Relic UHP Structures in Dabie-Sulu Region, China:Structural Expression and Geodynamic Significance

INTRODUCTIONIn recent years a num ber of detailed m ineralogical- petro-logical studies have been carried out on the UHP and HPmetamorphic belts in the Dabie- Sulu region,central China(see review papers by Jahn,1999;Ernst and L iou,1999;Wallis et al.,1999;Hacker et al.,1996 ;L iou et al.,1996 ;Cong et al.,1994) . Various tectonic evolution models for theUHP belt in the Dabie- Sulu region have been constructed(e.g.,Webb etal.,1999;Hacker et al.,1996 ;Cong et al.,1994) .However,as …     

南黄海盆地东北凹构造特征及伸缩率研究

通过选取南黄海盆地东北凹典型地震剖面,开展精细的构造解释,系统梳理了东北凹构造样式特征。采用平衡剖面恢复技术和伸缩率计算方法,恢复了东北凹各时期的地质演化剖面,分析了东北凹不同构造演化阶段的伸缩率变化特征。研究表明,南黄海盆地东北凹主要发育伸展构造、走滑构造（负花状）和反转构造等多种构造组合样式,经历了晚侏罗世的仪征运动和渐新世末的三垛运动,相应地在中—上侏罗统和渐新统沉积时期,东北凹处于明显的收缩阶段,伴随发育TK40和T20不整合界面。同时,本文结合区域应力场特征,探讨了南黄海盆地东北凹的构造演化历程：以两次构造运动为界,划分为3个构造演化阶段（晚三叠世—侏罗纪的初始断陷阶段、白垩纪—渐新世的裂陷-反转阶段、新近纪—第四纪的区域沉降阶段）。南黄海盆地东北凹伸缩率的时空变化及构造演化过程,是对“晚中生代以来,古太平洋板块相对欧亚板块俯冲汇聚速率和方向的改变”的局部响应。     

雁列式断层组合变形过程中的声发射活动特征

着重研究拉张或挤压型雁列式断层标本变形过程中声发射(简称AE，下同)的时空演化特征. 结果表明，预置构造对AE空间分布格局具有较强的控制作用，随着差应力的增加，AE首先在两个端点附近丛集，之后向两端点连线附近集中，出现明显的破裂局部化现象，较大事件还通常集中于某一端点附近反复发生. 前期微破裂丛集图象指示后期宏观破裂的扩展方向及扩展范围. 拉张和挤压型雁列区宏观破裂方向分别与轴向应力方向垂直和平行. 雁列式断层标本变形过程中，破裂前的弱化阶段相对较长、弱化过程明显. 微破裂事件累积频次指数增长可能是系统失稳前的典型征兆之一，而雁列区宏观破裂之后，AE数量逐渐减少、应变释放相对减弱. 摩擦滑动过程中，大的粘滑失稳前未见有AE活动前兆性的增强过程.雁列区的b值变化在失稳前显示趋势性降低——快速回升这一典型的变化过程，b值降低一般发生在差应力增强过程之中，并有可能延续至弱化阶段，而快速回升则一般发生在破裂失稳前的短时期内. 对比研究表明，构造差异所导致的b值差异远大于b值随差应力的增加而产生的变化量，而对同一构造标本，力学状态的改变会导致AE序列时序特征的急剧变化，较高的加载速率对应较高的应变能释放及明显的低b值. 先期破碎带由于较低的破坏强度，其对差应力的微小变化具有特殊敏感性，从而成为源、兆分离、窗口或敏感点效应等地震活动性前兆现象的一种可能的原因.      

Diffraction of plane P waves by a canyon of arbitrary shape in poroelastic half-space (Ⅰ): Formulation

This paper presents an indirect boundary integration equation method for diffraction of plane P waves by a two-dimensional canyon of arbitrary shape in poroelastic half-space. The Green's functions of compressional and shear wave sources in poroelastic half-space are derived based on Biot's theory. The scattered waves are constructed using the fictitious wave sources close to the boundary of the canyon, and magnitude of the fictitious wave sources are determined by the boundary conditions. The precision of the method is verified by the satisfaction extent of boundary conditions, the comparison between the degenerated solutions of single-phased half-space and the well-known solutions, and the numerical stability of the method.     

Measuring wave propagation characteristics in artificial sand-clay mixtures

Ultrasonic compressional (V _p ) and shear (V _s ) velocities have been measured on artificial sand-clay mixtures. The measurements were carried out in a drained triaxial load cell using a pulse transition method. The measuring device was equiped with a waveform storage facility. The investigated mixtures consisted mainly of kaolinite and quartz sand. Some mixtures also contained Na-montmorillonite, illites or quartz-flour. The acoustic behaviour was observed during a pressure increase up to 72 MPa vertical and 36 MPa horizontal pressure. At a given pressure,V _p andV _s in pure sand turned out to be similar to those in pure kaolinite. As predicted by the sand-clay model of Marion (1990), a velocity maximum corresponds to a minimum in total porosity. This porosity minimum marks the transition from a clayey sand to a sandy clay. It is not only reflected in bothV _p andV _s , but also in the quality of the received pulse. The effective tension of the received signal during 20µs after the first arrival, was used as an indication for P-wave pulse attenuation. This apparent attenuation decreases with increasing clay content and increases with increasing porosity. It is shown that clay mineralogy does not measurably affect wave velocities in clayey sands.     

西昆仑山前地区白垩系分布研究

白垩系是西昆仑山前地区最重要的储层,受区域构造演化控制,其岩性与分布在纵、横向上均发生变化。下白垩统为冲积扇辫状河相沉积的红色砾岩、砂岩夹泥岩;上白垩统英吉沙群在研究区西部为一套海相碳酸盐岩地层。白垩系在喀什凹陷最厚,往西、往东、往北均逐渐变薄,并发生相变与尖灭,控制储层发育。本文在研究区域首次通过地震相研究,根据白垩系反射特征精细追踪对比其层位,确定尖灭位置,进而确定白垩系分布范围。研究认为,地震相能在区域上宏观地反映白垩系的沉积特征与分布范围,进而指导油气勘探,具有很重要的现实意义。     

Dynamic Features of Angular Unconformity Formation——Extensional and Compressional Angular Unconformities

Angular unconformity is one of the most direct and strongest evidences for approving the tectonic movements of the earth's crust. Its dynamic genesis process has been understood to be mainly related to the compressional setting for a long time. Especially, in a detailed structural analysis for a specific region, when an angular unconformity is discovered people would regard it as the result of orogenic movements of a certain period or a certain episode and neglect the extensional facts. Based on a dialectical point of view of extension-compression, this paper has proved that angular unconformities can be formed not only in compressional settings, but also in extensional ones. Further more, their geological features are compared and he possible genetic mechanisms for angular unconformity under different dynamic settings are studied.     

高温高压下粗面玄武岩纵波速度异常原因初探

在１．０－５．０ＧＰａ,温度约１３５０℃条件下测量了福建塔庄粗面玄武岩的纵波速度。结果发现当ｐ〈３．０ＧＰａ,ｔ为５２９－８１６℃,ｐ＝４．０ＧＰａ,ｔ为５３７－８０７℃;ｐ＝５．０ＧＰａ,ｔ为６０７－８０２℃时,粗面玄武岩纵波速度随升高反而升高,显示出异常变化。通过对ｐ为１．０－５．０ＧＰａ条件下的最终实验产物及ｐ＝４．０ＧＰａ,ｔ为５８７,７２４,８８７℃温度点上的实验产物观察表明,实验产物中