North China Craton (NCC), and include the Deshengying, Xinisubei, Gulouban, and Kuisu plutons. Ion probe U-Pb zircon dating indicates that the granites were emplaced at 131 +/- 1, 140 +/- 4, 145 +/- 1, and 142 +/- 2 Ma, respectively. All of the granites are alkali- and potassium-rich, with high SiO2 (73.2-76.7 wt.%), K2O (4.50-5.57 wt.%), Na2O (3.60-4.93 wt.%), and K2O/Na2O (0.99-1.49), and low Al2O3 (12.3-14.5 wt.%), CaO (0.45-0.79 wt.%), and MgO (0.12 wt.%). The granites are light rare earth element enriched a La/YbIN = 5.6-48.7). The Xinisubei and Gulouban monzogranites and the Kuisu mylonitic monzogranite have small Eu anomalies (8Eu = 0.65-1.23), low Zr + Nb + Ce + Y (132-321 ppm), and exhibit a negative correlation between P2O5 and SiO2 contents, which are characteristic of highly fractionated I-type granites with a post-collisional origin. The Deshengying monzogranite is distinctive in being an aluminous A-type granite as evidenced by high 10,000 x Ga/AI (>2.6) and Zr + Nb + Ce + Y (312-532 ppm), low Ba and Sr, marked negative Eu anomalies (8Eu = 0.08-0.20), strong Ba, Sr, P, and Ti depletions, and an absence of alkali minerals. This granite was probably produced by partial melting of continental crust heated by hot mantle-derived magmas during crustal extension. The Deshengying monzogranite represents a post-kinematic pluton emplaced into the Daqingshan fold-and-thrust belt, whereas the Kuisu mylonitic monzogranite is a syn-kinematic pluton intruded along the Hohhot detachment fault. It is evident that the Daqingshan area experienced a change from a compressional to an extensional tectonic regime during 145-140 Ma. The post-orogenic collapse may have resulted in extension of the upper continental crust. Subsequently, as the thrust-detachment system became inactive, the lower crust of the NCC underwent modification and melting from 131 Ma. We conclude that the Early Cretaceous tectonic evolution of the Daqingshan area was caused by post-orogenic collapse and melting of the lower crust of the NCC. Delamination of the lower crust in the northern NCC resulted in crustal extension and asthenospheric upwelling, which produced A-type granites. As such, melting of the lower crust in the northwestern part of the NCC took place as early as the late Mesozoic.

  • 2.
    Zhang, Wen
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Chinese Academy of Geological Sciences, China; Peking University, China.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meng, Qingpeng
    Zheng, Rongguo
    Thomsen, Tonny B.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Geological Survey of Denmark and Greenland, Denmark.
    Wohlgemuth-Ueberwasser, Cora
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wu, Tairan
    Discovery of a Neoproterozoic granite in the Northern Alxa region, NW China: its age, petrogenesis, and tectonic significance2016In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 153, no 3, p. 512-523Article in journal (Refereed)
    Abstract [en]

    A Neoproterozoic granite (Western Huhetaoergai granite) from the Northern Alxa region, southern Central Asia Orogenic Belt (CAOB) is first recognized by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb zircon dating (889±8 Ma). It is a highly fractionated potassium-rich calc-alkaline pluton with low εNd(t) (−2.6 to −1.1) and high (87Sr/86Sr) t (0.727305–0.735626), and is probably derived from a mantle source and assimilated crustal rocks with very high 87Sr/86Sr. Regional geology implies that it may reflect the existence of a microcontinent, and the formation of the Western Huhetaoergai granite is related to the assembly of Rodinia.

  • 3.
    Zhang, Wen
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Chinese Academy of Geological Sciences, China; Peking University, China.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meng, Qingpeng
    Zheng, Rongguo
    Thomsen, Tonny B.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wohlgemuth-Ueberwasser, Cora
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wu, Tairan
    Timing, petrogenesis, and setting of granites from the southern Beishan late Palaeozoic granitic belt, Northwest China and implications for their tectonic evolution2015In: International Geology Review, ISSN 0020-6814, E-ISSN 1938-2839, Vol. 57, no 16, p. 1975-1991Article in journal (Refereed)
    Abstract [en]

    Late Palaeozoic granites are widely distributed in the southeastern Beishan area, which is located in the central part of the southern Central Asian Orogenic Belt (CAOB). U–Pb zircon dates of five late Palaeozoic granitic plutons from the southeastern Beishan area yield Permian ages: 285 ± 2 Ma (Shuwojing and Western Shuwojing plutons), 269 ± 3 Ma (Jianquanzi and Jiuquandihongshan plutons), and 260 ± 1 Ma (Jiujing pluton). The early Permian Shuwojing pluton, an unfractionated calc-alkaline biotite monzogranite with slightly positive εNd(t) (+0.7 and +0.6) and low initial 87Sr/86Sr (0.70722 and 0.70712), and the early Permian Western Shuwojing pluton, a high-K calc-alkaline biotite granite with slightly negative εNd(t) (−0.2 and −0.1) and low initial 87Sr/86Sr (0.70390 and 0.70919), are likely derived from a mixture of depleted (juvenile) mantle and upper continental crustal (or sedimentary) material. The mid-Permian Jianquanzi and Jiuquandihongshan monzogranites have highly fractionated potassium-rich calc-alkaline characteristics with negative εNd(t) (−4.3) and very high initial 87Sr/86Sr (0.71949), reflecting a continental crustal component. The compositionally diverse Jiujing pluton and the granodiorite and high-Sr monzogranite phases display adakite-like compositions with relatively low εNd(t) (−0.1 and −2.2) and high initial 87Sr/86Sr (0.70822 and 0.70913). The Jiujing low-Sr monzogranite has higher initial 87Sr/86Sr (0.73464) and lower εNd(t) (−2.8), indicating a significant continental crustal component in its genesis. This work, combined with the regional geology and previous studies, suggest that the early to middle Permian southern Beishan plutons formed in a post-collisional environment, probably an intracontinental rift environment linked to asthenospheric upwelling in response to the break-off of a subducted slab. In the late Permian, the southern Beishan area was in a compressive tectonic regime and thickening of the continental crust resulted in the formation of the Jiujing adakite-like granite.

  • 4.
    Zhang, Wen
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Chinese Academy of Geological Sciences, China; Peking University, China.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meng, Qingpeng
    Zheng, Rongguo
    Wu, Tairan
    Chen, Yan
    Gan, Lisheng
    Age and petrogenesis of late Paleozoic granites from the northernmost Alxa region, northwest China, and implications for the tectonic evolution of the region2017In: International journal of earth sciences, ISSN 1437-3254, E-ISSN 1437-3262, Vol. 106, no 1, p. 79-96Article in journal (Refereed)
    Abstract [en]

    The Wudenghan, Huhetaoergai and Zhuxiaobuguhe plutons, northern Alxa region, in the southern Central Asia Orogenic Belt are dated by U-Pb zircon to 383 +/- 3, 356 +/- 3 and 286 +/- 2 Ma, respectively. The late Devonian Wudenghan monzogranite, a highly fractionated I-type granite with epsilon (Nd)(t) (-0.2 to -0.1) and very low (Sr-87/Sr-86) (t) (0.704719-0.706113), is from mantle-derived magmas and shows volcanic arc characteristics. The early Carboniferous Huhetaoergai granodiorite with medium-K calc-alkaline peraluminous characteristics represents a volcanic arc granite generated from partial melting of lower continental crust combined with mantle-derived input. The early Permian Zhuxiaobuguhe pluton, an unfractionated calc-alkaline granodiorite with moderately low epsilon (Nd)(t) (-2.0 to -1.1) and low (Sr-87/Sr-86) (t) (0.708370-0.708462), was likely derived from partial melting of the mafic lower crust of a paleo-volcanic arc and represents a post-collisional granite. Our revised tectonic evolution of the region includes (1) northward subduction of the oceanic crust represented by the Engger Us Ophiolitic Belt and formation of the late Devonian Wudenghan monzogranite, (2) northward subduction of the ocean between the Huhetaoergai and Zhusileng tectonic zones and the formation of the Huhetaoergai volcanic arc granite during the early Carboniferous and (3) the emplacement of the Zhuxiaobuguhe pluton in the early Permian during post-collisional extension.

  • 5.
    Zhang, Wen
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Chinese Academy of Geological Science, China.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Whitehouse, Martin J.
    El-Sankary, Mohamed M.
    Shalaby, Mahmoud H.
    Pre-Neoproterozoic basement evolution of southwestern Egypt2019In: International Geology Review, ISSN 0020-6814, E-ISSN 1938-2839, Vol. 61, no 15, p. 1909-1926Article in journal (Refereed)
    Abstract [en]

    The only surviving Archaean fragment of the Saharan Metacraton is exposed in the Uweinat-Kamil Mountains of Egypt, Libya, and Sudan. To expand our knowledge of this rare Archaean crustal fragment, we investigate protolith ages and the timing of metamorphic events associated with it via U-Pb zircon geochronology and geochemistry of 10 samples from the Egyptian part of the Uweinat-Kamil region. Our work confirms that the orthogneisses represent a tonalite, trondhjemite, granodiorite (TTG) and granite suite of Archaean-early Paleoproterozoic age (3.25-2.49 Ga). Late Paleoproterozoic rocks include 2.15-2.00 Ga paragneiss, 2.00 Ga metagranite and 1.99 Ga trondhjemitic leucosome. Neodymium isotopes from the 3.25 Ga orthogneiss record an entirely juvenile mantle signature, whereas the 2.91 and 2.49 Ga orthogneisses record significant juvenile mantle input, and 2.86-2.68 Ga orthogneisses reflects recycling of older crustal rocks. At c. 2.0 Ga, a magmatic and metamorphic event associated with anatectic partial melting occurred in northern Africa, assimilating both granitic and leucocratic gneiss of the Archaean TTG crust. Detrital input contributing to the paragneiss was mainly from Uweinat-Kamil TTG rocks and sources to the east-southeast. The oldest 3.42 Ga detrital zircon from the paragneiss probably reflects the conjoined Saharan Metacraton-Congo craton.

  • 6.
    Zhang, Wen
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wu, Tairan
    Zheng, Rongguo
    Feng, Jicheng
    He, Yuankai
    Luo, Hongling
    Xu, Cao
    Discovery of an adakite-like pluton near Dongqiyishan (Beishan, NW China) - Its age and tectonic significance2012In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 142, p. 148-160Article in journal (Refereed)
    Abstract [en]

    The Dongqiyishan granitic pluton is exposed in the Eastern Beishan area, in the central part of the Southern Central Asia Orogenic Belt. SIMS U-Pb zircon dating indicates that the Dongqiyishan pluton was emplaced at 356 +/- 2 Ma. Geochemically the pluton is calc-alkaline and characterized by high SiO2 (> 65%), Al2O3 (mostly > 15%), Na2O/K2O ratios (1.3-3.9) and Sr (generally > 400 ppm). Samples display positive to weakly negative Eu anomalies (delta(Eu) = 0.81-2.32). low HREE, Y and Yb (Y < 18 ppm, Yb < 1.9 ppm), are enriched in LREE, LILE (Rb, Ba, Sr, U, and K), Zr, and Hf, and depleted in HFSE. They have relatively low epsilon(Nd)(t) values (-2.9-+ 0.6) and relatively high (Sr-87/Sr-86)(i) ratios (0.70581-0.70749). Together, these geochemical traits suggest an adakite-like composition that reflects melting of subducted oceanic crust and the involvement of older continental material. Assimilation and fractional crystallization (AFC) modeling requires significant crustal assimilation to modify an initial MORB-derived andesitic melt to produce the hybrid granitic melt, e.g. - the Dongqiyishan pluton. A back-arc basin to the south (represented by the Yueyashan-Xichangjing ophiolitic belt) closed before the Early Carboniferous Dongqiyishan adakite-like pluton was emplaced into the Silurian volcanic arc. Closure of the back-arc basin potentially provides the continental component seen in the isotopic signature of the Dongqiyishan pluton and required by the AFC modeling. Post-Ordovician flattening of the subducting slab together with crustal thickening from closure of the back-arc basin, led to the formation of a tightly coupled subducting slab and lower crust which resulted in the formation of Dongqiyishan adakite-like pluton. The Dongqiyishan pluton is consistent with southward subduction (represented by the Xiaohuangshan ophiolitic belt) and indicates that oceanic crust was still being produced in the Paleo-Asian Ocean during the Early Carboniferous. Adakite-like granitic rocks may be more abundant than previously thought in the Beishan region.

  • 7.
    Zhang, Wen
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Chinese Academy of Geological Sciences, China.
    Roberts, D.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Provenance characteristics and regional implications of Neoproterozoic, Timanian-margin successions and a basal Caledonian nappe in northern Norway2015In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 268, p. 153-167Article in journal (Refereed)
    Abstract [en]

    The autochthonous/parautochthonous lithostratigraphic successions of Varanger Peninsula, NE Norway, range in age from Tonian to Cambrian and constituted a passive (Baltican) margin depositional system throughout most of the Neoproterozoic. Sediment sources were mainly from the south on the Fennoscandian Shield. U-Pb zircon age spectra from sandstones of eight formations show significant input of Late Palaeoproterozoic and Mesoproterozoic age, as well as a prominent Neoarchaean peak. These mostly reflect derivation from rock complexes and terranes that are exposed on the present-day Baltic Shield, although the abundance of Mesoproterozoic zircon grains is less easy to explain. Possible sources may represent (i) possible basement of this age now concealed beneath the Caledonian nappes, (ii) a northward continuation of the Sveconorwegian orogen, (iii) recycling of a sandstone-dominated thrust sheet derived from the Rodinian margin and emplaced in the Tonian or (iv) recycled material from pre-existing extensive river systems farther south on the Fennoscandian Shield. One major exception to the above age-spectral pattern is provided by the Late Ediacaran to earliest Cambrian Stahpogieddi Formation in the immediately overlying Gaissa Nappe Complex. Sandstones in this unit are derived from a northeasterly source, and show a major zircon age peak at c. 550 Ma. The formation is considered to represent deposition in a foreland basin ahead of the rising Timanian orogen.

  • 8.
    Zhang, Wen
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Chinese Academy of Geological Sciences, China.
    Roberts, D.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Provenance of sandstones from Caledonian nappes in Finnmark, Norway: Implications for Neoproterozoic-Cambrian palaeogeography2016In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 691, p. 198-205Article in journal (Refereed)
    Abstract [en]

    U–Pb detrital zircon age spectra from four formations in the Laksefjord and Kalak nappe complexes, Finnmark Caledonides, northern Norway, show peaks ranging from Neoarchaean through Late Palaeoproterozoic to Late Mesoproterozoic. Together with an extensive database of palaeocurrent flow measurements indicating derivation of the sediments from source regions to the S-SE on the Fennoscandian Shield, the successions in the lower thrust sheets of the Kalak Nappe Complex and the entire Laksefjord Nappe Complex are inferred to be of Baltican origin. These results are contrary to a previous suggestion that the sandstone-dominated Middle Allochthon is exotic to Baltica.

    The lithostratigraphical successions in these two nappe complexes show a south to north progression from alluvial-fan conglomerates through extensive fluvial to shallow-marine facies into deeper-marine turbiditic sequences. This pattern reflects the palaeogeographic transition from the shallow platform to deep-basinal oceanic development recorded along the c. 2000 km pre-Timanian passive margin of the northeastern Fennoscandian Shield.

  • 9.
    Zhang, Wen
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wu, Tairan
    Zheng, Rongguo
    Feng, Jicheng
    Luo, Hongling
    He, Yuankai
    Xu, Cao
    Post-collisional Southeastern Beishan granites: Geochemistry, geochronology, Sr-Nd-Hf isotopes and their implications for tectonic evolution2012In: Journal of Asian Earth Sciences, ISSN 1367-9120, E-ISSN 1878-5786, Vol. 58, p. 51-63Article in journal (Refereed)
    Abstract [en]

    Bandaoshan granites are exposed in the Southeastern Beishan area, in the central part of the Central Asia Orogenic Belt (CAOB). LA-ICP-MS U-Pb zircon dating indicates that Bandaoshan granites were emplaced into Precambrian basement at 285 +/- 4 Ma and their geochemistry indicates that they are alkali-rich potassium-high granites. Initial epsilon(Nd) values (-4.3 to -2.7) and epsilon(Hf) values (-2.7 to +0.7) suggest that Bandaoshan granites were derived from mantle-derived melt and an upper continental crustal or sedimentary component. The latter plays a significant role in their genesis. In combination with regional geology, the Early Permian Bandaoshan pluton is interpreted to form in a post-collisional environment. In the Southeastern Beishan area Late Carboniferous Qiaowan granites, Early Permian Yin'aoxia granites and Middle Permian Xijianquanzi granites are also considered as post-collisional granites, and together with Bandaoshan granites indicate that the region was in a post-collisional stage from the end of Late Carboniferous to Middle Permian.

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