豫西南泥湖地区辉长岩地球化学特征及其与成矿关系          下载免费PDF全文

刘辉 《山东国土资源》2018,34(3)

豫西南泥湖钼矿集区是以花岗斑岩体为中心的钼多金属矿床系列,区内出露大面积加里东期变辉长岩和燕山期辉长岩。通过分析区内辉长岩的岩石学、年代学、地球化学和成矿元素等方面特征,研究其在成岩成矿过程中的作用。区内加里东期变辉长岩和燕山期辉长岩成矿元素总稀土含量低,稀土元素球粒陨石标准化曲线右倾平缓,具有明显的Eu,Tm元素的异常;同比世界基性岩,自晚元古代上地幔主要成矿元素(除钨元素以外)基本没有明显的富集,主成矿元素钼含量呈明显的亏损,预示燕山期成矿花岗质岩浆没有从上地幔获得主要成矿物质。初步认为大规模的钼多金属成矿带的形成与基性岩浆的底垫作用相关,基性岩浆的底垫作用为下地壳部分熔融形成岩浆房提供了热源。  相似文献   

Towards Regional Synergy: Reconciling Rangeland Ecological Functioning with Forage Production of Cultivated Pasture     

SHI Peili  ZHANG Xianzhou 《资源与生态学报(英文版)》2020,11(3):247-252

Animal husbandry and crop farming are specialized for development in separate areas on the Tibetan Plateau. Such a pattern of isolation has led to current concerns of rangeland and farming system degradation due to intensive land use. The crop-livestock integration, however, has been proven to increase food and feed productivity thorough niche complementarity, and is thereby especially effective for promoting ecosystem resilience. Regional synergy has emerged as an integrated approach to reconcile rangeland livestock with forage crop production. It moves beyond the specialized sectors of animal husbandry and intensive agriculture to coordinate them through regional coupling. Therefore, crop-livestock integration (CLI) has been suggested as one of the effective solutions to forage deficit and livestock production in grazing systems. But it is imperative that CLI moves forward from the farm level to the regional scale, in order to secure regional synergism during agro-pastoral development. The national key R & D program, Technology and Demonstration of Recovery and Restoration of Degraded Alpine Ecosystems on the Tibetan Plateau, aims to solve the problems of alpine grassland degradation by building up a grass-based animal husbandry technology system that includes synergizing forage production and ecological functioning, reconciling the relationship between ecology, forage production and animal husbandry, and achieving the win-win goals of curbing grassland degradation and changing the development mode of animal husbandry. It is imperative to call for regional synergy through integrating ecological functioning with ecosystem services, given the alarming threat of rangeland degradation on the Tibetan Plateau. The series of papers in this issue, together with those published previously, provide a collection of rangeland ecology and management studies in an effort to ensure the sustainable use and management of the alpine ecosystems.  相似文献   

岩体结构面各向异性变异系数的尺寸效应研究     

洪陈杰  黄曼  夏才初  罗战友  杜时贵 《岩土力学》2020,41(6):2098-2109

岩体结构面的各向异性与尺寸效应特征对其力学性质影响较大，综合考虑两者之间的相互关系对工程岩体稳定性评价具有重要意义。全面分析不同尺度结构面的各向异性分布，提出考虑正交方向三维形貌参数的各向异性变异系数AVC3D。通过渐进覆盖法统计4组天然岩体结构面10种不同采样尺寸的各向异性变异系数及其尺寸效应规律。结果表明：各向异性变异系数均随结构面尺寸增大而减小至定值，其与结构面尺寸具有较好的负对数函数关系；通过归一化处理，各向异性变异系数与结构面尺寸呈现较好的线性函数关系，表明各向异性变异系数具有分形结构，分维数D可以实现其尺寸效应的规律统计。该方法揭示了影响结构面形貌特征方向性变化的最大有效倾角 和粗糙系数C的增长幅度会随采样尺寸增大趋于稳定的变化机制，体现了当结构面达到各向异性尺寸效应的阈值后，会呈现出稳定的各向异性规律。  相似文献   

Impact of fractional probability distributions on statistics of hydraulic conductivity,dynamics of groundwater flow and solute transport at a low-permeability site     

Chengpeng Lu  Wei Qin  Ching-Sheng Huang  Yong Zhang  Tema Koketso Ealotswe 《水文研究》2020,34(21):4112-4127

The fractional Brownian motion (fBm) and fractional Lévy motion (fLm) can easily describe the geometry and the statistical structure of hydraulic conductivity (K) for real-world. However, the fBm and fLm models have not been systematically evaluated when building the K field for a low-permeability site. In this study, both the fBm and fLm are used to simulate the low-K field at NingCheGu (NCG), Tianjin, China. Groundwater flow and solute transport are then computed using MODFLOW and MT3DMS, respectively, and the influence of the fBm/fLm models for K on groundwater flow and solute transport is discussed. Results show that the fLm fits better the statistics of the low-K medium than fBm, and the random logarithmic K (LnK) field generated by fLm is more stable because the resultant LnK field captures more of the measured properties at the field site than that generated by fBm. In contrast, the LnK generated by fBm is more likely to form both high-K channels and low-K barriers. The fBm therefore predicts more extreme behaviours in flow and transport, including the preferential flow, low-concentration blocks and solute retention. The overall groundwater renewal period and solute travel time for the fLm simulation are slightly shorter than those for fBm. The impacts of the fLm and fBm models on the statistics of the resultant LnK fields and the dynamics of groundwater flow and solute transport revealed by this study shed light on the selection and evaluation of the fractional probability distribution models in capturing the K fields for low-K media.  相似文献   

A plasticity constitutive model for unsaturated,anisotropic, nonexpansive soils     

Panagiotis Sitarenios  Michael Kavvadas 《国际地质力学数值与分析法杂志》2020,44(4):435-454

The paper describes and evaluates an incremental plasticity constitutive model for unsaturated, anisotropic, nonexpansive soils (CMUA). It is based on the modified Cam-Clay (MCC) model for saturated soils and enhances it by introducing anisotropy (via rotation of the MCC yield surface) and an unsaturated compressibility framework describing a double dependence of compressibility on suction and on the degree of saturation of macroporosity. As the anisotropic and unsaturated features can be activated independently, the model is downwards compatible with the MCC model. The CMUA model can simulate effectively: the dependence of compressibility on the level of developed anisotropy, uniqueness of critical state independent of the initial anisotropy, an evolving compressibility during constant suction compression, and a maximum of collapse. The model uses Bishop's average skeleton stress as its first constitutive variable, favouring its numerical implementation in commercial numerical analysis codes (eg, finite element codes) and a unified treatment of saturated and unsaturated material states.  相似文献   

不同法截面子午线椭球衔接的研究及应用          下载免费PDF全文

李复才  姚德新 《全球定位系统》2020,45(1):88-92

为了满足高速铁路线路控制网的投影长度变形值不大于10 mm／km的要求,将长线工程线路分成多段并建立各自的法截面子午线椭球．针对相邻法截面子午线椭球的衔接问题,提出交点法线重合的方法,实现椭球变换之后交点位置的一致性,解决线路的衔接问题,从而大大加强法截面子午线椭球理论在工程线路弯曲性、复杂性及长度的适用性．   相似文献   

基于Ruger近似式预测裂缝型储层的可行性研究     

吴姗姗  高刚  桂志先  王鹏  李成毅 《煤田地质与勘探》2020,48(1):189-196

叠前纵波方位各向异性检测裂缝是目前应用最为广泛的方法，该方法主要是利用AVAZ地震资料椭圆拟合的长轴与短轴信息来评价裂缝，该方法在具体应用时，认为裂缝型储层AVAZ响应特征的变化仅由各向异性参数决定，而没有考虑非各向异性参数的影响，从而引起裂缝评价的多解性。为提高该技术的裂缝评价精度，从模型分析入手，将模型中各向异性参数及岩性参数设置为概率密度分布函数，然后采用Monte Carlo随机方法进行叠前AVAZ正演模拟。首先，对各向异性参数对椭圆拟合的影响进行简单分析，得出各向异性参数γ对椭圆扁率B/A与各向异性因子B影响最大、δ次之、ε最小。然后，进一步重点分析不同标准差的速度与密度模型的B/A与B响应特征，得出地层的速度与密度的变化在较小范围内时，该技术评价裂缝才具有一定的可行性，其中，地层纵波和横波速度的变化（尤其是纵波速度）对叠前AVAZ响应影响较大，地层密度几乎没有影响，故当横向岩性变化较大时，该方法在评价裂缝型储层时的结果具有一定的不确定性。   相似文献   

一种变形监测中中长基线的单历元模糊度解算算法     

温亚鑫  戴吾蛟 《大地测量与地球动力学》2019,39(9):942-946

针对已有单历元模糊度解算算法只适用于短基线的情形，根据误差传播率确定模糊度精度，依据误差确定模糊度搜索空间，提出一种利用GPS双频观测信息实现中长基线下单历元模糊度固定的算法。首先，利用电离层约束法得到双差模糊度之间的线性约束条件；其次，利用变形监测中监测站点坐标近似已知的条件进行约束，反算获得近似模糊度；最后，根据监测站点已有的观测数据精度给出搜索空间，搜索固定模糊度。结果表明，该方法可以实现中长基线下单历元的模糊度固定，对实时变形监测有一定的参考价值。  相似文献   

Anisotropic dual-continuum representations for multiscale poroelastic materials: Development and numerical modelling     

Mark Ashworth  Florian Doster 《国际地质力学数值与分析法杂志》2020,44(17):2304-2328

Dual-continuum (DC) models can be tractable alternatives to explicit approaches for the numerical modelling of multiscale materials with multiphysics behaviours. This work concerns the conceptual and numerical modelling of poroelastically coupled dual-scale materials such as naturally fractured rock. Apart from a few exceptions, previous poroelastic DC models have assumed isotropy of the constituents and the dual-material. Additionally, it is common to assume that only one continuum has intrinsic stiffness properties. Finally, little has been done into validating whether the DC paradigm can capture the global poroelastic behaviours of explicit numerical representations at the DC modelling scale. We address the aforementioned knowledge gaps in two steps. First, we utilise a homogenisation approach based on Levin's theorem to develop a previously derived anisotropic poroelastic constitutive model. Our development incorporates anisotropic intrinsic stiffness properties of both continua. This addition is in analogy to anisotropic fractured rock masses with stiff fractures. Second, we perform numerical modelling to test the DC model against fine-scale explicit equivalents. In doing, we present our hybrid numerical framework, as well as the conditions required for interpretation of the numerical results. The tests themselves progress from materials with isotropic to anisotropic mechanical and flow properties. The fine-scale simulations show that anisotropy can have noticeable effects on deformation and flow behaviour. However, our numerical experiments show that the DC approach can capture the global poroelastic behaviours of both isotropic and anisotropic fine-scale representations.  相似文献   

A stress and displacement discontinuity element method for elastic transversely anisotropic rock     

A. Bobet  V. García Marín 《国际地质力学数值与分析法杂志》2014,38(18):1898-1922

The paper presents closed‐form solutions for stress and displacement influence functions for stress discontinuity (SD) and displacement discontinuity (DD) elements, for a two‐dimensional plane‐strain elastic, transversely anisotropic medium. The solutions for SD elements are based on Kelvin's problem and for DD elements on the concept of dipoles. Stress and displacement influence functions are derived for the following elements: constant SD, linear SD, constant DD, linear DD, square root DD, parabolic DD, constant DD surface, and linear DD surface elements. The formulations are incorporated into FROCK, a hybridized boundary element method code, and are validated by providing comparisons between the results from FROCK and the finite element code ABAQUS. A limited parametric analysis shows the effects of slight anisotropy on the stress field around the tip of a crack and of the orientation of the crack with respect to the axes of elastic symmetry. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献