北秦岭构造带与华北板块关系探讨:来自宽坪杂岩变碎屑岩锆石U-Pb年代学与变质作用证据     

王海杰  陈丹玲  任云飞  朱小辉  宫相宽 《岩石学报》2021,37(5):1489-1507

宽坪杂岩是连接北秦岭构造带和华北板块的重要岩石-构造单元之一,其物质组成和变质变形特征可为探讨北秦岭构造带与华北板块构造关系及演化提供重要证据。本文在已有研究基础上,对宝鸡-眉县-洛南一带宽坪变碎屑岩进行了系统的岩石学、矿物学和碎屑锆石U-Pb年代学研究。结果表明,宽坪碎屑岩最年轻碎屑锆石年龄峰值为～550Ma,最主要碎屑锆石年龄集中区为～2.5Ga和1.0～0.9Ga,次要年龄集中区为1.3～1.0Ga和850～750Ma。通过与周缘可能物源区的年代学特征对比揭示,宽坪碎屑岩物源主要来自北秦岭新元古代花岗岩与秦岭岩群副片麻岩,部分来自南秦岭和扬子板块北缘新元古代花岗岩以及太古宙基底岩系,缺乏华北板块物质;宽坪碎屑岩的碎屑锆石年龄谱特征与南侧的二郎坪碎屑岩近乎一致,暗示两者可能形成于同一沉积盆地。相平衡模拟结果显示,洛南红土岭宽坪杂岩含石榴子石石英片岩记录了顺时针P-T演化轨迹,峰期变质条件为P=7.17～7.92kbar,T=557～563℃,形成于大陆碰撞过程。结合前人报道宽坪杂岩～440Ma的变质年龄,我们认为在早志留世时期宽坪和二郎坪沉积盆地闭合,北秦岭构造带与华北板块碰撞形成现今的构造格局,在此之前北秦岭构造带与华北板块不具有亲缘性。  相似文献   

A multi-channel approach for automatic microseismic event association using RANSAC-based Arrival Time Event Clustering (RATEC)     

《地震研究进展（英文）》2021,1(3):100008

In the presence of background noise, arrival times picked from a surface microseismic data set usually include a number of false picks that can lead to uncertainty in location estimation. To eliminate false picks and improve the accuracy of location estimates, we develop an association algorithm termed RANSAC-based Arrival Time Event Clustering (RATEC) that clusters picked arrival times into event groups based on random sampling and fitting moveout curves that approximate hyperbolas. Arrival times far from the fitted hyperbolas are classified as false picks and removed from the data set prior to location estimation. Simulations of synthetic data for a 1-D linear array show that RATEC is robust under different noise conditions and generally applicable to various types of subsurface structures. By generalizing the underlying moveout model, RATEC is extended to the case of a 2-D surface monitoring array. The effectiveness of event location for the 2-D case is demonstrated using a data set collected by the 5200-element dense Long Beach array. The obtained results suggest that RATEC is effective in removing false picks and hence can be used for phase association before location estimates.  相似文献   

High pressure elasticity and phase transformation in brucite, Mg(OH)2     

K. P. Jayachandran  Lin-gun Liu 《Physics and Chemistry of Minerals》2006,33(7):484-489

The first pressure derivatives of the second-order elastic constants have been calculated for brucite, Mg(OH)₂ from the second- and third-order elastic constants. The deformation theory and finite strain elasticity theory have been used to obtain the second- and third-order elastic constants of Mg(OH)₂ from the strain energy of the lattice. The strain energy ϕ is calculated by taking into account the interactions up to third nearest neighbors in the Mg(OH)₂ lattice. ϕ is then compared with the strain dependent lattice energy from continuum model approximation to obtain the expressions of elastic constants. The complete set of six second-order elastic constants C _IJ of brucite exhibits large anisotropy. Since C ₃₃ (= 21.6 GPa), which corresponds to the strength of the material along the c-axis direction, is less than the longitudinal mode C ₁₁ (= 156.7 GPa), the interlayer binding forces are weaker than the binding forces along the basal plane of Mg(OH)₂. The 14 nonvanishing components of the third-order elastic constants, C _IJK , of brucite have been obtained. All the C _IJK of brucite are negative except the values of C ₁₁₄ (= 230.36 GPa), C ₁₂₄ (= 75.45 GPa) and C ₁₃₄ (= 36.98 GPa). The absolute values of the C _IJK are, in general, one order of magnitude greater than the C _IJ ’s in the Mg(OH)₂ system as usually expected for a crystalline material. To our knowledge, no previous data are available to compare the pressure derivatives of brucite. The pressure derivatives of the two components viz., C ₁₄ and C ₃₃ become negative indicating an elastic instability in brucite while under pressure. This may be related to the phase transition of brucite largely involving rearrangements of H atoms revealed in the Raman spectroscopic, powder neutron diffraction and synchrotron X-ray diffraction studies.  相似文献   

西藏羊八井地区近地晴天大气电场周期变化   总被引：4，自引：0，他引：4       下载免费PDF全文

徐斌  张颖  贾焕玉  陈天禄  袁爱芳  孟宪茹 《高原气象》2009,28(2):314-318

基于西藏ARGO-YBJ实验,分析了2005年12月-2007年9月期间西藏羊八井地区近地晴天大气电场强度的周期变化,并重点讨论了其太阳日周期的相位变化.结果表明,晴天状态下大气电场强度存在明显的半日周期和太阳日周期变化.太阳日周期的相位变化呈现大陆复杂型(双峰、双谷),日变化曲线随季节变化,在冬季,电场强度水平较高,最大日变化幅度约30%;春、夏季电场强度水平较低,最大日变化幅度约15%.该初步研究结果对了解西藏地区晴天大气电特征具有十分重要的意义.  相似文献   

交互四元体系Li~+,Mg~(2+)//SO_4~(2-),B_4O_7~(2-)-H_2O 288K时相平衡研究     

桑世华  李明  李恒  孙明亮 《地质学报》2010,(11)

采用等温溶解平衡法研究了288K时Li+,Mg2+//SO42-,B4O72--H2O四元体系的固液相平衡关系,测定了该四元体系在288K时平衡液相的溶解度和密度。依据实验测定的平衡溶解度数据及对应的平衡固相,绘制了该四元体系的平衡相图及密度组成图。研究结果表明:交互四元体系Li+,Mg2+//SO42-,B4O27--H2O288K时平衡相图中有2个共饱点,5条单变量曲线,4个结晶区对应的平衡固相分别为Li2B4O7.3H2O,Li2SO4.H2O,MgB4O7.9H2O和MgSO4.7H2O。  相似文献   

Correction of apparent position shifts caused by GNSS antenna changes     

Lambert Wanninger 《GPS Solutions》2009,13(2):133-139

Antenna changes at GNSS reference stations frequently produce discontinuities in the coordinate time series. These apparent position shifts are mainly caused by changes of carrier-phase multipath effects and different errors in the antenna phase center corrections. A monitoring method was developed and successfully tested, which requires additional GNSS observations from a local, temporary reference station. Changes of carrier-phase measurement errors due to the antenna change are determined and stored in L1 and L2 phase maps. These phase maps provide corrections to be applied either to the observation data obtained before the antenna change or to the observation data obtained after the antenna change. The observation corrections are able to remove coordinate discontinuities independent of the selected coordinate estimation algorithm.

Lambert WanningerEmail:

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Review of the systematics of CO₂–H₂O fluid inclusions     

Larryn W. Diamond   《Lithos》2001,55(1-4):69-99

Aqueous solutions that contain volatile (gas) components are one of the most important types of fluid in the Earth's crust. The record that such fluids have left in the form of fluid inclusions in minerals provides a wealth of insight into the geochemical and petrologic processes in which the fluids participated. This article reviews the systematics of CO₂–H₂O fluid inclusions as a starting point for interpreting the chemically more complex systems. The phase relations of the binary are described with respect to a qualitative P–T–X model, and isoplethic–isochoric paths through this model are used to explain the equilibrium and non-equilibrium behaviour of fluid inclusions during microthermometric heating and cooling. The P–T–X framework is then used to discuss the various modes of fluid inclusion entrapment, and how the resulting assemblage textures can be used to interpret the P–T conditions, phase states, and evolution paths of the parent solutions. Finally, quantitative methods are reviewed by which bulk molar volume and composition of CO₂–H₂O fluid inclusions can be determined from microthermometric observations of phase transitions.  相似文献   

Characteristics Of Chaotic Attractors In Atmospheric Boundary-Layer Turbulence   总被引：3，自引：1，他引：3  

Li Xin  Hu Fei  Liu Gang 《Boundary-Layer Meteorology》2001,99(2):335-345

In this paper, the attractors of turbulent flows in phase space are reconstructed by the time delay technique using observed data of atmospheric boundary-layer turbulence, which include high resolution temperature, humidity andthree-dimensional wind speed measurements in Gansu province and Beijing, China. The correlation dimensions and largest Lyapunov exponents have been computed. The results indicate that all the largest Lyapunov exponents in different conditions of time, site and atmospheric stability are greater than zero. This means that the atmospheric boundary-layer turbulence system is really chaotic and has appropriate low-dimensional strange attractors whose dimension numbers range from 3 to 7 and vary with different variables (dynamical variables or non-dynamical variables) and atmospheric stability. Turbulent kinetic energy is first applied to reconstruct the attractor of turbulence, and is found to be feasible.  相似文献   

1982/1983 年季风准双周振荡的位相传播及地理特征   总被引：2，自引：0，他引：2       下载免费PDF全文

彭茹  武炳义 《应用气象学报》1995,6(2):206-212

选取１９８２／１９８３年夏季（６～８月）欧洲中期预报中心８５０ｈＰａ、３００ｈＰａ两层纬向风场的网格点资料，采用复经验正交函数（ＣＥＯＦ）讨论了准双周振荡的位相传播及振荡的地理特征。结果表明：①２０°Ｎ以南对流层高层（３００ｈＰａ）１９８２年振荡显著区域是印度半岛至菲律宾东部一个西西北－东东南走向的带状区域４低层（８５０ｈＰａ）１９８２年５°～１５°Ｎ之间以及中国东南部及其沿海地区都是振荡的显著区域；而１９８３年３０°Ｎ以南振荡明显比１９８２年弱，只有中国东南沿海部分地区及孟加拉湾东南、马来西亚北部是振荡的显著区域。②对流层高层（３００ｈＰａ）１９８２年８５°～９０°Ｅ，３０°～４０°Ｎ的青藏高原是振荡的源区，其南传支波列可传到盂加拉湾北部的２０°Ｎ附近；而１９８３年青藏高原上８０°～９０°Ｅ，３５°～４０°Ｎ区域是振荡的汇区。  相似文献   

A nonlinear time-lag differential equation model for predicting monthly precipitation     

Peng Yongqing  Yan Shaojin  Wang Tongmei 《大气科学进展》1995,12(3):319-324

This paper investigates the nonlinear prediction of monthly rainfall time series which consists of phase space con-tinuation of one-dimensional sequence, followed by least-square determination of the coefficients for the terms of the time-lag differential equation model and then fitting of the prognostic expression is made to 1951-1980 monthly rainfall datasets from Changsha station Results show that the model is likely to describe the nonlinearity of the an-nual cycle of precipitation on a monthly basis and to provide a basis for flood prevention and drought combating for the wet season.  相似文献