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Lithospheric seismic fabrics of Sulu ultrahigh-pressure metamorphic belt

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Science china Earth sciences 2005年第5期48卷 585-600页

作者： YANG Wencai 1 , YANG Wuyang 1 , JIN Zhenmin 2 & CHENG Zhenyan 1 1. institute of geology, chinese academy of Geological sciences, beijing 100037, china 2. china University of Geosciences, Wuhan 430074, china chinese academy of Geological sciences Institute of Geology Beijing China china University of Geosciences Wuhan China

Calibration of seismic reflectors appearing in the crust of the chinese continent sci- entific drilling site can be completed through the correlation studies between direct evidences, such as the drill cores, and geophysical signatures; therefore the interpretation of geophysical data could produce reliable results of crustal structure and composition. On the other hand, there are two cenozoic volcanoes close to the scientific drilling site; analyzing composition of xenoliths existent in the volcanoes and evaluating their seismic velocities can also offer information about the mantle and lower crust. After the calibration via cores and well-logging data, the seismic re- flectors appearing in the UHP belt can be caused by lithological changes within the UHP rock slice, ductile shearing rock-suites, and later fracture zones. Among these sources, ductile shearing resulted in displacement and detachment of original rock-sheets, producing some rock-interbeds of several hundred meters thick that are named the ductile shearing rock-suites. A suite consists of mylonized gneiss and eclogite slices that underwent shearing, becoming the major mechanism responsible to generate regional strong reflections. The UHP rock-slice is characterized by complicated structures and high density, high seismic velocity and high electri- cal resistivity, its thickness is usually less than 11 km. Velocity and density of the gneiss-layer beneath gradually tend to normal with increasing depth. Based on the xenoliths we can infer that the middle crust contains a lot of gneisses, and the lower crust consists of different granulites. The lithospheric mantle has multi-layer structures and consists mainly of spinal lherzolite and harzburgite, implying late Mesozoic lithospheric thinning. The seismic fabrics with different ori- gins were possible products of different geodynamic processes. For instance, the UHP rock-slice was produced by the UHP metamorphic process and the exhumation of subducted supe

关键词： deep seismic reflection, ultrahigh-pressure belt, Sulu china, calibration of reflectors, lithospheric fabrics.

^(40)Ar-^(39)Ar dating and geological implication of auriferous altered rocks from the middle-deep section of Q875 gold-quartz vein in Xiaoqinling area, Henan,china

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chinese Science Bulletin 2002年第20期47卷 1750-1755页

作者： WANG Yitian, MAO Jingwen, LU Xinxiang & YE Anwanginstitute of Mineral Resources, chinese academy of Geological sciences, beijing 100037, china institute of Geological sciences, Henan Province, Zhengzhou 450053, china Lingbao Bureau of geology and Mineral institute of Mineral Resources Chinese Acad. of Geological Sciences Beijing 100037 China institute of Geological sciences Henan Province Zhengzhou 450053 China Lingbao Bur. of Geol./Mineral Rsrc. Henan Province Lingbao 472500 China

The 40Ar-39Ar age method is employed in this work to analyze the auriferous altered rocks from the middle-deep section of the Q875 gold-quartz vein in the Xiao-qinling area, and the results show that the main gold deposition of the Q875 occurred in ca. 12.-12. Ma. As a typical gold-bearing quartz vein in this gold-rich area, the age data obtained from the Q875 also constrain on the metallogenic time of the lode gold deposits developed in the same geological settings. This geochronological study supplies new evidence for further understanding the timing of gold mineralization, the genesis of gold deposits and the geodynamic settings in Xiaoqinling area.

关键词： 40Ar-39Ar dating auriferous altered rock Q875 gold-quartz vein lode gold deposit metallogenic time Xiaoqinling.

Drastic climatic shift at～2.8 Ma as recorded in eolian deposits of china and its implications for redefining the Pliocene-Pleistocene boundary

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Drastic climatic shift at～2.8 Ma as recorded in eolian depo...

SHRIMP zircon U-Pb age and Nd isotopic study on the Nyainqêntanglha Group in Tibet

中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： Shiling Yang~*,Zhongli Ding key Laboratory of cenozoic geology and environment,institute of geology and geophysics,chinese academy of sciences,19,BeiTuChengXi Road,beijing 10002.,china

There has been a long-running debate over the position of the Pliocene-Pleistocene boundary,i.e.1.8 Ma versus 2.6 *** study presents litho- and pedo-stratigraphic characteristics,grain size,magnetic susceptibility,and dust sedimentation rates for ’red clay’-loess sequences over northern china,in order to assess the drastic climatic event(s) recorded in the quasi-continuous eolian deposits,and to readdress the position of the Pliocene-Pleistocene *** complete chinese loess sequences,33 soil-loess couplets have been identified and labeled with Si-Li ***,the base of chinese loess has been designated at the bottom of loess unit ***,a typical loess layer within the uppermost ’red clay’ is identified and formally designated here as L34 and the soil unit between L33 and L34 as S33, which lowers the basal age of chinese loess from 2.6 Ma to～2.8 *** the Neogene ’red clay’ and the overlying Quaternary loess are both of windblown origin,they have quite different pedogenic *** loess consists of alternating reddish soil and yellowish loess layers,while the ’red clay’ is composed of soils with much redder colour and carbonate nodule *** general,the"red clay"has been subjected to stronger pedogenic processes than the overlying loess,and can be regarded as an extremely thick soil *** alternation of loess and soils reflects large-scale oscillations between glacial and interglacial conditions,whereas the well-developed ’red clay’ deposition indicates a relatively stable climate ***～2.8 Ma,shortly before the Gauss/Matuyama boundary,the eolian sequences show a sedimentary transition from the well-weathered ’red clay’ to the alternating loess and paleosol deposits,accompanied by coarser particle size,increased dust accumulation rates,and change of magnetic susceptibility *** indicate a large climatic shift from long-lasting warm-humid conditions to large-amplitude cold-dry and warm-humid fluc

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Science china Earth sciences 2005年第9期48卷 1377-1386页

作者： HU Daogong1, WU Zhenhan1, JIANG Wan1, SHI Yuruo2, YE Peisheng1 & LIU Qisheng1 1. institute of Geomechanics, chinese academy of Geological sciences, beijing 100081, china 2. institute of geology, chinese academy of Geological sciences, beijing SHRIMP Centre, beijing 100037, china institute of Geomechanics Chinese Academy of Geological Sciences Beijing China institute of geology Chinese Academy of Geological Sciences Beijing SHRIMP Centre Beijing China

The Nyainqêntanglha Group is traditionally viewed as the oldest metamorphic basement in the Lhasa block, but its formation age and tectonic setting remain debate. Zircons extracted from the metamorphic sequence of volcanics and intrusions of the Nyainqêntanglha Group, 10 km west of Nam Co in northern Lhasa block, have been investigated by cathodolu- minescence (CL), backscattered (BSE) and dated by ion microprobe (SHRIMP). We conclude that the U-Pb age of 787±9 Ma of zircons from the trondhjemite imposes a constraint on maxi- mum protolith age, and minimum formation age of the Nyainqêntanglha Group is constrained by U-Pb age of 748±8 Ma of zircons from the granite. The formation age of the Nyainqêntanglha Group is consistent with sedimentary age of Greater Himalayan rocks, showing that they devel- oped coevally in an arc-basin tectonic setting of Neoproterozoic active continental margin along the northern margin of the India shield. The inherited zircons from the tholetiite and granite give older 207Pb/206Pb ages from 947 to 1766 Ma. The positive εNd( t ) value indicates that the mafic rocks were derived from the depleted mantle, but contaminated by the older continental crustal material. Integrated Nd model age and U-Pb age data provide excellent evidence for the exis- tence of Mesoproterozoic basement in the Lhasa block during Neoproterozoic time.

关键词： Nyainqêntanglha Group, SHRIMP dating, Nd isotope, Neoproterozoic, Tibet.

Isotope Method for Confined Groundwater Recharge of the Lower Reaches of the Heihe River,Inner Mongolia,china

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Acta Geologica Sinica(English Edition) 2007年第4期81卷 668-673页

作者： CHEN Jiansheng ZHAO Xia FAN Zhechao and WANG Jiyang 1 State key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University,Nanjing 210098,china 2 institute of Isotope Hydrology Research,Hohai University,Nanjing 210098,china 3 institute of geology and geophysics,chinese academy of Science,beijing 100018,china Hohai Univ Stae Key Lab Hydrol Water Resources & Hydraul E Nanjing 210098 Peoples R China Hohai Univ Inst Isotope Hydrol Res Nanjing 210098 Peoples R China chinese Acad Sci Inst Geol & Geophys Beijing 100018 Peoples R China

environmental isotopes have been appfied to analyze confined groundwater recharge in the lower reaches of the Heihe River, Inner Mongolia. CFC is regarded as a tracer that determines the date of groundwater, the date being less than 45 a. The confined groundwater within the Gurinai area and Ejin Basin other than the surface water of Heihe River might have originated from precipitation from Qilian Mountain or/and the Tibetan Plateau. The deep confined groundwater overflows into an upper aquifer and emerges into the ground, forming springs and lakes within the low-lying area. The recharge volume is estimated to be around 400 million-cubic meters.

关键词： isotope CFC Ejin Basin Gurinai groundwater recharge precipitation Qilian Mountain

Oxygen isotopic compositions of quartz in the sand seas and sandy lands of northern china and their implications for understanding the provenances of aeolian sands

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Oxygen isotopic compositions of quartz in the sand seas and ...

Ce Anomalies of the Yangtze Region,South china,through the Ordovician and Silurian Transition

中国科学院地质与地球物理研究所2008学术年会

作者： Xiaoping Yang ~*,Feng Zhang ~1,Xudong Fu ~2,Xiaoming Wang~3 key Laboratory of cenozoic geology and environment,institute of geology and geophysics,chinese academy of sciences,beijing,china

A better understanding of aeolian sand provenance in deserts would be useful for studying interactions between various Earth surface processes occurring in arid and semiarid *** this study we examined oxygen isotopic compositions of quartz in sand samples taken from Taklamakan and Badain Jaran deserts of northwestern china and from the Hunshandake and Hulunbeier sandy lands in northeastern *** fractions of grain sizes were chosen for *** preparation followed the chemical principals described in geochemistry and final measurements were performed with mass *** the sands from the Badain Jaran Desert theδO value is generally low,with a mean of 12.1‰in the coarse fraction (0.200-0.250 mm) and a mean of 13.2‰in the fine fraction(0.12.-0.154 mm).The sands of the Taklamakan Desert show a meanδO value of 15.4‰in the main grain size fraction 0.064-0.150 *** contrast,the meanδO values in all grain size fractions of sand samples from the Hunshandake Sandy Land and from the Hulunbeier Sandy Land are much lower,varying between 6.8‰and 9.9‰.The outcome established a preliminary database aboutδO distributions in quartz sands throughout china’s large deserts and sandy *** results show regional differences between each of the sand seas and sandy lands,indicating different provenances of the aeolian *** detailed comparison of theδO values between the deserts and loess stratigraphy in the Loess Plateau would provide information about changes in areas of loess sources and evidence of palaeocirculation.

关键词： Sand seas Aeolian sand Sand provenance Oxygen isotope Sandy land china

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Journal of Earth Science 2009年第6期20卷 941-948页

作者：严德天张丽琴李双建 key Laboratory of Tectonics and Petroleum Resources of Ministry of Education China University of GeosciencesWuhan institute of geology and geophysics Chinese Academy of Sciences School of Geodesy and Geomatics Wuhan University key Laboratory of Geospace environment & Geodesy of Ministry of Education Wuhan University Petroleum Exploration and Production institute of SINOPEC

Systematic Ce anomalies for whole-rock have been obtained from the shale-dominated, continuous, and pelagic sedimentary sequences spanning the Ordovician/Silurian （O/S） boundary at the Tieshui （铁水） of Xiushan （秀山）, Chongqing （重庆）, South china. Ce anomalies across the O/S boundary are recognized in three intervals, Wufeng （五峰）, Guanyinqiao （观音桥） and Longmaxi （龙马溪）. The calculated Ce/Ce＊ values of Wufeng Formation range from 0.84 to 0.96 （avg. 0.90）. In the Guanyinqiao Formation, the values of calculated Ce/Ce＊ range from 0.73 to 0.85 （avg. 0.79）. The Ce/Ce＊ values of uppermost Longmaxi Formation range from 0.87 to 0.96 （avg. 0.91）. All along the section, the magnitude of the Ce anomaly is always negative, but is more significant in the Guanyinqiao Formation. The relatively higher Ce/Ce＊ values in the Wufeng and Longmaxi shales are likely to be due to the sediments deposited under rather reducing conditions. The Ce anomaly apparently does play some regular roles in the anoxic events that accompany prominent mass extinctions, and this work provides new data of critical importance for constraining models on the end-Ordovician anoxic events and mass extinctions.

关键词： Ce anomaly redox mass extinction Ordovician/Silurian boundary Yangtze platform.

Evidence for metasomatic mantle carbonatitic magma extrusion in Mesoproterozoic ore-hosting dolomite rocks in the middle Kunyang rift, central Yunnan, china

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Progress in Natural Science:Materials International 2008年第8期18卷 965-974页

作者： Yongbei Zhanga,b,c, Hua Bia,*, Longshi Yua, Shihua Sunc, Jiaxiang Qiub, Chengyan Xub, Hao Wang b, Renjing Wang b a The Department of Resources, environment and Tourism, Hainan Normal University, No. 432, Yinpo Road, Longshepo, Haikou 57000, china b key Laboratory of Mineral Resources, institute of geology and geophysics, chinese academy of sciences, beijing 10002., china c Faculty of Earth sciences, china University of Geosciences, Wuhan 470074, china The Department of Resources Environment and Tourism Hainan Normal University No. 432 Yinpo Road Longshepo Haikou 57000 China key Laboratory of Mineral Resources Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Faculty of Earth sciences China University of Geosciences Wuhan 470074 China

The Kunyang rift lying on the western margin of the Yangtze platform is a rare Precambrian Fe-Cu mineralization zone. WudingLufeng basin that is an important part of the zone is located on the west edge in the middle of the rift. The most important ore-hosting rocks are Mesoproterozoic dolomite rocks in the basin controlled by a ring fracture system, which is a fundamental structure of the basin. Plenty of silicate minerals and acicular apatite, feldspar phenocrysts and small vesicular, flown line and flown plane structures, melt inclusion and high temperature fluid inclusion found in most ore-hosting dolomites suggest that this kind of rocks could not be sedimentary dolomite, marble or hydrothermal carbonate rocks. The Zr/Hf and Nb/Ta values of the rocks are identical with those of associated mantle-derived rocks, and vary widely. For the monomineral dolomite, d18OSMOW‰ = +5.99 to +18.4 and d13CPDB‰ = à3.01 to +0.94, which fall within the range for all carbonatitic volcanic rocks of the world. As for the accessory minerals, the values of d18OSMOW‰ of magnetite (=+3.47 to +5.99‰) are close to that of the mantle (34S‰ values of sul?des (à5.09 to +5.78, averaging +1.50) are close to that of meteorite. For all the ore-bearing dolomite rocks, eNd = +0.19 to +2.27, and the calculated ISr = 0.699143, while for the associated mantle-derived rocks, eNd = +3.18 to +3.72. All the data suggest that the mineral assemblage is not only igneous but also of metasomatic mantle origin. And the presence of acicular apatite indicates that the rocks were formed by magma rapidly cooling. And the phenocryst texture and vesicular, flown and ropy and pyroclastic structures suggest that the igneous rocks were extrusive. Therefore, the ore-bearing dolomite rocks are carbonatitic volcanic rocks. This conclusion implies that most iron and copper ore deposits hosted in the dolomite rocks should be of the carbonatite type.

关键词： Central Yunnan Kunyang rift Precambrian Mineralization Carbonatitite Volcanic rocks Petrogenesis Iron and copper ore deposit

A new method for spatio-temporal prediction of rainfall-induced landslide

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Science china Earth sciences 2006年第4期49卷 421-430页

作者： DING Jixin1,2, YANG Zhifa2, SHANG Yanjun2, ZHOU Shenghua1 & YIN Juntao3 1. china Non-ferrous Metals Resource Geological Survey, beijing 100012. china 2. institute of geology and geophysics, chinese academy of sciences, key Laboratory of Engineering Geomechanics, beijing 10002., china 3. School of Geoscience & environmental Engineering, Central South University, Changsha 410083, china china Non-ferrous Metals Resource Geological Survey Beijing China institute of geology and geophysics Chinese Academy of Sciences Key Laboratory of Engineering Geomechanics Beijing China School of Geoscience & environmental Engineering Central South University Changsha China

Geological condition and rainfall are two most principal conditions inducing landslides in the Chongqing region. By analyzing the forming conditions of rainfall-induced landslides, a new method for spatio-temporal prediction of rainfall-induced landslide is brought forward on the basis of grading and overlapping geological condition and rainfall factor in this paper. At first, semi-quantitative assessment and grading for the geological condition of a certain area or slope can be carried out with the multi-factor interactive matrix. Then the severity of rainfall in that area is grading according to the maximum daily rainfall and the total rainfall in a rainfall course. Finally, the “landslide probability judgement factor” can be worked out through grading and overlapping “geological condition influenc- ing factor” and “rainfall influencing factor”, by which the landslide can be graded into 4 grades, they are landslide extremely easily happening, landslide easily happening, landslide difficultly happening and landslide hardly ever happening respectively. More accurate spatio-temporal prediction of rain- fall-induced landslides can come true on the ground of detailed geological survey of some dangerous slopes in an area and more precise weather forecast. Finally, the reliability and feasibility of carrying out the spatio-temporal prediction of rainfall-induced landslides with the method of “two factors” grading and overlapping are validated by the example of Jipazi landslide.

关键词： rainfall-induced landslide, geological condition, rainfall, two factors, grading and overlapping, interactive matrix, spatio-temporal prediction.