有关蛇绿岩研究的一些新进展   总被引：3，自引：0，他引：3  

高俊 《地质科技情报》1992,11(4):35-40

本文扼要介绍有关蛇绿岩的形成环境、成因类型划分及有关上地幔岩变形特征方面的新成果。  相似文献   

Upper mantle structure from long-period differential traveltimes and free oscillation data     

Robert L. Woodward  Guy Masters 《Geophysical Journal International》1992,109(2):275-293

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上地幔流体的性质和作用——从女山幔源二辉橄榄岩捕虏体获得的证据   总被引：2，自引：0，他引：2  

夏林圻  夏祖春  张诚 《西北地质科学》1992,(2)

玄武岩浆从地幔深处挟带上来的超镁铁质捕虏体含有地幔流体的直接证据,它们对于阐明地幔深部地质作用(部分熔融作用、地幔交代作用)的机制十分重要。女山幔源二辉橄榄岩的研究结果表明,初始的地幔流体除富含CO_2外,尚含有H_2O和少量CO、CH_4、SO_2、C1、F。地幔中的初始流体(挥发组分)在源部是溶解于地幔橄揽岩的高压固体矿物相中,它们在地幔上隆减压时出溶,形成细小的最早期流体包裹体。这些自由流体相在一定部应聚集,使得地幔固相线(和液相线)下降,引起上地幔发生减压部分熔融。初始的部分熔融主要发生于矿物边界,以单斜辉石最易遭受,形成矿物边缘的海绵状部分熔融带。当地幔剪切流动时,初始的部分熔融体珠滴联合成大的珠滴,并开始渗透,在变形橄榄岩中相连成脉状网络,晚期含C0_2岩浆包裹体及填隙玻璃即为其代表。由于剪裂作用,熔体(和流体)压裂开上覆橄榄岩,产生岩墙状通道,并在上地幔的某些低压区聚集成岩浆库。流体和熔体均为地幔交代作用的介质。在流体参与下,上地幔低度部分熔融产生的熔体将高度富集不相容元素。这些熔体和流体与亏损地幔间的相互作用,可以带来不相容元素重大的局部富集。当流体(和熔体)中H_2O浓度低时,仅发生隐交代作用;当H_2O浓度较高时,部分熔融程度也较高,相应有含水相(如角闪石等)成核,出现矿物交代作用。  相似文献   

Element Abundances of China‘s Continental Crust and Its Sedimentary Layer and Upper Continental Crust   总被引：4，自引：0，他引：4  

Li Tong 《中国地球化学学报》1995,14(1):26-32

China’s continental crust (CCC) has an average thickness of 47km, with the upper continental crust (CUCC) being 31 km and the sedimentary layer(CSL) 5 km in thickness. The CCC, CUCC and CSL measure 12.437 × 10⁻¹⁷, 8.005 × 10⁻¹⁷ and 1.146 × 10¹⁷ metric tons in mass, respectively. The mass ratio of the upper continental crust to the lower one is 1.8:1. The element abundances were calculated for the CCC, CUCC and CSL respectively in terms of the chemical compositions of 2246 samples of various types and some complementary trace element data. The total abundance of 13 major elements accounts for 99.6% of the CCC mass while the other minor elements only account for 0.4%. REE characteristics, the abundance ratios of element pairs and the amounts of ore-forming elements are also discussed in the present paper.  相似文献   

中国东部早第三纪玄武岩中幔源包体的变形特征及其上地幔流变学意义     

林传勇  史兰斌  陈孝德  张小鸥 《岩石矿物学杂志》1995,14(4):299-312

中国东部含幔源包体的早第三纪玄武岩已发现的有吉林双辽、河北阳原和山西繁峙。本文详细研究了这三个地点幔源包体的变形特征，结果表明，这些地点的幔源包体以尖晶石二辉橄榄岩为主，其结构主要为残斑结构。  相似文献   

The Evolution of Alpine Ultramafic Rocks and Partial Melting of the Upper Mantle     

Bao Peisheng  Wang Xibin  Hao Ziguo  Peng Genyong Institute of Geology  Chinese Academy of Geological Sciences  Beijing Fei Zhenbi 《《地质学报》英文版》1993,67(1)

Ultramafic rocks of Tibet and Xinjiang are the products of partial melting of the upper mantle. The evolution of their mineral composition is marked by two parallel evolutionary series: one is the progressive increase of the 100 Mg/(Mg+Fe~(2+) ratio of silicate minerals in order of lherzolite→harzburgite→dunite, i.e. the increase in magnesium; the other is the increase of the 100 Cr/(Cr+Al) ratio of accessory chrome spinel in the same order, i. e. the increase in Chromium. The above-mentioned evolutionary trends are contrary to that of magmatic differentiation. The evolution of fabrics of ultramafic rocks is characterized by progressive variation in order of protogranular texture→melted residual texture, symplectic texture and clastophyritic texture→equigranular mosaic texture and tabular mosaic texture. Experiments of partial melting of lherzolite have convincingly shown that the evolution of Alpine ultramafic rocks resulted from the partial melting of pyrolite. Various subtypes of them represent different degrees of partial melting. The vertical zoning marked by more basic rocks in the upper part and more acid rocks in the lower actually belongs to the fusion zoning of pyrolite.  相似文献   

The phase velocities of Rayleigh waves and the lateral variation of lithospheric structure in Tibetan Plateau   总被引：1，自引：0，他引：1  

Guo-Ying Chen  Rong-Sheng Zeng  Francis T. Wu  Xiao-Lan Su 《地震学报(英文版)》1993,6(2):289-297

According to a Sino-U. S. joint project, eleven broadband digital PASSCAL seismometers had been deployed inside the Tibetan Plateau, of which 7 stations were on the profile from Lhasa to Golmud and other 4 stations situated at Maxin, Yushu, Xigatze and Linzhi. Dispersions and phase velocities of the Rayleigh surface waves (10s–120s) were obtained on five paths distributed in the different blocks of Tibetan Plateau. Inversions of the S-wave velocity structures in Songpan-Ganzi block, Qiang-Tang block, Lhasa block and the faulted rift zone were obtained from the dispersion data. The results show that significant lateral variation of the S-wave velocity structures among the different blocks exists. The path from Wenquan to Xigatze (abbreviated as Wndo-Xiga) passes through the rift-zone of Yadong-Anduo. The phase velocities of Rayleigh waves from 10s to 100s on this path are significantly higher than that on other paths. The calculated mean crustal velocity on this path is 3.8 km/s, much greater than that on other paths, where mean crustal velocities of 3.4–3.5 km/s are usually observed. Low velocity zones with different thicknesses and velocities are observed in the middle-lower crust for different paths. Songpan-Ganzi block, located in the northern part of Tibetan Plateau is characterized by a thinner crust of 65 km thick and a prominent low velocity zone in the upper mantle. The low velocity zone with a velocity of 4.2 km/s is located at a depth form 115 km to 175 km. While in other blocks, no low velocity zone in the upper mantle is observed. The value of Sn in Songpan-Ganzi is calculated to be 4.5 km/s, while those in Qiang-Tang and Lhasa blocks are about 4.6 km/s. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 566–573, 1992.  相似文献   

Three-dimensional structure of the crust and upper mantle beneath the south China area from long period surface waves     

《地震学报(英文版)》1993,6(3):619-629

In the present study the long period surface wave records of 238 wave-paths from 79 earthquakes within China and its adjacent regions received by 30 seismic network stations are measured by using the improved match-filtering frequency-time analysis technique and the grid dispersion inversion method to obtain the rayleigh pure-path dispersion values for 147 slant grids of 4° × 4° in this area, then a three-dimensional shear wave velocity model of the crust and upper mantle beneath south China area to a depth of 170 km is inversed. It is found that there are obvious differences among the main structural units, and there are also certain differences among the subordinate elements even in the individual unit. The crustal thickness of this area is ranging from 30 to 43 km, and is getting thicker gradually from the east to the west. The average shear velocity of crust is ranging form 3.48 to 3.68 km/s with the lowest in the northeast part and highest in the west part. No obvious crustal low velocity layer of large scale is detected. There exist upper mantle low velocity zones in the most of south China area with the starting depth ranging from 75 to 106 km. The lowest shear velocity within the low velocity zones is about 4.28–4.38 km/s. Despite of the existing of upper mantle low velocity zones beneath the most of south China area, the interfaces between the important layers are quite clear, the variation of the bedding surfaces is very gentle, and the lateral changes measured in a larger scale of the underground structure are rather small. It may indicate that the crustal and upper mantle structure of the main part of south China area belongs to the relatively stable structure of the continental blocks except for the fringe areas such as the fold-faulted region in the west part and the fault system along the southeastern coast which may belong to the tectonically active area. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 159–167, 1993. This subject is supported by the National Science Foundation of China.  相似文献   

威宁宣威组底部硅质页岩Rb-Sr古混合线年龄及其地质意义   总被引：1，自引：0，他引：1  

许连忠  张正伟  张乾  朱笑青  祝朝辉  黄艳  黄海明 《矿物学报》2006,26(4):387-394

在滇黔相邻地区,二叠纪宣威组下部发育一层硅质页岩和碳质页岩。页岩层位稳定、分布广泛,与下伏峨眉山玄武岩组上部凝灰岩层呈假整合接触关系。用迭代法恢复硅质页岩的Rb-Sr同位素古混合线,得到硅质页岩的年龄为(255±12)Ma。这个年龄不仅支持地层古地磁研究结果,而且符合地层年代学研究结果,表明Rb-Sr同位素古混合线年代学方法在中生代地层能够适用。这个年龄与普遍认为的峨眉山玄武岩主喷发期258Ma从时代关系上相符,而且有效地约束了峨眉山玄武岩喷发的上限。  相似文献   

重庆市矸石山环境地质灾害效应及稳定性分析   总被引：3，自引：1，他引：3  

董倩  刘东燕  彭文轩 《中国地质灾害与防治学报》2006,17(1):97-101

煤矸石是我国排放量及积存量最大的工业废弃物。我国现有矸石山1500余座,累计存量约34亿t。矸石排放量的持续增加造成严重的地质灾害隐患。论文分析了矸石山的污染效应、自燃效应、占地效应、爆炸效应、结构侵蚀效应、失稳效应及景观破坏效应系列环境地质灾害效应。为避免矸石山失稳所造成的危害,对重庆地区的矿区进行现场调研踏勘。根据其结果对影响矸石山稳定的因素及几种失稳模式进行了分析,并在此基础上,依据塑性极限分析原理,针对矸石山边坡失稳主要形式,利用极限分析上限定理推出了矸石山边坡稳定堆积高度的计算公式,并采用在重庆地区矿区调研踏勘及现场直剪试验所得到的参数进行计算,做出对应表格及曲线。其结果可作为确定矸石山实际堆放高度的理论依据。  相似文献