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Uncertainty in magnetic activity indices

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Science China(Technological sciences) 2008年第10期51卷 1659-1664页

作者： XU WenYao institute of geology and geophysics, Chinese {3. of sciences, beijing 10002., China institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 China

Magnetic activity indices are widely used in theoretical studies of solar-terrestrial coupling and space weather prediction. However, the indices suffer from various uncertainties, which limit their application and even mislead to incorrect conclu-sion. In this paper we analyze three most popular indices, Kp, AE and Dst. Three categories of uncertainties in magnetic indices are discussed: "data uncertainty" originating from inadequate data processing, "station uncertainty" caused by in-complete station covering, and "physical uncertainty" stemming from unclear physical mechanism. A comparison between magnetic disturbances and related indices indicate that the residual Sq will cause an uncertainty of 1―2 in K meas-urement, the uncertainty in saturated AE is as much as 50%, and the uncertainty in Dst index caused by the partial ring currents is about a half of the partial ring cur-rent.

关键词： magnetic activity indices Kp AE Dst solar-terrestrial coupling space weather

^(40)Ar/^(3.)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, {3. 100081, China 2. institute of geology, Chinese academy of Geological sciences, {3. 10003., China 3. institute of geology and geophysics, Chinese academy of sciences, beijing 10002., China institute of Geomechanics Chinese Academy of Geological Sciences Beijing 100081 China institute of geology Chinese Academy of Geological Sciences Beijing 100037 China institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 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 3.0℃. 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/3.Ar dating, late Cenozoic.

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 {3., 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

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 {3., 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.

Early-Middle Permian Reef Frameworks and Reef-building Models in the Eastern Kunlun Mountains

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Acta Geologica Sinica(English Edition) 2001年第2期75卷 115-125页

作者： TIAN Shugang institute of geology, Chinese academy of Geological {3., beijing 10003.and FAN Jiasong institute of geology and geophysics, Chinese academy of {3., beijing 10002. institute of geology Chinese Academy of Geological Sciences Beijing 100037 institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 [?]3.ian Shugang Born in September 1951 graduated from beijing University in 1977 and received his MS. and Ph. D. degrees at China University of Geosciences (beijing) in 1985 and 1988 respectively working now in the institute of geology Chinese Academy of Geological Sciences. He has long been engaged mainly in studies of biostratigraphy palaeoecology sequence-stratigraphy and reefs. Tel: 010–68328223 E-Mail: sgtian2001@***

Reef frameworks and building models of the Early-Middle Permian in the eastern Kunlun Mountains have been verified through studies of reef-building communities, palaeoecology and carbonate facies. The eastern Kunlun reefs are built mainly by 6 reef-building communities, which include 11 major categories of frame-building organisms and 6 categories of reef-associated organisms. Eight types of reef-frames have been distinguished and eleven kinds of rocks identified to belong to 6 reef facies. Three sorts of reefs classified by previous researchers, namely mudmounds, knoll reefs and walled reefs, are well developed in the study area. Such reef-facies association and reef distribution show that there are 4 models of reef growth and development, i.e. the tidal-bank knoll-reef model, the plateau-margin wall-reef model, the composite wall-reef model and the deep-water mudmound model. The reefs are mainly constructed by calcareous sponge and calcareous algae, which are similar to all Permian reefs in other area

关键词： reef model Early-Middle Permian eastern Kunlun reefs

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 {3. of sciences,beijing 10002., China institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 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.

Landscape evolution and precipitation changes in the Badain Jaran Desert during the last 3. 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 {3. 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 3. 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 3. 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.

SHRIMP zircon U-Pb geochronology of early Mesozoic felsic igneous rocks from the southern Lancangjiang and its tectonic implications

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Science China Earth sciences 2006年第10期49卷 1032-1042页

作者： PENG Touping1,2, WANG Yuejun1, FAN Weiming1, LIU Dunyi3. SHI Yuruo3.& MIAO Laicheng4 1. Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou institute of Geochemistry, Chinese academy of sciences, Guangzhou 510640, China 2. Graduate University of Chinese academy of sciences, beijing 10003., China 3. SHRIMP isotope Laboratory, Chinese academy of Geological sciences, beijing 10003., China 4. institute of geology and geophysics, Chinese academy of sciences, beijing 10002., China Key Laboratory of Isotope Geochronology and Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou China Graduate University of Chinese academy of sciences Beijing China SHRIMP isotope Laboratory Chinese Academy of Geological Sciences Beijing China institute of geology and geophysics Chinese Academy of Sciences Beijing China

The SHRIMP zircon U-Pb geochronology of three typical samples, including two monzo nitic granites from the Lincang batholith and a rhyolite from the Manghuai Formation are presented in the southern Lancangjiang, western Yunnan Province. The analyses of zircons for the biotite monzonitic granites from the northern (02DX-13.) and southern (20JH-10) Lincang batholith show the single and tight clusters on the concordia, and yield the weighted mean 206Pb/23.U ages of 229.4 ± 3.0 Ma and 23..4 ± 3.6 Ma, respectively, representing the crystallized ages of these granites. The zircons for the rhyolitic sample (02DX-95) from the Manghuai Formation give a weighted mean 206Pb/23.U age of 23..0 ± 5.0 Ma. These data suggest that the igneous rocks from the Lincang granitic batholith and Manghuai Formation have a similar crystallized age. In combination with other data, it is inferred that both were generated at a narrow age span (~23. Ma) and were originated from the postcollisional tectonic regime. An early Proterozoic 206Pb/23.U apparent age of 1977±44 Ma is additionally obtained from one zircon from the biotite monzonitic granite (southern Lincang batholith), indicative of devel- opment of the early Proterozoic Yangtze basement in the region. These precisely geochronological data provide important constraints on better understanding the Paleozoic tectonic evolution of the Tethys, western Yunnan Province.

关键词： SHRIMP zircon U-Pb dating, Middle Triassic, Lincang granitic batholith, Manghuai Formation rhyolite, southern Lancangjiang.

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 {3. of sciences, beijing 10002., China Key Laboratory of Mineral Resources, institute of geology and geophysics, Chinese {3. 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.