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地壳中的成矿地质流体体系 总被引：9，自引：0，他引：9
本文论述了地质流体研究的学科前缘性．认为地壳中可划分出六大类不同的成矿地质流体体系：（1）与大陆地壳中─酸性岩浆热事件有关的热液流体体系（2）与海底基性火山活动有关的热浪喷流派体体系（3）与海相沉积盆地演化有关的盆地流体体系（4）与区域变质作用有关的变质流体体系（5）与地幔排气过程有关的深部流体体系（6）与大型剪切带的发生演化有关的流体体系并简要讨论了每个成矿流体体系的发生、演化、特征和成矿作用． 相似文献
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地壳岩石均含有一定数量的缺陷损伤,是强非均质和各向异性材料,性质复杂,取决于其所处的构造和地质环境。实验表明,裂纹对岩石的孔隙度贡献不大,几乎可以忽略,但却是影响岩石有效弹性性质的主导因素而非孔隙。增加裂纹损伤会显著地引起岩石物理性质,包括强度、弹性性质、力学性质以及各向异性等的变化。另外,大部分地壳岩石的裂纹和孔隙都处于流体饱和状态,裂纹中的流体通过化学和力学作用显著影响岩石性质的变化。因此理解脆性岩石受力变形过程中的损伤和物理性质的演化具有重要意义,是岩石力学的长期目标之一。 相似文献
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岩石中的孔隙按形状划分，可以大致分成孔洞和裂纹两类。孔洞的纵横比大，形状近似于球形，它与油气储藏有密切关系。孔洞孔隙度是岩石孔隙度的主要贡献。裂纹纵横比小，形状细长，它所造成的孔隙度是岩石总孔隙度的一小部分。但是岩石中裂纹的存在和裂纹孔隙度的变化，对于岩石的各向异性和S波的分裂有重要的影响。本文利用两类不同形状孔隙对流体静压力的不同响应，利用改变流体静压力的实验对岩石中的裂纹孔隙率进行了测定；实验得到的裂纹孔隙率和岩石裂纹的闭合压力，为了解岩石各向异性、S波分裂以及地壳动力学提供了基础数据。 相似文献
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用两层介质中存在的一膨胀圆台体作为模型以便模拟地幔物质上涌孕震的力源模式．计算了层状介质结构条件下结构底部膨胀圆台模拟力源在不同横向、纵向尺度以及不同锥角时的应力场、应变场及位移场的变化．结果表明，介质中及地表附近的应力场、应变场、位移场不仅与上涌力源的几何参数和物理参数有关，而且也受到层状介质结构参数的制约和影响．这种数值模拟不仅为解释上地幔物质向地壳下部侵入的现象提供了一种有意义的方法，而且表明对于考虑地幔物质上涌孕震过程有关的前兆场分布而言，必须认真考虑介质结构不均匀性问题． 相似文献
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探讨了地壳内高导层的碳膜成因说和卤水成因说，中下地壳存在卤水，卤水使碳膜连通，增大了岩石的电导率，因而认为卤水是形成壳内高导层的关键物质，进而探讨了不同浓度的卤水在高温高压下的物态及其电导率变化规律，以及壳内高导层中卤水的封存机制．壳内高导层是壳－幔流体演化形成的 相似文献
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壳内岩石膨胀可能是形成某些大陆地震前兆的一个重要机制。为了揭示孕震体内岩石膨胀的作用,进行必要的膨胀模型的研究及相应的模拟计算是重要途径之一。在这方面,Nur 已做了开拓性工作。但是,为了更加适合地壳内部的情况,还应考虑某些因素的作用,如围压对膨胀的影响,起始膨胀的应力判别准则等。本文就是在考虑了上述因素的条件下,对Nur提出的膨胀本构关系做了一些必要的扩充。同时,为了模拟实际的孕震过程,将此模型编制成有限元程序,装在IBM-PC机上。最后,利用一个二维剖面模型,对地壳内不同深度产生膨胀的可能性及膨胀后地表垂直位移的变化进行了计算和讨论。 相似文献
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探讨了地壳内高导层的碳膜成因说和卤水成因说，中下地壳存在卤水，卤水使碳膜连通，增大了岩石的电导率，因而认为卤水是形成壳内高导层的关键物质，进而探讨了不同浓度的卤水在高温高压下的物态及其电导率变化规律，以及壳内高导层中卤水的封存机制．壳内高导层是壳-幔流体演化形成的. 相似文献
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《地球物理学进展》2017,(6)
矿物和岩石电导率的实验研究一直都是国内外专家学者所关注的重点内容,目前电导率的实验测量主要采用交流阻抗谱的方法.从实验结果来看,地壳矿物和岩石电导率的影响因素主要分为外部环境和内部性质两部分,包括矿物和岩石所受到的温度和压力大小、内部赋存的流体和熔体、岩石颗粒边缘的碳膜、岩石的颗粒大小和面理方向以及矿物晶格赋存的结构水与晶格方向等.结合地球物理探测结果,前人对下地壳高导层成因提出了各自不同的看法,同时电导率的实验数据对于解释地下岩层结构、动力学特征也带来了一定的帮助.通过总结可以发现对于断层带的电导率性质目前仍然知之甚少,在今后的实验研究中则需要重点关注. 相似文献
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Hidemi Tanaka Shin-Ichiro Hinoki Kazuo Kosaka Aiming Lin Keiji Takemura Akihiro Murata Takao Miyata 《Island Arc》2001,10(3-4):381-391
Abstract This paper describes the results of petrographical and meso- to microstructural observations of brittle fault rocks in cores obtained by drilling through the Nojima Fault at a drilling depth of 389.52 m. The zonation of deformation and alteration in the central zone of the fault is clearly seen in cores of granite from the hanging wall, in the following order: (i) host rock, which is characterized by some intragranular microcracks and in situ alteration of mafic minerals and feldspars; (ii) weakly deformed and altered rocks, which are characterized by transgranular cracks and the dissolution of mafic minerals, and by the precipitation of zeolites and iron hydroxide materials; (iii) random fabric fault breccia, which is characterized by fragmentation, by anastomosing networks of transgranular cracks, and by the precipitation of zeolites and iron hydroxide materials; and (iv) fault gouge, which is characterized by the precipitation of smectite and localized cataclastic flow. This zonation implies that the fault has been weakened gradually by fluid-related fracturing over time. In the footwall, a gouge layer measuring only 15 mm thick is present just below the surface of the Nojima Fault. These observations are the basis for a model of fluid behavior along the Nojima Fault. The model invokes the percolation of meteoric fluids through cracks in the hanging wall fault zone during interseismic periods, resulting in chemical reactions in the fault gouge layer to form smectite. The low permeability clay-rich gouge layer sealed the footwall. The fault gouge was brecciated during coseismic or postseismic periods, breaking the seal and allowing fluids to readily flow into the footwall, thus causing a slight alteration. Chemical reactions between fluids and the fault breccia and gouge generated new fault gouge, which resealed the footwall, resulting in a low fluid condition in the footwall during interseismic periods. 相似文献
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《中国科学:地球科学(英文版)》2015,(8)
The subduction channel is defined as a planar to wedge-like area of variable size,internal structure and composition,which forms between the upper and lower plates during slab subduction into the mantle.The materials in the channel may experience complex pressure,temperature,stress and strain evolution,as well as strong fluid and melt activity.A certain amount of these materials may subduct to and later exhume from100 km depth,forming high to ultra-high pressure rocks on the surface as widely discovered in nature.Rock deformation in the channel is strongly assisted by metamorphic fluids activities,which change composition and mechanical properties of rocks and thus affect their subduction and exhumation histories.In this study,we investigate the detailed structure and dynamics of both oceanic and continental subduction channels,by conducting highresolution petrological-thermomechanical numerical simulations taking into account fluid and melt activities.The numerical results demonstrate that subduction channels are composed of a tectonic rock melange formed by crustal rocks detached from the subducting slab and the hydrated mantle rocks scratched from the overriding plate.These rocks may either extrude sub-vertically upward through the mantle wedge to the crust of the upper plate,or exhume along the subduction channel to the surface near the suture zone.Based on our numerical results,we first analyze similarities and differences between oceanic and continental subduction channels.We further compare numerical models with and without fluid and melt activity and demonstrate that this activity results in strong weakening and deformation of overriding lithosphere.Finally,we show that fast convergence of orogens subjected to fluid and melt activity leads to strong deformation of the overriding lithosphere and the topography builds up mainly on the overriding plate.In contrast,slow convergence of such orogens leads to very limited deformation of the overriding lithosphere and the mountain building mainly occurs on the subducting plate. 相似文献
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本文重点报道了高温高压下流体与流体-岩石相互作用实验结果,提供了中地壳条件下流体性质和水岩反应速率数据.这些数据有助于理解中地壳的一些地球物理现象.作者进行了25℃~435℃和22~39 MPa条件下水-岩相互作用反应动力学实验.同时,研究水在近临界区至超临界区的性质.一般地说,中地壳大致位于10(15)至25 km的深度范围.各地的地壳厚度不同,但是中地壳高导-低速层的深度范围十分相似.中地壳的顶界温度处于300℃,底界大致为450℃范围,压力高达200 MPa以上.流体-岩石相互作用实验表明:硅酸盐矿物和岩石的硅最大溶解速率出现在300℃~400℃.此时,硅酸盐矿物格架解体.通常,地壳里普遍存在水、流体.地壳构造活动导致断裂空隙、减压、流体流动.这时,有可能导致中地壳处于300℃~450℃流体的压力减低,由超临界区进入临界态、亚临界态.这会引发强烈流动的水与岩石相互作用.溶解反应导致岩层的硅淋失,硅的强烈淋失又会导致硅酸盐矿物格架解体,岩石崩塌.同时,进一步促进流体的流动.实验表明300℃~400℃下的强烈水岩相互作用促进了岩石破坏,并有可能影响岩层的地球物理性质,如高导层出现.另外,实验和理论研究表明处于300℃~400℃流体具有高电导率性质.这些水岩相互作用会使中地壳出现高导-低速层. 相似文献
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Catherine Mvel 《Earth and Planetary Science Letters》1987,83(1-4)
Gabbro breccias were recovered from an anomalously shallow level of the ocean crust during DSDP Leg 82. The rocks display evidence of metamorphic crystallization related either to localized deformation or to hydrothermal circulation of a seawater-derived fluid under static conditions. Secondary phases consist of plagioclase, amphibole and minor clinopyroxene, ilmenite, sphene and chlorite. Petrological study indicates that deformation took place at high temperature, under anhydrous conditions, and was followed by hydrothermal circulation. The compositions of secondary minerals (i.e. strong zonations, presence of chlorine in amphiboles, varying compositions of secondary plagioclase) indicate that reactions of the gabbros with the fluids occurred at a low water/rock ratio. Relations between Cl, Na and K in amphiboles suggest penetration of at least two distinct fluids of different compositions. Metamorphic crystallization stopped when greenschist facies conditions were reached( 350°C), probably because hydrothermal circulation faded out. 相似文献
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Alexander Y. Rozhko 《Geophysical Prospecting》2020,68(2):631-656
It is evident from the laboratory experiments that shear moduli of different porous isotropic rocks may show softening behaviour upon saturation. The shear softening means that the shear modulus of dry samples is higher than of saturated samples. Shear softening was observed both at low (seismic) frequencies and high (ultrasonic) frequencies. Shear softening is stronger at seismic frequencies than at ultrasonic frequencies, where the softening is compensated by hardening due to unrelaxed squirt flow. It contradicts to Gassmann's theory suggesting that the relaxed shear modulus of isotropic rock should not depend upon fluid saturation, provided that no chemical reaction between the solid frame and the pore fluid. Several researchers demonstrated that the shear softening effect is reversible during re-saturation of rock samples, suggesting no permanent chemical reaction between the solid frame and the pore fluid. Therefore, it is extremely difficult to explain this fluid–rock interaction mechanism theoretically, because it does not contradict to the assumptions of Gassmann's theory, but contradicts to its conclusions. We argue that the observed shear softening of partially saturated rocks by different pore fluids is related to pore-scale interfacial phenomena effects, typically neglected by the rock physics models. These interface phenomena effects are dependent on surface tension between immiscible fluids, rock wettability, aperture distribution of microcracks, compressibility of microcracks, porosity of microcracks, elastic properties of rock mineral, fluid saturation, effective stress and wave amplitude. Derived equations allow to estimate effects of pore fluids and saturation on the shear modulus and mechanical strength of rocks. 相似文献
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In this paper we present the results of a geostructural study on active faults in central Italy, where seismogenic fault zones occur as part of a Quaternary network dissecting and/or inverting earlier tectonic features of the central Apennines fold and thrust belt. In our work we focus on the possibility of using structurally-oriented quantitative analysis of fault fabrics and fluid inclusion studies for assessing the hydraulic properties and scaling relations of fault zones in order to evaluate the role and effects of the interaction between rock and fluids in the brittle deformation of strained crustal rock volumes. The results of our study show that this approach is appropriate for (i) assessing the structural permeability of faulted and fractured rock volumes, (ii) defining the conduit/barrier behaviour of fault zones to fluid flow, (iii) mapping spatial variations of the fluid pressure across different fault segments, (iv) evaluating the maturity of a structural network and the degree of interaction of linked structural discontinuities, (v) assessing fluid composition and the conditions of deformation by means of microstructural and fluid inclusion data. 相似文献
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Xuemei Cheng Shuyun Cao Junyu Li Zunpu Yu Yanlong Dong Meixia Lv Junlai Liu 《中国科学:地球科学(英文版)》2018,61(8):1023-1041
Diancangshan metamorphic massif is one of the four metamorphic massifs developed along the Ailaoshan-Red River strike-slip fault zone, Yunnan, China. It has experienced multi-stage metamorphism and deformation, especially since the late Oligocene it widely suffered high-temperature ductile shear deformation and exhumation of the metamorphic rocks from the deep crust to the shallow surface. Based on the previous research and geological field work, this paper presents a detailed study on deformation and metamorphism, and exhumation of deep metamorphic rocks within the Diancangshan metamorphic massif, especially focusing on the low-temperature overprinted retrogression metamorphism and deformation of mylonitic rocks. With the combinated experimental techniques of optical microscope, electron backscatter diffraction attachmented on field-emission scanning electron microscopy and cathodoluminescence, our contribution reports the microstructure, lattice preferred orientations of the deformed minerals, and the changes of mineral composition phases of the superposition low-temperature retrograde mylonites. All these results indicate that: (1) Diancangshan deep metamorphic rock has experienced early high-temperature left-lateral shear deformation and late extension with rapid exhumation, the low-temperature retrogression metamorphism and deformation overprinted the high-temperature metamorphism, and the high-temperature microstructure and texture are in part or entirely altered by subsequent low-temperature shearing; (2) the superposition of low-temperature deformation-metamorphism occurs at the ductile-brittle transition; and (3) the fluid is quite active during the syn-tectonic shearing overprinted low-temperature deformation and metamorphism. The dynamic recrystallization and/or fractures to micro-fractures result in the strongly fine-grained of the main minerals, and present strain localization in micro-domians, such as micro-shear zones in the mylonites. It is often accompanied by the decrease of rock strength and finally influences the rheology of the whole rock during further deformation and exhumation of the Diancangshan massif. 相似文献
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利用新方法制作出含可控裂缝的双孔隙人工砂岩物理模型,具有与天然岩石更为接近的矿物成分、孔隙结构和胶结方式,其中裂缝密度、裂缝尺寸和裂缝张开度等裂缝参数可以控制以得到实验所需要的裂缝参数,岩样具有真实的孔隙和裂缝空间并可以在不同饱和流体状态下研究流体性质对于裂缝介质性质的影响.本次实验制作出一组具有不同裂缝密度的含裂缝人工岩样,对岩样利用SEM扫描电镜分析可以看到真实的孔隙结构和符合我们要求的裂缝参数,岩样被加工成八面棱柱以测量不同方向上弹性波传播的速度,用0.5 MHz的换能器使用透射法测量在饱和空气和饱和水条件下各个样品不同方向上的纵横波速度,并得出纵横波速度、横波分裂系数和纵横波各向异性强度受裂缝密度和饱和流体的影响.研究发现流体对于纵波速度和纵波各向异性强度的影响较强,而横波速度、横波分裂系数和横波各向异性强度受饱和流体的影响不大,但是对裂缝密度的变化更敏感. 相似文献
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通过反演由大量的纵、横波地震数据组成的综合数据集,获得了南北地震带地壳的多参数三维精细结构,探讨和分析了南北地震带的高地震活动性和强震频发的原因.成像结果表明,尽管1976年松潘一平武地震(M7.2)与2008年汶川地震(M8.0)以及2013年芦山地震(M7.0)均发生在高速、低泊松比异常区域,并且在其震源的下方均有一低速、高泊松比异常区域.我们认为,上述三个地震的触发与流体侵入导致的地壳形变之间有密切的联系.1955年炉霍地震(M7.4)和1973年康定地震(M7.1)均发生在鲜水河断裂带上,其震源中心区域表现为低速、高泊松比异常,可以解释为下地壳中的流体沿断层面上涌.在震源区的周边区域兼有高速、高泊松比异常,低速、高泊松比异常以及高速、低泊松比异常,可能分别与含流体的岩石、沿断裂带发育的变质岩以及坚硬的克拉通块体对应.流体的侵入不仅能够改变断层面上的应力情况,还能降低岩石骨架的岩石力学强度,进而触发地震.1970年云南通海大地震(M7.1)发生在哀牢山一红河断裂带附近的曲江断裂上,其震源处于高速度、低泊松比异常与低速度、高泊松比异常之间的边界区域,被认为是流体挤压后的应变能积累,最终导致脆性破裂,以至于发生地震.根据本次研究获得的多参数结构图像,结合前人的研究成果,我们认为南北地震带地壳强烈形变与流体侵入是造成该区域地震活动性较高及强震频发的两个主要因素. 相似文献
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Tomoyuki Ohtani Hidemi Tanaka Koichiro Fujimoto Takayuki Higuchi Naoto Tomida Hisao Ito 《Island Arc》2001,10(3-4):392-400
Abstract The internal structures of the Nojima Fault, south-west Japan, are examined from mesoscopic observations of continuous core samples from the Hirabayashi Geological Survey of Japan (GSJ) drilling. The drilling penetrated the central part of the Nojima Fault, which ruptured during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake) ( M 7.2). It intersected a 0.3 m-thick layer of fault gouge, which is presumed to constitute the fault core (defined as a narrow zone of extremely concentrated deformation) of the Nojima Fault Zone. The rocks obtained from the Hirabayashi GSJ drilling were divided into five types based on the intensities of deformation and alteration: host rock, weakly deformed and altered granodiorite, fault breccia, cataclasite, and fault gouge. Weakly deformed and altered granodiorite is distributed widely in the fault zone. Fault breccia appears mostly just above the fault core. Cataclasite is distributed mainly in a narrow (≈1 m wide) zone in between the fault core and a smaller gouge zone encountered lower down from the drilling. Fault gouge in the fault core is divided into three types based on their color and textures. From their cross-cutting relationships and vein development, the lowest fault gouge in the fault core is judged to be newer than the other two. The fault zone characterized by the deformation and alteration is assumed to be deeper than 426.2 m and its net thickness is > 46.5 m. The fault rocks in the hanging wall (above the fault core) are deformed and altered more intensely than those in the footwall (below the fault core). Furthermore, the intensities of deformation and alteration increase progressively towards the fault core in the hanging wall, but not in the footwall. The difference in the fault rock distribution between the hanging wall and the footwall might be related to the offset of the Nojima Fault and/or the asymmetrical ground motion during earthquakes. 相似文献