滇西新生代富碱斑岩的岩石特征与成因   总被引：87，自引：0，他引：87       下载免费PDF全文

邓万明  黄萱 《地质科学》1998,33(4):412-425

对滇西金沙江-墨江缝合带中段新生代富碱斑岩的岩石地球化学和同位素组成的研究表明,这一套岩石形成在板内造山后的剪切和拉张构造环境,是壳-幔混合层物质部分熔融,快速上升浅部定位所形成。本区壳-幔过渡带可能是先期生成的一种富集源区。文中还讨论了壳-幔过渡带的成因及富碱斑岩岩浆活动与岩石圈演化的关系。  相似文献   

上地幔交代氧化物及其相关矿物──金伯利岩中复杂氧化物的相互关系及地幔交代作用探讨     

陆琦  周湖云  刘惠芳  雷新荣 《矿物学报》1998,(4)

用微束分析和微区图像分析技术,研究了山东金伯利岩中沂蒙矿（系列）、蒙山矿（系列）、桂红石、Zr－REE－Ti氧化物、钛铁矿（富镁）、钙钛矿和亚铁板钛矿的成分、产出特征和相互关系。这些关系包括：①镁钛铁矿-尖晶石的固溶体分离及伴生的交代作用──沂蒙矿的形成;②蒙山矿的熔融交代作用及其形成的亚铁板钛矿;③斑点、微脉交代充填作用及其形成的柱红石、Zr－REE－Ti氧化物等新矿物相。通过研究,总结了上地幔中与氧化物矿物相关的一些显交代作用的规律,提出了上地幔中不相容元素的显交代作用可分为早、中、晚三期。这些为地幔流体交代作用的总成分目录和机理作出了重要的补充。  相似文献   

Rheological Properties of Mantle Peridotites at Yushigou in the North Qilian Mountains and Their Implicationsfor Plate Dynamics     

SONG Shuguang  SU LiXi''an Institute of Geology  Mineral Resources  CAGS  East Youyi Rd.  Xi''an  Shaanxi 《《地质学报》英文版》1998,72(2):131-141

This paper discusses in detail the deformation textures, glide system, petrofabrics and olivine dislocation microstructures of mantle peridotites at Yushigou in the North Qilian Mountains, northwestern China. The peridotites have undergone high-pressure, high-temperature and low-strain rate plastic flow deformation. According to the dynamic recrystallized-grain size of olivine and the average spacing between the dislocation walls as well as the chemical composition of enstatite, the authors calculated the rheological parameters of the ancient upper mantle in the study area as follows: temperatures 1025-1093℃; pressures 3043-4278 MPa; depths 95-132 km; deviatoric stress 28-32 MPa; strain rates 0.2×10-14-2.13×10-14s-1 and equivalent viscosities 0.45×1020-4.65×1020 Pa · s. These parameters suggest that the position where plastic flow took place was correspondent to the low-velocity zone beneath the oceanic lithosphere and that oceanization characterized by middle-velocity (1-3 cm/a) sea-floor spreadi  相似文献   

地幔流体与地球的放气作用   总被引：7，自引：0，他引：7  

朱永峰 《地学前缘》1998,(Z1)

地幔流体的形成、聚集和渗透是引起地幔交代作用的主要营力。地幔交代作用发育的强弱决定着所生成岩浆的碱性程度。地幔流体和部分熔融体高度富集不相容元素,它们与亏损地幔的相互作用可以使后者发生ＬＲＥＥ和不相容元素的局部富集。通过板块俯冲作用使地球表层的ＣＯ２进入地幔,参加地球的碳循环。热点岩浆来源的ＣＯ２中含有部分循环的ＣＯ２,而大洋中脊玄武岩中的ＣＯ２主要是原始地球的ＣＯ２。携带ＣＨ４和Ｈ２Ｏ的流体渗透至被俯冲带带入地幔的物质,使碳酸盐化的榴辉岩还原而形成含金刚石的榴辉岩和富水流体,并诱发局部熔融,所形成的熔体以火山喷发的形式上升到地表。地幔岩石中含有大量的流体,它们主要以流体包裹体的形式存在于地幔矿物中。几乎在所有的上地幔环境下形成的矿物中均找到了流体包裹体。包裹体内流体的成分主要是ＣＯ２,ＣＨ４,Ｈ２Ｏ及少量Ｈ２,Ｎ２等。  相似文献   

壳幔化学不均一性与块体地球化学边界研究   总被引：13，自引：1，他引：12  

朱炳泉 《地学前缘》1998,5(1):72-82

壳幔派生岩石的多元同位素体系研究表明,地球存在块体的化学不均一性,可划分出地球化学省,并以地球化学急变带作为边界。全球总体上分成东冈瓦纳（如华夏与青藏—印支）、西冈瓦纳、太平洋（如佳木斯、中蒙古、辽胶渤、北疆—南戈壁）与劳亚（如华北、中朝、兴安、塔里木等）四种类型的地球化学省。地球化学急变带与地球物理场变化存在密切关系。在构造上,地球化学急变带可分成构造显性与构造隐性两种类型。应用深、浅构造立交模型及其相互转化可对两种类型地球化学急变带的出现作出较合理的解释。地球化学急变带,特别是急变带的转折端对超大型矿床和成矿密集区的分布有密切控制作用;显性急变带主要表现为与动力变质和岩浆活动有关的改造成矿作用,隐性急变带主要表现为火山与热水沉积成矿作用。具有工业意义的油气田均位于构造隐性急变带与中新生代盆地的立交地段。  相似文献   

豫西中新生代地球动力学探讨     

司马献章 《河南国土资源》1998,(3)

以隆断区和断陷盆地地壳厚度的显著差异,隆断区与盆地分界的深大断裂（边缘断裂,与地幔斜坡对应）,隆断区和盆地的岩浆作用及现代地热活动,盆地沉降历史四个地质特征为依据,作者认为本区盆岭构造形成的动力学机制是：中新生代上地幔起伏和下地壳不均匀岩浆熔融并由此产生的岩浆作用和热能、重力地质作用等引起的物质膨胀和岩浆侧向上侵入、岩浆冷凝和体积收缩导致同沉积断层运动,形成本区盆岭构造。  相似文献   

The electrical conductivity of the mantle beneath Europe derived from C-responses from 3 to 720 hr   总被引：6，自引：0，他引：6  

Nils Olsen 《Geophysical Journal International》1998,133(2):298-308

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Mantle convection with a brittle lithosphere: thoughts on the global tectonic styles of the Earth and Venus   总被引：5，自引：0，他引：5  

Louis Moresi  & Viatcheslav Solomatov 《Geophysical Journal International》1998,133(3):669-682

Plates are an integral part of the convection system in the fluid mantle, but plate boundaries are the product of brittle faulting and plate motions are strongly influenced by the existence of such faults. The conditions for plate tectonics are studied by considering brittle behaviour, using Byerlee's law to limit the maximum stress in the lithosphere, in a mantle convection model with temperature-dependent viscosity.
When the yield stress is high, convection is confined below a thick, stagnant lithosphere. At low yield stress, brittle deformation mobilizes the lithosphere which becomes a part of the overall circulation; surface deformation occurs in localized regions close to upwellings and downwellings in the system. At intermediate levels of the yield stress, there is a cycling between these two states: thick lithosphere episodically mobilizes and collapses into the interior before reforming.
The mobile-lid regime resembles convection of a fluid with temperature-dependent viscosity and the boundary-layer scalings are found to be analogous. This regime has a well defined Nusselt number–Rayleigh number relationship which is in good agreement with scaling theory. The surface velocity is nearly independent of the yield stress, indicating that the 'plate' motion is resisted by viscous stresses in the mantle.
Analysis suggests that mobilization of the Earth's lithosphere can occur if the friction coefficient in the lithosphere is less than 0.03–0.13—lower than laboratory values but consistent with seismic field studies. On Venus, the friction coefficient may be high as a result of the dry conditions, and brittle mobilization of the lithosphere would then be episodic and catastrophic.  相似文献   

Eigendecomposition of the two-point correlation tensor for optimal characterization of mantle convection     

S. Balachandar 《Geophysical Journal International》1998,132(1):111-127

The two-point correlation tensor provides complete information on mantle convection accurate up to second-order statistics. Unfortunately, the two-point spatial correlation tensor is in general a data-intensive quantity. In the case of mantle convection, a simplified representation of the two-point spatial correlation tensor can be obtained by using spherical symmetry. The two-point correlation can be expressed in terms of a planar correlation tensor, which reduces the correlation's dependence to only three independent variables: the radial locations of the two points and their angular separation. The eigendecomposition of the planar correlation tensor provides a rational methodology for further representing the second-order statistics contained within the two-point correlation in a compact manner. As an illustration, results on the planar correlation are presented for the thermal anomaly obtained from the tomographic model of Su, Woodward & Dziewonski (1994 ) and the corresponding velocity field obtained from a simple constant-viscosity convection model Zhang & Christensen 1993 ). The first 10 most energetic eigensolutions of the planar correlation, which constitute an almost three orders of magnitude reduction in the data, capture the two-point correlation to 97 per cent accuracy. Furthermore, the energetic eigenfunctions efficiently characterize the thermal and flow structures of the mantle. The signature of the transition zone is clearly evident in the most energetic temperature eigenfunction, which clearly shows a reversal of thermal fluctuations at a depth of around 830  km. In addition, a local peak in the thermal fluctuations can be observed around a depth of 600  km. In contrast, due to the simplicity of the convection model employed, the velocity eigenfunctions exhibit a simple cellular structure that extends over the entire depth of the mantle and do not exhibit transition-zone signatures.  相似文献   

Advection of plumes in mantle flow: implications for hotspot motion, mantle viscosity and plume distribution   总被引：8，自引：0，他引：8  

Bernhard Steinberger  & Richard J. O'Connell 《Geophysical Journal International》1998,132(2):412-434

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