东昆仑哈拉尕吐岩浆混合花岗岩：来自锆石 U-Pb年代学的证据

东昆仑造山带东部哈拉尕吐花岗闪长岩体中发育了较多的暗色闪长质微粒包体。通过详细的野外地质调查和岩石学研究及LAICPMS锆石 UPb定年,得到寄主岩形成年龄为（255.3±3.6）Ma,暗色包体形成时代为（252.9±2.5）Ma,二者年龄基本一致,从而排除了暗色微粒包体为捕虏体或源区难熔残余物质的可能性,也排除了花岗质岩浆固结后基性岩浆侵入的可能性。这一结果从年代学的角度证明了哈拉尕吐花岗闪长岩体是晚二叠世岩浆混合作用的产物。寄主岩石花岗闪长岩是混合时的酸性端员,而暗色闪长质微粒包体则是岩浆混合时未混合完全的残余基性部分。晚二叠世时,阿尼玛卿洋向北俯冲,在区域挤压应力环境下发生幔源岩浆底侵作用,壳幔物质相互混合,形成岩浆混合花岗质的岩浆房并向上侵入形成哈拉尕吐岩体。     

模糊综合评判法在岩石可钻性分级中的应用

将传统的岩石物理力学性质测试方法与模糊理论中的模糊综合评判法相结合,总结出一种相对简单但有效的岩石可钻性分级模型.结合实际钻进的岩石,确定分级模型的影响因素分别是为压入硬度、摆球塑性系数、金刚石钻进时效;以正态分布函数作为隶属函数来计算模型的评价矩阵,通过模型确定岩石的可钻性等级.运用Matlab软件将计算过程实现程序化,模型计算结果表明该方法能够对岩石可钻性作出较客观精确的分析.     

单根无黏结预应力筋对加筋体力学性能的影响

采用缩尺模型试验研究了无黏结预应力加筋土技术中水平土压力的大小及分布对预应力加筋体力学性能的影响。试验采用钢砂模拟中砂,解决了缩尺模型相似比的问题。完成了两个工况的试验,一个普通加筋土工况,一个具有单根无黏结预应力筋的工况。对比分析表明：对无黏结预应力筋施加预拉力前加筋体的顶部沉降小于普通加筋体的顶部沉降,施加预拉力后却增加了顶部沉降,但在堆载后具有单根无黏结预应力筋的加筋体的竖向变形更小;随着预拉力的增加,与无黏结预应力筋相邻的玻纤格栅应变相应减小,在距离墙面板较近位置测点玻纤格栅的应变减小得尤为明显,而底部玻纤格栅应变逐渐增加,在距离墙面板较近位置测点增加得较为明显;在堆载过程中,无黏结预应力筋的预拉力保持不变,堆载完成后略有增加。     

西天山晚石炭世岩浆混合花岗岩的确定及其地质意义——来自玉奇布拉克和乌图精河岩体的LA-ICP-MS锆石U-Pb年龄和岩石地球化学证据

西天山博罗科努地区的玉奇布拉克和乌图精河岩体中发育大量暗色闪长质包体,包体发育矿物相互包裹的嵌晶及岩浆冷凝矿物不平衡结构,同时出现淬冷形成的针状磷灰石,指示岩体形成过程经历了二元岩浆的混合作用。包体较寄主花岗岩有明显低的SiO_2、K_2O,高CaO、FeO~T和MgO,但二者的微量元素高度一致,相对富集Rb、Th、U、K等LILE,贫HFSE,亏损Sr、Nb、Ta、P和Ti等元素,为二元岩浆混合作用所致。经LA-ICP-MS锆石U-Pb定年,两个岩体寄主花岗岩和包体分别获得301 Ma、308 Ma和303 Ma、298 Ma的形成年龄,指示同期不同源岩浆活动并存。寄主花岗岩的ε_(Hf)(t)值分别为+4.20~+8.33和+4.97~+7.0;Hf陆壳模式年龄T C_(DM)为782~1045 Ma和863~998 Ma,揭示它们主要源自新元古代早期陆壳物质。包体的εHf(t)值分别为+2.75~+6.41和+4.63~+7.92,与区域上同期基性岩脉正的εHf(t)和εNd(t)值相当。结合区域上同期花岗岩类高ε_(Hf)(t)和ε_(Nd)(t)、中等n(~(87)Sr)/n(~(86)Sr)推断,该期花岗岩是新元古代早期陆壳物质部分熔融的岩浆与被消减带组分改造的略亏损岩石圈地幔岩浆混合作用的结果,并构成由晚石炭世高钾钙碱性花岗岩向早二叠世富钾花岗岩/或A型花岗岩转换的岩浆演化系列,表明晚石炭世—早二叠世期间西天山造山带转入后碰撞晚期向伸展转化的构造环境。陆壳伸展导致幔源基性岩浆上侵,诱发陆壳部分熔融产生壳源岩浆,二者混合形成晚古生代以来西天山最为广泛的花岗岩浆活动,成为区内一次重要的地壳垂向增生事件。     

小间距隧道施工性态监测与稳定性分析

在分岔隧道施工过程中,小间距段支护体系力学性态直接反映分岔隧道的稳定状况,结合沪－蓉线庙垭分岔隧道,对小间距中墙薄弱处侧向加固进行了理论分析,通过对围岩变形和围岩压力、钢支撑内力、锚杆轴力等支护体系监测成果的系统分析,以及中墙爆破振动现场试验研究,评判了小间距隧道的稳定状况,所得结论可为日后同类工程的设计、施工、监测提供有益的借鉴。     

Modelling of seasonal exchange flows through the Dardanelles Strait

The Dardanelles Strait is a remarkable example of a long, narrow, shallow, and strongly stratified strait with bidirectional exchange that is governed by both baroclinic and barotropic forcing with a wide spectrum of variability. A three-dimensional free surface primitive equation model is applied to study seasonal hydrodynamics variability in this strait. The calculated vertical structure of temperature, salinity, and velocity fields agrees well with available survey data. Seasonal monthly values of the volume exchange at the Aegean and Marmara exits are estimated. It is found that the seasonal exchange dynamics is governed by the turbulent friction and entrainment at the Nara Passage area. The mean annual water transport in the upper layer is increased by 80% after the Nara Passage. About 25% of water entering in the Dardanelles bottom layer reaches the Marmara Sea in winter, and 50% reaches it in summer. The estimate of the Dardanelles hydrodynamics according to hydraulic and viscous–advective–diffusive regime classification shows significant deviation from the two-layer hydraulic asymptotic. However, according to three-layer hydraulic theory, the flow is found to be critical in the Nara Passage area.     

Effects of bedrock groundwater discharge on spatial variability of dissolved carbon,nitrogen, and phosphorous concentrations in stream water within a forest headwater catchment

The quantitative evaluation of the effects of bedrock groundwater discharge on spatial variability of stream dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorous (DIP) concentrations has still been insufficient. We examined the relationships between stream DOC, DIN and DIP concentrations and bedrock groundwater contribution to stream water in forest headwater catchments in warm-humid climate zones. We sampled stream water and bedrock springs at multiple points in September and December 2013 in a 5 km² forest headwater catchment in Japan and sampled groundwater in soil layer in small hillslopes. We assumed that stream water consisted of four end members, groundwater in soil layer and three types of bedrock groundwater, and calculated the contributions of each end member to stream water from mineral-derived solute concentrations. DOC, DIN and DIP concentrations in stream water were compared with the calculated bedrock groundwater contribution. The bedrock groundwater contribution had significant negative linear correlation with stream DOC concentration, no significant correlation with stream DIN concentration, and significant positive linear correlation with stream DIP concentration. These results highlighted the importance of bedrock groundwater discharge in establishing stream DOC and DIP concentrations. In addition, stream DOC and DIP concentrations were higher and lower, respectively, than those expected from end member mixing of groundwater in soil layer and bedrock springs. Spatial heterogeneity of DOC and DIP concentrations in groundwater and/or in-stream DOC production and DIP uptake were the probable reasons for these discrepancies. Our results indicate that the relationships between spatial variability of stream DOC, DIN and DIP concentrations and bedrock groundwater contribution are useful for comparing the processes that affect stream DOC, DIN and DIP concentrations among catchments beyond the spatial heterogeneity of hydrological and biogeochemical processes within a catchment.     

粉质黏土水泥土冻胀融沉特性研究

为研究水泥土冻胀融沉特性,对南京地区典型粉质黏土进行了不同条件下的冻胀融沉试验.试验控制因素包括水泥掺入比、含水率、龄期、冷端温度和荷载等,各控制因素在包含基准数值的区间内选取代表性条件进行单一变量试验.试验采用自制冻胀融沉仪进行,冻胀融沉仪下部为制冷块,上部设置补水装置,模拟真实土体冻结时水分迁移过程.结果表明:粉质...     

Carbon and Oxygen Isotope Compositions of Calcite and Rhodochrosite from Geothermal Exploratory Drills TH‐4 and TH‐6 near the Toyoha Deposit,Hokkaido, Japan

We studied calcite and rhodochrosite from exploratory drill cores (TH‐4 and TH‐6) near the Toyoha deposit, southwestern Hokkaido, Japan, from the aspect of stable isotope geochemistry, together with measuring the homogenization temperatures of fluid inclusions. The alteration observed in the drill cores is classified into four zones: ore mineralized zone, mixed‐layer minerals zone, kaolin minerals zone, and propylitic zone. Calcite is widespread in all the zones except for the kaolin minerals zone. The occurrence of rhodochrosite is restricted in the ore mineralized zone associated with Fe, Mn‐rich chlorite and sulfides, the mineral assemblage of which is basically equivalent to that in the Toyoha veins. The measured δ¹⁸O_SMOW and δ¹³C_PDB values of calcite scatter in the relatively narrow ranges from ?2 to 5‰ and from ?9 to ?5‰, respectively; those of rhodochrosite from 3 to 9‰ and from ?9 to ?5‰, excluding some data with large deviations. The variation of the isotopic compositions with temperature and depth could be explained by a mixing process between a heated surface meteoric water (100°C δ¹⁸O =?12‰, δ¹³C =?10‰) and a deep high temperature water (300°C, δ¹⁸O =?5‰, δ¹³C =?4‰). Boiling was less effective in isotopic fractionation than that of mixing. The plots of δ¹⁸O and δ¹³C indicate that the carbonates precipitated from H₂CO₃‐dominated fluids under the conditions of pH = 6–7 and T = 200–300°C. The sequential precipitation from calcite to rhodochrosite in a vein brought about the disequilibrium isotopic fractionation between the two minerals. The hydrothermal fluids circulated during the precipitation of carbonates in TH‐4 and TH‐6 are similar in origin to the ore‐forming fluids pertaining to the formation of veins in the Toyoha deposit.     

川藏交通干线帕隆藏布段冰碛物特性研究进展

作为冰川运动的遗迹,冰碛物由于其宽级配、大孔隙、非均质、渗透性等特点,成为川藏铁路和高速公路帕隆藏布路段规划选线中的一类特殊岩土体,并与藏东南地区的冰川型地质灾害具有关联,使得帕隆藏布流域地质灾害的成因机理及防治研究愈发复杂。本文通过分析近年来国内外学者围绕冰碛物物性特征取得的研究成果,结合实地调查和室内外测试结果,归纳了冰碛物的分布特征、沉积构造、物理性质和工程力学特性,梳理了冰碛物的物理力学研究进展,凝练了帕隆藏布流域冰碛物研究中的3个关键问题,针对性地提出下一步研究思路,旨在为后续的冰碛物研究和川藏交通干线规划与建设管理提供参数依据。