Li-Sr-Nd isotope signatures of the plume and cratonic lithospheric mantle beneath the margin of the rifted Tanzanian craton (Labait)   总被引：3，自引：2，他引：1  

Sonja Aulbach  Roberta L. Rudnick  William F. McDonough 《Contributions to Mineralogy and Petrology》2008,155(1):79-92

Lithium concentrations and isotopic compositions of olivine and ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd of coexisting clinopyroxene from peridotite xenoliths from the Quaternary Labait volcano, Tanzania, document the influence of rift-related metasomatism on the ancient cratonic mantle. Olivines show negative correlations between Fo content and both δ⁷Li and Li concentrations. Olivines in iron-rich peridotites (Fo_85–87) have high Li concentrations (3.2–4.8 ppm) and heavy δ⁷Li (+5.2 to +6.6). In contrast, olivines in ancient, refractory peridotites have lower Li concentrations (∼2 ppm) and relatively light δ⁷Li (+2.6 to +3.5). This reflects mixing between ancient, refractory cratonic lithosphere and asthenosphere-derived rift magmas. A uniquely fertile, deformed, high-temperature garnet lherzolite, interpreted to be from the base of the lithosphere, has a ⁸⁷Sr/⁸⁶Sr of 0.7029 and ¹⁴³Nd/¹⁴⁴Nd of 0.51286, similar to HIMU oceanic basalts. It provides the best estimate of the Sr–Nd isotope composition of the upwelling mantle (i.e., plume, sensu lato) underlying this portion of the East African Rift, and is slightly less radiogenic compared to previous estimates of the plume that were based on rift basalts. Although elevated δ⁷Li are not exclusive to HIMU source regions, the data collectively indicate that the plume beneath Labait has HIMU characteristics in Sr, Nd and Li isotope composition. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Time-series analysis of abundance indices of young fish     

Gudmundsson  G. 《ICES Journal of Marine Science》2004,61(2):176-183

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The flow of Atlantic water to the North Icelandic Shelf and its relation to the drift of cod larvae   总被引：1，自引：0，他引：1  

Jonsson  Steingrimur; Valdimarsson  Hethinn 《ICES Journal of Marine Science》2005,62(7):1350-1359

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Predicting total allowable catches for Icelandic capelin, 1978-2001     

Gudmundsdottir  Asta; Vilhjalmsson  Hjalmar 《ICES Journal of Marine Science》2002,59(5):1105-1115

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长江口羽状锋海区浮游植物的生态研究：—昼夜分布动态   总被引：5，自引：0，他引：5  

杨蕉文  顾新根 《海洋学研究》1994,12(1):47-57

本文对长江口羽状锋海区浮游植物的昼夜变动进行了初步研究，结果表明，浮游植物数量的昼夜变化明显，潮汐作用是影响数量昼夜分布变化的主导因素，同时也与该地区浮游植物的水平分布有着密切的联系。  相似文献   

峨眉山玄武岩的地幔热柱成因   总被引：32，自引：4，他引：32  

宋谢炎  侯增谦  汪云亮  张成江  曹志敏  李佑国 《矿物岩石》2002,22(4):27-32

根据峨眉山玄武岩的岩石组合、岩相学特征将峨眉火成岩省分为盐源-丽江岩区、攀西岩区、贵州高原岩区和松潘-甘孜岩区。通过对研究区二叠世的区域地质背景和古地理环境的分析，对峨眉山玄武岩喷发与地幔热柱的关系及其火山喷发的大地构造背景进行了进一步系统归纳和总结。根据地层学关系大致确定峨眉山玄武岩的主喷发期是阳新世（中二叠）晚期-乐平世（晚二叠）早期，时限大致为259Ma-257Ma。峨眉山玄武岩微量元素地幔标准化曲线特征与OIB基本一致，反映出其成因与地幔热柱活动有密不可分的关系。  相似文献   

塑膜温室油桃休眠期的温度变化     

孙智辉  吴刚  吴涛 《山西气象》2003,(4):15-16

本文详尽分析了冰岛低压和大西洋高压的长期变化规律，发现两者均具有明显的阶段性变化，而且冰岛低压和大西洋高压的强度具有明显的反相关。同时，还分析了大西洋高压和冰岛低压与我国气候的关系，发现大西洋高压与我国冬季气温基本呈正相关，而冰岛低压与我国气温大致呈反相关，但均没有显著影响，所以两者都不是影响我国气候变化的重要天气系统。  相似文献   

Laboratory and Numerical Studies of the Convective Boundary Layer Capped by a Strong Inversion     

Yuji Ohya  Takanori Uchida 《Boundary-Layer Meteorology》2004,112(2):223-240

The convective boundary layer (CBL) with a wide range of stability is simulated experimentally using a thermally stratified wind tunnel, and numerically by direct numerical simulation (DNS). The turbulence structures and flow characteristics of various CBL flows, capped by a strong temperature inversion and affected by surface shear, are investigated. The various vertical profiles of turbulence statistics similar to those from the observed CBL in the field are successfully simulated in both the wind-tunnel experiment and in DNS. The comparison of the wind-tunnel data and DNS results with those of atmospheric observations and water-tank studies shows the crucial dependence of the turbulence statistics in the upper part of the layer on the strength of the inversion layer, as well as the modification of the CBL turbulence regime by the surface shear.  相似文献   

The seismic structure of the Saurashtra crust in northwest India and its relationship with the Réunion Plume     

G. Surya Prakasa Rao  H. C. Tewari 《Geophysical Journal International》2005,160(1):319-331

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Continental rift systems and anorogenic magmatism   总被引：1，自引：0，他引：1  

James W. Sears  Gregory M. St. George  J. Chris Winne 《Lithos》2005,80(1-4):147-154

Precambrian Laurentia and Mesozoic Gondwana both rifted along geometric patterns that closely approximate truncated-icosahedral tessellations of the lithosphere. These large-scale, quasi-hexagonal rift patterns manifest a least-work configuration. For both Laurentia and Gondwana, continental rifting coincided with drift stagnation, and may have been driven by lithospheric extension above an insulated and thermally expanded mantle. Anorogenic magmatism, including flood basalts, dike swarms, anorthosite massifs and granite-rhyolite provinces, originated along the Laurentian and Gondwanan rift tessellations. Long-lived volcanic regions of the Atlantic and Indian Oceans, sometimes called hotspots, originated near triple junctions of the Gondwanan tessellation as the supercontinent broke apart. We suggest that some anorogenic magmatism results from decompression melting of asthenosphere beneath opening fractures, rather than from random impingement of hypothetical deep-mantle plumes.  相似文献