不同温压下岩石弹性波速度、衰减及各向异性与组构的关系   总被引：16，自引：0，他引：16  

刘斌 《地学前缘》2000,7(1):247-257

结合岩石组构分析 ,阐述了岩石弹性波传播速度和衰减以及它们的各向异性与岩石组构之间的关系。在不同温压条件下对具有很强晶格优选方位的岩石样品的研究表明 ,随着围压的增加 ,波速和Q值均增大 ,但是在相互正交的 3个方向上 (垂直或平行于层理面及线理方向 )增大的速度并不相同 ,这与微裂隙的逐渐闭合密切相关。观测到的波速和Q值的各向异性具有不同的形成机理 ,波速各向异性主要与定向分布的微裂隙和主要矿物的晶格优选方位等构造因素有关 ;高围压下Q值各向异性与速度各向异性正好相反 ,可能是由于定向排列的矿物晶体沿不同方向其边界之间接触程度不同造成的。对岩石组构的研究不仅可以揭示岩体的变形机制、变形的动力学过程及其有关的热力学信息 ,还可以对宏观岩石的各种物理性质 ,尤其是力学特性 ,从微观机理上加以解释。文中特别强调了岩石组构分析对研究岩石物理性质的各向异性具有十分重要的意义。  相似文献   

Compressional behavior of clayey sand and transition fines content     

Mehmet Murat Monkul  Gurkan Ozden   《Engineering Geology》2007,89(3-4):195-205

Clayey sand can be considered as a composite matrix of coarse and fine grains. The interaction between coarser and finer grain matrices affects the overall stress–strain behavior of these soils. Intergranular void ratio, e_s (which is the void ratio of the coarser grain matrix) can be utilized as an alternative parameter to express the compressive response of such soils. Oedometer tests conducted on reconstituted kaolinite–sand mixtures indicate that initial conditions, percentage of fines, and stress conditions influence the compression characteristics evidently. Tests showed that, up to a fraction of fines, which is named as transition fines content (FC_t), compression behavior of the mixtures is mainly controlled by the sand grains. When concentration of fines exceeds FC_t, kaolinite controls the compression. It was found that FC_t varies between 19% and 34% depending on the above mentioned factors. This range of fines content is also consistent with various values reported in literature regarding the strength alteration. Performed direct shear tests revealed that there is also a close relationship between transition fines content and shear strength, which is harmonic with the oedometer test results.  相似文献   

Salt weathering in dual-porosity building dolostones   总被引：2，自引：0，他引：2  

D. Benavente  J. Martínez-Martínez  N. Cueto  M.A. García-del-Cura   《Engineering Geology》2007,94(3-4):215-226

The influence of rock fabric on physical weathering due to the salt crystallization of selected brecciated dolostones is discussed. These dual-porosity dolostones are representative of heterogeneous and anisotropic building rocks, and present highly complex and heterogeneous rock fabric features. The pore structure of the matrix and clasts is described in terms of porosity and pore size distribution, whereas the relative strength for each textural component is assessed using the Knoop hardness test. The whole characterisation process was carried out using the same samples as those used in the standard salt durability test (EN-12370), including connected porosity, the water saturation coefficient, fissure density, compressional wave velocity and waveform energy.

Results show the most important rock fabric elements to be considered are the matrix and clast properties and the nature of fissures. Firstly, a relatively weak matrix was the focus of major granular disintegration as it presents high porosity, low pore radius and reduced strength. Secondly, narrow micro-fissures appear to be important in the decay process due to the effectiveness of crystallization pressure generated by salt growth. On the contrary, macro-fissures do not contribute greatly to rock decay since they act as sinks to consume the high supersaturations caused by growth of large crystals. Additionally, an analysis of stress generated by crystallization was carried out based on the general situation of a lenticular crystal geometry. Finally, the relationships between whole petrophysical properties and durability were established using a principal component analysis. This analysis has clearly established that the durability of rocks affected by salt crystallization mechanisms diminishes in weaker and anisotropic rocks with high porosity and fissure density.  相似文献   

Experimental Investigation of Eclogite Rheology and Its Fabrics at High Temperature and Pressure   总被引：7，自引：0，他引：7  

J. ZHANG  H. W. GREEN 《Journal of Metamorphic Geology》2007,25(2):97-115

Eclogite plays an important role in mantle convection and geodynamics in subduction zones. An improved understanding of processes in the deeper levels of subduction zones and collision belts requires information on eclogite rheology. However, the deformation processes and associated fabrics in eclogite are not well understood. Incompatible views of deformation mechanism have been proposed for both garnet and omphacite. We present here deformation behaviour of eclogite at temperatures of 1027–1427 °C, confining pressures of 2.5–3.5 GPa, and strain rates of 1 × 10^?5 s^?1 to 5 × 10^?4 s^?1. We obtained a power‐law creep for the high temperature and pressure deformation of a ‘dry’ eclogite (50 vol.% garnet, 40% omphacite and 10% quartz) with A = 10^{3.3 ± 1.0}, n = 3.5 ± 0.4, ΔE =403 ± 30 KJ mol^?1 and ΔV = 27.2 cm³ mol^?1. The two principal minerals of eclogite have greatly different strengths. Progressive increase of garnet results in a smooth increase in strength. Analysis by electron back‐scattered diffraction shows that: (1) garnet displays pole figures with near random distributions of misorientation angle under both dry and wet conditions; (2) omphacite shows pronounced lattice preferred orientations (LPOs), suggesting a dominant dislocation creep mechanism. Further investigation into the water effects on eclogite show: (3) water content does not influence the style of omphacite fabric but increases slightly the fabric strength; (4) grain boundary processes dominate the deformation of garnet under high water fugacity or high shear‐strain conditions, yielding a random LPO similar to that of non‐deforming garnet, despite the strong shape preferred orientation (SPO) observed. {110} [001] slip may dominate the deformation of rutile. Quartz displays complicated and inconsistent LPOs in eclogite. These results are remarkably similar to observations from deformed eclogites in nature.  相似文献   

东天山秋格明塔什黄山韧性剪切带变形特征分析     

杨兴科  张连昌  姬金生  曾章仁  陶洪祥 《地球科学与环境学报》1998,20(3):42

东天山秋黄韧性剪切带位于新疆东部两大板块碰撞接合地带,东西延长逾６００ｋｍ,由石炭系组成,规模巨大,分带明显,宏微观变形标志清晰,石英Ｃ轴组构呈点极密型,分为四期变形,序列演化明显,应变测量属平面单剪,剪切位移量达７５ｋｍ以上,存在脆韧性变形转换,变形时代为海西中晚期,强弱应变相间排列的标度不变性特征明显,变形机制属地壳中深层次塑性流变和韧性剪切,与板块间的俯冲碰撞构造演化密切相关。控制着金铜矿分布。  相似文献   

新类型金矿──萤石型金矿的矿石物质成分及组构特征     

帅德权  张寿庭  徐旃章  胡晓强 《浙江国土资源》1998,(2)

浙江东南地区的萤石型金矿,系一新类型金矿床。矿石学研究表明,其主要工业矿物为银金矿,与之共生的矿物有黄铁矿、黄铜矿、方铝矿、闪锌矿、辉银矿等。矿石结构构造有多种,矿床的形成有多期次。成矿与硅化,黄铁矿化和萤石化相关。  相似文献   

Particle fabric in a small, type-2 ignimbrite flow unit (Laacher See, Germany) and implications for emplacement dynamics     

Simon R. Hughes  Timothy H. Druitt 《Bulletin of Volcanology》1998,60(2):125-136

 Ignimbrites of the 13-ka Upper Laacher See Tephra were deposited from small, highly concentrated, moderately fluidized pyroclastic flows. Their unconsolidated nature, and the prominence of accidental Devonian slate fragments, make these ignimbrites ideal for clast fabric studies. The upper flow unit of ignimbrite M14 has characteristics typical of a type-2 ignimbrite. Layer 2a and the lower part of layer 2b of the flow unit have strong, upstream-inclined a[p] fabrics (a[p] means long particle axes parallel to flow direction). Only clasts with a/b axial ratios of 2.5 or greater preserve good a[p] fabrics, whereas the a–b planes of flat fragments dip upstream irrespective of axial ratio. The a-axis fabric becomes weaker, flatter, and more girdle-like in the upper half of layer 2b. At one locality the a-axis fabric appears to rotate 40° up through the flow unit, suggesting either shear decoupling of different levels in the moving flow or unsteadiness effects in a flow depositing progressively at its base. The existence of similarly strong a[p] fabrics in layer 2a and the lower half of layer 2b appears inconsistent with the common interpretation that ignimbrite flow units are emplaced as a plug of essentially non-shearing material (layer 2b) on a thin shear layer (layer 2a), and that the entire flow freezes en masse to form the deposit. The data suggest that, if the flow froze en masse, it was shearing pervasively through at least half its thickness. Another possibility is that the flow unit aggraded progressively from the base up, and that the fabrics record the integrated history of shear directions and intensities immediately above the bed throughout the duration of deposition. Received: 13 February 1997 / Accepted: 4 April 1998  相似文献   

Reconstruction of natural groundwater flow paths in the multiple aquifer system of the northern Negev (Israel), based on lithological and structural evidence     

G. Weinberger  E. Rosenthal 《Hydrogeology Journal》1998,6(3):421-440

 The Judea Group, a limestone and dolomite karstic aquifer of late Albian–Turonian age, is one of the most important sources of water in Israel. In the western part of the country, the Judea Group aquifer is also known as the Yarkon–Taninim basin. In the northern Negev, the Judea Group is a recipient for fresh water flowing southward from the Hebron Mountains and of brackish paleowater flowing northward from Sinai. Very little is known of the hydraulic properties of this aquifer. In order to outline assumed natural flow paths that existed in this karstic environment prior to groundwater exploitation, use was made of lithological, structural, and paleomorphological features. A detailed hydrogeological conceptual model of the Judea Group aquifer in northern Negev was established by the geological interpretation of high-resolution seismic reflection and by analysis of lithological evidence from boreholes. Isopach, isolith-contour, and isolith-ratio maps were compiled for the main lithological components. Increase in transmissivity values is inversely proportional with the cumulative thickness of argillaceous components. The lithological and hydraulic evidence provides the basis for subdividing the subsurface into distinctive permeability zones for the upper and lower sections of the aquifer; for outlining possible preferential groundwater flow paths for both subaquifers; and for improving understanding of groundwater-salinty variations that result from lithological variability, direction of groundwater flow paths, groundwater flow rates, and the duration of rock/water interactions. In an earlier conceptual model of the basin, the Judea Group aquifer was regarded as a continuous and undisturbed entity. The present study reveals an intricate groundwater flow pattern that is controlled by lithological and structural factors that create zones of preferential flow. This interpretation bears on the overall evaluation of groundwater resources and their management and exploitation. Received, December 1996 · Revised, October 1997, June 1998 · Accepted, July 1998  相似文献   

Some current methods to represent the heterogeneity of natural media in hydrogeology   总被引：4，自引：0，他引：4  

G. de Marsily  F. Delay  V. Teles  M. T. Schafmeister 《Hydrogeology Journal》1998,6(1):115-130

We have known for a long time that the material properties of the subsurface are highly variable in space. We have learned that this variability is due to the extreme complexity and variation with time of processes responsible for the formation of the earth's crust, from plate tectonics to erosion, sediment transport, and deposition, as well as to mechanical, climatic, and diagenetic effects. As geologists, we learned how to "read" this complex history in the rocks and how to try to extrapolate in space what we have understood. As physicists, we then learned that to study flow processes in such media we must apply the laws of continuum mechanics. As mathematicians using analytical methods, we learned that we must simplify by dividing this complex continuum into a small number of units, such as aquifers and aquitards, and describe their properties by (constant) equivalent values. In recent years, as numerical modelers, we learned that we now have the freedom to "discretize" this complex reality and describe it as an ensemble of small homogeneous boxes of continuous media, each of which can have different properties. How do we use this freedom? Is there a need for it? If the answer is "yes," how can we assign different rock-property values to thousands or even millions of such little boxes in our models, to best represent reality, and include confidence levels for each selected rock property? As a tribute to Professor Eugene S. Simpson, with whom the first author of this paper often discussed these questions, we present an overview of three techniques that focus on one property, the rock permeability. We explain the motivation for describing spatial variability and illustrate how to do so by the geostatistical method, the Boolean method, and the genetic method. We discuss their advantages and disadvantages and indicate their present state of development. This is an active field of research and space is limited, so the review is certain to be incomplete, but we hope that it will encourage the development of new ideas and approaches.  相似文献   

枞树板铅锌矿磁组构研究     

许顺山  陈柏林  董法先  刘建民 《吉林大学学报(地球科学版)》1998,(2)

研究了枞树板铅锌矿区的磁组构特征。结果表明,在变形较弱及无应变标志体的地区,利用磁组构进行构造变形分析是非常有效的,其结果不仅与其它方法的结果大体一致,而且能够获得用其它方法难以获得的认识（如变形类型问题）。据此可以分析控矿构造的变形性质及演化,查明构造控矿的规律。  相似文献