下地幔及核幔边界结构及地球动力学   总被引：9，自引：2，他引：9  

朱介寿 《地球科学进展》2000,15(2):139-142

新一代高分辨率下地幔及核幔边界的地震层析成像,改变了我们对全球构造模式及地球动力过程的认识。古海洋岩石圈板片一直俯冲到下地幔底部,其残留体在核幔边界积累,并支持了地幔整体对流模式。位于核幔边界上的D″层有着十分复杂而精细的结构。紧靠核幔边界的地幔一侧发现了超低速层(ULVZ),它们可能是D″层内的局部熔融物,是引起地表热点的上升地幔柱的源头。  相似文献   

The massive hot core associated with G31.41+0.31     

C. M. Walmsley  R. Cesaroni  L. Olmi  E. Churchwell  P. Hofner 《Astrophysics and Space Science》1995,224(1-2):173-175

We have used the IRAM Plateau de Bure Interferometer to observe the ground state and vibrationally excited lines of Methyl Cyanide towards the UCHII region G31.41+0.31. We also obtained a map of the continuum emission at a frequency of 110 GHz. We detect a hot molecular core in the emission both of methyl cyanide and of the 110 GHz continuum. We estimate a temperature of 200 K and a mass of 1000 M for this compact massive region. We also detect a velocity gradient or shift across the methyl cyanide core whose origin could be due to rotation.  相似文献   

南沙群岛永暑礁区近百万年来的古气候变化——南永1井的锰含量分析     

郭丽芬  陈婉颜  陈丽虹 《热带海洋学报》1993,(4)

用锰含量的变化,将南永1井岩心划分为21个锰阶段,与洛川黄土、深海沉积物、柴达木盆地察尔汗盐湖的气候旋回进行对比,在布容、松山极性期界线(730ka)以上,存在9次气候旋回,锰含量相对高的奇数阶段代表相对湿热的气候环境,而偶数阶段代表相对干冷的气候。Mn/Ca和Cd/Ca比值的正异常段反映三期(Q_1,Q_2,Q_3)围区的火山活动影响。锰的变化反映全球性的气候事件和本地区的局部地质事件。  相似文献   

Fluid infiltration associated with seismic faulting: Examining chemical and mineralogical compositions of fault rocks from the active Chelungpu fault   总被引：3，自引：0，他引：3  

Wei-min Donald Chen  Hidemi Tanaka  Hui-jen Huang  Chung-bin Lu  Chy-yu Lee  Chien-ying Wang 《Tectonophysics》2007,443(3-4):243

In order to understand the fault zone architecture and mechanisms that caused the Chi-Chi earthquake, the Chelungpu drilling project was conducted during April 2000 through a collaborative project between Japan and Taiwan. In this study, chemical and mineralogical variations within the overall Chelungpu fault zone, including variations between less damaged host rocks, damaged zones, and fault cores caused by the Chi-Chi earthquake were examined. Slopes of TiO₂ immobile isocons were consistently > 1 for analyses comparing host rocks with rocks from damaged zones or with gouges from fault cores, indicating that volume loss occurred in damaged zones and the fault cores. These results strongly imply that pervasive fluid infiltration occurred within the fault zone. Volume loss within the damaged zone and fault core is interpreted to result from a two-stage process involving: (i) coseismic mechanical wearing and/or dissolution in the fault core, and (ii) fluid infiltration within the fault zone during postseismic and interseismic periods along cracks caused by seismic failure. Semi-quantitative XRD analysis indicates that the kaolinite content consistently increases from the less damaged host rocks to the damaged zone and gouges in each fault core. Mineralogic changes indicate that pervasive acidic fluid infiltration occurred within the fault zones and reacted with the feldspars or muscovite to form kaolinite. Enrichment of kaolinite and illite found in the fault zones of southern drilling site could play some role on the slipping behavior of the southern part of the Chelungpu fault. Greater volume loss in the fault core may have resulted from moderate permeability, combined with the very fine grain nature of pulverized material in the fault core, which enhanced chemical reactions including transformation of feldspars and muscovite to clay minerals. The study results indicate that pervasive fluid infiltration occurred and changed the mineralogical and chemical architecture of fault zones caused by the cyclic earthquakes.  相似文献   

The inner core and the geodynamo     

Stéphane Labrosse  Mélina Macouin 《Comptes Rendus Geoscience》2003,335(1):37-50

Using energy and entropy constraints applicable to the Earth's core, the heat flow at the core–mantle boundary (CMB) needed to sustain a given total dissipation in the core can be computed. Reasonable estimates for the present Joule dissipation in the core gives a present heat flow of 6 to 10 TW at the CMB. Palaeointensity data acquired from rocks younger than 3.5 Ga provide support that the Joule dissipation in the core before inner core crystallization was between today's value and four times lower than today. Prior to inner core crystallization (around 1 Ga), the magnetic field was maintained by thermal convection driven by core cooling, and our calculations of the two extreme cases predict that the heat flow at the CMB at that time was either 14 to 24 TW in the case of constant dissipation, or essentially the same as today in the lower field intensity case.  相似文献   

潮汐解算中地核问题的分析   总被引：8，自引：0，他引：8  

彭龙辉  李国营  许厚泽 《测绘学报》1998,27(4):287-292

随着地球模型越来越接近真实地球,对潮汐的数值模拟理论也不断深化,潮汐解算过程中随之将出现新的问题。在解算三维地球模型潮汐响应前,首先要获得径向对称地球模型沿径向的分布,其中最大的困难是在地核中的解算,本文通过一转换解决了这一问题。  相似文献   

Montcornet钻孔岩芯的古地磁研究   总被引：8，自引：2，他引：6       下载免费PDF全文

杨振宇 More.  MG 《地球物理学报》1998,41(5):652-657

Montcornet非定向钻孔岩芯的古地磁研究表明,利用岩石不同时期形成的磁性组分,可以对钻孔岩芯的定向提供一种可靠的、快速简捷的方法．通过岩石磁性组构的研究,不仅能验证岩芯的定向,而且对于沉积相中古水流方向,沉积相的划分、分布研究提供重要的基础资料．在盆地分析和油气探测中有可能开发出更广泛的、潜在的应用前景．  相似文献   

Lake catchment based studies of erosion and denudation in the merevale catchment,Warwickshire, U.K.     

I. D. L. Foster  J. A. Dearing  A. Simpson  A. D. Carter  P. G. Appleby 《地球表面变化过程与地形》1985,10(1):45-68

Sediment yields estimated from contemporary stream monitoring of suspended sediment in the Merevale forested catchment, North Warwickshire, were compared with the sediment yield record obtained from analysis of lake sediment in the downstream reservoir. Total sediment volume and mass for nine periods since 1861 were calculated by extrapolation of synchronous levels in 54 cores, identified from magnetic susceptibility and other magnetic measurements, and by using ²¹⁰Pb and ¹³⁷Cs analysis to provide an absolute sediment chronology. Sediment yield estimated from the two methods show comparable but low (50-200 kg ha^?1 yr^?1) levels of sediment loss. While suggesting that lake sediments can be a useful means for extending the period over which contemporary monitoring exists, the study stresses the need for detailed historical records of land use and climate against which long term sediment yield records can be evaluated.  相似文献   

青藏高原地球科学研究中的核心问题与理念的厘定   总被引：5，自引：3，他引：2       下载免费PDF全文

滕吉文  司芗  王谦身  张永谦  杨辉 《地球物理学报》2015,58(1):103-124

在青藏高原的地球科学研究中,国外科技界曾提出过六大论点——喜马拉雅山脉是地壳均衡的典范;青藏高原地壳乃是两个地壳的垂向重叠;雅鲁藏布江是印度洋板块和欧亚板块的缝合带;青藏高原西部的南北走向断裂带全为裂谷带;青藏高原腹地深部物质的向东逃逸;青藏高原下地壳物质通道流以及汶川MS8.0大地震的发生.这一系列论点确为国人广为引用与跟随,并发表了若干篇论著.然而在不断理解和深化研究的基点上提出了质疑,并基于新的认识提出了新的论点与论据,且在科学理念上给予了重新厘定.因为科学是为宇宙提供真正的写真.  相似文献   

CM4模型数据与台站实测数据的对比研究   总被引：2，自引：2，他引：0  

李细顺  高登平  李琪  王静  梁斌  胡秀娟  王利兵  罗娜  宋昭 《震灾防御技术》2015,10(2):418-425

本文利用第四代地磁场综合模型(Comprehensive Model 4,CM4),计算了1982—2002年隆尧地磁台站的磁层源磁场及其感应场、电离层源磁场及其感应场的地磁北向分量X、东向分量Y、垂直分量Z,分析了各场源磁场随时间的变化特征。磁层源磁场及其感应场呈现出11年和27天的周期性变化,有些年的27天周期性变化显著,有些年则不太显著;电离层源磁场及其感应场具有明显的季节变化,不同年相同季节的变化形态一致但幅度不同;日变化分析显示,磁静日和磁扰日期间的模型数据与台站实测数据变化一致性较好,相关性较高。  相似文献