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The crystal structure of (Fe_(4)Cr_(4)Ni)_(9)C_(4)

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Science china Earth sciences 2005年第3期48卷 338-345页

作者： SHI Nicheng1, MA Zhesheng1, XIONG Ming1, DAI Mingquan1, BAI Wenji2, FANG Qingsong2, YAN Binggang2 & YANG Jingsui2 1. X-ray Diffraction Laboratory, china University of Geosciences, beijing 100083. china 2. institute of geology, chinese academy of geological sciences, beijing 100037, china 1. X-ray Diffraction Laboratory China University of Geosciences 100083 Beijing China 2. institute of geology Chinese Academy of Geological Sciences 100037 Beijing China

(Fe4Cr4Ni)9C4 is a metal carbide mineral formed by combination of Fe, Cr and Ni with C. It occurs in a chromite deposit in the Luobusha ophiolite, Tibet. Based on the determina- tion of its crystal structure, the empirical formula is (Fe4.12Cr3.84Ni0.96)8.92C3.70 and the simplified formula is (Fe4Cr4Ni)4C9. The mineral is hexagonal with a = 1.3.3.2(2) nm, c = 0.44690(9) nm, space group P63.m c, Z=6 and the calculated specific gravity Dx = 7.089 g/cm3. Fe, Cr and Ni occupy different crystallographic sites and their coordination numbers are approximately 12, forming an alternate stacking sequence of flat and puckered layers along the c axis. Some me- tallic atoms have a defect structure. The interatomic distances of Fe, Cr and Ni are 0.2525— 0.2666 nm, and the distances between Fe, Cr, Ni and C are 0.1893.0.2169 nm. The coordina- tion number of carbon is 6. It occurs in interstices of the metallic atoms Fe, Cr and Ni to form trigonal-prismatically coordinated polyhedra. These coordination polyhedra are linked with each other via shared corners or shared edges into a new type of metal carbide structure.

关键词： Luobusha of Tibet, metal carbide, crystal structure.

Palaeoclihlatic Indicators of china's Quaternary Saline Lake Sediments and Hydrochemistry

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Acta Geologica Sinica(English Edition) 2000年第2期74卷 259-265页

作者： ZHENG Mianping, ZHAO Yuanyi and LIU JunyingResearch & Development center of Saline Lake and Epithermal Deposits,chinese academy of {3. sciences, beijing 100037

In this paper the authors classify saline lake sediments into the cold, warm and eurythermal phases, reveal the consistency between the zoning of hydrochemical types of modern saline lake water and climatic zoning and give climatic parameters under the conditions of typical cold phase (mirabilite and natron), warm phase (thenar-dite) and slightly warm phase (bloedite) saline lake deposition.

关键词： Saline lake sediments hydrochemistry palaeoclimatic indicator Quaternary

shrimp dating of the Bangong Lake SSZ-type ophiolite: Constraints on the closure time of ocean in the Bangong Lake-Nujiang River,northwestern Tibet

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chinese Science Bulletin 2007年第7期52卷 936-941页

作者： SHI RenDeng1,2 1 School of Earth and Space sciences, University of Science and Technology of china, Hefei 23.026, china 2{3., chinese academy of geological sciences, beijing 100037, china (email: shird@***) School of Earth and Space sciences University of Science and Technology ofChina Hefei 230026 China

The Bangong Lake ophiolite is located in the westernmost part of the Bangong Lake-Nujiang River suture zone. It is a tectonic mélange consisting of numerous individual blocks of peridotite, pillowed and massive lavas and mafic dykes with SSZ-type ophiolitic geochemical affinity formed at the end of a Wilson circle. The shrimp U-Pb ages of the co-magmatic zircon domains from one gabbroic dyke (Sample 01Y-155) range from 162.5±8.6 Ma to 177.1±1.4 Ma with an average of 167.0±1.4 Ma (n = 12, MSWD = 1.2), suggesting that the subduction of the Bangong Lake Neo-Tethyan Ocean started before the Middle Jurassic. It is inferred that the tectonic transform from spreading to subduction of the Neo-Tethyan Ocean began before the Middle Jurassic in the Bangong Lake area.

关键词：西藏班公湖怒江缝合带古海洋闭合时期 SSZ型蛇绿岩 shrimp 测年

TAKE ANOTHER VISION TO THE UPLIFT OF THE QING—ZANG (TIBETAN) PLATEAU BASED ON CENOZOIC VOLCANISM

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地学前缘 2000年第S1期7卷 370-371页

作者： Liu Jiaqi [WT5,5”BX](institute of geology and Geophysics,chinese {3. of sciences,beijing 100029, china)

The emergence of the Qing—Zang plateau is among the most important geological events on the globe since the Cenozoic Era. Many geological issues can find answer from here. The major issues concerning plateau probably have three: (1) geodynamics, timing and speed of the plateau uplift;(2) The plateau uplift impact on surrounding environment;(3. mineral resources in the plateau. The authors want to focuses on first issue based on volcanisms occurred in interior and surrounding of the plateau, The new opinions are following:(1) Each volcanic eruptive episode corresponded to strong uplift stage;(2) The dynamic mechanism of the plateau uplift can not ignore another force from west beyond collision between Indian and Eurasia plates from South;(3. The surrounding volcanic chain is not only related to the collision from South, but also from west.

关键词： Tibetan plateau the Cenozoic volcanism volcanic chain surro unding plateau west collision uplift mechanism

Sequence Stratigraphy and Relative Sea Level Changes in Sinian System of Yichang, Hubei Province

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Journal of Earth Science 1996年第1期15卷 29-37页

作者： Wang Ziqiang (Department of geology and Mineral Resources, china University of Geosciences, {3. 100083. Gao Linzhi (institute of geology, chinese academy of geological sciences, beijing 100037) Zhang Linghua Jiang Ganqing Zhang Chuanheng Yin Yong (Dep

The study on outcrop sequence stratigraphy of the Sinian section in the Yangtze Gorges an important step in the comprehensive stratigraphy for the Sinian stratotype. In this paper, the base of the Nantuo tillite is selected as the bottom boundary of the Sinian, and the top of the Baimatuo Member of the Dengying Formation is taken as the top boundary. The Sinian lasted from 740 the to 570 Ma. According to the features of sequence boundary facies and the parasequence sets, two supersequences are recognized in the Sinian with six sequences. In this paper, the authors discuss the correlation of those sequences. On the basis of the subsidence rate and the thickness of decompressed deposits, the authors discuss the mechanism of tectonic and sedimentation of the Dengying Formation and the features of high-frequency rhythms as well as the 3.d-order sequences in the Yangtze Gorges.

关键词： Sinian System sequence supersequence stacking parasequence set.

Serpentinization of peridotites from the southern Mariana forearc

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Progress in Natural Science:Materials International 2009年第10期19卷 1287-1295页

作者： Xiaomei Wang a,b,Zhigang Zenga,Junbing Chenc a Key Laboratory of Marine geology and Environment,institute of Oceanology,chinese {3. of sciences,7 Nanhai Road,Qingdao 266071,china b Graduate School of chinese {3. of sciences,19 Yuquan Road,beijing 100049,china c geological Brigade of Hydrogeology and Engineering geology,Zhejiang geological Prospecting Bureau,206 Baoshan Road,Ningbo 3.5012,china [a]Key Laboratory of Marine geology and Environment Institute of Oceanology Chinese Academy of Sciences 7 Nanhai Road Qingdao 266071 China [b]Graduate School of chinese academy of sciences 19 Yuquan Road Beijing 100049 China [c]geological Brigade of Hydrogeology and Engineering geology Zhejiang Geological Prospecting Bureau 206 Baoshan Road Ningbo 315012 China

A detailed petrologic and mineralogic study was carried out on serpentinized peridotites dredged from the southern landward slopes of the Mariana Trench,in order to reveal the serpentinization process of these unusual rocks and to identify the sole presence of the mineral *** constituent minerals of these southern Mariana forearc peridotites are olivine,amphibole and spinel,as well as serpentine,chlorite and *** with serpentinite seamounts,the serpentinized peridotites from the southern Mariana forearc are characterized by the absence of magnetite and brucite,and the common presence of talc;besides,the serpentine mineral variety is simplex,only *** mineral chemistry and mineral phase relationships,we conclude that(1) the absence of magnetite in the serpentinized peridotites is due to incomplete serpentinization,other than magnetite,the iron end-member in olivine forms Ferich brucite and Fe-rich serpentine;(2) brucite is not stable with high silica activity,reacting with later SiO2-rich fluid and then forming lizardite,leading to a lack of brucite in these serpentinized peridotites;(3. the occurrence of talc is the result of later SiO2-rich fluid reactions with lizardite;and(4) the reason for the sole occurrence of lizardite is that the temperature condition of our study are awas nothig henough for the formation of antigorite(whichisstable at >500 °C).Despite the broad overlap of lizardite and chrysotile in growth temperature,differences in the modes of occurrence of lizardite and chrysotile,such as the scarcity of H2O,low porosity and permeability,as well as the actual situation of initial serpentinization in the study area,result in the absolute prevalence of lizardite over chrysotile in the area.

关键词： Peridotite Serpentinization Mineral chemistry Lizardite Mariana

Age of Yingfeng rapakivi granite pluton on the north flank of Qaidam and its geological significance

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Science china Earth sciences 2004年第4期47卷 357-365页

作者： XIAO Qinghui1,2, LU Xinxiang1,3. WANG Fei4, SUN Yangui5, WEI Xiangdong3.& XING Zuoyun6 1. Division of Granite geology, china geological Survey, Yichang 443.03. china 2. Information center of Ministry of Land and Resources, beijing 100812, china 3. geological Survey of Henan Province and institute of geological Research of Henan Province, Zhengzhou 450053. china 4. geological institute, china Seismological Bureau, beijing 100029, china 5. geological Survey institute of Qinghai Province, Xining 81003., china 6. china University of Geosciences, Wuhan 43.074, china Division of Granite geology China Geological Survey Yichang 443003 China Information center of Ministry of Land and Resources Beijing 100812 China geological Survey of Henan Province and institute of geological Research of Henan Province Zhengzhou 450053 China geological institute China Seismological Bureau Beijing 100029 China geological Survey institute of Qinghai Province Xining 810032 China china University of Geosciences Wuhan 430074 China

The Yingfeng rapakivi granite on the north flank of Qaidam is a newly discovered Proterozoic rapakivi pluton in china, which was found after the discovery of Shachang rapakivi in Miyun County, beijing and Kuandian rapakivi in Jilin Province. Yingfeng rapakivi pluton is ex-posed on the north side of the suture belt between Qinling-Kunlun orogenic belt and North china plate. U-Pb zircon isotopic dating and Ar-Ar isotopic dating of both hornblende and K-feldspar from the Yingfeng rapakivi granite have been conducted. The results show that the age of (1776±3.)Ma at the upper intercept in Concorde diagram represents the age of formation of the plu-ton, whereas the age of (526 281) Ma at the lower intercept and Ar-Ar mineral dating of horn-blende and K-feldspar correspond to the age of a later event affecting the pluton, suggesting that Yingfeng pluton has ever been affected by strong regional Caledonian-Hercynian tectonic movement after its formation. The discovery of middle Proterozoic Yingfeng rapakivi granite pro-vides a petrologic evidence for the timing of cratonization of both the continental crust basement in western china and the basement of the North china plate and for a rifting event taking place in the mid-Proterozoic, suggesting that an amalgamation of ancient china continents had ever happened during the L liang Movement?between the early Proterozoic and the mid-Proterozoic.

关键词： rapakivi, U-Pb dating, Ar-Ar dating, Kunlun-Qinling orogenic belt.

Active Tectonic Belts in Tibet and Their Control on Earthquakes

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Acta Geologica Sinica(English Edition) 1986年第4期 23-29+99页

作者： Han Tonglin institute of geology, chinese academy of geological sciences, beijing

A series of nearly N-S-trending active tectonic belts are found in Tibet. The earthquakes there mostly belong to shallow-focus ones, and are characterized by high frequency, high intensity and short recurrence intervals. The epicentres are mainly located near the boundary faults along the active tectonic belts. They are most concentrated, with small earthquake magnitudes, at the turning or intersecting parts of the boundary faults, and are less concentrated, bat with big earthquake magnitudes, in other parts of the boundary faults. The mechanic properties of the seismic fracture belts are generally related to their strike: the NW-trending ones are of dextral strike-slip nature and the NE-trending ones are of sinistral strike-slip nature, while the nearly N-S-trending ones exhibit the nature of tensional normal faults. In the region the earthquakecontrolling structures are considered to be the active tectonic belts, while the seismogenetic structures are the boundary faults in the active tectonic belts.

关键词： Active Tectonic Belts in Tibet and Their Control on Earthquakes

Metallogenic characteristics of epithermal gold deposits in Tianshan, Xinjiang, china

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chinese Science Bulletin 1999年第S2期44卷 138-139页

作者： FENG Jianzhong~1, FU Shuixing~2, WU Dewen~3.and YANG Zian~3.1. Department of geology, Peking University, beijing 100871, china 2. beijing institute of geology for Mineral Resources, beijing 100012, china 3. center of Remote Sensing for geology, CNNC, beijing 101601, china Department of geology Peking University Beijing 100871 China beijing institute of geology for Mineral Resources Beijing 100012 China center of Remote Sensing for geology CNNC Beijing 101601 China

TIANSHAN in southern Xinjiang belongs to the Paleozoic island arc system in which volcanic rocks are extensively distributed. A series of epithermal gold deposits such as the Axi, Xitan, Cuiling andShuangfengshan gold deposits have been discovered. 1 geological settings of epithermal gold deposits in Tianshan, southern Xinjiang Tianshan in southern Xinjiang belongs to the Paleozoic island arc system. To its north is the Kazakhstan plate, and to its north is the Tarim plate. From west to east, the tectonic units are characterizedby Yili island arc, southern Tianshan arc-basin, Jiaoluotage island arc and Xingxingxia island arc. TheEW-trending Tianshan ore belt is controlled by Kanggurtag geosuture. In its west part, it is controlled byShenglidaban geosuture. The linear structure is NNW-trending; from north to south, the faults

关键词： metallogenic characteristics gold deposits Tianshan Xinjiang.