The uplifting processes of the Tibetan Plateau since 0.5 Ma B.P.

There is no final conclusion yet on the uplifting mechanism and epoch of the Tibetan Plateau, which is a hot point of the geological research. This paper discusses the epoch and scales of the hydrothermal activities based on the ESR ages of hot-spring sediments. The ESR ages show that hydrothermal activities mainly happened in four periods: 50×10⁴a, 50×10⁴–47×10⁴, 40×10⁴–35×10⁴, 27×10⁴–20×10⁴ and 10×10⁴—0 aB.P. This conclusion is supported by the geophysical data and the inner plateau and surrounding sediments. Through analyzing the constraints of the deep restraint mechanism and uplift tensile function of the plateau, the uplifting processes of the Tibetan Plateau since 50×10⁴a B.P. is elucidated.     

内蒙古固阳村空山地区麻粒岩的锆石U-Pb年龄及其对年龄解释的启示

从内蒙古固阳 -武川地区的麻粒岩中 ,新近获得了 ( 2 648.5± 4 .6)Ma的单颗粒锆石U Pb不一致线上交点年龄和 2 673Ma2 0 7Pb /2 0 6Pb表面年龄 ,这是内蒙古地区 (包括晋冀蒙交界地区 )迄今获得的最大的锆石U -Pb年龄值 ,为华北陆台北缘 (西段 )麻粒岩相带的地壳演化研究提供了可靠的年代学依据。结合地质体之间的野外地质关系 ,对所获得的年龄信息进行了合理的地质解释 ,认为它代表研究区最后一次麻粒岩相变质作用的时代。同时探讨了后期岩浆作用、变形变质作用对测年数据地质解释的影响。     

POTENTIAL VORTICITY STRUCTURE OF SUMMER CYCLONES OVER THE CHANGJIANG-HUAIHE VALLEY*

Based on the theory of Ertel potential vorticity,the isentropic potential vorticity maps and vertical profiles of potential vorticity for two summer cyclones over the Changjiang-Huaihe Valley are analysed.After discussing a possible mechanism for the genesis and development of such systems and their differences from typical extratropical cyclones,a conceptual model for their activities is proposed:A weak disturbance in the midlevel of troposphere originated from around the Qinghai-Xizang Plateau may cause heavy precipitation under favourable conditions and latent heat release in the mid-troposphere leads to downward extension of cyclonic circulation and a wave on the quasi-stationary front.This weak cyclone can develop substantially and become a typical extratropical cyclone only when air from the lower stratosphere flows downslope along isentropic surfaces into the region of interest.     

辽宁东部凹陷南部地区地球物理资料的综合解释

介绍了对辽宁东部凹陷南部地区1:5万重、磁、电磁测深资料的综合研究工作结果,提供了较为丰富的地质信息,为进一步深化认识该区的地质构造特征提供了依据.文中重点讨论了该区基底形态及结构、断裂特征、火山岩分布、中生界地层分布等地质问题.对该区基底结构、中央凸起带的南延等问题提出了新的认识.     

蒙脱石晶体结构和水结构的矿物物理特征

本文利用矿物物理研究方法对我国内蒙、浙江、甘肃等地的钙基、钠基、镁基蒙脱石的物质成分、晶体结构和层间OH,H_2O的排布结构进行了研究,并获得下列结论: 1.由X衍射和拉曼分子光谱分析深入研究了蒙脱石阳离子配位体结构特征,提出其空间群为C_2/m型。 2.建立了蒙脱石水结构模式,有3种主要类型:①层间大阳离子附近的束缚态水分子;②层间无大阳离子位置上的非束缚态水分子;③颗粒表面依靠氢键相连的水分子集合体。 3.利用群理论,提出了蒙脱石OH~-的振动模式,由振动分析指出蒙脱石中OH~-具有12个振动模式。     

华北地区拆离滑脱带控震作用初探

华北东部盆岭区以地震多、震级大、损失惨重而称。以往地震地质研究多注重断裂交汇、拐点、分枝等部位的控震作用。但是，华北盆岭区多次大震的烈度并不呈线型展布，震源也并非沿陡倾断裂走向分布，而是在一定深度上(近水平)弥散展布，故人们开始注意深部滑脱带控震的探讨。笔依据近十余年华北地幔亚热柱的研究认为，华北断陷区之下为—强烈上隆的地幔亚热柱。地幔物质的上隆及上侵作用使上地壳裂解断陷，而中地壳在地幔、下地壳的影响下形成相间展布的低速—高导层。在地幔亚热柱热物质流向外拆离的带动下，中、下地壳亦由亚热柱顶部向外围拆离滑脱。当中、下地壳拆离到上地壳裂陷盆地边缘受到造山带的阻挡而减慢时，两之间便产生剪切作用，导致应力不断积聚并阶段性释放，从而造成亚热柱外围地震频繁发生。     

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.      

天津地区海积软土结构强度及其对力学特征的影响

海积软土是一种结构性土，具有结构连结强度。其压缩曲线呈现出超固结土的压缩的曲线形式。强度曲线为二段折线，在应力小于σ'k时表现出超固结土的力学特征。而当应力水平高于这一临界值时，表现出正常固结土的力学特性。对其结构连结的成因进行了简单探讨。     

Research on paleoearthquakes in Jiuxian trenches across Nankou-Sunhe fault zone in Changping County of Beijing plain

An abundance of the phenomena of tectonic deformation and paleoseismic events of different times and their recurrent interval, as well as coseismic vertical displacements is exposed in Jiuxian trenches across the Nankou-Sunhe fault zone in Changping County. The research result shows three paleoearthquakes occurring during the Holocene. They were dated as 10643 ± 250 a B.P.-9706 ± 1235 a B.P., 7894±150 a B.P.-7640 ± 650 a B.P., and 3987±100 a B.P.-3670 ± 310 a B.P., respectively. The coseismic vertical displacements are 1.0 m, 2.0 m, and 2.0 m, respectively. From a statistical formula of relation between historic earthquake magnitudes and surface seismic dislocations in North China, the magnitudes of these paleoearthquakes are inferred to be in a range from M 7.7 to M 7.9. The research shows that the Holocene fault activity in the plain can be traced in the trenches according to the micro-geomorphic features. Many micro-structural phenomena are also found in these trenches. Identification of the paleoearthquakes in the Nankou-Sunhe fault zone during the Holocene time is of significance for assessment of future seismic risk in Beijing area.