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101.
Avalanche in Tuban: a hazard with no defense 总被引:1,自引:0,他引:1
Xiang-Zhou Xu Guo-Dong Song Jie Liu Wei-Qin Dang Hang Gao Zhen-Yi Liu Hong-Wu Zhang 《Natural Hazards》2015,79(3):2181-2187
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XIONG Xiao ZHU Laimin LI Ben ZHANG Guowei GONG Hujun ZHENG Jun JIANG Hang 《《地质学报》英文版》2015,89(6):1926-1946
Precise in situ zircon U-Pb dating and Lu–Hf isotopic measurement using an LA-ICP-MS system, whole-rock major and trace element geochemistry and Sr–Nd isotope geochemistry were conducted on the volcanic host rocks of the Tongyu copper deposit on the basis of further understanding of its geological characteristics. Three zircon samples from the volcanic host rocks yielded 206Pb/238 U weighted average ages ranging from 436±4 Ma to 440±5 Ma, which are statistically indistinguishable and coeval with the ca. 440 Ma northward subduction event of the Paleo-Qinling oceanic slab. The volcanic host rocks were products of magmatic differentiation that evolved from basalt to andesite to dacite to rhyolite, forming an integrated tholeiitic island arc volcanic rock suite. The primitive mantle-normalized trace element patterns for most samples show characteristics of island arc volcanic rocks, such as relative enrichment of LILE(e.g. Th, U, Pb and La) and depletion of HFSE(e.g. Nb, Ta, Ti, Zr and Hf). Discrimination diagrams of Ta/Yb vs Th/Yb, Ta vs Th, Yb vs Th/Ta, Ta/Hf vs Th/Hf, Hf/3 vs Th vs Nb/16, La vs La/Nb and Nb vs Nb/Th all suggest that both the volcanic host rocks from the Tongyu copper deposit and the volcanic rocks from the regional Xieyuguan Group were formed in an island arc environment related to subduction of an oceanic slab. Values of ISr(0.703457 to 0.708218) and εNd(t)(-2 to 5.8) indicate that the source materials of volcanic rocks from the Tongyu copper deposit and the Xieyuguan Group originated from the metasomatised mantle wedge with possible crustal material assimilation. Most of the volcanic rock samples show good agreement with the values of typical island arc volcanic rocks in the ISr-εNd(t) diagram. The involvement of crustal-derived material in the magma of the volcanic rocks from the Tongyu copper deposit was also reflected in the zircon εHf(t) values, which range from-3.08 to 10.7, and the existence of inherited ancient xenocrystic zircon cores(2616±39 Ma and 1297±22 Ma). The mineralization of the Tongyu copper deposit shows syn-volcanic characteristics such as layered orebodies interbedded with the volcanic rock strata, thus, the zircon U-Pb age of the volcanic host rocks can approximately represent the mineralization age of the Tongyu copper deposit. Both the Meigou pluton and the volcanic host rocks were formed during the ca. 440 Ma northward subduction of the Paleo-Qinling Ocean when high oxygen fugacity aqueous hydrothermal fluid released by dehydration of the slab and the overlying sediments fluxed into the mantle wedge, triggered partial melting of the mantle wedge, and activated and extracted Cu and other ore-forming elements. The magma and ore-bearing fluid upwelled and erupted, and consequently formed the island arc volcanic rock suite and the Tongyu VHMS-type copper deposit. 相似文献
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105.
一次黄海海雾成因分析及数值模拟试验 总被引:2,自引:0,他引:2
根据GOES-9(Geostationary Operational Environmental Satellite)可见光卫星云图和韩国济州岛探空资料等,利用RAMS(Regional Atmospheric Modeling System)模式(6.1版)对2009年3月17-18日发生在黄海海域的一次大风条件下出现的海雾天气进行模拟。结果表明:与卫星云图所显示的雾区范围相比,模拟结果对海雾的生成、发展、移动都有较好吻合;云水混合比是影响大气水平能见度分布的主要因子,云水混合比大值区主要集中在距地面300 m以下的低空;雾区存在几个云水混合比大值区,并分布在不同的高度,说明海雾的团状不均匀结构;海上平流雾常发生在风速较大的情况下,RAMS模式对此具有一定的模拟能力。 相似文献
106.
We study the excitation of density and bending waves and the associated angular momentum transfer in gaseous discs with finite thickness by a rotating external potential. The disc is assumed to be isothermal in the vertical direction and has no self-gravity. The disc perturbations are decomposed into different modes, each characterized by the azimuthal index m and the vertical index n , which specifies the nodal number of the density perturbation along the disc normal direction. The n = 0 modes correspond to the two-dimensional density waves previously studied by Goldreich & Tremaine and others. In a three-dimensional disc, waves can be excited at both Lindblad resonances (LRs; for modes with n = 0, 1, 2, … ) and vertical resonances (VRs; for the n ≥ 1 modes only). The torque on the disc is positive for waves excited at outer Lindblad/vertical resonances and negative at inner Lindblad/vertical resonances. While the n = 0 modes are evanescent around corotation, the n ≥ 1 modes can propagate into the corotation region where they are damped and deposit their angular momenta. We have derived analytical expressions for the amplitudes of different wave modes excited at LRs and/or VRs and the resulting torques on the disc. It is found that for n ≥ 1 , angular momentum transfer through VRs is much more efficient than LRs. This implies that in some situations (e.g. a circumstellar disc perturbed by a planet in an inclined orbit), VRs may be an important channel of angular momentum transfer between the disc and the external potential. We have also derived new formulae for the angular momentum deposition at corotation and studied wave excitations at disc boundaries. 相似文献
107.
对XPer新发射相连续四年的光学光谱和近红外光度监测结果,XPer近两年的变化不同寻常,主要表现以下两点:(1)尽管它的光学光度V星等只恢复至失去气壳前的亮度,但Ha发射线等值宽度和近红外,J,H和K光度地超过了历史记录的最大值,分别达到了16.34A和5.3^m,5.3^m和5.1^m,表明XPer新发射相气南的密度和尺度较都大,(2)我们首次观测到XPer近红外光度和Hα发射线等值宽度变化趋势 相似文献
108.
XPer的新发射相:光谱与红外观测 总被引:1,自引:0,他引:1
XPer的新发射相:光谱与红外观测杭恒荣,夏剑萍中国科学院紫金山天文台,南京210008中国科学院光学天文联合实验室关键词Be星/X射线双星,发射线,JHK测光1引言XPer是一颗Be/X射线双星(4U0352+30)的光学对应体[1-3],中子星的... 相似文献
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3维实景电子地图的建模方式多种多样,从成本和效率角度出发,笔者认为基于影像级实景模型的建模方式优势明显,文章详细叙述了基于影像级实景模型的3维实景电子地图技术方案。 相似文献