波浪作用下单桩基础周围海床液化机制研究

建立波浪作用下单桩周围三维海床动力响应模型,考虑自重影响下的海床长时间固结过程。采用已有物理模型试验数据对模型进行验证,证实其具有较好的适用性。模拟波浪作用下单桩周围三维海床液化区域,通过定量分析超孔隙水压力和土体初始有效应力的变化,讨论单桩插入深度对海床液化的影响机制。研究表明,单桩插入深度发生变化时,土体初始有效应力对海床液化的影响要大于超孔隙水压力,且影响程度随着插入深度的增加而逐渐增大。     

西南地区前兆震群以及显著地震与区域强震的时空特征

本文系统清理并分析了西南划分的五个预报区[1]中的强震发生前的前兆震群和显著性地震特征。在西南划分的五个预报区中,各区域的前兆震群和显著地震存在共性特征,但又具有明显的区域个性。从共性特征上看,西南划分的五个预报区的前兆震群和显著性地震发生后1-2年可能发生强震,强震一般发生在前兆震群或显著性地震附近地区或相关联构造带上;川滇往往是块体内部构造较复杂的区域,发生的强震会有前兆震群或显著性地震发生。从个性特征上看,西南划分的五个预报区的前兆震群和显著性地震发生与西南地区的地震地质构造具有一定关系,也就是说特殊的构造使得各区域的前兆震群和显著性地震具有明显的个性特征。     

阿拉善地块北缘雅干花岗岩体地球化学、地质年代学及其对区域构造演化制约

位于阿拉善北部中蒙边境地区的雅干花岗岩体以二长花岗岩为主,岩体的锆石离子探针U-Pb年龄为283.2±2.2Ma (n=14,MSWD=0.016).该花岗岩体具有相对较低的SiO2含量(66.96％～70.71％),和较高的A12O3(15.05％～16.05％)和(Na2O+ K2O)含量(7.24％～9.19％),且岩体钠含量稍高(Na2O/K2O＞1).雅干花岗岩体总体上表现为高钾钙碱性及偏铝质-过铝质的特征.岩体稀土元素总合量为101.9×10-6～133.1 ×1O-6,在稀土元素配分模式图中,岩体表现为轻-重稀土元素中等程度-强烈分异,同时具有明显的负Eu异常(δEu =0.59 ～0.77);在微量元素原始地幔标准化蛛网图中,岩体表现为亏损Nb、Ta、P、Ti,富集Ba、Rb、Cs、Th、K等大离子亲石元素;岩体同位素特征则表现为具有高的(87 Sr/86 Sr)i值(0.707654 ～0.710235)以及负εNd(t)值.根据雅干花岗岩体的形成时代、地球化学特征以及相关的沉积建造特征,可推断该岩体形成于后碰撞环境,表明古亚洲洋在阿拉善地块北缘北部地区的分支于早二叠世(283.2 ±2.2Ma)之前已经闭合.     

Tidal effects on temperature front in the Yellow Sea

Temperature front (TF) is one of the important features in the Yellow Sea, which forms in spring, thrives in summer, and fades in autumn as thermocline declines. TF intensity ⋎S _T ⋎ is defined to describe the distribution of TF. Based on the MASNUM wave-tide-circulation coupled model, temperature distribution in the Yellow Sea was simulated with and without tidal effects. Along 36°N, distribution of TF from the simulated results are compared with the observations, and a quantitative analysis is introduced to evaluate the tidal effects on the forming and maintaining processes of the TF. Tidal mixing and the circulation structure adapting to it are the main causes of the TF. Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No. 49736190).     

关于波浪作用下粉土质海床中共振现象的解释

本文详细讨论了粉土质床在波浪作用下所呈现共振现象的力学机制。利用有限深海床下波浪载荷对土层响应的研究，系统地比较了理论计算结果和实验结果。提出在波浪作用下粉土质土层中存在着一硬土层，从而引发Ｂｒａｇｇ共振。     

云南保山红岩剖面晚三叠世诺利期碳酸盐岩特征及沉积相分析

云南保山地块红岩剖面晚三叠世诺利期发育了一套海相碳酸盐岩沉积(大水塘组).通过野外剖面观察、实测以及室内显微薄片观察,采用微相分析的方法对红岩剖面晚三叠世诺利期大水塘组碳酸盐岩的生物组合、微相类型和沉积环境进行了研究,将保山红岩剖面大水塘组沉积归纳为8种微相:骨针—放射虫粒泥灰岩、生屑—似球粒泥粒灰岩、含放射虫泥晶灰岩...     

黄陵地块内部北西向雾渡河断裂的再研究

阐述了黄陵地块内部北西向雾度河断裂的几何学分段、运动方式和剩余变特征，指出晚更新世以来雾渡河断裂可能较为稳定。在暂不考虑全断层同时滑破的前提下，分段计算各段潜在地震强度为５．０≤Ｍ≤６．０。     

武当地块基性岩墙群的Sm-Nd定年及其相关问题讨论

武当地块是卷入南秦岭构造带的前震旦纪基底岩块,该基底岩块中广泛发育变形变质的基性岩墙群,获得岩墙群的ＳｍＮｄ全岩等时年龄为ｔ＝７８２±１６４（２σ）Ｍａ,ＩＮｄ＝０．５１１７１±１６（２σ）,εＮｄ（ｔ）＝＋１．５±１．０。据此并综合区域地质实际,对南秦岭元古代古陆块的存在及其裂解等相关问题进行了讨论。     

祁漫塔格印支期铝质A型花岗岩的确定及初步研究

祁漫塔格小红山印支期钾长花岗岩的岩石化学成分为过铝质(A/NKC介于1.03～1.06之间),高硅(SiO2>76%),偏碱性(ALK=7.77%～8.22%),K2O>Na2O,FeOT/MgO比值高(9.4～21.7),CaO、MgO、TiO2和P2O5含量低(分别为<0.78%,≤0.14%,≤0.1%和≤0.02%)。岩石富Rb、Th、U、Y、Zr、Nb和Hf,贫Sr、Ba、Eu、Cr和Ni,Ga/Al比值高,明显不同于I型和S型花岗岩,显示了铝质A型花岗岩的特征,形成于造山后的伸展环境。该A型花岗岩的确定证明了祁漫塔格地区晚三叠世之前碰撞造山作用的存在,以及祁漫塔格与东昆仑造山带的亲缘性。     

Mineralogical and Petrological Characteristics of the Neoproterozoic Orthoamphibolite and Orthogneisses in the Mutki Area, the Bitlis Massif, Southeast Turkey

<正>The rocks form as amphibolite±garnet±epidote and orthogneisses in the Pan-African basement of the Bitlis Massif.The petrochemical data of the studied metamorphic rocks suggest different igneous protoliths ranging from calcalkaline basalt to andesite in composition. Petrochemically,the rocks can be classified as group 1(low Zr and La) and group 2(high Zr and La), all showing various enrichments in large ion lithophiles and light rare earth elements,and a depletion in high-field strength elements,suggestive of a destructive plate margin setting.The protoliths of the all samples might have formed mostly by the partial melting of an enriched source,possibly coupled with the fractional crystallization of plagioclase,apatite,and titaniferous magnetite±olivine±clinopyroxene±amphibole in relation with subduction-related magmatism neighboring the Andeantype active margins of Gondwana.The group 2 samples could,however,be generated by a relatively lower degree of the partial melting of an inhomogeneous source with a preponderance of a high-level, fractional crystallization process in comparison to group 1.The protoliths of the samples were metamorphosed up to amphibolite facies conditions,which destroys original igneous texture and mineral assemblages.Geothermobarometric calculations show that the metamorphic rocks are finally equilibrated between 540 and 610℃and～5 kbars,following a clockwise P-T-t path.