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Liu G.,China Academy of Geological science | Zhou Y.,China Earthquake Administration | Shi Y.,University of Chinese Academy of Sciences | Miao S.,China Earthquake Administration | He C.,China Earthquake Administration
Journal of Structural Geology | Year: 2017

We performed deformation experiments on foliated granitic mylonites under high-temperature and -pressure conditions. To investigate the effects of pre-existing fabric properties on the rheology of the rocks, these experiments were carried out at different compression directions 30°, 45°, and 60° relative to the foliation, at temperatures of 600–850 °C, under confining pressures of 800–1200 MPa, within a strain rate range of 1 × 10−4/S – 2.5 × 10−6/S. The results of the experiments show that the deformation of three group samples is in the semi-brittle region at temperatures between 600 and 700 °C, and that the deformation of the samples transforms to plastic deformation by power-law creep with the stress exponent n = 3 ± 0.3 at temperatures between 800 and 850 °C. In the semi-brittle region, the mechanical data show that strength reaches its minimum value at an angle of 30° between the compression direction and the original foliation. In the plastic deformation regime, strength reaches its minimum value at an angle of 45° between the foliation and the orientation of the maximum principal stress. The strength with angles between 30° and 60° is lower than that of the compression direction perpendicular to foliation and the compression direction parallel to foliation. Microstructure analysis based on optical and electron microscopy of the deformation microstructures showed plastic deformation of aggregates of biotite and quartz at 800–850 °C. This deformation was extensive and formed new foliation. Quartz c-axis fabrics analysis by EBSD show that at temperatures of 600–700 °C, the c-axis fabric patterns could have been formed by the dominant activity of basal slip, similar with the starting granitic mylonite samples, but the dominant slip systems have been changed and transformed from basal slip to rhomb slip and prism slip at temperature of 800 °C and 850 °C. Microfractures were developed in hornblende and feldspar grains with local plastic deformation. Dehydration reaction was observed in grain rims of hornblende and biotite, where new fine-grained hornblende and biotite crystals grew, accompanied by partial melting. This was followed by experimental deformation and replacement of the original foliation of the samples. The mechanical microstructure data show that there is a significant effect of fabric on the strength of rock, but almost no effect on brittle-plastic transition and deformation mechanism. © 2017 Elsevier Ltd

Xie Y.,University of Science and Technology Beijing | Hou Z.,China Academy of Geological Science | Cooke D.R.,University of Tasmania | Danyushevsky L.,University of Tasmania | And 3 more authors.
Ore Geology Reviews | Year: 2015

The Mianning-Dechang (MD) REE belt of Sichuan, China is one of the most important REE belt in China, which includes Maoniuping, the third largest REE deposit in the world and a series of large to small REE deposits. Mineralization styles varied across the belt, as well as within different parts of the same deposit. Styles include vein-stockworks, pegmatites, breccias and disseminated REE mineralization. Based on geological, geochemical and inclusion studies, this paper proposes a new model for carbonatite hosted REE mineralization. The results show that ore-forming fluid is derived from carbonatite magma, which has high temperature, pressure and density, and is characterized by high K, Na, Ca, Sr, Ba, REE and SO4 contents. The supercritical ore fluid underwent a distinctive evolution path including phase separation, exolution of sulfate melt and unmixing between aqueous fluid and liquid CO2. Rapid geochemical evolution of a dense carbonatite fluid causes REE mineralization and associated alteration to occur within or proximal to the source carbonatite. Veins, pegmatites and carbonatite comprise a continuum of mineralization styles. Veins occur in the outer zone of the upper levels of the deposit. Pegmatites occur in the inner zone of upper levels, whereas disseminated REE ore occurs at the base of the carbonatite. High water solubility in the carbonatite magma and low water, high REE in the exsolved ore-forming fluids, imply that a giant carbonatite body and deep magma chamber are not necessary for the formation of giant REE deposits. © 2014 Elsevier B.V.

Lingang X.,Clausthal University of Technology | Lehmann B.,Clausthal University of Technology | Jingwen M.,China Academy of Geological science
Economic Geology | Year: 2011

The Early Cambrian Niutitang Formation in South China consists of a black shale sequence with a synsedimentary organic carbon-rich polymetallic sulfide layer with extreme metal enrichment locally mined as Ni- Mo-PGE-Au ore. We report a new composite Re-Os isochron age of the sulfide ore layer of 521 ± 5 Ma (n = 14) from three mine sites (Dazhuliushui and Maluhe in the Guizhou province and Sancha in the Hunan province) several hundred kilometers apart. This age corresponds to the biostratigraphic Tommotian age, and is in agreement with recent interpolated Pb-Pb and SHRIMP zircon U-Pb ages from an underlying tuff unit. The initial 187Os/188Os value of the sulfide ore is 0.87 ± 0.07, which is equal to the initial 187Os/188Os ratio of ̃0.80 of the black shale host rock, consistent with the seawater origin of the metals under depositional conditions of very low clastic input. © 2011 Society of Economic Geologists, Inc.

Wang X.,Nanjing University | Chou I.-M.,U.S. Geological Survey | Hu W.,Nanjing University | Burruss R.C.,U.S. Geological Survey | And 2 more authors.
Geochimica et Cosmochimica Acta | Year: 2011

Raman spectroscopy is a powerful method for the determination of CO2 densities in fluid inclusions, especially for those with small size and/or low fluid density. The relationship between CO2 Fermi diad split (Δ, cm-1) and CO2 density (ρ, g/cm3) has been documented by several previous studies. However, significant discrepancies exist among these studies mainly because of inconsistent calibration procedures and lack of measurements for CO2 fluids having densities between 0.21 and 0.75g/cm3, where liquid and vapor phases coexist near room temperature.In this study, a high-pressure optical cell and fused silica capillary capsules were used to prepare pure CO2 samples with densities between 0.0472 and 1.0060g/cm3. The measured CO2 Fermi diad splits were calibrated with two well established Raman bands of benzonitrile at 1192.6 and 1598.9cm-1. The relationship between the CO2 Fermi diad split and density can be represented by: ρ=47513.64243-1374.824414×Δ+13.25586152×Δ2-0.04258891551×Δ3 (r2=0.99835, σ=0.0253g/cm3), and this relationship was tested by synthetic fluid inclusions and natural CO2-rich fluid inclusions. The effects of temperature and the presence of H2O and CH4 on this relationship were also examined. © 2011 Elsevier Ltd.

PubMed | Water Resources University, China Academy of Geological science, U.S. Geological Survey, China Institute of Metrology and China University of Geosciences
Type: | Journal: The Science of the total environment | Year: 2015

Although As concentrations have been investigated in shallow groundwater from the Hetao basin, China, less is known about U and As distributions in deep groundwater, which would help to better understand their origins and fate controls. Two hundred and ninety-nine groundwater samples, 122 sediment samples, and 14 rock samples were taken from the northwest portion of the Hetao basin, and analyzed for geochemical parameters. Results showed contrasting distributions of groundwater U and As, with high U and low As concentrations in the alluvial fans along the basin margins, and low U and high As concentrations downgradient in the flat plain. The probable sources of both As and U in groundwater were ultimately traced to the bedrocks in the local mountains (the Langshan Mountains). Chemical weathering of U-bearing rocks (schist, phyllite, and carbonate veins) released and mobilized U as UO2(CO3)2(2-) and UO2(CO3)3(4-) species in the alluvial fans under oxic conditions and suboxic conditions where reductions of Mn and NO3(-) were favorable (OSO), resulting in high groundwater U concentrations. Conversely, the recent weathering of As-bearing rocks (schist, phyllite, and sulfides) led to the formation of As-bearing Fe(III) (hydr)oxides in sediments, resulting in low groundwater As concentrations. Arsenic mobilization and U immobilization occurred in suboxic conditions where reduction of Fe(III) oxides was favorable and reducing conditions (SOR). Reduction of As-bearing Fe(III) (hydr)oxides, which were formed during palaeo-weathering and transported and deposited as Quaternary aquifer sediments, was believed to release As into groundwater. Reduction of U(VI) to U(IV) would lead to the formation of uraninite, and therefore remove U from groundwater. We conclude that the contrasting distributions of groundwater As and U present a challenge to ensuring safe drinking water in analogous areas, especially with high background values of U and As.

Zhang H.,Jilin University | Zhang H.,China Academy of Geological science | Sun F.-Y.,Jilin University | Hu A.-X.,Jilin University
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2013

The primary compositions of the anticline core at Shangyupo are Beiyu meta-granitoid, meta-rhyolite and meta-mafic rocks. The age and petrogenesis of the biotite schist have been under debate for a very long time. The petrology features and geochemistry of Shangyupo amphibole/scapolite biotite schist are cricoid gradually distributed from the anticlinal core to its edge. The K, Ca, Na, Rr, Sr and Ba have been changed systematically by the high salinity fluid from the ductile shear belts, and Ta and LREE are also shown to have been dramatically changed in this event. LA-MC-ICPMS zircon U-Pb dating for the Shangyupo meta-rhyolite and the meta-ryholite of Jiangxian group yield the weighted mean 207Pb/206Pb age of 2160.5±7.8 Ma and 2161.3±1.5 Ma respectively. The Shangyupo meta-ryhorite and biotite schist may have been formed during the Jiangxian volcano event between 2.20~2.15 Ga, based on the chronology and comparison to related rocks. The HFSE pairs show that the biotite schist is a subalkaline mafic rocks instead of the alkaline mafic rocks as previously suggested. The Jiangxian event may represent a tensional event related to the subduction, based on the comprehensive geological information of Zhongtiaoshan area.

Lingang X.,Clausthal University of Technology | Jingwen M.,China Academy of Geological science | Fuquan Y.,China Academy of Geological science | Hennig D.,Clausthal University of Technology | Jianmin Z.,China University of Geosciences
Journal of Asian Earth Sciences | Year: 2010

The Mengku iron deposit (110Mt at 44% Fe) in the eastern extension of the Rudnyi Altai mineral belt, Xinjiang, NW China, is hosted in an Early Devonian volcano-sedimentary sequence affected by prograde skarn formation (clinopyroxene, garnet, scapolite and albite) and retrograde alteration (actinolite, epidote, chlorite and apatite). Ore minerals are magnetite, with minor chalcopyrite, pyrrhotite and pyrite. Gangue minerals include predominantly diopside, andradite, epidote, chlorite, quartz and calcite. Fluid inclusions in garnet and clinopyroxene yield homogenization temperatures (Th) of 241-500°C, and salinities of 9.6-13.0wt.% NaCl equivalent. Fluid inclusions in quartz consist of two varieties: (1) liquid-vapor-solid inclusions with (Th) of 348-458°C and salinities of 38.2-57.1wt.%, and (2) two-phase inclusions with (Th) of 166-382°C and salinities of 9.6-13.0wt.% NaCl equivalent. Two-phase inclusions in calcite vary from 145 to 265°C, with salinities of 1.2-9.6wt.% NaCl equivalent. The fluid evolution progressed from high temperature and moderate salinity (prograde skarn stage) to moderate T and salinity (retrograde stage), to low T and salinity (sulfide stage). Stable isotope data of quartz and calcite (-84‰ to -110‰ δD, 5.5-7.0‰ δ18OSMOW, and -3.8‰ to -6.1‰ δ13CPDB) reflect late-stage interaction of meteoric water with granitic rocks. Skarn formation was likely related to a Late Devonian tonalite (378±7Ma, U-Pb zircon age). The geological and geochemical evidence suggests magnetite skarn formation from granite-related fluids which reacted with andesitic to mafic volcanics and their intercalated carbonate beds and lenses, contrary to earlier interpretations of the deposit as of synsedimentary-exhalative origin or related to iron-oxide magma. © 2010 Elsevier Ltd.

Li Q.,Xi'an University of Science and Technology | Li Q.,Chang'an University | Li Y.,China Academy of Geological science
Geophysical Prospecting for Petroleum | Year: 2014

To improve the precision and identification capacity of anisotropic parameter spectrum extracted from seismic data, based on traveltime-distance equation of reflection wave in anisotropic media, selective correlation method is introduced. The selected-correlation method is used to improve the mapping of anisotropic parameter spectrum and the extraction precision of anisotropic parameters spectrum. Model test with synthetic data indicates that the resolution of seismic anisotropic parameters spectrum with selected-correlation method is greatly improved and thin layers can be identified. The application to seismic gathers from real data in weak anisotropic area demonstrates that stretching distortion of seismic event with large-offset data is reduced after conventional NMO correction. The quality of seismic imaging in complicated geologic area is improved.

Zhang X.-F.,China Academy of Geological science | Zheng M.-P.,China Academy of Geological science
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2014

The present article chooses the core from the borehole SZK01 in Zabuye Lake as the main research object. According to the results of X-ray powder diffraction of clay minerals, the major components are illite, illite and smectite mixed layer mineral(I/S), kaolinite and chlorite. According to the different species and contents of clay, integration of the characteristics of mineral and the results of δ18O, we reestablished the evolution process of paleoclimate in Zabuye Lake. In compaison with SZK02 core in Zabuye, Greenland GISP2 and GRIP and Guliya ice core, it contains 5 stages since 115 ka in Zabuye: the last interglacial (115~75.5 ka), the earlier last glacial(75.5~60 ka), the interstage of the last glacial (60~30.1 ka), the last glacial maximum (30.1~16.7 ka) and deglacial-holocene(since 16.7 ka). We also recognized 6 Heinrich events (H1-H6) and warm event in 71 ka. In particular, the content of kaolinite is low, with the negative-skewed value of δ18O in 52~53 ka, while the value of δ18O in SZK02 and Guliya ice core is negative-skewed too, indicating the cold event in Tibet plateau, named H5-1. All the above demonstrated that the climate in Tibet plateau is global since the earlier last glacial, and it also has regional characteristics.

Li J.H.,University of Science and Technology of China | Chi Z.Q.,China Academy of Geological science | Chen H.F.,National Taiwan Ocean University
Advanced Materials Research | Year: 2011

NaY zeolite molecular sieves have been synthesized using diatomite as a main starting material via a hydrothermal method. In this approach, the mixture of diatomite and Na2CO3 in mass ratio of 1.0/1.46 was first calcined at temperature of 830 °C for about 1.5 h. The calcined materials were then dissolved in water to obtain a solution and the composition is 15.1 Na2O : 1 Al2O3 : 11.5 SiO2 : 832 H2O. The solution was used to synthesize NaY zeolite by the crystals seeds (27.76Na2O·1.00Al2O 3·25.07SiO2·305.66H2O) via hydrothermal treatment. The hydrothermal temperature is 100 °C and the percentage of added crystal seeds is 10% (volume) relative to calcined materials. The obtained zeolite was identified by X-ray diffraction (XRD), and was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and nitrogen sorption analysis, which showed that a high yield of NaY type with a high crystalinity was obtained. © (2011) Trans Tech Publications.

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