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Discovery of eclogite and its geological significance in Qiangtang area, central Tibet

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Science Bulletin 2006年第9期51卷 1095-1100页

作者： LI Cai1, ZHAI Qingguo2, DONG Yongsheng1 & HUANG Xiaopeng11. college of earth sciences, jilin university, changchun 130061, china 2. Institute of Geology, Chinese Academy of Geological sciences, Bei- jing 100037, china college of earth sciences Jilin University Changchun 130061 China Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China

Eclogite is first discovered from Qiang- tang area, central Tibet, which occurs as a lens in the high-pressure metamorphic belt comprising glauco- phane-muscovite schist and garnet-muscovite schist, along the south margin of Lungmu Co-Shuanghu Paleo-Tethys suture. A glaucophane 40Ar/39Ar age of 220 Ma and a phengite 40Ar/39Ar age of 221.9 Ma have been obtained from blueschists associated with eclogite. The rock consists of garnet, omphacite, amphibole, phengite, and rutile, etc, and the jadeite content in omphacite ranges from 32.7% to 38.95%. It is estimated that the temperature of the eclogite is <500℃ and pressure varies in the range of 1.56― 2.35 GPa. The discovery of Qiangtang ecologite fur- ther supports that there is a suture zone of Indo- Chinese epoch in central Qiangtang area, and is very important for discssing the evolution of the pa- leo-ocean and paleo-plate tectonics in this area.

关键词： Qianghai-Tibet Plateau Qiangtang eclogite tectonics.

SHRIMP U-Pb dating and Hf isotopic analyses of Middle Ordovician meta-cumulate gabbro in central Qiangtang, northern Tibetan Plateau

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Science china earth sciences 2010年第5期53卷 657-664页

作者： ZHAI QingGuo1 WANG Jun1, LI Cai2 & SU Li3 1 Institute of Geology, Chinese Academy of Geological sciences, Beijing 100037, china 2 college of earth sciences, jilin university, changchun 130061, china 3 The Geological Laboratory Center and State Key Laboratory of Geological Processes and Mineral Resources, china university of Geo- sciences, Beijing 100083, china 1. Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China2. College of Earth Sciences Jilin University Changchun 130061 China3. The Geological Laboratory Center and State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing 100083 China

Metabasites consisting of metamorphic ultra-mafic rocks, cumulate gabbro, gabbro (diabase), basalt, and plagiogranite are exposed at the Taoxinghu area in central Qiangtang, northern Tibetan Plateau. Zircon SHRIMP U-Pb dating for the cumulate gabbro yields a weighted mean age of 467±4 Ma, which is the oldest and most reliable magmatic age in this area. Zircon 176Hf/177Hf ratios range from 0.282615 to 0.282657, with εHf(t) values of 5.02±0.28, indicating that the cumulate gabbro was mainly derived from the depleted mantle. In addition, geochemical data of metabasites suggest that they have similar characteristics to those in the mid-ocean ridge basalts (MORB). The Taoxinghu metabasites may represent the fragment of Early Paleozoic ophiolite in the "Central Uplift" of the Qiangtang, northern Tibetan Plateau.

关键词： Qiangtang cumulate gabbro SHRIMP dating Hf isotope

Geological features and genesis of Gaotaigou borate deposit, jilin, china

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Global Geology 2005年第Z1期 65-71页

作者： XIAO Li-mei, SUN Feng-yue college of earth sciences, jilin university, changchun 130061, jilin, china

Gaotaigou borate deposit in Ji’an area, southeastern jilin, is located in the easten end of Liaoning-jilin (Liaoji) Proterozoic paleo-rift, which is a medium-sized deposit and makes up 67% of the total borate reserves in jilin Province. The original borate ore bodies were formed by sedimentary exhalative process in Paleoproterozoic, but were activated and enriched by later metamorphism. In late stage of metamorphistn, hydrothermal fluid of metamorphic origin made wallrocks be altered and the borate ore bodies be reformed. Ore bodies are strictly controlled by strata and their lithologies. In addition, the shape and spatial distribution of ore bodies are also defined by the Gaotaigou syncline. Combined with the ore-controlling factors and mineralizing features, it has been proposed that Gaotaigou borate deposit is a metamorphosed and hydrothermally altered sedimentary exhalative deposit.

关键词： Gaotaigou borate deposit ascharite metamorphism Liaoji Paleo-rift genesis of deposit

Macro-and microscopic mechanical behaviour of flow of coal samples experimentally deformed at high temperatures and pressures

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Chinese Science Bulletin 2005年第S1期50卷 59-66页

作者： LIU Junlai , YANG Guang & MA Rui State Key Laboratory of Geological Processes and Mineral Resources, china university of Geosciences, Beijing 100083, china Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education, china university of Geosciences, Beijing 100083, china college of earth sciences, jilin university, changchun 130061, china china Univ Geosci State Key Lab Geol Proc & Mineral Resources Beijing 100083 Peoples R China china Univ Geosci Minist Educ Key Lab Lithosphere Tecton & Lithoprobing Technol Beijing 100083 Peoples R China jilin Univ Coll Earth Sci Changchun 130061 Peoples R China

Coal samples from Qinshui Basin, Shanxi, china are experimentally deformed at temperatures and confining pressures of 200 - 500℃and 200 - 500 Mpa, strain rate of 0.5×10-5/s and total strain of 10%. The vitrinite reflectance of the coal samples varies from 3.04 to 1.79. It is shown that the strengths of the deformed samples change obviously with coeval increasing temperatures and pressures (T/P). At the experimental range of T/P, the effects of increasing temperature predominate over that of increasing pressure. Microstructural analysis indicates a brittle to ductile transition under experimental T/P conditions from 200 to 300℃, and 200 to 300Mpa. Brittle deformation microstruc-tures include macroscopic fracture zones and penetrative fracture associations. Elongation, undulose or irregular extinction, deformation lamellae and dynamic recrystallization of grains are the main ductile deformation microstructures. The variation of deformation mechanisms of the experimentally deformed coal samples is related to both the components of coals and T/P conditions. At low T/P, fractures occur in both inertinite and vitrinite of the samples. At higher T/P, crystalline plastic deformations are observed in the inertinite only.

关键词： coal experimental deformation brittle to ductile transition.

Ginkgo from Lower Cretaceous Changcai Formation in Helong of jilin, NE china

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Global Geology 2005年第Z1期 1-8页

作者： SUN Yue-wu, WANG Yu-xin, WEI Wen-yan Research Center of Palaeontology & Stratigraphy, jilin university, changchun 130026, jilin, china college of earth sciences, jilin university, changchun 130061, jilin, china

Based on gross morphological and cuticular study, two species of Ginkgo From the Lower Cretaceous Changcai Formation in Helong of jilin. were identified from this area for the first time, including Ginkgo coriacea Florin and G. sibirica Heer. The study is significant for better understanding the paleophytogeographic, paleoecologic and stratigraphic characters of the Early Cretaceous Changcai flora.

关键词： Ginkgo cuticle Lower Cretaceous Changcai Formation jilin of china

The fragment of Paleo-Tethys ophiolite from central Qiangtang, Tibet:Geochemical evidence of meta-basites in Guoganjianian

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Science china earth sciences 2007年第9期50卷 1302-1309页

作者： ZHAI QingGuo1,2, LI Cai2 & HUANG XiaoPeng2 1 Institute of Geology, Chinese Academy of Geological sciences, Beijing 100037, china 2 college of earth sciences, jilin university, changchun 130061, china 1. Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China 2. college of earth sciences Jilin University Changchun 130061 China

N-MORB-type metabasites are discovered in the Guoganjianian area, central Qiangtang, Tibet, which are mainly metagabbro with cumulate structure and metabasalt. The rocks are distributed nearly from west to east unconformably underlying the Wanghuling Group of upper Triassic. On the basis of geo- chemical analysis, we find that the content of SiO2 is 43.03%―53.42%, and TiO2 1%―2.67%, Al2O3 16.75%―21.52%, CaO 7.03%―11.13%, K2O 0.05%―0.38%; the REE pattern is slight depletion or flat, and the trace spider diagram is like that of N-MORB, so we consider that the metabasite was formed under the setting of mid-ocean ridge or adult back-arc basin, and it is the fragment of Paleo-Tethys ophiolite.

关键词： Qiangtang, metabasite, Paleo-Tethys, ophiolite

SHRIMP zircon U-Pb dating in Jingshan "migmatitic granite", Bengbu and its geological significance

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中国科学：地球科学英文版 2005年第2期48卷 185-191页

作者： XU Wenliang, WANG Qinghai, YANG Debin, LIU Xiaochun & GUO Jinghui college of earth sciences, jilin university, changchun 130061, china Institute of Geomechanics, Chinese Academy of Geological sciences, Beijing 100081, china Institute of Geology & Geophysics, Chinese Academy of sciences, Beijing 100029, china 1. college of earth sciences Jilin University 130061 Changchun China 2. Institute of Geomechanics Chinese Academy of Geological Sciences 100081 Beijing China 3. Institute of Geology & Geophysics Chinese Academy of Sciences 100029 Beijing China

The petrographic characteristics of Jingshan "migmatitic granite" and the occurrence of the magmatic zircons indicate that the granite was formed by normal crystallization of felsic melts. All zircons in the granite have inherited cores and fine-scale oscillatory zoning rims of magmatic origin. It is realized that the granite was formed at 160.2±1.3 Ma through dating magmatic zircons. The generation of the granitic magma could be related to the lithospheric mantle and/or lower crust delamination after the ultrahigh pressure metamorphism (UHPM) in Triassic. Most inherited zircons yield the ages of 217.1±6.6 Ma, which is consistent with the peak UHPM in the Dabie-Sulu orogenic belt. Some of the inherited zircons (433-722 Ma) constitute a discordia line with the upper intercept age of 850+85/-68 Ma and a lower intercept age of 261+100/-140 Ma. These ages imply that the granite could be derived from the partial melting of the crustal materials of the South china Block that was intensively superimposed by the UHPM. The UHPM could be the reason for the major Pb loss at ±220 Ma.

关键词： zircon, U-Pb dating, migmatitic granite, geological significance, Bengbu.

^(40)Ar/^(39)Ar age evidence for Altyn fault tectonic activities in western china

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Chinese Science Bulletin 2003年第18期48卷 2024-2030页

作者： LIU Yongjiang1, J. Genser2, GE Xiaohong1, F. Neubauer2, G. Friedl2, CHANG Lihua1, REN Shoumai3 & R. Handler2 1. college of earth sciences, jilin university, changchun 130061, china 2. Institute of Geology and Paleontology, Salzburg university, Salzburg A-5020, Austrilia 3. Statigraphic Research Center for Oil and Natural Gas, Ministry of Land and Resources, Beijing 100034, china Correspondence should be addressed to Liu Yongjiang (e-mail: liuyj@ ***) college of earth sciences Jilin University Changchun 130061 China

Four 40Ar/39Ar age groups of mica, hornblende and K-feldspar were obtained from Proterozoic and early Paleozoic metamorphic rocks in the Aksay-Dangjin Pass area, western china. The samples away from the middle shear zone of the Altyn fault belt yield two plateau age groups in the range of 461—445.2 Ma and 414.9—342.8 Ma, respec-tively. They represent the tectono-thermal events that had been recorded in the rocks that were displaced by the Altyn strike-slip fault in late Ordovician-early Silurian and Devo-nian, respectively. These two age groups should be related to the closures of Northern and Southern Qilian Oceans. The deformed granitic gneiss from the northern belt gives a pla-teau age group of 178.4—137.5 Ma, which is interpreted as the active age of the Altyn fault in the middle-late Jurassic- early Cretaceous and should be related to the accretion of Lhasa block to the north. The sample from the middle shear zone of the Altyn fault belt yields two plateau ages of 36.4 and 26.3 Ma, respectively, suggesting the strike-slip move-ment with strong metamorphism at greenschist facies along the Altyn fault in the late Eocene. This event occurred in the most areas of the northern Tibet Plateau and should be in response in the north to the collision between Indian and Eurasian continents. The present study demonstrates that the Altyn fault is characterized by multiple pulse-style activi-ties under the tectonic setting of convergence between the Indian and Eurasian continents.

关键词： Altyn fault 40Ar/39Ar age tectono-thermal event western china

Facies-controlled volcanic reservoirs of northern Songliao Basin, NE china

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Global Geology 2005年第Z1期 72-77页

作者： WANG Pu-jun, HOU Qi-jun, SHU Ping, HUANG Yu-long, GUO Zhen-hua, LI Jin-long college of earth sciences, jilin university, changchun 130061, jilin, china jilin Petroleum Company, Songyuan 131100, jilin, china Daqing Petroleum Company, Daqing 163712, HeiLongjiang, china

Volcanic rocks of the late Mesozoic are very important reservoirs for the commercial natural gases including hydrocarbon, carbon dioxide and rare gases in the northern Songliao Basin. The reservoir volcanic rocks include rhyolite, andesite, trachyte, basalt and tuff. Facies of the volcanic rocks can be classified into 5 categories and 15 special types. Porosity and permeability of the volcanic reservoirs are facies-controlled. Commercial reservoirs were commonly found among the following volcanic subfacies: volcanic neck (I1) , underground-explosive breccia (I3), pyroclastic-bearing lava flow (II3), upper effusive (III3) and inner extrusive ones (IV1). The best volcanic reservoirs are generally evolved in the interbedded explosive and effusive volcanics. Rhyolites show in general better reservoir features than other types of rocks do.

关键词： Songliao Basin Cretaceous volcanic fades natural gas reservoir