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Landscape evolution and precipitation changes in the Badain Jaran Desert during the last 30 000 years

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chinese Science Bulletin 2000年第11期45卷 1042-1047页

作者： YANG Xiaopinginstitute of geology and geophysics, chinese academy of sciences, beijing 10002., china institute of geology and geophysics Chinese Academy of Sciences Beijing China

On the basis of field expeditions into different parts of the Badain Jaran Desert, new evidence of landscape evolution and precipitation changes during the last 30 000 years has been found from the geomorphological, sedimentological and geochronological studies of the megadune. Different cemented surfaces of palaeo-dunes have been observed in many localities, which are representatives of relatively moister environment. The chronological data show that four periods of more humid environment occurred in the past 30 000 years. The stabilization of dunes in a large scale and the existence of many palaeo-lakes and lacustrine terraces confirm the periodic fluctuations of climate. It implies that the intensity of westerlies and Eastasian monsoons varied in the region of Alashan, and the periods of higher precipitation took place even in the times close to the last glacial maximum.

关键词： desert palaeo-dune lake global change Badain Jaran.

Fossil bacteria in Xuanlong iron ore deposits of Hebei Province

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Science china Earth sciences 2004年第4期47卷 347-356页

作者： DAI Yongding, SONG Haiming & SHEN Jiying institute of geology and geophysics, chinese academy of sciences,beijing 10002., china institute of geology and geophysics Chinese Academy of Sciences Beijing China

Discovered in Early Proterozoic Xuanlong iron ore deposits are six genera of fossil iron bacteria, i. e. sphere (coenobium of) rod-shaped (monomer) Naumanniella, ellipsoid elliptical Ochrobium,sphere spherical Siderocapsa and chain spherical Siderococcus, chain rod-shaped Leptothrix and Lieskeella, and six genera of fossil blue bacteria, namely sphere spherical Gloeocapsa, Synechocystis and Globobacter, chain spherical Anabaena and Nostoc, and con-strictive septate tubular Nodularia. The biomineralized monomers and coenobia of the two cate-gories of bacteria, together with hematite plates made up the bacteria pelletal, bacteria silky, bacteria fibrous and clasty bacteria pelletal textural lamina. The bacteria pelletal laminae com-bined with other bacteria laminae to make up oncolite, stromatolite and laminate. The precipita-tion of iron oxide was accelerated due to iron and blue bacteria cohabiting on microbial film or mat. The Xuanlong iron ore deposits are microbial binding ore deposits of ocean source.

关键词： iron and blue bacteria, bacteria textural lamina, microbial ore deposits, Late Early Proterozoic.

Indosinian Foreland Fold-and-Thrust Belt Bordering Yunnan and Guangxi, china

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Acta Geologica Sinica(English Edition) 2001年第4期75卷 391-397页

作者： WU Genyao institute of geology and geophysics, chinese academy of sciences, beijing 10002. chinese Acad Sci Inst Geol & Geophys Beijing 100029 Peoples R China

Recent discoveries of ophiolites indicate that there must be a Palaeotethyan geosuture zone bordering china and Vietnam, which separates the Vietbac block from the South china subcontinent. The Indosinian foreland fold-and-thrust belt bordering Yunnan and Guangxi provided further evidence for the palaeotethysides. The oceanic crust was subducted southwestwards while the magmatic arc migrated northeastwards, and the continent-arc collision occurred in the Late Triassic with the thrusting being extended towards the north or northeast. The features of thrust-nappe structure are discussed, which proved the continental margin of the Palaeotethyan ocean there to be a complicated one. A face-to-face collision occurred first along the NW-striking segment and then along the ENE-striking segment accompanied by transpression or oblique thrusting occurring along the NW-striking one.

关键词： thrust-nappe structure foreland fold-and-thrust belt palaeotethysides border between Yunnan and Guangxi

Reinterpretation of the Guangxian Orogeny

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chinese Science Bulletin 2000年第13期45卷 1244-1248页

作者： WU Haoruoinstitute of geology and geophysics, chinese academy of sciences, beijing 10002., china institute of geology and geophysics Chinese Academy of Sciences Beijing China

The Guangxian Orogeny, as an important concept on geology of South china, was created 70 years ago. It is generally regarded as an erogenic movement caused by the convergence of the Cathaysian and Yangtze blocks at the end of Silurian. Based on the recent progress of the geological research on Guangxi and adjacent areas, western Guangxi and Liuzhou-Heshan area of central Guangxi may belong to a stable block of Early Paleozoic. The Guangxian Orogeny originated from the northward translation of the Yunkai Block on its south at the end of Cambrian, and formed the Damingshan-Dayaoshan fold belt between the two blocks. It was possibly related with the Late Pan-African Orogeny. The convergence of the Cathaysian and Yangtze blocks occurred in Late Ordovician to Early Silurian and mainly had effect on Hunan and Jiangxi provinces. The term 'Chongyu Orogeny' may be suitable for it. At the end of Silurian orogenic movement did not occur in this area.

关键词： South china tectonics Paleozoic Guangxian Orogeny Yunan Orogeny Chongyu Orogeny.

PGE patterns of ores of Dajing Cu-polymetallic deposit in Linxi County, Inner Mongolia:Indicator to source of metallogenic elements

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chinese Science Bulletin 2002年第13期47卷 1119-1124页

作者： CHU Xuelei, SUN Min & ZHOU Meifuinstitute of geology and geophysics, chinese academy of sciences, beijing 10002., china Key Laboratory of Mineral Resources, institute of geology and geophysics, chinese academy of sciences, beijing 100101, china Department institute of geology and geophysics Chinese Academy of Sciences Beijing China Key Laboratory of Mineral Resources Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China Department of Earth sciences The University of Hong Kong Hong Kong China

By comparing PGE patterns of sulfide ores with that of basic-ultrabasic dikes occurring in the Dajing Cu-polymetallic deposit, we discover that there are similar positive slopes between the basic-ultrabasic dikes and the black ores composed mainly of sphalerite and galena, reflecting affinity of their source. The PGE patterns of the yellow ores composed basically of chalcopyrite, arsenopyrite and pyrite are actually different. One is close to the pattern of the mantle 1herzolite, and others resemble the pattern of the basic rocks. However, the concentrations of Ru are higher in the yellow ores, reflecting that sulfur attains or approaches saturation in their parent magma. The PGE characteristics of ores and dikes show that the magmas derived from the deep of crust and the metallogenic elements were supplied mainly by growth material of the crust. In addition, the mantle-derived magma also offered some elements.

关键词： Da Hinggan area polymetallic deposit PGE pattern hypomagma.

^(40)Ar/^(39)Ar dating of shear deformation of the Xianshuihe fault zone in west Sichuan and its tectonic significance

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Science china Earth sciences 2004年第9期47卷 794-803页

作者： ZHANG Yueqiao1, CHEN Wen2, 3 & YANG Nong1 1. institute of Geomechanics, chinese academy of Geological sciences, beijing 100081, china 2. institute of geology, chinese academy of Geological sciences, beijing 100037, china 3. institute of geology and geophysics, chinese academy of sciences, beijing 10002., china institute of Geomechanics Chinese Academy of Geological Sciences Beijing China institute of geology Chinese Academy of Geological Sciences Beijing China institute of geology and geophysics Chinese Academy of Sciences Beijing China

Based on field geological survey, structural measurements and classical Ar/Ar dating of mica, biotite and K-feldspar, we obtain cooling ages for Miocene left-lateral shear along the Xianshuihe fault zone. The results document two thermal events during the sinistral shear. The early event (12-10 Ma) corresponds to rapid cooling of the Zheduoshan granitic massif from above 700℃ to below 350℃. The late event (5-3.5 Ma) corresponds to cooling of granites intruded along the eastern side of the fault zone. These dating results provide important thermochronological constraint on the timing of late Cenozoic eastward extrusion of the Chuan-Dian Block in the SE Tibetan margin.

关键词： Xianshuihe fault zone, Zheduoshan granitic massif, sinistral shear deformation, 40Ar/39Ar dating, late Cenozoic.

δD values of escaped H_2 from hot springs at the Tengchong Rehai geothermal area and its origin

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chinese Science Bulletin 2002年第2期47卷 146-149页

作者： SHANGGUAN Zhiguan & HUO Weiguo institute of geology, china Seismological Bureau, beijing 10002., china institute of geology and geophysics, chinese academy of sciences, beijing 10002., china institute of geology China Seismological Bureau Beijing 100029 China

Here we give the δD values of escaped H2 from hot springs at the Tengchong Rehai and adjacent regions, and deal with a genetic correlation between the increment H2 in escaped gases from middle-shallow reservoirs and the H2S, CH4 derived from deep sources. Isotopic compositions of H2 indicate that the generation of increment H2 may be related to recent strong activity of N-W trending fault at the Rehai area. Trace monitoring the H2 release could be significant in order to keep watch on present activity of that fault.

关键词： Rehai geothermal area hydrogen stable isotopic composition.

Compositions of heavy minerals in Northeastern china sandlands and provenance analysis

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Science china Earth sciences 2007年第11期50卷 1715-1723页

作者： XIE Jing1,2 & DING ZhongLi1 1 institute of geology and geophysics, chinese academy of sciences, beijing 10002., china 2 Graduate University of chinese academy of sciences, beijing 100049, china institute of geology and geophysics Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

Sand samples deposited since the Last Glacial Maximum (LGM) from the Hulun Buir, Horqin and Otin-dag sandlands were measured for their assemblages of heavy minerals and chemical compositions of detrital garnets and tourmalines. Heavy mineral assemblages of these three sandlands consist mainly of garnet, ilmenite, epidote and minor amphibole and magnetite. Garnets consist mainly of high Mg type-A ones (58% on average), and minor type-B ones. Toumalines are mainly composed of Mg-rich and minor Fe-rich ones. Compared with those of central-southern Mongolia and central Tarim, these three sandlands are derived from the Phanerozoic rocks of the Central Asian Orogenic Belt and the Archean and Paleoprotorozoic basement rocks of the North china Craton. Our results provide direct evidence that the present-day sands may be reworked from LGM ones. Differences of heavy mineral composi-tions occur between the samples of the three sandlands and Taklimakan Desert, indicating that the material of the western arid regions contributes little to the eastern sandlands.

关键词： heavy minerals,provenance,Northeastern china,garnet,tourmaline

Quantitative Evaluation of the Sea-level Drop at the End-Permian: Based on Reefs

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Acta Geologica Sinica(English Edition) 2003年第1期77卷 95-102页

作者： WU Yasheng and FAN Jiasong institute of geology and geophysics, chinese academy of sciences, beijing 10002. chinese Acad Sci Inst Geol & Geophys Beijing 100029 Peoples R China

The amplitude of pre-Quaternary sea level drop, H, can be calculated by usingthe formula H = D + To, where To is the original thickness from the top of the tidal deposits onthe reef core to the bottom of the tidal deposits on the reef front, or to the bottom of the ancientmeteoric vadose zone, or to the edge of the mixed-water dolostone zone. The identity and similaritybetween the sea-level drop amplitudes calculated from different reefs far away from each otherindicates that such sea-level changes are eustatic rather than relative changes. Evidence of anend-Permian sea-level drop has been found on the Changxingian (i.e. the end of the Palaeofusulinazone) reefs at Ziyun in South china, including algal laminated deposits, sabkha-related dolostone,desiccation cracks, dissolution collapse breccia. According to calculation based on the meteoricdissolution zone of the reef-core sequence at Ziyun, Guizhou province, the amplitude of thesea-level drop at the end-Permian is about 89.3 m. Calculation via the dolomitized upper part of theChangxingian reef in Lichuan, Hubei Province, yields an 88.9 m amplitude of the sea-level drop atthe end-Permian. Comparison shows that the sea-level drop recorded in the two distantly locatedreefs may be of eustatic type. So the amplitude of the sea level drop of the Tethys Sea at theend-Permian might be at least 89.3 m.

关键词： sea-level drop eustatic reef Permian Changxingian