Influence of plasticity on the seismic soil–micropiles–structure interaction

This paper includes an analysis of the influence of soil plasticity on the seismic response of micropiles. Analysis is carried out using a global three-dimensional modeling in the time domain. The soil behavior is described using the non-associated Mohr–Coulomb criterion. Both the micropiles and the superstructure are modeled as three-dimensional beam elements. Proper boundary conditions are used to ensure waves transmission through the lateral boundaries of the soil mass. Analyses are first conducted for harmonic loadings and then for real earthquake records. They show that plasticity could have a significant influence on the seismic response of the soil–micropiles–structure systems. This influence depends on the amplitude of the seismic loading and the dominant frequencies of both the input motion and the soil–piles–structure system.     

黔东南地区新元古代下江群的地层年代及其地质意义

黔东南地区下江群是分布在江南造山带西段的一套前寒武纪浅变质陆源碎屑岩夹火山碎屑岩组合, 其地层时代归属与划分特别是区域地层对比一直未能得到很好解决.在对该区前寒武纪地层广泛而详细的剖面测制和地质调查基础上, 运用LA-ICP-MS技术, 对地层中沉凝灰岩、含凝灰质碎屑岩和碎屑岩进行锆石U-Pb年代学测试, 获得一批高精度的年龄.四堡群河村组顶部的碎屑岩和下江群乌叶组第1段顶部的含凝灰质碎屑岩、清水江组底部与中部的沉凝灰岩、平略组中上部的含凝灰质碎屑岩、隆里组中下部的碎屑岩等样品中锆石U-Pb最小年龄组的加权平均年龄分别为819.8±6.4Ma和779.5±4.7Ma、764.0±6.3Ma与(756.8±7.6Ma、756.0±13.0Ma)、733.9±8.8Ma及725.0±10.0Ma.这些数据将四堡群和下江群的时代限制为新元古代.结合研究区隆里组与长安组整合接触关系和全球低纬度南华系冰期起始年龄(717.4Ma)的地质事实, 将下江群沉积时限约束在815~717Ma之间.根据区域岩浆事件进一步约束了下江群各组段的地层时限, 并开展江南造山带下江群及其相当层位的地层划分与对比, 认为新元古代岩浆作用制约着黔东南下江群盆地的演化.      

海南岛抱板群岩石高温高压实验及金成矿机理探讨

高温高压实验岩石学是地质学、岩石学领域中的“硬科学”犤1999,王德滋,等犦。目前高温高压实验岩石学研究主要是针对单一岩石的熔化和融离实验,而针对多物源成因的花岗岩模拟其物源贡献大小的实验岩石学及同时发生的成矿作用研究基本上是一个空白。文章根据海南岛戈枕含金剪切带中元古代花岗岩的物源特征及与之有关的戈枕式金矿成因特点,通过高温高压实验岩石学模拟,初步探讨古中元古代抱板群岩石高温高压下的熔融行为及金的成矿机理。实验结果表明,具原地-半原地性质的中元古代花岗岩很可能是由6份(或4份)石英绢云母片岩+1份斜长角闪片麻岩、在压力为1.879～2.143GPa、温度849～901℃的条件下部分熔融形成的,部分熔融过程同时还发生了金的聚集和活化迁移。     

实验标定的一种地质温压计及其应用

本文简略回顾了堇青石-石榴石-矽线石-石英地质温压计的研究历史,并介绍由Aranovich等人完成的最新实验研究。以内蒙古南部贺兰山群的麻粒岩相矽线石榴堇青片麻岩的温压计算为例,用Aranovich等人实验标定的温压计计算结果与石榴石-堇青石Fe-Mg交换反应温度计和石榴石-斜长石-矽线石-石英压力计的计算结果相当吻合;而应用含有假定的热力学参数的哈奇森的温压计与其它温压计计算结果有较大差别,温度明显偏低,与岩石形成于麻粒岩相变质条件这一地质事实不符。     

Giant HVC’s and the Rotation Curves of the Milky Way and M31

We have modelled, for the cases of Milky Way and M31, the effects on the galactic discs, of the arrival at high velocity (≥150 km s⁻¹) of giant HI clouds, with masses of up to 10⁸M⊙. Predictions are compared with the detailed structure of the observed rotation curves for these two galaxies. The model explains the rises and falls observed at large distances from the centre of each galaxy, distributed with a degree of regularity in radius, in terms of a specific type of perturbations driven by the infall of the high velocity clouds (HVC's) arriving from the intracluster medium of the Local Group. The underlying rotation curve is explained conventionally via the distribution of the baryonic and dark matter components of the galaxy in question. This scenario, though tested here on the two major Local Group objects, is in principle applicable to galaxies undergoing minor mergers with subgalactic mass gas clouds.     

Dark matter in dwarf spheroidals – II. Observations and modelling of Draco

We present stellar radial velocity data for the Draco dwarf spheroidal (dSph) galaxy obtained using the AF2/WYFFOS instrument combination on the William Herschel Telescope. Our data set consists of 186 member stars, 159 of which have good quality velocities, extending to a magnitude   V ≈19.5  with a mean velocity precision of ≈2 km s⁻¹. As this survey is based on a high-precision photometric target list, it contains many more Draco members at large radii. For the first time, this allows a robust determination of the radial behaviour of the velocity dispersion in a dSph.
We find statistically strong evidence of a rising velocity dispersion consistent with a dark matter halo that has a gently rising rotation curve. There is a <2 σ signature of rotation about the long axis, inconsistent with tidal disruption as the source of the rising dispersion. By comparing our data set with earlier velocities, we find that Draco probably has a binary distribution and fraction comparable to those in the solar neighbourhood.
We apply a novel maximum likelihood algorithm and fit the velocity data to a two parameter spherical model with an adjustable dark matter content and velocity anisotropy. Draco is best fit by a weakly tangentially anisotropic distribution of stellar orbits in a dark matter halo with a very slowly rising rotation law  ( v _circ∝ r ^0.17)  . We are able to rule out both a mass-follows-light distribution and an extended halo with a harmonic core at the 2.5 to 3 σ significance level, depending on the details of our assumptions about Draco's stellar binary population. Our modelling lends support to the idea that the dark matter in dwarf spheroidals is distributed in the form of massive, nearly isothermal haloes.     

辽宁省大石桥－吉洞峪一带辽河岩群变质地层的对比研究

辽宁省大石桥－吉洞峪一带出露的主要为古元古代的变质层状岩系，由云母片岩、长英质粒岩和大理类组成。区域上形成一大型北东向的复式向斜构造。复向斜南北两翼变质地层对比问题是辽吉东部辽河岩群研究的主要内容之一。作者根据五年来在大石桥－吉洞峪一带进行１∶５万区调所获得的新资料，从标志层及组合标志层、岩相学特征、主要标志层的岩石化学和稀土地球化学特征、变质作用演化等方面的研究入手，讨论了复向斜两翼变质地层对比的问题。结果表明，辽河岩群构成复向斜南北两翼的变质地层是完全可以对比的，从而进一步证实辽河岩群是一个不可分割的整体     

五台山蒋村地区四集庄组——对滹沱群时代的再限定

滹沱群是华北最典型的古元古界地层之一,限定其时代对建立早期地层年代格架和探讨华北早前寒武纪地质演化过程意义重大。本文对五台山地区蒋村镇附近的滹沱群地层进行了详细研究,从与蒋村砾岩中石英斑岩砾石相同的基岩中选取了2件石英斑岩样品,并获得其锆石U-Pb年龄结果分别为(2166±17)Ma和(2138±17)Ma。据此,限定蒋村地区碎屑沉积岩时代应小于2138 Ma。结合四集庄组底部发育厚层的砾岩和区域内2.2~2.1 Ga岩浆事件,我们进一步认为滹沱群底界年龄为~2.2 Ga。由于滹沱群豆村亚群和东冶亚群经历了同期褶皱变形作用,而侵入于蒋村四集庄组未变形正长花岗岩脉的锆石U-Pb年龄结果为(1816±18)Ma。因此,本文限定豆村亚群、东冶亚群的时代为2.2~1.82 Ga。石英斑岩中锆石Lu-Hf同位素分析结果为176Lu/177Hf为0.000717~0.002239,176Hf/177Hf为0.281399~0.281563,其176Hf/177Hfi为0.281315~0.281496和εHf(t)为–3.37~4.11,变化范围较大,初步认为其源自于新太古代早期上地壳的部分熔融并有地幔物质添加。     

冀东蓟县群白云岩中锂资源的成因与赋存状态研究

唐山丰润蓟县群雾迷山组中发现了Li含量达781×10^-6(折合Li₂O含量0.16%)的富锂白云岩,其厚度大、分布广,是重要的潜在沉积型锂资源。本文通过野外考察、样品分析测试等手段,对该区雾迷山组中锂的分布、成因和赋存状态进行了探讨,研究表明：该地区泥晶白云岩、泥质白云岩、白云质泥岩和泥岩样品中富集锂,白云岩、硅化白云岩及硅质岩不富集锂;锂的含量与伊利石含量存在显著相关性,指示伊利石可能为锂的主要赋存矿物;锂赋存位置为矿物间的非晶质伊利石等粘土矿物;样品中几乎不含吸附状态的锂,认为锂应该赋存在矿物晶格中呈类质同象状态;富锂样品和贫锂样品为同一源岩风化的产物;源岩(钙质泥岩)风化为锂富集提供稳定物质来源,含氧、干旱、浅水沉积环境有利于锂的富集。