The dip equator over Peninsular India and its secular movement

A ground geomagnetic survey conducted in peninsular India has demarkated the dip equator for the epoch 1991.0. A well-defined southward migration in the last two decades is evident. The secular trend in the vertical component and the direction of the migration in the India zone are shown to be consistent. The migratory movement of the dip equator in different longitude sectors is compared to highlight the complex nature of the secular trends.     

构造应力作用下流体运动的动力学分析——构造流体动力学

本文从流体动力学的基本规律出发,应用渗流力学、岩土力学及弹性力学的理论及方法,推导出了考虑应力状态的可变形介质中流体运动的动力学方程,由该方程可以看出：应力状态是影响流体运动的一个非常重要的因素,它通过３种方式来影响流体的运动,其一是：应力的作用改变介质的渗透性能,从而影响流体运动;其二是：平均正应力的变化速率影响介质的含流体能力,它以源汇项的形式反映在方程中;其三是：应力的作用影响流场的初始状态及边界状态,通过影响定解条件反映在动力学方程中,从而影响运动特征。构造应力场对流体运动的最终影响是这３方面作用     

暴雨作用下排土场平台–边坡系统土壤侵蚀过程模拟研究

为了探究冻融循环作用对土体结构和力学性质的影响机理,以内蒙古元宝山露天煤矿内排土场典型黏土为研究对象,采用室内冻融循环试验和MatDEM数值模拟,进行土体内部温度场、水分场和应力场的模拟分析。结果表明：排土场土料经过冻融循环后发生冻缩现象;低围压时应力−应变曲线呈现应变软化型,发生剪切破坏,围压升高后向应变硬化型转变,发生剪胀破坏;抗剪强度的劣化受前3次冻融作用的影响最为显著,在第3次达到最低值;温度的传递过程可划分为温度快速下降、缓慢相变过程、继续降温、温度稳定4个阶段;水分运移主要在温度传递的前2个阶段发生,且第二阶段的水分运移量居多;颗粒受冻融作用后整体半径缩小、分散性增大;温度和水分运移引起的颗粒胀缩、冰−水相变、冷生结构的形成等,导致颗粒的大小、位置、连接状态和颗粒间的应力等反复变化,共同驱动土体产生不可逆的结构性损伤,进而造成强度劣化。水分运移不仅为冷生构造的生长提供水源条件,还产生溶蚀、冲刷破坏,与水的相变共同成为冻融循环作用导致土体发生结构调整和应力场变化的主要原因。通过离散元法模拟冻融循环,有助于了解土体内部的力学特征和强度劣化机理,为冻区露天煤矿内排土场边坡及其他工程建设的稳定性研究提供参考。

     

Testing mathematical uranium migration models in combined ESR/U-series dating of fossil teeth from open-air sites

Several mathematical models have been suggested to describe uranium migration kinetics for ESR dating of fossil tooth. In the present study, different U-uptake models were used to calculate ages for fossil teeth from two open-air Paleolithic sites in Nihewan Basin – Donggutuo and Hougou and compared with independent age control of the sites. For Donggutuo site, the results show that the ages of three teeth calculated by EU and AU models were much younger than magnetostratigraphic age. At Hougou site, two teeth from the top of Nihewan lacustrine deposits give the consistent EU and AU ages within errors but younger than sediment OSL age. This study indicates that mathematical modeling could not always give convincing results for the open-air sites, which may experience dramatic hydrological variations and high erosion rates.     

塔里木北部周缘前陆盆地早二叠世快速迁移与沉积相突变:俯冲板片拆沉的响应

塔里木北部周缘前陆盆地发育于泥盆纪末至早三叠世期间,完整地记录了南天山造山带的发育过程。该盆地在早二叠世由复理石盆地转化为磨拉石盆地,同时发生快速南移。同期幔源物质加入,有山根地壳熔融的岩浆活动、南天山造山带的整体隆升、热液成矿作用集中发育和变形、变质作用的激化使俯冲岩片的拆沉成为盆地转化与迁移的最佳机制。相同的转化过程及深部机制在其他造山带中也明显存在,表明俯冲岩片拆沉是造山作用一个不可或缺的环节。     

Crystallographic orientations of high-angle grain boundaries in dynamically recrystallized quartz: First results

The crystallography and geometry of high-angle grain boundaries from dynamically recrystallized quartz have been studied. On the basis of combined electron backscatter diffraction and universal stage measurements, the complete crystallographic orientation of the grain boundaries could be calculated. The u-stage rotation of the grain boundaries to a vertical position reveals that they are never curved but always consist of straight segments. Our results show that these segments preferentially occupy rhombohedral, trapezohedral and bipyramidal orientations, i.e., orientations in a  25–50° girdle to the c-axis. A specific, albeit low, number of segments with special crystallographic orientation, with respect to a neighbouring quartz grain, often shows another special orientation with respect to the other neighbouring grain. Preferred combinations of grain boundary orientations related to both neighbouring grains are (i) low-index rhombohedral and high index trapezohedral, (ii) low-index bipyramidal and low-index trapezohedral or high-index rhombohedral, and (iii) low-index trapezohedral and low or high index trapezohedral. In certain cases, such as at triple junctions, the boundaries occupy specific trapezohedral orientations with a constant angle to the c-axis. This argues for energy isotropy of trapezohedral planes with the same angle to the quartz c-axis. In general, good match coincidence site lattice (CSL) orientations are not preferentially occupied so that most of the studied grain boundaries represent general boundaries. The formation of straight segments in special crystallographic orientations indicates the crystallographic control and implies an energy reduction of certain general boundaries.     

塔里木盆地天然气运聚系统与运聚模式

对塔里木盆地东部地层压力结构和天然气性质差异的研究表明,塔里木盆地东部具有多个独立的天然气运聚系统。这些运聚系统具有流体封存箱的特征。天然气只能在运聚系统内部进行短距离的运移,不能进行大规模侧向运移。因此天然气藏的形成具有近源的特点。由于不同运聚系统特征的差异,塔里木盆地大致有三种天然气运聚模式。     

断裂密集带在油运聚成藏中的作用——以三肇凹陷和尚2井区块扶杨油层为例

为研究三肇凹陷和尚2井区块扶杨油层油气成藏规律,采用断裂密集带与油气分布叠合的方法,分析断裂密集带在油气成藏分布中的作用.结果表明:三肇凹陷扶杨油层发育35条断裂密集带,尚2井区块扶杨油层发育9条断裂密集带;油主要分布在断裂密集带两侧,少量分布在断裂密集带内部.断裂密集带对油运移的控制作用表现在2方面:(1)断裂密集带边界断裂为油输导断裂;(2)断裂密集带不利于油横穿其侧向运移,但可沿其侧向运移.断裂密集带对油聚集的控制作用表现在2方面:(1)断裂密集带两侧的地垒和断阶构造是油聚集的有利部位;(2)断裂密集带内部的背形构造也是油聚集的有利部位.     

尼日尔深水区海底扇水道地震形态与迁移历史

尼日尔下陆坡深水区的水道发育具多期次特征,内部结构与外形复杂多变,其地理位置与沉积环境不利水道体系的研究.通过地层切片、RMS振幅属性等方法展示不同时间单元水道形态,分析水道体系的期次变换与内部结构的变形过程,探讨水道体系的迁移演化历史.结果表明:中新世中期多发育孤立水道,晚期二级海平面大幅度下降引发大规模浊积事件,促使大量加积式水道形成,在平直处以垂向加积为主,弯曲处呈现垂向加积同时伴随侧向迁移特征.水道演化大致可分为3个阶段:初始侵蚀、切割与充填交替进行、废弃阶段,伴随3个阶段水道弯度发生由中到高再下降的变化.水道的交互式切割与充填基本贯穿第2阶段,切割与充填作为水道弯曲变形一对驱动力,使水道在平面上发生3种迁移方式:侧向摆动、下行迁移、侧向与下行混合迁移.     

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