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Electron microscopy study of the sakhaite from endogenous borate deposit in Hunan, china

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Science china Earth Sciences 2004年第3期47卷 232-238页

作者： LIU Xiangwen1,2. YANG Guangming2. ZOU Huamin3, QU Jing1 & ZHAO Wenxia4 1. Graduate School, china university of {2., wuhan 430074, china 2. Test Center, china university of {2., wuhan 430074, china 3. Physics and Technology College, wuhan university, wuhan 430072. china 4. Test Center, Zhongshan university, Guangzhou 5102.5, china china Univ Geosci Grad Sch Wuhan 430074 Peoples R China china Univ Geosci Test Ctr Wuhan 430074 Peoples R China wuhan Univ Phys & Technol Coll Wuhan 430072 Peoples R China Zhongshan Univ Test Ctr Guangzhou 510275 Peoples R China

Sakhaite specimens from an endogenous borate deposit in Hunan Province, china have been studied in detail by means of transmission electron microscopy (TEM). The selected area electron diffraction (SAED) patterns obtained with different crystal zone axes show that the crystal system is cubic, with a = 1.463 nm. The convergent beam electron diffraction (CBED) patterns indicate that the point group and space group of sakhaite is m3m and Fd3m, respec-tively. The space group of synthetic sakhaite determined by Chichagov (1974) is F4132. The possible reasons why the space groups of the natural and the synthetic sakhaites are different are discussed.

关键词： sakhaite, space group, convergent beam electron diffraction (CBED).

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,{2., china 1. Chinese Academy of Geological Sciences Institute of Geology 100037 Beijing China 2. china university of geosciences 430074 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.

Synthesis of todorokite by refluxing process and its primary characteristics

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Science china Earth Sciences 2004年第8期47卷 760-768页

作者： FENG Xionghan1, LIU Fan1, TAN Wenfeng1, LIU Xiangwen2.& HU Hongqing1 1. College of Resources and Environment, Huazhong Agricultural university, wuhan 430070,{2. 2. Testing Center,{2. university of geosciences, wuhan 430074,{2. 1. College of Resources and Environment Huazhong Agricultural University 430070 Wuhan China 2. Testing Center China University of Geosciences 430074 Wuhan China

Single phase and well-crystallined todorokite were synthesized by heating and refluxing process from birnessite as a precursor. The average chemical composition of the synthesized todorokites by refluxing for 8 h and for 2. h was Mg0.19MnO2.11(H2.)1.15 and in0.17-MnO2.10(H2.)0.88, respectively. The crystallinity of the todorokite increased and no other phase was produced with increasing refluxing period. The synthesized todorokites have the same morphologies and the similar structural characteristics with the natural todorokites and hydro-thermally synthesized samples. The chemical compositions of the synthetic tordorokites by refluxing process are close to those of todorokites synthesized by hydrothermal process, except a higher average oxidation state of Mn for the former.

关键词： todorokite,birnessite,manganese oxide,refluxing,hydrothermal,synthesis.

Pathways of birnessite formation in alkali medium

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Science china Earth Sciences 2005年第9期48卷 1438-1451页

作者： FENG Xionghan1, TAN Wenfeng1, LIU Fan1, HUANG Qiaoyun1 & LIU Xiangwen2.1. College of Resources and Environment, Huazhong Agricultural university, wuhan 430070,{2. 2. Testing Center,{2. university of geosciences, wuhan 430074,{2. 1. College of Resources and Environment Huazhong Agricultural University 430070 Wuhan China 2. Testing Center China University of Geosciences 430074 Wuhan China

Birnessite is a common weathering and oxidation product of manganese-bearing rocks. An O2.oxidation procedure of Mn(OH)2.in the alkali medium has been used to synthesize birnessite. Fast and powder X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), energy dispersed X-ray analysis (EDAX), infrared spectroscopy (IR) techniques and chemical composition analysis, Eh-pH equilibrium diagram approaches were employed to investigate the reaction process and pathways of birnessite formation. Results showed that the process of the birnessite formation could be divided into four stages: (1) forma- tion stage for hausmannite and feitknechtite, (2. stage of transformation of hausmannite and feitknechtite to buserite, (3) buserite crystal growing stage, and (4) stage of conversion of buser- ite into birnessite. Mn(OH)2.was mainly present as amorphous state only for a short initial time of oxidation reaction. In the oxidation process, buserite formed following two pathways by recrys- tallization after dissolution of the intermediates, and the transformations of the minerals de- pended on the Eh determined by the dissolved O2.concentration on their surfaces. The results are fundamental in further exploration on the mechanism of birnessite formation in the alkali medium. A great practical significance would also be expected with respect to the areas of mate- rial sciences.

关键词： birnessite, pathway of formation, reaction process, Eh-pH diagram, hausmannite, feitknechtite.

Trace elements in volcanic rocks from Yangba Formation, Bikou Group, Qinling area, china——Implications for tectonics

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Chinese Science Bulletin 1999年第S2期44卷 44-46页

作者： DING Zhenju~(1,2. and LIU Congqiang~1 1. Open Laboratory of Ore Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002. china 2. china university of geosciences,{2., china Open Laboratory of Ore Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China china university of {2. Wuhan 430074 China

YANGBA Formation of Bikou Group is located in south Qinling, a famous orogenic belt separating Chinesecontinent into two parts: North china plate and Yangzi plate. The Yangba Formation comprises the maficand felsic volcanic rocks formed in an ancient seafloor environment during the Proterozoic era. The suitesof mafic and felsic volcanic rocks are petrochemically divided into tholeiite and calc-alkaline dacite, respectively, showing characteristics of bimodal volcanic rock mainly by lithology and major element content, and a lack of typical intermediate rocks. These signatures indicate that the volcanic rocks of YangbaFormation were generated in rift tectonics setting. The tholeiites of Yangba Formation are similar in trace element content to mid-ridge basalt, displaying a slight depletion to enrichment in light rare earth elements (LREE’s) (La/Yb_n = 0.6-1.4), slightfractionation between LREE (La/Sm_n =0.55-1.14) and HREE (Gd/Lu_n = 1.09-1.50), and relative flat patterns in whole. The decoupling of Eu to its neighboring elements in two samples likely indicates an effect of fractional crystallization in magma evolution. The La-La/Sm, Ni-La, Ni-Th, Ni-Ta,and Ni-Hf diagrams all support a conclusion that the mafic rocks are generated by partial melting pro-

关键词： trace element volcanic rock tectonics setting Bikou Group.

Sr and Pb isotopic constraints on ore formation of the copper deposits in Bikou-Group rocks, Qinling area, china

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Chinese Science Bulletin 1999年第S2期44卷 48-50页

作者： DING Zhenju~(1,2., LIU Congqiang~1, YAO Shuzhen~2.and ZHOU Zonggui~2.1. Open Laboratory of Ore Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002. china 2. china university of geosciences,{2., china Open Laboratory of Ore Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China china university of {2. Wuhan 430074 China

BIKOU Group comprises spilite and keratophyre, which are lower-grade (greenschist facies) metamorphosed and interbedded by main basic rocks at the bottom and acid rocks on the top. Some copper deposits and ore spots such as Damaoping, Faziba and Yangba have been found in spilite stratum. Becauseresearches have not been well carried out on geology of these ore deposits, some basic problems concerning ore source, characteristics of ore-forming fluid and mineralization age, etc. remain unsolved. Thispaper mainly discusses the mineralization mechanism and mineralization age.

关键词： Sr and Pb isotope copper deposit Bikou Group.

Tectonic affinity of Paleozoic stratigraphic slices along the northern margin in Dabie Orogen,central china: evidence from Pb isotope of rocks

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Progress in Natural Science:Materials International 2002年第6期 40-46页

作者： XU Qidong, OUYANG Jianping, ZHANG Benren and KUANG Shaoping(1. Faculty of Earth Resources, china university of {2., wuhan 430074, china 2. Institute of Geochemistry, china university of {2., wuhan 430074, china) Faculty of Earth Resources China University of Geosciences Wuhan 430074 China Institute of Geochemistry China University of Geosciences Wuhan 430074 China

Metavolcanic and metasedimentary rocks from the Paleozoic tectono-stratigraphic units along the northern margin in the Dabie orogen show that there are two types of Pb isotopic compositions, which have some affined regularity with tectonic subdivision. Compared with the main tectonic units of the Qinling orogen, the Dingyuan Formation should be the part of the South Qinling orogenic belt or the northern margin of the Yangtze craton, characterized by less radiogenic Pb isotopic composition, and the Guishan Formation, Nanwan Formation-Foziling Group and the Carboniferous should be the part of the North Qinling orogenic belt which is extended to the east, characterized by more radiogenic Pb isotopic composition. These facts combined with the distribution of the geological units suggest that the Paleozoic subduction zone between the Yangtze and North china cratons should be located in the north boundary of the Nanwan Formation-Foziling Group or somewhere that is covered by the Nanwan Formation-Foziling Grou

关键词： Pb isotope tectono-stratigraphic onit tectonic affinity subduction zone Beihuaiyang.

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对数正态分布下边坡稳定性二元指标体系研究

山地学报 2005年第4期23卷 4442-4446页

作者：罗文强龚珏王亮清方云中国地质大学数理学院中国地质大学图书馆中国地质大学工程学院中国地质大学工程学院湖北武汉430074

安全系数不能考虑边坡系统中实际存在的不确定性,可靠性理论缺乏丰富的工程实践经验,因此,将工程实践经验丰富的安全系数与先进的可靠性理论相结合,建立传统安全系数与可靠性相耦合的二元评价体系具有重要的理论意义和应用价值。设安全... 详细信息

安全系数不能考虑边坡系统中实际存在的不确定性,可靠性理论缺乏丰富的工程实践经验,因此,将工程实践经验丰富的安全系数与先进的可靠性理论相结合,建立传统安全系数与可靠性相耦合的二元评价体系具有重要的理论意义和应用价值。设安全系数服从对数正态分布,取系列的最大可能安全系数(中值安全系数)和变异系数,计算得到最大可能安全系数及在不同变异系数下的破坏概率Pf。从而可由最大可能安全系数和可靠性(R=1-Pf)共同度量边坡的稳定性。将最大可能安全系数与边坡可靠性相乘,对最大可能安全系数进行折减,得到边坡可靠的安全系数。根据折减后安全系数的极限状态,可计算出不同最大可能安全系数的临界变异系数和临界破坏概率。根据不同最大可能安全系数及它的临界破坏概率,绘出边坡稳定性分区图,并建立安全系数和破坏概率相结合的边坡稳定性判别的二元指标体系。文中提供了小样本条件下,利用3倍方差原理估计参数方差的计算方法,并给出了边坡稳定性二元指标体系的研究实例。

关键词：边坡稳定性最大可能安全系数对数正态分布可靠性二元指标体系

Sr and Pb isotopic constraints on ore formation of the copper deposits in Bikou Group rocks, Qinling area, china

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Science Bulletin 1999年第S2期 221-223页

作者： DING Zhenju~(1,2., LlU Congqiang~1, YAO Shuzhen~2.and ZHOU Zonggui~2.1. Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002. china 2. china university of geosciences,{2., china

THE Bikou Group comprises spilite and keratophyre, characterized by lower-grade (greenschist facies)metamorphism, with interbedded basic and acid rocks at the bottom to main basic rock at the top. Somecopper deposits and ore spots such as Damaoping, Faziba and Yangba have been found in spilite stratum. Because researches on geology of these ore deposits have not been well carried out, some basic questionsconcerning matter source, characteristics of ore-forming fluid, mineralization age, etc. remain *** note mainly discusses the mineralization mechanism and mineralization age. 1 Sr isotopic constraints of superimposed mineralization and its age Rb-Sr isochronal ages of vein sulfides of Faziba, Yangba, Damaoping copper deposit are calculatedaccording to the data listed in table 1, which are (342.75)Ma, (347±16)Ma and (12.9±5)Ma,

关键词： Sr Pb isotope ore formation copper deposits.