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THE ALTUN—NORTH QAIDAM ECLOGITE BELT IN WESTERN CHINA—ANOTHER HP-UHP METAMORPHIC BELT TRUNCATED BY LARGE SCALE STRIKE-SLIP FAULT IN CHINA

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地学前缘 2000年第S1期7卷 254-255页

作者： zhang jianxin, xu zhiqin, yang jingsui, Li Haibing, Wu Cailai(institute of geology, chinese academy of geological sciences, 26 Baiwanzhuang, beijing 100037,China, E\|mail: zjx66@***)

The Altun and North Qaidam Mountains at the northern margin of Qinghai\|Tibet plateau are separated by the Altyn Tagh sinistral strike\|slip fault, which is one of the largest strike\|slip fault systems in the world and was considered as the key element in the escape tectonics model for Euraisa\|India continent\|continent ***,the eclogites within quratzifeldspathic gneisses or pelitic gneisses characterized by amphibolite\|facies paragenesis were discovered in the Altun and the North Qaidam Mountains(Fig.1). They occur as lens or boundins within the Altun Group and Dakendaban Group respectively which previously were considered as metamorphic basement of Tarim block and Qaidam block. Our studies indicate that the eclogites outcrop in both the Altun and North Qaidam Mountains show similar occurrences, associated country rocks, rock and mineral assemblages, p\|T\% estimates, geochemistryand protolith feature and ages of peak metamorphism (see table) . The garnet\|omphacite\|phengite geothermobarometer gave equilibrium condition of \%p\%=2 8～3 0GPa and t =820～850℃ for the Altun eclogite and p =2 8GPa and \%t\%=730℃ for North Qaidam eclogite respectively(Fig..2). These p\|T conditions are in the coesite stability field. Moreover, Po lycrystalline quartz pseudomorphs after coesite have been identified in the Dulan area, North Qaidam Mountains (Song et al, in review). Therefore, these features suggest that both eclogites of Altun and North Qaidam Mountains probably are a same HP\|UHP metamorphic belt formed from the same of Early Paleozoic age deep subduction and collision, and subsequently displaced by the Altyn Tagh *** case is similar to the Dabie\|Sulu HP\|UHP metamorphic zone which was truncated by the Tanlu sinistral strike\|slip fault and splitted it into two distincts, the Dabie region and Sulu region. These correlations support an about 350～400km displacement of the Altyn Tagh sinistral strike\|slip fault (Fig.1).

关键词： Altun mountains North Qaidam Mountains HP\|UHP metamorphic b elt Altyn Tagh fault

THREE-DIMENSIONAL DEFORMATION ALONG THE ALTYN TAGH FAULT ZONE AND UPLIFT OF THE ALTYN MOUNTAIN, NORTHERN TIBET

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地学前缘 2000年第S1期7卷 257-258页

作者： Li Haibing, yang jingsui, xu zhiqin, zhang jianxin, Wu Cailai,Shi Rendeng (institute of geology, chinese academy of geological sciences, 26 Baiwanzhuang Road, beijing 100037, China,E\|mail: lihaibing@*** yangjsui@***)

he convergence between India and Eurasia is partly accommodated by motion of a few large blocks along strike\|slip faults. About 1800km long Altyn Tagh fault strikes in N60～80°E and allows the northeastward displacement of the Tibet plateau relative to the Tarim. The Altyn Tagh fault zone is a typical transpressional fault zone, characterized by blocks rotation and crustal shortening and vertical extrusion of blocks within the Altyn Tagh strike\|slip system. Differences of three\|dimensional deformation and configuration of the active structures are recognized at different segment of the Altyn Tagh fault zone.1\ Structural configuration of the Altyn Tagh fault zone\;In the Altyn Tagh strike\|slip fault zone, the assemblage pattern of the (active) faults is in the form of parallel plumes, especially in the eastern and the western segments of the Altyn Tagh fault zone. These plumes structures in the eastern segment are assembled by string\|like left lateral strike\|slip fault and broom\|like thrusting faults, and in the western segment by arc\|like left lateral strike\|slip faults along with thrusting faults and normal faults. In the middle segment of the Altyn Tagh fault zone, the structures are characterized by the string\|like left lateral strike\|slip faults in the center and reverse thrusting faults on the two sides.

关键词： three\|dimensional deformation uplift mountain building t ranspression Altyn Tagh fault Tibet

CRETACEOUS (?) VOLCANIC ROCKS ON THE NORTH END OF THE ALTYN TAGH FAULT:CHARACTERISTICS AND TECTONIC IMPLICATIONS

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地学前缘 2000年第S1期7卷 218-220页

作者： Meng Fancong, yang jingsui, zhang jianxin, Wu Cailai, Shi Rendeng, Li Haibing, Li Tianfu [WT5,5”BX](institute of geology, chinese academy of geological sciences, beijing 100037, China)

The age and evolutional history of the Altyn Tagh fault and its role in the formation and uplift of the Qinghai—Tibetan plateau have been focused for years. Many geologists believe that the formation of the fault is a result of the collision between India and Asia. Some people thought that it should have formed earlier than Cenozoic but have no critical evidence. Here we report a preliminary result from our recent investigation on the volcanic rocks at the north end of the Altyn Tagh fault.1 The volcanic rocks on the north end of the Altyn Tagh fault The volcanic rocks are located on the north end of the Altyn Tagh fault, northern Qinghai—Tibetan plateau. The investigated volcano occurs in the Jiuxi basin, a Cretaceous and Tertiary depositional basin. It is about 300m×100m in size and form about a 100m high cliff above the folded Cretaceous strata. It likes relic neck of a volcano rather than a kind of widely distributed lava flow commonly seen in the northern Tibet. The country rocks are Cretaceous sandstone, silt and fine\|grained conglomerate. The cliff formed most likely due to the differing erosion between the hard volcanic rocks and soft rocks.

关键词： volcanic rocks Altyn Tagh fault Jiuxi Hoh Xil Tibet Gansh u

AGE OF THE ALTYN TAGH STRIKE—SLIP FAULT

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地学前缘 2000年第S1期7卷 208-209页

作者： Li Haibing 1, yang jingsui 1, xu zhiqin 1, Wu Cailai 1, zhang jianxin 1, wan Yushen 1, Shi Rendeng 1, Juhn G. Liou 2,Trevor R. Ireland 2 (1 institute of geology, chinese academy of geological sciences, beijing 100037, China 2 Department of

A 100～500m\|wide mylonite zone in the Altun Group of Lower Proterozoic age was discovered along the Altyn Tagh strike\|slip fault. The zone is mainly composed of amphibolitic and granitic mylonites. The planar joints of the rocks strike in NE70 and dip steeply (nearly vertical), coincident with the striking of Altyn Tagh fault zone, and their stretched lineations are nearly horizontal. Shear strains are well developed and show sinistral sheared. The amphibolitic and granitic mylonites are most probably the products of deep\|seated melting caused by sinistral strike\|slip shearing as suggested by the evidence below: (1) The migmatization is intensely developed and spatially controlled by the shear zone, and the rock has a set of NNE perspective foliation which is in accord with the direction of the Altyn Tagh strike\|slip fault zone. (2) The recrystallized hornblende aggregate is distributed in band with obvious nebulous texture, indicating the characteristics of anatexis, and the hornblendes are oriented and form the nearly horizontal stretching lineation; some hornblendes have titanite inclusions, and magmatic long\|columnar zircons are in directional arrangement.(3) The banded felsic material is developed, and the plagioclase is characteristic of high\|temperature plastic deformation and shows sinistral shear stain. (4) In mylonites, all the axis C fabric of quartz shows the feature of sinistral shearing and the majority is generally middle to low temperature fabric, but there also exists high temperature fabric, which suggests that high temperature shearing occur in the early stage of strike\|slip deformation and it is characterized by middle to low temperature shearing at the beginning of anatexis or in the late stage of the deformation. (5) On the XZ plane of mylonite and mylonitized rocks, there exists the consistent sinistral shear stain, which suggests the products of the same strike\|slip *** were separated from three samples of mylonitized gra

关键词： Altyn Tagh fault Tibet plateau SHRIMP dating mylonite

Eclogitic metapelites in the western segment of the north Qaidam Mountains:Evidence on"in situ"relationship between eclogite and its country rock

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Science China Earth sciences 2004年第12期47卷 1102-1112页

作者： zhang jianxin MENG Fancong yang jingsui institute of geology Chinese Academy of Geological Sciences Beijing 100037 China Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China

In Yuka-Luofengpo area of the north Qaidam Mountains, eclogitic metapelites are recognized. The metapelites enclosed lenses of eclogites, and locally intercalated with eclogites. Their typical mineral assemblages are garnet+kyanite+chloritoid+phengite+quartz+rutile. Strong growth zoning is preserved in garnets of metapelites, and phengite contains up to 3.4 Si per formula units. The petrographic observations and textural relations testify to the following sequence of mineral assemblages connected to three metamorphic stage: (1) Grt+ChlI+CldI +PheI ± StI+Qtz; (2) Grt+Ky+PheII±CldII+Qtz; and (3) Grt+CldIII+ChlII+PheIII+StII ± ky+ Qtz. Applying THERMOCALC Program, Grt-Phe thermometer and Grt-Ky-Phe-Qtz barometry, P-T conditions for three metamorphic stages were obtained: P=1.07±0.31GPa, T=564±22? (prograde stage); P=2.3–3.1GPa, T=615–700°C-(peak stage); and P =1.22 ± 0.26GPa, T=581±20°C (retrograde stage). A hairpin shape P-T path similar to that of adjacent eclogite is inferred. In combination with eclogitic mineral relics in marbles and orthogneisses enclosing eclogites, we thought that the relationship between eclogites and country rocks is “in situ” rather than “tectonic emplacement”.

关键词： eclogitic metapelites, in situ, tectonic emplacement.

Determination of the Altyn Tagh strike-slip fault basin and its relationship with mountains

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chinese Science Bulletin 2002年第7期47卷 572-577页

作者： Li Haibing yang jingsui Shi Rendeng Wu Cailai P.Tapponnier wan yusheng zhang jianxin Meng Fanchong institute of geology Chinese Academy of Geological Sciences100037BeijingChina Institut de Physique du Globe 4 Place Jussieu75252ParisCedex 05France

A special extended basin topography is developed in the middle segment of the Altyn Tagh Fault Zone. The ratio of its length to width is over 50. The long boundaries at the two sides of the basin are controlled by the straight normal faults with strike-slip component. Within the basin, the Cenozoic strata are spread. The Altyn Tagh main fault goes through the basin, and a series of strike-slip topography was formed within the basin. The reverse thrust structures were formed at the two sides of the center of the basin, thus making the geological bodies composed of old metamorphic rocks at the two sides of the basin extrude vertically, and forming the extended massif (mountain) at the sides of the basin and parallel to the basin. This special topography was called the strike-slip fault basin. The giant extended strike-slip fault basin began to form during Pliocene, and its topography was basically formed during the late Pleistocene. It is the special topography formed during the strike-slip deformation

关键词： strike-slip fault basin transpression uplifting Altyn Tagh Fault Zone.

LARGEST ALTYN TAGH LITHOSPHERIC SHEAR FAULT IN CENTRAL ASIA

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地学前缘 2000年第S1期7卷 231-232页

作者： xu zhiqin 1, yang jingsui 1, zhang jianxin 1, Jiang Mei 1, Li Haibing 1,Liou J.G. 2[WT5,5”BX](1 institute of geology,CAGS, 26 Baiwanzhuang St., beijing 100037,China,Fax:86\|10\|68311293 2 Department of geological & Environmental sciences,St

The Altyn Tagh fault (ATF) extending in NEE—SWW direction lying at the northwestern boundary of Qinghai—Tibet plateau is the largest strike\|slip fault in Central Asia. On the basis of recent geologic mapping and detailed study of lithotectonic characteristics for the paleotectonic units at the two sides of the Altyn Tagh Fault ( Altun Mt. to west and the Qilian Mt. to east ) we propose that the paleotectonic units in the Altun Mt. can be correlated with those in the Qilian Mt. assuming 400km left\|lateral displacement for the Altyn Tagh fault. Natural seismic data across the Altun Mt. indicate that the Altyn Tagh fault is a lithospheric shear fault and the lithospheric shearing is probably related to southward intracontinental oblique subduction of the Tarim terrane beneath the Altun Mt.1\ Comparison of the major paleotectonic units at the two sides of the Altyn Tagh fault\;(1) The Alxa\|Dunhuang Massif:The Alxa massif lying at the southern margin of the Sino\|Korean craton consists mainly of an Early Proterozoic basement including high\|grade and middle\|grade metamorphic rocks, which were intruded by granite at 1719Ma. The Paleozoic passive margin sediments is well developed. In the Altun Mt., the Early Proterozoic and late Archean basement of the Duhuang massif includes high\|grade and middle\|grade metamorphic rocks dating 2789Ma (Sm\|Nd method) and 2405Ma (U\|Pb method).

关键词： lithospheric shear fault paleotectonic unit seismic the Altyn Tagh fault Central Asia

SHRIMP U-Pb geochronology of the detrital zircons from the Longshoushan Group and its tectonic significance

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chinese Science Bulletin 2007年第10期52卷 1414-1425页

作者： KuoAn TUNG HoungYi yang LIU DunYi zhang jianxin ChienYuan TSENG wan yusheng Department of Earth sciences Cheng Kung University Tainan 701 China Museum of Natural Science Taichung 404 China beijing SHRIMP Centre Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China institute of geology Chinese Academy of Geological Sciences Beijing 100037 China

Sixty-two geologically meaningful U-Pb dates were obtained by using SHRIMP technique for the detrital zircons in three metasedimentary rocks from stratigraphically uppermost parts of the Longshoushan Group in the present study. Eighty percents of these dates range from 1.7 Ga to 2.2 Ga with a peak at 1.8-2.0 Ga and twenty percents from 2.3 Ga to 2.7 Ga. The youngest detrital zircon is dated at 1724±19 Ma which is interpreted as the maximum depositional age of the metasedimentary rocks. Therefore, the age for the diagenesis and lithification of the original sedimentary rocks of the Longshoushan Group before the metamorphism must be younger than 1724±19 Ma. Comparison of the age histograms of these detrital zircons with the ages of the igneous rocks on the surrounding older massifs suggests that the sediments of the Longshoushan Group were most likely derived from the Alaxa Block and Tarim Craton. This implies that the affinity between Alaxa Block and Tarim Craton was strong and that they might have been a unified craton during middle-early Proterozoic time.

关键词：甘肃龙首山组 SHRIMP U-Pb 地球年代学岩屑锆石变质沉积岩

SHRIMP U-Pb geochronology of the zircons from the Precambrian basement of the Qilian Block and its geological significances

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chinese Science Bulletin 2007年第19期52卷 2687-2701页

作者： Kuoan TUNG Huai-Jen yang Houng-Yi yang LIU DunYi zhang jianxin wan yusheng Chien-Yuan TSENG Department of Earth sciences Cheng-Kung University Tainan 701 China Museum of Natural Science Taichung 404 China beijing SHRIMP Centre Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China institute of geology Chinese Academy of Geological Sciences Beijing 100037 China

Origin and tectonic evolution of the Qilian Precambrian basement on NW China were investigated using zircon U-Pb ages with collaborating stratigraphic and paleontological evidence. Zircon grains were separated from two schists, two granitic gneisses and one mylonized gneiss and dated with SHRIMP. Seventy percent of sixty-one detrital zircon ages from two schists ranges from 0.88 Ga to 3.09 Ga, mostly within 1.0 Ga to 1.8 Ga with a peak at 1.6 Ga to 1.8 Ga, and twenty percent varies from 2.0 Ga to 2.5 Ga. A few falls in the Archean and Neoproterozoic periods. The two granitic gneisses were dated 930±8 Ma and 918±14 Ma, whereas the mylonized granitic gneiss was dated 790±12 Ma. These ages represent two periods of magmatisms, which can be correlated with the early and late stages of magmatisms associated with the Jinningian movement on the yangtze Blocks. The results from this and previous studies indicate that the ages of the Precambrian detrital zircons from the Qilian Block are widely distributed in the Proterozoic era, distinct from the North China Block which was stable in the Neo-Mesoproterozoic era. By contrast, the age histograms of the detrital zircons from the Qilian Block is similar to those from Precambrian basement of the yangtze Craton. Therefore, it is suggested that the Qilian Block had a strong affinity toward the yangtze Craton and might belong to the supercontinent Gondwana in the Neoproterozoic time. This inference is supported by Nd model age (TDM), stratigraphic, and paleontological evidence. It is further considered that the Qilian Block was rifted from the supercontinent Gondwana during late Sinian to form an isolated continent in the Proto-Tethyan Ocean, moving towards the Alaxa Block in the North China Craton. The part of Proto-Tethyan Ocean between the Qilian and Alaxa Blocks should correspond to the so-called Paleo-Qilian Ocean. Following the closure of the Paleo-Qilian Ocean in the early Paleozoic, the Qilian Block collided with the Alaxa B

关键词：地球年代学锆石前寒武纪古地中海特提斯海