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| 1 | Detrital zircon age model of Ordovician Wenquan quartzite south of Lungmuco-Shuanghu Suture in the Qiangtang area, Tibet: Constraint on tectonic affinity and source regions显示文摘Early to Middle Ordovician strata, including Wenquan quartzite, occur widely in the Himalaya, Lhasa, and south Qiangtang blocks. The Wenquan quartzite occurs on the south side of the Lungmuco-Shuanghu Suture in the Qiangtang area, Tibet. A total of 145 analyses on detrital zircons from the quartzite show five age ranges of 520-700, ca. 800, 900-1100, 1800-1900, and 2400-2500 Ma, with particularly distinct age peaks of 625 and 950 Ma. The reliable youngest detrital zircon age is 525 Ma, and the oldest, 3180 Ma. Detrital zircons show large variations in Hf isotope composition, with depleted mantle model ages t DM (Hf) ranging from 750 to 3786 Ma. Based on data obtained in this study and by others, the main conclusions are as follows: 1) Low-grade metamorphic sedimentary rocks are distributed extensively in the south of the Lungmuco-Shuanghu Suture and are Phanerozoic in age; 2) Pan-African and Grenville-Jinning tectono-thermal events were well developed in the source region of the Wenquan quartzite; 3) the source region shows crustal addition and recycling of different periods; 4) Wenquan quartzite was derived from the Gondwana metamorphic basement, suggesting that the Qiangtang block is a Gondwanan fragment. | DONG ChunYan LI Cai WAN YuSheng WANG Wei WU YanWang XIE HangQiang LIU DunYi | 2011 | Science China Earth Sciences2011，54，7： | 39 |
| 2 | Pan-African and early Paleozoic tectonothermal events in the Nyainrong microcontinent:Constraints from geochronology and geochemistry显示文摘To better understand the Pan-African-early Paleozoic tectonothermal events of the Nyainrong microcontinent and the constraints on its tectonic evolution,here we report the results of zircon LA-ICP-MS U-Pb dating and geochemical features of Amdo gneiss in the Nyainrong microcontinent.The outcrops of Amdo gneiss is about 30 km south of Amdo County in northern Tibet.The field occurrence,mineral composition,textural characteristics,and whole-rock geochemical features of the four gneiss samples indicate the protolith of the gneisses is intermediate-acid intrusive rock.Gneiss zircon trace element tracing and genetic analysis shows that zircon has typical characteristics of magmatic zircon.The206Pb/238U concordant age of zircon is505–517 Ma,corresponding to the Middle-Late Cambrian,which is the formation age of the protolith.The samples have characteristics of high silicon,alkali-rich,alkalic rate AR=1.73–3.7,the differentiation index DI=70.78–90.28;rock aluminum saturation index ranges from 1.02 to 1.05,FeO/MgO ranges from 2.63 to 4.50,10000×Ga/Al ranges from 2.12 to 2.41,and P2O5and Al2O3content decreased with SiO2increasing.Th and Y contents have a good positive correlation with Rb content;the genetic type of protolith of the gneiss is the differentiation of subalkaline over aluminum I-type granite.Combined with regional data,the tectonic setting of the Amdo gneiss protolith is closely related to the collision orogenic process.The preliminary view is that the Middle-Late Cambrian magmatic events developed on the microcontinent could be the result of Andeantype orogeny along the Gondwana super-continental margin after the end of the Pan-African orogeny. | XIE ChaoMing LI Cai SU Li WU YanWang XIE YaoWu | 2013 | Science China Earth Sciences2013，56，12： | 11 |
| 3 | Opening of the Longmu Co–Shuanghu–Lancangjiang ocean:constraints from plagiogranites显示文摘This paper reports new zircon U-Pb ages,and Hf isotope and whole-rock major and trace element data for Cambrian plagiogranites from the Tuobeiling ophiolite in central Qiangtang,Tibetan Plateau.Zircon SIMS and LAICP-MS U-Pb dating of the plagiogranites yield weighted mean ages of 504.8±4.2 and 491.6±1.5 Ma,respectively.The zircons from plagiogranites exhibit positive eHf(t)values(ranging from 11.46 to 15.16),indicating that the plagiogranites are derived from depleted mantle.These plagiogranites are characterized by high SiO2and Na2O,low K2O,low REE contents,and flat REE distribution patterns.These rocks have geochemical compositions typical of oceanic plagiogranite and,considered along with their petrography and field relationships,are interpreted to have derived from anatexis of hydrated amphibolites by ductile shearing during transports of the oceanic crust.The formation age of such type of plagiogranite is slightly younger than that of the associated section of oceanic crust.Thus the new results from these plagiogranites suggest that the Longmu Co–Shuanghu–Lancangjiang ocean had probably opened before the Middle Cambrian. | Peiyuan Hu Cai Li Yanwang Wu Chaoming Xie Ming Wang Jiao Li | 2014 | Chinese Science Bulletin2014，59，25： | 9 |
| 4 | Petrology, Geochemistry and Tectonic Significance of the Metamorphic Peridotites from Longmuco-Shuanghu Ophiolitic Melange belt, Tibet显示文摘Taoxinghu metamorphic peridotite is a firstly reported mantle sequence of ophiolite since Longmuco-Shuanghu-Lancangjiang suture zone (LSLSZ) was proposed, and it is also an important discovered for ophiolite studying in central Qiangtang. Based on detailed analyses of whole-rock geochemistry of Taoxinghu metamorphic peridotites and contrast to metamorphic peridotites in typical ophiolites worldwide, the paper investigates their petrogenesis and geological implication. The petrologic results show that the protolith of Taoxinghu metamorphic perdotites have the mineral assemblage and texture characteristic of mantle peridotite. Most metamorphic peridotites hav near global abyssal peridotites major elements contents, while the few is similar to SSZ-type peridotites. They exhibit typically U-shaped REE patterns, characterized by slight enrichment of LREE and HREE relative to MREE and a low fractionated LREE to HREE segment. Trace elements contents are low and all samples are strong enrichment in Cs, U, Pb, weak enrichment in Ba and depletion in Th, but negative Nb anomalies are only observed in few samples. That suggests Taoxinghu metamorphic peridotites have depletion mantle and suprasubduction affinities. A two-stage evolution history is considered: Taoxinghu metamorphic peridotites originated as the residue from melting at a ridge with 7%-20% degree of fraction melting and were subsequently modified by interaction with mafic melt and aqueous fluid within mantle wedge on subducted zone. Combined with previous studies, we preliminarily propose Taoxinghu metamorphic peridotites may be the Products of initial rifting of palo-Tethys, forming at middle Ordivician-upper Cambrian, and they may be the direct evidences for spreading of palo-Tethys. | WU Yanwang LI Cai XIE Chaoming WANG Ming HU Peiyuan | 2013 | Acta Geologica Sinica(English Edition)2013，87，2： | 9 |
| 5 | Zircon U-Pb Age,Geochemical Data:Constraints on the Origin and Tectonic Evolution of the Metamafic Rocks from Longmuco-Shuanghu-Lancang Suture Zone,Tibet显示文摘Bulk-rock major and trace elements and zircon U-Pb data are reported for Permian metamafic rocks from Guoganjianan, in the western part of Longmuco-Shuanghu-Lancang suture zone. These results offer new insights into mantle source characteristics and geodynamic setting of Permian ophiolitic fragments. U-Pb isotopic dating using SHRIMP II method reveals that the metamafic rocks were formed at 274.7± 3.9 and 279.8± 3.6 Ma. The metamafic rocks mostly show N-MORB-typed rare earth element patterns and are enrichment in large-ion lithophile elements, indicating that they are probably derived from partial melting of a depleted mantle in a back-arc basin. Our new data, together with recent studied results on Paleozoic ophiolitic fragments suggest the Paleo-Tethys Ocean in Central Qiangtang opened at Cambrian and widened between Ordovician and Devonian. Northward subduction started in the Late Devonian–Early Carboniferous and a back-arc basin developed during Permian. | Yanwang Wu Cai Li Mengjing Xu Chaoming Xie Ming Wang | 2017 | Journal of Earth Science2017，28，3： | 7 |
| 6 | The Petrology, Geochemistry, and Petrogenesis of E-MORB-type Mafic Rocks from the Guomangco Ophiolitic Mélange, Tibet显示文摘The Guomangco ophiolitic mélange is situated in the middle part of the Shiquanhe–Yongzhu–Jiali ophiolitic mélange belt(SYJMB) and possesses all the subunits of a typical Penrosetype ophiolite pseudostratigraphy. The study of the Guomangco ophiolitic mélange is very important for investigating the tectonic evolution of the SYJMB. The mafic rocks of this ophiolitic mélange mainly include diabases, sillite dikes, and basalts. Geochemical analysis shows that these dikes mostly have E-MORB major and trace element signatures; this is the first time that this has been observed in the SYJMB. The basalts have N-MORB and IAB affinities, and the mineral chemistry of harzburgites shows a composition similar to that of SSZ peridotites, indicating that the Guomangco ophiolitic mélange probably originated in a back-arc basin. The Guomangco back-arc basin opened in the Middle Jurassic, which was caused by southward subduction of the Neo-Tethys Ocean in central Tibet. The main spreading of this back-arc basin occurred during the Late Jurassic, and the basalts were formed during this time. With the development of the back-arc basin, the subducted slab gradually retreated, and new mantle convection occurred in the mantle wedge. The recycling may have caused the metasomatized mantle to undergo a high degree of partial melting and to generate EMORBs in the Early Cretaceous. E-MORB-type dikes probably crystallized from melts produced by about 20%–30% partial melting of a spinel mantle source, which was metasomatized by melts from low-degree partial melting of the subducted slab. | XU Mengjing LI Cai WU Yanwang XIE Chaoming | 2014 | Acta Geologica Sinica(English Edition)2014，88，5： | 3 |
| 7 | ^(40)Ar/^(39)Ar Thermochronology Constraints on Jurassic Tectonothermal Event of Nyainrong Microcontinent显示文摘To reveal the Jurassic tectonothermal event occurring to the Nyainrong microcontinent which is gripped among the Bangong-Nujiang suture zone,40Ar/39Ar dating was carried out on the basement orthogneiss and Jurassic granitc gneiss in the microcontinent.In the heating stage,four samples exhibited a flat plateau age,with the value Tp concentrated in the range of 166–176 Ma;isochron age Ti was concentrated in the range of 165–175 Ma,and their corresponding ages were the consistent within allowable range.The ages should be representative of the era of the final deformation of the Amdo gneiss and cooling emplacement of the magmatic rock in the Jurassic.The geochronological studies have shown that the final deformation of microcontinent crystalline basement and the cooling of the Mesozoic large-scale tectonothermal events occurred in late Middle Jurassic.In Middle Jurassic,Nyainrong microcontinent experienced strong tectonic movement.Combining with the geochronological with isotope geochemistry for the microcontinent,the cause of the tectonothermal event should be attributed to the collision between the Nyainrong microcontinent and South Qiangtang Block following the northward subduction of Bangong-Nujiang oceanic crust. | Chaoming Xie Cai Li Yanwang Wu Ming Wang Peiyuan Hu | 2014 | Journal of Earth Science2014，25，1： | 2 |
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