刚果(金)绿纱铜钴矿床黑色页岩Rb-Sr测年及其区域成矿意义

中非铜钴矿带是全球最大最具经济价值的沉积型层状铜成矿带之一.区域内铜钴矿床形成分布主要受区域地层和构造控制,成矿具有多期特征.含矿地层中发育大量褶皱前浸染状和顺层脉状矿化,指示可能存在成岩之后和造山主构造变形之前的矿化叠加作用.本文通过绿纱铜钴矿床矿化黑色页岩全岩Rb-Sr测年及Sr-Nd同位素研究,获得早期浸染状矿化...     

珠江三角洲的新构造运动及其与三角洲演化的关系

综合已有资料。重新对珠江三角洲的新构造运动进行了系统的分析．分析结果表明该地区的新构造运动以断裂活动和断块差异升降运动为主要特征．这些特征在珠江三角洲的演化过程中起着非常重要的作用。大多数在第四纪形成或重新活化的基底断裂把三角洲切割成一系列的断块,并且在垂直运动上以沉降为主导,为珠江三角洲的第四系沉积创造了空间。另外,第四系两期河流相砂砾层分布的差异反映了古河道在晚更新世海侵后、全新世海侵前所发生的变迁。这主要是断裂活动的结果。因此,在珠江三角洲的形成和演化过程中。新构造运动既影响着三角洲的沉积又控制着河道的变迁．     

辽宁北西向断裂构造

辽宁北西向断裂构造发育,通常表现为由多条断裂组成的北西向断裂带,多被中基性岩脉充填。北西向断裂(带)在磁场上主要表现为负磁场带,构成一个完整的北西向磁性块体;重力场则处于布伽重力异常等值线疏密突变带上。北西向断裂(带)具有多期活动的特点,是一组控岩、控矿构造,对金矿的控制作用尤其明显。     

马鞍桥金矿控矿构造规律及成矿预测

在讨论矿区构造变形序列、变形期次、深度层次、构造组合及变形机制的基础上,重点对马鞍桥金矿的控矿韧性剪切带类型及其与成矿关系进行了研究,根据剪切带的几何要素,用作图法求出矿带的东延方向,综合其他找矿标志,预测出清水河处矿体可能出现的部位。     

A note on the stress-dilatancy relation for simulated fault gouge

Theoretical constraints on the stress-dilation relation for a deforming Coulomb material requirev ifC=0 andv sin^-1( _m / _m ) always, wherev is the dilation angle, is the friction angle,C is cohesion, _m is the maximum shear stress, and _m is the mean effective stress. Recent laboratory measurements of friction and dilatancy of simulated fault gouge show that small amplitude shear-load cycling causes compaction and consolidation. Comparison of the data with theory indicates that such load cycling produces: (1) increased coefficient of friction (or friction angle), (2) increased cohesion, and (3) increased dilatancy rate (or dilation angle). Under certain conditions of load cycling without significant plastic shear strain accumulation ( ^p <0.005) we find thatv exceeds both and, in contrast to theory, sin^-1( _m / _m ). This result is interpreted in terms of enhanced cohesion and overconsolidation, which lead to residual stresses within the gouge. An analogy is drawn between these special loading conditions and those extant on natural faults. In particular, our results imply that jostling and minor stress variations associated with microearthquakes may produce strengthening of fault gouge and changes in the fault zone's stress-dilatancy relation. Hence, compaction associated with microseismicity may lead to subsequent dilation of fault gouge, even for faults with large displacement rates and large net offsets (e.g., San Andreas). In regions where such dilation persists over sufficient displacements (on the order of the critical slip distance for seismic faulting) it may tend to inhibit unstable slip.     

Formation and development of normal-fault calderas and the initiation of large explosive eruptions

The ring fractures that form most collapse calderas are steeply inward-dipping shear fractures, i.e., normal faults. At the surface of the volcano within which the caldera fault forms, the tensile and shear stresses that generate the normal-fault caldera must peak at a certain radial distance from the surface point above the center of the source magma chamber of the volcano. Numerical results indicate that normal-fault calderas may initiate as a result of doming of an area containing a shallow sill-like magma chamber, provided that the area of doming is much larger than the cross-sectional area of the chamber and that the internal excess pressure in the chamber is smaller than that responsible for doming. This model is supported by the observation that many caldera collapses are preceded by a long period of doming over an area much larger than that of the subsequently formed caldera. When the caldera fault does not slip, eruptions from calderas are normally small. Nearly all large explosive eruptions, however, are associated with slip on caldera faults. During dip slip on, and doming of, a normal-fault caldera, the vertical stress on part of the underlying chamber suddenly decreases. This may lead to explosive bubble growth in this part of the magma chamber, provided its magma is gas rich. This bubble growth can generate an excess fluid pressure that is sufficiently high to drive a large fraction of the magma out of the chamber during an explosive eruption. Received: 2 January 1997 / Accepted: 22 April 1998     

利用地震矩张量反演汾渭断裂系现今运动学特征

探讨了利用地震矩张量反演断裂形变带运动学参数的方法,将其应用于汾渭断裂带现今运动学特征的研究．结果表明,汾渭断裂带的运动呈Ｎ２２°Ｗ方向拉伸,Ｎ６８°Ｅ方向压缩．其平均拉伸位移速率为０．１５ｍｍ／ａ．     

西秦岭北缘活断层带断层气的基本特征

通过对西秦岭北缘活断层带断层气活动基本特征的研究认为：本活断层带是本区地球排气的主要通道;在走滑断层拉分区,地球排放气体活动的强度与地震活动有密切的关系;本带东段断层排气活动比较强,西段断层排气活动比较北,并讨论了两形成差异的原因。     

河北矾山盆地北缘断层八营段的古地震重复模型

通过实测断错地貌面,开挖在探槽以及系统的地层年代采样,推断和揭露出矾出盆地北缘断层八营段９万年来总移量量为３４ｍ。经７．５万年来共发生过９次古位移事件。其中大探槽揭露的４次事件分别发生在距今：Ａ,２．８万年;Ｂ．１．４万年;Ｃ,０．７５万年和Ｄ,６５６年（？）左右。该段落古地震地重复模型分为两个阶段：９￣１．４万年间符合“时间可推测模型”;１．４万年来以来则为“位称衰减模型”。     

珠江三角洲及其邻近海域第四纪地质与地震危险性

从第四纪地质研究的角度分析了珠江三角洲地区的地震危险性,认为北东,近东西和北西向三组断裂带把整个珠江三角洲断陷分割成７个次一级断块,并根据控制各次级断块的断裂第四纪活动性的强弱。