长江粘土矿物示踪标记稳定性的初步研究

选择物质来源相对单一、区域较广的浙江沿岸东海内陆架区，以4种主要粘土矿物(伊利石、蒙皂石、高岭石、绿泥石)为研究对象，以探讨长江粘土矿物作为示踪标记的稳定性问题。研究区5组沉积物样品中粘土矿物的X射线衍射实验及含量分析结果表明，伊利石、蒙皂石和高岭石的相对含量较稳定，具有作为长江物源示踪标记的价值．而各区域的绿泥石含量之间不具有显著的统计相似性。现有资料还不能完全解释长江口及邻近东海内陆架区内粘土矿物组合的相对稳定状态，今后应对絮凝作用、沉积分异作用、海底生物地球化学作用等因素的效府做进一步的研究。     

山东荣成月湖潮汐汊道系统的沉积物平衡问题——兼论人类活动的影响

在月湖进行了沉积物采样和潮汐水文观测,分析计算了表层沉积物类型、泥沙输运率、现代沉积速率,讨论了月湖的沉积物平衡。结果显示,月湖的沉积速率较快。按目前的数据和资料估算,月湖每年的沉积通量约为(1.8~2.3)×10⁴ t,而正常情况下的沉积物供应量每年只有(0.5~1.2)×10⁴ t。研究表明,人类活动还改变了月湖的物理与生态过程。由于土地利用的方式及其强度发生了变化,月湖汇水盆地的侵蚀量大为增加,侵蚀模数可能远大于400 t/(km²·a),从而使流域侵蚀量大大超出了正常范围,加剧了月湖的淤积。     

InSAR可检测的最大最小变形梯度的函数模型研究

InSAR干涉图中的相位噪声是相干性和视数的函数.InSAR能检测的地表最大最小形变梯度,除了受到InSAR硬件的限制外,还直接受到InSAR干涉图中噪声强弱的影响.此外,由于多视处理会改变像元的大小,也会引起可检测的最大最小形变梯度显著变化.本文研究了InSAR可检测的地表最大最小形变梯度与相干性和视数的关系,并建立了视数为1、5和20时（ERS和ENVISAT常采用的多视数）InSAR可检测的最大最小形变梯度的经验函数模型.最后,本文用伊朗Bam地区的Enivsat ASAR数据进行了试验,结果表明该模型能够准确地判别不同视数和相干性情况下地表变形能否被InSAR技术所检测.与Baran只考虑了相干性的模型相比,本文的模型适用范围更广.     

汶川8.0级地震前区域地壳运动与变形动态过程

利用GPS等观测资料研究了2008年汶川8.0级地震前的区域地壳运动与构造变形、应变积累,以及大区域地壳运动微动态变化过程,结合同震位移场分布等分析、讨论了汶川地震前近10年区域地壳变形的表象所反映的大震孕震最后阶段的物理过程.结果表明,发生汶川8.0级地震的龙门山断裂带1999～2004年相对稳定的华南地块无明显的相对运动,2004～2007年有一定程度的相对运动显示,以右旋活动为主,年速率为1.6mm/a.龙门山断裂带西北侧的巴颜喀拉地块东部为右旋剪切为主兼有推挤的大尺度缓慢变形状态,右旋扭动变形率为2.1±0.2(10^-8/a),地壳总体缩短变形率为-0.7±0.1(10^-8/a).由GPS基准站资料计算的基线时间序列显示,2005年以来大尺度北东向地壳缩短的相对运动明显增强,青藏块体相对华南地块的北东向运动明显增强.对汶川大地震前应变积累的特殊性等问题进行了初步讨论,分析认为,汶川大地震的发生是四川盆地西缘的龙门山断裂带受到其西侧巴颜喀拉地块推挤导致大尺度、长时期、缓慢的地壳应变积累的结果.在发震前不仅龙门山断裂带为显著闭锁状态,且孕震区域可能存在地壳弹性变形趋于极限后难以发生变形的相持阶段,大尺度地壳运动与动力环境的动态变化对汶川大地震的发生有促进影响.     

曲线坐标系下的块体运动与应变模型研究

本文建立了顾及地球扁率和局部切标架随点变化特性的椭球坐标系下的刚体运动模型和块体运动与应变模型,以及球坐标系下顾及局部切标架随点变化特性的严密的块体运动与应变模型,分析了球坐标系下块体运动与应变模型及椭球坐标系下的块体运动与应变模型间的差异;通过计算具体讨论了地球扁率和曲线坐标系的局部切标架随点变化特性对欧拉矢量与应变张量的影响.结果表明：地球扁率对刚体欧拉矢量和应变参数的影响甚小,具体计算时可以不予考虑,但曲线坐标系的局部切标架随点变化特性对两者的影响较大,在建模过程中需要顾及,常用的Savage模型需要修正.     

广西栗木矿区牛栏岭岩体印支期年龄的厘定及其意义

本文对牛栏岭细粒铁锂云母花岗岩和似斑状铁锂云母花岗岩进行了锆石U-Pb 年代学和岩石地球化学研究,讨论了 岩体的形成时代、成因类型、源区性质及其与成矿关系。两种岩性锆石的LA-ICP-MS U-Pb 定年表明,其加权平均年龄分 别为（223.6±1.7）Ma 和（223.7±1.7）Ma,属印支晚期构造岩浆活动的产物。岩石相对富集SiO2,K2O,Na2O,P2O5 和贫 CaO,MgO,TiO2 ;A/CNK 值为1.08~1.31,落入强过铝质花岗岩区域;CIPW 计算结果给出的岩体标准矿物刚玉的含量为 1.6%~4.5%;岩体的球粒陨石标准化稀土配分曲线呈轻微右倾形,具有强烈的Eu负异常,δEu为0.01~0.05。岩体富集Cs, Rb,K 等大离子亲石元素（LILE）和U,Pb,Hf,Ta 等高场强元素（HFSE）,明显亏损Ba,Sr,Ti 等元素;锆石饱和温度 介于631℃ ~681℃之间,低于S 型花岗岩的平均锆石饱和温度。岩体中发现有（248±4）Ma 和（1947±23）Ma 的继承锆石, 暗示其源区可能为晚古元古代的壳源物质,印支早期岩浆物质也可能参与了岩体的形成。岩体的地质地球化学特征研究表明, 岩体可能为牛栏岭地区的W-Sn 成矿作用提供W-Sn 来源,暗示牛栏岭地区可能存在有224 Ma 左右的成矿作用,印支期成矿 作用可能成为栗木矿区乃至南岭西段今后找矿工作的一个重点方向。     

乌鲁木齐市断层附近地应力特征与断层活动性

为了查明乌鲁木齐西山—碗窑沟断裂带地应力分布特征, 在研究区20 km×20 km的范围内布置12个基岩应力钻孔,采用水压致裂地应力测量技术进行了基岩原地应力测量;共布置了2条观测剖面,第一剖面是沿断层走向布置了7个钻孔,第二剖面在垂直断层走向布置了6个钻孔(与第一剖面共用1个钻孔).根据实测的地应力资料,断层附近最大水平主压应力方向为NE—NEE向,与区域构造应力SN—NNE向主压方向有一些差异,说明受断层活动影响,断层附近的应力状态与区域应力场明显不同.利用地应力实测资料,研究了断层的活动性,在测量深度域内水平和垂直应力的关系为σ_H＞σ_h＞σ_v,该应力状态有利于逆断层活动,与地质资料反映的以逆断层活动为主基本一致.利用库仑摩擦滑动准则,摩擦系数取0.6~1.0分析,断层附近的现今地应力状态达到或超过产生逆断层摩擦滑动的临界值,表明测区现今构造应力有利于逆断层活动.     

南极中山站F-lacuna特征分析

F-lacuna是高纬极区电离层测高仪频高图上经常出现的一种F层回波描迹部分或全部消失的现象,直接影响电离层参数的标定,其表征的电离层物理过程尚未定论.利用南极中山站测高仪频高图数据,本文统计分析了Flacuna在不同太阳风速度水平下的发生频率,主要对2012年2月15日一次F2-lacuna观测实例的粒子沉降及电离层特性进行了分析.观测特征表明,F2-lacuna发生期间,电离层电子总含量TEC明显减小,昭和站SuperDARN高频雷达观测到的中山站上空电离层Bragg后向散射增强,但对应来自磁层的电子和离子沉降并不明显.这可能是由磁层亚暴引起的极区电离层电流体系扰动,触发电离层F-B不稳定性,产生沿场向排列的小尺度不规则体,其热效应导致F2层密度减小,F2-lacuna出现.     

Late Jurassic I-type rhyolites from the Duobuza region,north-central Tibet: evidence for the occurrence of juvenile lower crust and crustal growth in the Southern Qiangtang Terrane

ABSTRACT

Previous studies of the Southern Qiangtang (SQ) Terrane in Tibet have shown significant growth of continental crust during the late Mesozoic (ca. 170–120 Ma) through underplating of mantle-derived melts beneath ancient lower crust. However, the mechanism of crustal growth remains defective during the Late Jurassic. In this contribution, we report new zircon U–Pb ages, whole-rock major and trace element concentrations, and zircon Hf isotopic compositions of Late Jurassic rhyolites from the Duobuza area in the SQ Terrane. Zircon LA–ICP–MS U–Pb dating yields concordant ages and weighted mean ²⁰⁶Pb/²³⁸U ages of 151–149 Ma, indicating that the rhyolites were erupted during the Late Jurassic. The rhyolite samples yield high SiO₂ (69.1–73.4 wt.%) and Na₂O (3.82–6.49 wt.%) concentrations, high values of the differentiation index (95.4–98.5), moderate Al₂O₃ (13.1–15.5 wt.%) and K₂O (2.55–3.26 wt.%) concentrations, and relatively low TiO₂ (0.34–0.44 wt.%), MgO (0.14–0.67 wt.%), and MnO (0.01–0.10 wt.%) concentrations and Mg# values (8.9–33.5). They are enriched in Rb, Th, Ba, and Pb, depleted in Nb, Ta, Sr, Ti, and P, and yield negative Eu anomalies. These characteristics suggest that the Duobuza rhyolites represent medium- to high-K calc-alkaline, highly fractionated I-type granitoids. Variations in major and trace element concentrations indicate that the rhyolites underwent significant fractionation of Fe–Ti oxides, plagioclase, K-feldspar, hornblende, biotite, and apatite. The samples yield positive zircon ε_Hf(t) values (+0.08 to +10.9) and young T^CD _M model ages (816–386 Ma), indicating that they were generated through partial melting of juvenile lower crust of the SQ Terrane. These data are distinct from those of Late Jurassic intermediate–felsic plutons in the SQ Terrane that generally yield negative ε_Hf(t) values and ancient T_C ^DM model ages. We suggest that the occurrence of the Duobuza rhyolites is the significant witness. The presence of juvenile lower crust beneath the SQ Terrane during the Late Jurassic (ca. 150 Ma) rather than during the Early Cretaceous (ca. 120Ma). The transition from ancient to juvenile lower crust has already began in the SQ Terrane during the Late Jurassic.     

Impact of Megacity Shanghai on the Urban Heat-Island Effects over the Downstream City Kunshan

The impact of upstream urbanization on the enhanced urban heat-island (UHI) effects between Shanghai and Kunshan is investigated by analyzing seven years of surface observations and results from mesoscale model simulations. The observational analysis indicates that, under easterly and westerly winds, the temperature difference between Shanghai and Kunshan increases with wind speed when the wind speed \(<\) 5 m s \(^{-1}\) . The Weather Research and Forecasting (WRF) numerical model, coupled with a one-layer urban canopy model (UCM), is used to examine the UHI structure and upstream effects by replacing the urban surface of Shanghai and/or Kunshan with cropland. The WRF/UCM modelling system is capable of reproducing the surface temperature and wind field reasonably well. The simulated urban canopy wind speed is a better representation of the near-surface wind speed than is the 10-m wind speed at the centre of Shanghai. Without the urban landscape of Shanghai, the surface air temperature over downstream Kunshan would decrease by 0.2–0.4  \(^{\circ }\) C in the afternoon and 0.4–0.6  \(^{\circ }\) C in the evening. In the simulation with the urban landscape of Shanghai, a shallow cold layer is found above the UHI, with a minimum temperature of about \(-0.2\) to \(-\) 0.5  \(^{\circ }\) C during the afternoon hours. Strong horizontal divergence is found in this cold layer. The easterly breeze over Shanghai is strengthened at the surface by strong UHI effects, but weakened at upper levels. With the appearance of the urban landscape specific humidity decreases by 0.5–1 g kg \(^{-1}\) within the urban area because of the waterproof property of an urban surface. On the other hand, the upper-level specific humidity is increased because of water vapour transferred by the strong upward vertical motions.