The geometry of listric normal faults and deformation in their hangingwalls

In cross-sections containing listric extensional faults, area balancing techniques for depth to décollement are usually based on either bed length conservation or displacement conservation. Listric fault geometry may be constructed from a hangingwall roll-over profile using the ‘Chevron construction’. This construction, based on conservation of heave, necessitates a reduction in fault displacement with decreasing fault dip. A modification of this construction utilizing conservation of fault displacement predicts a listric fault that detaches at a shallower depth. A new construction based on slip lines uses fault-perpendicular displacement segments to generate listric fault shape. Fault propagation strain may be responsible for anomalous hangingwall geometries, and these can be predicted by forward modelling using either a modified Chevron construction or a slip-line construction.     

Relay zone geometry and displacement transfer between normal faults recorded in coal-mine plans

Overlap lengths, separations and throw gradients were measured on 132 relay zones recorded on coal-mine plans. Throws on the relay-bounding fault traces are usually ≤ 2 m and individual structures are recorded on only one seam. Throw gradients associated with relay zones are not always higher than on single faults, but asymmetry of throw profiles is diagnostic of relay zones. Bed geometries around larger faults in opencast mines are used to assess the displacement accommodated by shear in the vertical plane normal to the faults and displacement transfer accommodated by shear in the fault-parallel plane. Three-dimensional structure is defined for two relay zones, each recorded on five seam plans. These relay zones are effectively holes through the fault surfaces and overlap occurs between salients or lobes of the parent fault surfaces. Lobes initially terminated at tip-lines but, as the faults grew, gradually rejoined the main fault surfaces along branch lines. This type of relay zone originates by bifurcation of a single fault surface at a locally retarded tip-line and is an almost inevitable result of a tip-line irregularity.     

On the relationship between ore-controlling faults, Late Cretaceous sedimentary basins, and hydrocarbon shows

A combination of hidden NS- and neotectonic EW-trending faults exert control on the distribution of very large ore deposits. At the same time, the largest potentially petroleum-bearing regions of northeastern Russia are known to be associated with the same fault zones within Late Cretaceous sedimentary basins and offshore areas of the East Siberian, Chukchi, and Bering seas, as well as the Sea of Okhotsk.     

The temporal relationship between joints and faults

Examples are presented of three temporal relationships between joints and faults: joints that pre-date faults; joints that are precursors to, or synchronous with, faults; and joints that post-date faults. Emphasis is placed on strike-slip faults in carbonate beds, but other examples are used. General rules are given for identifying the three temporal relationships between joints and faults. Joints that formed before faults can be dilated, sheared or affected by pressure solution during faulting, depending on their orientation in relation to the applied stress system. Faulted joints can preserve some original geometry of a joint pattern, with pinnate joints or veins commonly developing where faulted joints interact. Joints formed synchronously with faults reflect the same stress system that caused the faulting, and tend to increase in frequency toward faults. In contrast, joints that pre- or post-date faults tend not to increase in frequency towards the fault. Joints that post-date a fault may cut across or abut the fault and fault-related veins, without being displaced by the fault. They may also lack dilation near the fault, even if the fault has associated veins. Joints formed either syn- or post-faulting may curve into the fault, indicating stress perturbation around the fault. Different joint patterns may exist across the fault because of mechanical variations. Geometric features may therefore be used in the field to identify the temporal relationships between faults and joints, especially where early joints affect or control fault development, or where the distribution of late joints are influenced by faults.     

陡倾断层上下盘开挖引起地表变形的数值模拟分析

考虑地下开挖区与断层相对位置关系,采用简化数值模型对陡倾断层上下盘开挖引起的地表变形特征进行了数值模拟。结果表明,当断层位于地下开挖引起地表变形的压缩区且开挖区位于下盘时,地表出现不连续变形的可能性小;当断层位于地下开挖引起地表变形的压缩区且开挖区位于上盘时,随下向开挖进行地表断层处裂缝有减小趋势;而当断层位于地下开挖引起的地表变形拉张区时,断层出露处水平拉张明显,表现为拉张裂缝,随下向开挖深度增加、规模增大,不论开挖区位于上盘还是下盘,极可能导致地表出现正断层式的错动．     

正断层控制下冲积扇沉积过程与沉积构型模拟实验

正断层构造广泛发育于盆地内和造山带中,其对可容空间分配及沉积物分布具有明显的控制作用,从而影响了冲积扇形态。为进一步探究正断层构造对冲积扇沉积过程及其内部构型的控制作用,利用水槽实验对正断层构造发育背景下的冲积扇发育过程进行模拟再现。研究表明,携带大量沉积物的碎屑流优先在上盘近断层处泄载,后经牵引流的改造,形成沿断面垂向生长、尖端指向物源的三角形分水滩。水动力较强时碎屑流越过分水滩并在分水滩尾部发育越滩朵体,水动力较弱时碎屑流遇分水滩尖端分流后沿断面在分水滩两侧发育断面朵体。受控于断面及分水滩的阻挡,冲积扇表面不同位置的沉积物泄载过程差异较大,粒度差异明显,上盘扇体中分水滩沉积物偏粗,越滩朵体次之,断面朵体最细。冲积扇的发育过程依据分水滩砂体厚度和断距大小之间的差异,共分为3个阶段。断距大小还会影响冲积扇沉积构型,断距越大,上盘可容空间越大,分水滩发育时间越长,扇体内部砂体叠置样式越复杂。受控于正断层的冲积扇内部构型在垂直物源剖面上从近端至远端,分别发育纵向沙坝、分水滩及碎屑流朵体,在平行物源剖面上以复合水道主控、分水滩叠复体主控、多期朵体叠复体主控为主。     

Simulation experiment of sedimentary process and sedimentary architecture of alluvial fan under the control of normal faults

Normal fault structures are widely developed in basins and orogenic belts,which control the accommodation space and the distribution of sediments and thus affecting the morphology of alluvial fans. A flume tank experiment was carried to simulate and clarify the control of normal faults on the sedimentary process and internal architecture of alluvial fans.The results show that the large amount of sediments carried by debris flow tend to be unloaded near the hanging wall of faults and are subsequently reworked by traction current,which result in a triangular distributary gravel bar grows vertically on fault plane with the tip pointing to the source area. When the hydrodynamic force is strong,debris flow goes across distributary gravel bar and forms over-bar lobe at the tail of the distributary gravel bar. When the hydrodynamic force is weak,debris flow forms fault plane-dominated lobe along fault plane and is located on both sides of the distributary gravel bar. Under the control of normal faults and the barrier of distributary gravel bar,the unloading process of sediments varies greatly at different positions on the surface of alluvial fan. The particle size varies greatly among different facies,with coarsest grains developed on the fans of hanging wall,finer grained on over-bar lobe and finest sediments on fault plane-dominated lobe. The development process of alluvial fan can be divided into three stages,according to the sandbody thickness and fault throw of distributary gravel bar. The fault throw also affects the sedimentary architecture of alluvial fan,with larger the fault throw generating larger the accommodation space of hanging wall,longer development time of distributary gravel bar and more complex of the superposition pattern of the sand bodies inside the fan. The internal architecture of alluvial fan that is controlled by normal faults includes longitudinal sandbar,distributary gravel bar and debris flow lobe in the profile vertical perpendicular to the sediment source direction from the proximal to the distal end. Along sediment longitudinal section,composite channel,superimposed distributary gravel bar complex and superimposed bodies of multi-phased lobes are dominant facies.     

The geometry of planar domino-style normal faults above a dipping basal detachment

Geometrical analysis of planar domino-style normal faults rooted into a dipping basal detachment fault allows derivation of equations which relate: (1) horizontal extension within the upper plate; (2) dip of the detachment; (3) final fault dips; (4) rotation that faults and beds undergo; and (5) net slip on domino-style faults. Past geometrical models have focused on extremely idealized and non-unique geometries, in which domino-style faults are parallel and similar cut-off points are all at the same elevation after faulting. This corresponds to evenly spaced domino-style faults above a horizontal detachment. Considering non-parallel faults and dipping detachments introduces unique geometries, which allows calculation, for example, of permissible depth ranges to the detachment. Horizontal extension varies significantly: (1) with dip of the detachment; and (2) for synthetic and antithetic cases, in which the domino-style faults dip in the same or opposite direction, respectively, as the detachment. When other factors (e.g. rotation and fault dips) are held constant, horizontal extension greatly increases for moderate detachment dips and moderately decreases for antithetic detachment dips, as compared to the horizontal detachment case. This is important because the synthetic case has been widely reported.     

正断层上盘煤与瓦斯突出特征与地应力场控制机理

断层带是煤与瓦斯突出发生的主要地质单元.大量煤与瓦斯突出案例统计显示,对于正断层,发生在上盘的突出次数和强度明显大于下盘,但造成这一现象的地质机理研究不多,特别是正断层上盘的地应力场在采动前后的变化规律及其对突出发生的控制机理尚未完全揭示.基于此,以河南焦作矿区中马村煤矿DF4正断层为地质模型,应用FLAC3D软件,模...     

沉积盆地中金属成矿与油气成藏的耦合关系

沉积盆地中与油气密切相关的金属矿床主要包括密西西比河谷型(MVT)铅锌矿床、砂页岩型铜-铀矿床、黑色页岩中的金属硫化物矿床、沉积岩容矿的金-锑-砷-汞-铊矿床等。金属矿床与(古)油气藏在空间上的密切共生/伴生关系,暗示了二者成因上的有机联系。在许多MVT铅锌矿床和砂页岩型铜矿床中,与成矿关系密切的原油及其衍生物形成于矿化前,它们为随后的金属成矿直接提供还原硫或充当硫酸盐还原反应的还原剂。在另一些情况下,某些低温热液金属矿床,特别是Au、As、Hg、Sb、Tl矿床与油气表现出同源、同运、同聚的耦合关系,金属成矿与油气成藏同时或近同时进行。与油气具不同耦合关系的金属矿床常表现出不同的特点。与成藏和/或成矿有关的盆地流体大致可分为以碳氢化合物为主的有机流体、以含金属盐水溶液为主的无机流体以及同时富含烃类和金属组分的有机成矿流体3类,盆地中的成矿、成藏作用及其耦合关系受控于这三类流体的演化过程。沉积盆地中金属矿床与油气藏空间上密切的共生/伴生关系以及成矿、成藏过程和机理的相似性,使金属与油气矿产资源的协同勘探和综合预测成为可能。     

Analysis of the relationship between displacements and dimensions of faults

Displacement gradients on single fault surfaces are a function of the maximum displacement on a fault and the dimensions of the fault surface. Data on the maximum lateral dimensions (widths) and maximum displacements on normal faults and thrusts, with maximum displacements from 4 mm to 40 km, are used to derive an expression relating width, displacement and material properties. The basis of this expression is a fault growth model in which width is proportional to the square root of displacement. Width/displacement ratios vary systematically with the size of a fault from values of ca 30,000, which are characteristic of a single slip event, to about 10 in the case of thrusts with displacements of 40 km. Rocks from which the fault data are derived have a likely range of shear moduli from ca 0.1 to ca 30 GPa, which is sufficient to account for the range of data.Data on widths and maximum displacements of 308 fault traces recorded on British coalmine plans are shown to be consistent with variation of shear modulus of about half an order of magnitude. Data on 58 further fault traces are shown to be consistent with the fault growth model. Synsedimentary faults may have growth curves characteristically different from those of other faults.It is suggested that the increase in dimensions of a fault is a postseismic process of subcritical crack propagation for which the significant material property is fracture toughness.     

The relationship between principal stress directions and the geometry of kinks in foliated rocks

This paper describes the results of a series of experiments carried out on card decks and foliated rock in order to study the nucleation and growth of kinks. Parameters varied in the experiments were confining pressure and the angle of inclination between the foliation and the direction of maximum shortening.The results showed that most kinks initiated as symmetric or monoclinal buckles which rapidly changed to an angular, stable form similar to that observed in nature. The amount of strain required to set up this stable geometry is small. The effect of increasing confining pressure is to diminish the size of the kinks while that of changing the angle of inclination of the foliation to the direction of maximum shortening is to modify the style of deformation from the development of a set of conjugate kinks at small angles (0 – 5°), to a single set of kinks at larger angles (5 – 15°), and, finally, to a combination of sliding along the foliation and kinking at the largest angles (15 – 30°) investigated.During this change in mode of deformation, the angular relationships between the kinks and the directions of the applied loads change systematically and graphs are presented which may be of use in relating the geometry of natural kinks to the principal stress directions.     

东非海岸重点盆地渐新世构造事件—沉积体系耦合关系研究

本论文以东非海岸鲁伍马、坦桑尼亚及拉穆盆地为对象，利用钻井、测井及地震资料，揭示了渐新世构造事件—古地貌特征—沉积系统的耦合关系，服务研究区油气勘探选区。结果表明，（1）板块构造事件控制宏观地貌格局及沉积环境变化。随着印度—塞舌尔板块与非洲板块分离，印度洋逐渐扩张，海水南侵，沉积环境由陆相变为海相。由于Afar地幔柱作用及地层抬升等作用，东非海岸整体呈西高东低地貌格局；（2）洋中脊扩展及断层活动控制盆地隆坳格局及沉积体系宏观展布规律。研究区发育西部坳陷带、中部斜坡带及东部深海平原带，东部Davie东及Davie西断层构成Davie构造带。从西向东依次发育 4 大河流—三角洲—海底扇沉积体系；西部坳陷带以三角洲沉积为主，中部斜坡带发育海底扇，东部深海平原带以半深海—深海泥最为常见，沉积体系多发育在Davie构造带以西；（3）次级断层活动影响沉积体系的发育规模及分布。沉积体系多发育在西部坳陷带及中部斜坡带的凹陷中。因凹陷及次级断裂影响，鲁伍马盆地北部、坦桑尼亚盆地南部沉积体系呈北偏特征，而拉穆盆地具南偏趋势。     

Problems of the relationship between lithology and tectonics in the study of sedimentary basins

Interrelation of tectonic and sedimentary processes is realized at different hierarchical levels (from a common geodynamic setting of sedimentary basin to the behavior of its local structures) and at different stages of basin evolution (from sedimentation to rock formation). Based on several examples, the paper considers issues related to the reflection of tectonic processes in sedimentary sequence, the development of complex tectonosedimentation models of sedimentary basins, the identification of mineralogical-petrographical and petrochemical indicators of tectonic settings, as well as the study of mutual influence of tectonic and lithogenetic factors on the rock formation in the basins.     

The problem of revealing the absolute kinematics of the opposite walls of faults

The existing kinematic classification of disjunctive dislocations takes into account only the relative displacements of their walls along the displacement surface in opposite directions. The topic of their absolute displacement has not yet been worked out, either in structural geology or in tectonophysics. As a result of analyzing various structural features, unconventional and often unexpected versions of their absolute displacements were worked out: the displacement of one wall along the displacement surface with an immovable second wall; displacement of both walls along the displacement surface in different (but not opposite) directions; displacement of one or both walls not along the displacement surface. It is imperative to concentrate one’s attention on the geological bodies themselves, and not on the fault boundaries between them, for thorough understanding of the faulting kinematics.     

青藏高原的地幔结构:地幔羽、地幔剪切带及岩石圈俯冲板片的拆沉

正断层位移长度关系是近年来研究正断层的一种常用方法 ,它将断层的研究从二维扩展到三维。研究正断层位移长度关系对于研究正断层演化、盆地演化以及油气勘探等方面具有重要意义。讨论了影响正断层位移距离剖面形态的主要因素 :断层端的脆韧性变形、围岩强度、远程应力以及断层之间的相互作用和连接等。根据正断层位移距离剖面的几何形态和断层发育阶段 ,可将断层的位移模式分为 3个类型 :(1)对称的椭圆状或钟状代表简单的单条断层 ;(2 )不对称的似椭圆状或钟状代表断层间的相互作用 ;(3)不规则的锯齿状代表由多条断层连接而成的断层。介绍了伴随正断层发育的传递斜坡、盆内高地等构造单元以及断层位移距离剖面的测量制作方法。测量时应注意恢复其剥蚀部分。     

羌塘盆地生物礁岩特征与沉积模式

在三叠纪-白垩纪，特提斯海域内发育有大量的生物礁岩，羌塘盆地内亦广泛发育。生物礁沉积序列可划分为4类：(1)浅滩相生屑灰岩、核形石灰岩→生物礁岩→开阔台地相泥晶灰岩→斜坡相角砾岩；(2)开阔台地相灰岩→生物礁岩→局限台地相白云质灰岩；(3)浅滩相生屑灰岩→滨岸相碎屑岩；(4)潮坪相粉砂岩、泥灰岩→潮坪砂坝生屑灰岩→生物礁岩→潮坪砂坝生屑灰岩→潮坪相泥灰岩。生物礁岩可分为骨架岩、障积岩与粘结岩3种成因类型。成岩作用有重结晶、胶结、压实、压溶与破裂、溶蚀作用等。主要孔隙类型包括原生孔隙、裂隙与溶蚀孔、缝三类。晚三叠世造礁生物主要为珊瑚和藻类；中晚侏罗世以珊瑚礁与海绵礁为主。生物礁岩以海进体系为主，高位体系域也有发育，低位体系域中少见。可分为珊瑚礁、海绵礁、藻礁和层孔虫礁。南羌塘坳陷西部以珊瑚礁为主，东部以海绵礁为主；北羌塘坳陷西部为藻类珊瑚礁、层孔虫礁，台地内部有珊瑚礁、海绵礁。按古地理位置可分为台地边缘礁和台地内部礁，前者分布规模大，在地震剖面上也有明显的反映，有可能成为重要的油气储层。生物礁的发育状况全球海平面升降所控制。     

沉积盆地油气与砂岩型铀矿成矿关系研究

国内外许多砂岩型铀矿产于含油气盆地,油气参与砂岩型铀成矿作用越来越受到人们的重视;沉积盆地控制着油气田和砂岩型铀矿床的分布,多数盆地总体形成内部油气-边部铀矿、下部油气-上部铀矿的分布规律。文章认为油气藏与砂岩铀矿床相互联系的储集层系统及盆地有机/无机成因流体是两者同盆共存的物质基础,吸附作用和还原作用是油气参与砂岩型铀矿成矿的两种主要作用方式,重力流驱动的含铀流体与油气成藏过程中油气扩散形成的烃类流体相互混合是铀成矿作用的主要动力学机制,构造则是两种流体联系的纽带;油气与铀矿相互共生、相互作用,为"以铀找油"和"以油找铀"提供了基础。根据油气与铀的成因联系,结合石油勘探开发资料,提出利用油气田资料"二次开发"寻找砂岩型铀矿的思路和方法。利用油气田资料来寻找砂岩型铀矿,可节约大量勘探资金,提高油气田经济效益,经济价值高。     

松辽盆地北部古龙地区登娄库组沉积与构造演化耦合关系研究

为明确松辽盆地北部古龙地区登娄库组沉积与构造演化的耦合关系,本文利用古龙地区的地震、钻井、测井和岩心等资料,通过古龙地区登娄库组的构造演化特征、层序地层格架和沉积特征综合研究,对古龙地区登娄库组构造演化对沉积充填特征的控制作用进行分析,结果表明,古龙地区登娄库组沉积时期为断坳转换期,可进一步划分为断陷盆地萎缩阶段早期和晚期、坳陷盆地孕育阶段早期和晚期4个构造演化阶段,分别对应4个三级层序(Sq1-Sq4); 古龙地区登娄库组主要发育冲积扇、扇三角洲、湖底扇、河流相、辫状河三角洲、浅水三角洲、湖泊沉积等沉积体系; 登娄库组构造演化控制着沉积充填演化,各构造演化阶段沉积体系分布特征及沉积演化模式具有明显的差异性,即沉积充填特征与构造演化过程具有良好的耦合关系。具体表现为:断陷盆地萎缩阶段早期(Sq1)和晚期(Sq2)下部地层受断陷作用控制,沉积充填特征符合陆相断陷湖盆沉积演化模式; 断陷盆地萎缩阶段晚期(Sq2)上部、坳陷盆地孕育阶段早期(Sq3)和晚期(Sq4)地层具有坳陷层序地层特征,其中萎缩阶段晚期(Sq2)上部和坳陷盆地孕育阶段早期(Sq3)属于坳陷盆地"河流-浅水三角洲"沉积模式; 坳陷盆地孕育阶段晚期(Sq4)发育干旱背景下的坳陷湖盆"洪水-河漫湖"沉积模式。     

Cycles and subsidence: their relationship in different sedimentary and tectonic environments in the Scottish Carboniferous*

Ten data sets have been collected from stratigraphical intervals in the Upper Carboniferous of Central Scotland. They represent six structural units and both distal and proximal deltaic environments, plus a meandering river environment. All show a definite tendency towards a linear relationship between the number of deltaic or fluvial cycles and the total thickness of strata in the interval. This relationship is, however, much stronger in sequences laid down in actively subsiding depositional basins than in areas where subsidence is thought to have been controlled by block faulting in the basement or in areas where there is no clearly defined pattern or subsidence. With respect to facies, the relationship is less close in successions that were frequently affected by widespread marine transgressions. The slopes of linear regression lines fitted to the data sets vary much more than had hitherto been supposed. Thus they are no longer thought to provide possible evidence of some ubiquitous underlying process, such as ductile flow in the upper mantle, which affected all the structural units equally. The line which represents proximal deltaic deposits of Westphalian A age in the Kincardine Basin slopes twice as steeply as any of the eight lines representing other dominantly deltaic successions and considerably more steeply than the line representing a succession of Namurian fluvial cycles. Second- and third-degree polynomial regression lines were also fitted to each data set but these generally satisfy little more of the total variation than do the corresponding linear regression lines, and F-test results indicate that the gains are not statistically significant. Eight of the second-degree lines however share a common shape that suggests a general tendency for both deltaic and fluvial cycles to be somewhat thicker in the areas of greatest net subsidence.