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Physical mechanisms of plant roots affecting weathering and leaching of loess soil

Science china Earth sciences 2006年第9期49卷 1002-1008页

作者： LI Yong1,2, ZHANG Qingwen1,2, WAN Guojiang3. HUANG Ronggui3. PIAO Hechun3. BAI Lingyu2 & LI Lu2 1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, institute of Soil and Water Conservation, chinese Academy of sciences, Yangling 712100, {3. 2. institute of Agro-Environment and Sustainable Development, chinese Academy of Agricultural sciences, Beijing 100081, {3. 3. institute of geochemistry, chinese Academy of sciences, guiyang 550002. china 1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water Conservation Chinese Academy of Sciences Yangling 712100 China 2. institute of Agro-Environment and Sustainable Development Chinese Academy of Agricultural Sciences Beijing 100081 China 3. institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

Plant roots have potential impacts on soil mineral weathering and *** objective is to understand the physical mechanisms of plant roots affecting weathering andleaching of loess soil. Root densities were measured through the method of a large-size dug profile,and transport fluxes of soil elements were determined using an undisturbed monolith soilinfiltration device on the hilly and gully regions of the chinese Loess Plateau. The results showthat the improvement effects of soil environment by plant roots are mainly controlled by the densityand weight of the fibrous roots with the diameters less than 1 mm. Plant roots have the strongereffects on soil physical properties than chemical properties. The principal components analysis(PCA) indicates that soil physical properties by plant roots account for 56.7% of variations in soilenvironment whereas soil chemical properties and pH contribute about 24.2% of the soil *** roles of plant roots in controlling soil weathering and leaching increased in the followingorder: infiltration enhancement > increase of bio-active substance > stabilization of soilstructure. The effects of plant roots on soil mineral weathering and leaching can be quantifiedusing the multiple regression models with the high prediction accuracies developed in this study.

关键词： plant roots, soil weathering and leaching rates, soil environment field, principal components analysis (PCA), chinese Loess Plateau.

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Advances in geochemical research on nanometer materials

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Progress in Natural Science:Materials International 2006年第4期16卷 331-337页

作者： ZHU Xiaoqing and WANG Zhonggang Key Laboratory of Ore Deposit geochemistry, institute of geochemistry, {3. Academy of sciences, guiyang 550002. china [a]Key Laboratory of Ore Deposit geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang China

Important advances have been made in the field of geochemistry since nanometer science and technology were introduced into the field of geoscience. The nanometer particulates have been discovered in naturally-occurring ore deposits, volcano-eruptive materials and geo-gases, and a more detailed exploration of the metallogenic mechanism of endogenic metallic ore deposits has been conducted. It is considered that some ore-forming metals may transport in the form of native particulates. Because they have very strong capabilities of adsorption, adsorption is always regarded as an important mechanism of metallogenesis under supergenic and low temperature conditions. Therefore, a new technology of ore exploration has also been developed. This paper attempts to review the new advances in geochemical research on nanometer materials, as well as its perspectivess.

关键词： nanometer geochemistry adsorption metallogenic theory prospecting method.

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Population information extraction in Chaohu watershed based on RS and GIS

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chinese Science Bulletin 2003年第2期48卷 181-183页

作者： LIU Jianjun1,2 & LI Chunlai3.1. institute of geochemistry, chinese Academy of {3., guiyang 550002. china 2. Graduate School, chinese Academy of {3., Beijing 10003., china 3. National Astronomical Observatories, chinese Academy of {3., Beijing 100012, china Correspondence should be addressed to Liu Jianjun (e-mail: dhsliujj@ ***) institute of geochemistry Chinese Academy of Sciences Guiyang China Graduate School Chinese Academy of Sciences Beijing China National Astronomical Observatories Chinese Academy of Sciences Beijing China

It is always difficult to extract population in-formation of small watershed during the region environment assessment. The report adopted compound areal interpola-tion to study the population in Chaohu watershed with the GIS technique and landuse interpretation data from remote sensing. The result indicated that the method is effective to extract population information of small watershed.

关键词：巢湖流域人口分布信息提取 RS GIS 小流域生态环境评价

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Mantle-derived sulfur and its time constraints on gold mineralization of Ailaoshan gold belt, china

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chinese Science Bulletin 1999年第S2期44卷 242-244页

作者： BI Xianwu institute of geochemistry, chinese Academy of {3., guiyang 550002. china institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

IN the previous studies of hydrothermal deposits much attention was paid to their material sources ratherthan the mechanisms of dynamic association of ore-forming fluids. In recent years many studies haveshown that ore-forming elements were transferred into ore-forming solutions after some suitable mineralizerwas incorporated into hydrothermal solutions. Therefore, the time at which the mineralizer is incorporated into hydrothermal solutions could, to a great extent, reflect the time of ore deposition. In the dynamic study of the origin of ore deposits on a trial basis the author took the Ailaoshan gold belt in YunnanProvince as an example and carried out investigations into the sources of mineralizers (the anion coordinates of stable complexes of gold in hydrothermal solutions) in ore-forming hydrothermal solutions and theconstraints of relevant geological events on gold mineralization.

关键词： sulfur isotope mantle-derived sulfur dating gold mineralization Ailaoshan gold belt.

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Evidence of acid nature of ore-forming solutions

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chinese Science Bulletin 1999年第S2期44卷 199-201页

作者： CHEN Fu institute of geochemistry, chinese Academy of {3., guiyang 550002. china institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

THE author thinks that the ore-forming solution is formed not by the near-neutral brine but by the strongacid solutions. Some evidence are the following: （i） The simulating experiments showed that, all near-neutral supergenic water as volcanic hotspring water of Tengchong, K-brine of Mengyejing, seawater of Qingdao, oil-gasses-bearing water of Chitianhua, rain water of guiyang and CO2-bearing rain cannot form metal-bearing solutions by heating mixedabove-mentioned supergenic water with ore-source rocks as basalt, ore-bearing carbonate, sandstone andshale. The most content of Cu, Pb, Zn, Hg, Sb, As, Ag in solutions is only （0.3.0.5）×10-6.They cannot form any ore deposit. Oppositely, the acid solution of pH=1.0 is easy to form metal-bearingsolutions with every ore-source rocks. The most content of metal in solution is n×10-n×1000 × 10-6i.e. rose in 3.5 grades. The content of metals in humic acid-bearing solutions is variable, perhaps dueto the changes of humic components and content and due to easy-decomposition by oxidation or *** the best one in solutions to form ore-forming solution is only the acidic water.

关键词： ore-forming solution acid solution in nature genesis of brine.

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Epithermal gold deposits in china and potential assessment

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chinese Science Bulletin 1999年第S2期44卷 164-166页

作者： QIU Yuzhuo institute of geochemistry, chinese Academy of {3., guiyang 550002. china institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

THE epithermal gold deposit (epi-gold) is one of the most important types in various gold deposits all overthe world. The discovery of several superlarge deposits of this type around the circum-Pacific Rim duringthe 1980s, greatly stimulated the interest in searching for epi-golds in the world as well as in china. Theepi-gold has become a major target in gold exploration in china during last two-decade "Golden *** discovery of the Zijinshan Cu (Au) deposit in SE china and the Axi and other Au deposits in NWchina is the significant success in gold prospecting in this field. The author suggested that it is the timeto do an overview and the potential assessment of epi-golds in china Some people are holding an optimistic idea on this topic mainly based on the following considerations: (i) as a host rock, the subaerial volcanic rocks of Mesozoic are widespread in East china; (ii)

关键词： epithermal gold deposit china potential assessment.

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Experimental measurement of the electrical conductivity of single crystal olivine at high temperature and high pressure under different oxygen fugacities

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Progress in Natural Science:Materials International 2006年第4期16卷 387-393页

作者： DAI Lidong, LI Heping, LIU Congqiang, CUI Tongdi, SHAN Shuangming, YANG Changjun, LIU Qingyou and DENG Heming Laboratory of the Earth’s Interior Materials and Fluid geochemistry, institute of geochemistry, {3. Academy of sciences, guiyang 550002. china Graduate School of the {3. Academy of sciences, Beijing 10003., china institute of geochemistry, {3. Academy of sciences, guiyang 550002. china Guizhou University, guiyang 550004, china Laboratory of the Earth's Interior Materials and Fluid geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China Graduate School of the chinese Academy of sciences Beijing 100039 China institute of geochemistry chinese Academy of {3. Guiyang 550002 China Guizhou University Guiyang 550004 China

At 1.0-4.0 GPa and 1123.1473.K and under oxygen fugacity-controlled conditions (Ni + NiO, Fe + Fe3.4, Fe + FeO and Mo+ M0O2 buffers), a YJ-3.00t Model six-anvil solid high-pressure apparatus and a Sarltron-1260 Impedance/Gain-Phase analyzer were employed to conduct an in situ measurement of the electrical conductivity of single crystal olivine. Experimental results showed that: (1) within the range of experimentally selected frequencies (103.106 Hz), the electrical conductivity of the sample is of great dependence on the frequency; (2) with the rise of temperature ( T), the electrical conductivity (σ) will increase, and the Arrenhius linear relationship is established between lgσ and 1/T; (3. under the control of oxygen buffer Fe+ Fe3.4, with the rise of pressure, the electrical conductivity tends to decrease whereas the activation enthalpy and independent-of-temperature preexponential factor tend to increase, with the activation energy and activation volume of the sample estimated at (1. 25 ± 0.08) eV and (0.105 ±0.025) cm3.mol, respectively; (4) under given pressure and temperature conditions, the electrical conductivity tends to increase whereas the activation energy tends to decrease with increasing oxygen fugacity; and ( 5) the mechanism of electrical conduction of small polarons can provide insight into the behavior of electrical conduction of olivine under high pressure and high temperature.

关键词： olivine high temperature and high pressure electrical conductivity oxygen fugacity small polaron.

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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, {3. Academy of sciences, Guangzhou 510640, china 2. Graduate University of {3. Academy of sciences, Beijing 10003., china 3. SHRIMP isotope Laboratory, {3. Academy of Geological sciences, Beijing 10003., china 4. institute of Geology and Geophysics, {3. Academy of sciences, Beijing 100029, 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.

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Geological setting of some classical selenium-bearing formations in china

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chinese Science Bulletin 1999年第S2期44卷 185-186页

作者： WEN Hanjie and QIU Yuzhuo institute of geochemistry, chinese Academy of {3., guiyang 550002. china institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

SELENIUM is a highly dispersed element with a lower Clarke of 0.05×10-6 and rarely forms its own independent deposits in the crust. In recent years by the discovery of a series of selenium-bearing deposits（such as Laerma selenium-gold deposit and Yutangba selenium deposit） and selenium-rich strata （westHubei, Laerma, Ziyang, Langao, northwest Hunan, etc.）, the character and genesis of the seleniumbearing formation （SBF） have been noted by many researchers. 1 Some classical SBF in china In china the classical SBFs include: （i） The Lower Cambrian SBF in Laerma, west Qinling: Thebackground value of selenium is 5.47×10-6, and the selenium content of the sillcalite and slate （mainrock type） averages 8.70×10-6 and 3.05×10-6 respectively. （ii） The Lower Cambrian SBF inZiyang and Langao, east Qinling: Selenium is present in relatively high abundance in the SBF, averaging3.89×10-6 in the slate, 2.86×10-6 in the sillcalite. （iii） The Lower Cambrian SBF in northwest Hu-

关键词： selenium selenium-bearing formation geological setting.

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^(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, Beijing 100081, {3. 2. institute of Geology, chinese Academy of Geological sciences, Beijing 10003., {3. 3. institute of Geology and Geophysics, chinese Academy of sciences, Beijing 100029, {3. 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.

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