Hu R.-Z.,Chinese Academy of science |
Zhou M.-F.,University of Hong Kong
Mineralium Deposita | Year: 2012
Mesozoic mineral deposits in South China include world-class deposits of W, Sn and Sb and those that provide the major sources of Ta, Cu, Hg, As, Tl, Pb, Zn, Au and Ag for the entire country. These deposits can be classified into polymetallic hydrothermal systems closely related to felsic intrusive rocks (Sn-W -Mo granites, Cu porphyries, polymetallic and Fe skarns, and polymetallic vein deposits) and low-temperature hydrothermal systems with no direct connection to igneous activities (MVT deposits, epithermal Au and Sb deposits). Recent studies have shown that they formed in the Triassic (Indosinian), Jurassic-Cretaceous (Early Yanshanian), and Cretaceous (Late Yanshanian) stages. Indosinian deposits include major MVT (Pb-Zn-Ag) deposits and granite-related W-Sn deposits. Early Yanshanian deposits are low-temperature Sb-Au and high-temperature W-Sn and Cu porphyry types. Many Late Yanshanian deposits are low-temperature Au-As-Sb-Hg and U deposits, and also include high-temperature W-Sn polymetallic deposits. The formation of these deposits is linked with a specific tectonothermal evolution and igneous activities. This special issue brings together some of the latest information in eight papers that deal with the origins and tectonic environments of mineral deposits formed in these stages. We anticipate that this issue will stimulate more interests in these ore deposits in South China. © 2012 Springer-Verlag.
Dai L.,Yale University |
Dai L.,Chinese Academy of science |
Karato S.-I.,Yale University
Earth and Planetary Science Letters | Year: 2014
Experimental studies on electrical conductivity in hydrated olivine had been made only at relatively low temperatures. The extrapolation of these data to asthenosphere temperatures shows that explaining high and highly anisotropic conductivity by hydrogen is difficult. We present new experimental results on the electrical conductivity in hydrated olivine single crystals measured under a broader temperature range than before (T (temperature) = 573-1373 K at P (pressure) = 4 GPa). The new results agree well with the previous results at low temperatures (T<. 900K), whereas at higher temperatures (T>. 1000K) substantial deviations from the previous results are observed: (i) anisotropy in conductivity increases with temperature, and (ii) activation energies at high temperature regime are substantially higher than those at lower T. The high temperature behavior is consistent with a model invoking diffusion of two-protons at M-site vacancy, whereas the low temperature behavior suggests conduction by more mobile species such as free proton. The present results (i) explain the discrepancy between different previous studies conducted under different temperature regimes, and (ii) show that most of geophysical observations on the electrical conductivity in the asthenosphere including the high and highly anisotropic conductivity can be explained by high water content in the asthenosphere that is consistent with the geochemical model. Combining with a previous model of low seismic wave velocity of the asthenosphere, a subsolidus model invoking the role of hydrogen provides a unified explanation for the geophysical anomalies of the asthenosphere. © 2014 Elsevier B.V.
Sun Q.,Peking University |
Qin C.,Chinese Academy of science
Chemical Geology | Year: 2011
Raman spectroscopy is an efficient method which has been widely employed in many research fields. However, this method is more commonly associated with qualitative study than with quantitative analysis. In this work, a quantitative measurement using Raman spectroscopy is provided. According to the theoretical analysis of Raman intensity, Raman quantitative measurement should be based on the intensity ratio, which can be classified into external and internal standards. This allows the influence from measurement conditions to be eliminated. For aqueous solutions, it is reasonable to treat the Raman OH stretching band of water as an internal standard. In this study, the intensity ratio ICO32-/IW is used to determine carbonate concentrations in solutions, where ICO32- is the intensity of the carbonate band, and IW is the sum of intensities of the two used OH stretching sub-bands. © 2011 Elsevier B.V.
Wang H.,Xihua University |
Han G.,Chinese Academy of science
Atmospheric Research | Year: 2011
A comprehensive study on the chemical compositions of rainwater was carried out from Jan. to Dec. in 2008 in Chengdu, a city located on the acid rain control zone of southwest China. All samples were analyzed for pH and major ions (F-, Cl-, NO3-, SO42-, K+, Na+, Ca2+, Mg2+, and NH4+). The pH increased due to the result of neutralization caused by the base ions. It was observed that Ca2+ was the most abundant cation with a VWM value of 196.6μeq/L (17.3-1568.7μeq/L), accounting for 49.7% (9.4%-79.2%) of the total cations. SO42- was the most abundant anion with VWM value of 212.8μeq/L (41.8-1227.6μeq/L). SO42- and NO3- were dominant among the anions, accounting for 90.4%-99.1% of the total measured anions. The concentrations of NO3- were higher than the most polluted cities abroad, which indicated Chengdu has been a severe polluted city over the world. The high fuel consumption from urbanization and the rapid increase of vehicles resulted in the high emission of SO2 and NOx, which were the precursor of the high concentration of acidic ions NO3- and SO42-. It was the main reason of the severe acid rain in Chengdu. The high concentrations of alkaline ions (mainly Ca2+, NH4+) in Chengdu city atmosphere have played an important role to neutralize the acidity of rainwater and the pH value has increased by 0.7 units since 1989. It is worth noting that the emission of NOx from the automobile exhaust is increased and is becoming the important precursor of acid rain now. © 2010.
Zhang B.,Chinese Academy of science |
Zhang B.,Okayama University
AIP Advances | Year: 2014
On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (α, δ, γ and Éphases) have been successfully reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature range (500-2500 K) and pressure range (0-100 GPa), compare favorably well with experimental or theoretical ones when the uncertainties are considered. © 2014 Author(s).