共查询到20条相似文献，搜索用时 265 毫秒
1.
野外地质调查结果显示,断层带常富集碳质.断层带中碳的分布结构是影响断层带电导率特征的一种重要参数.本文在室温、室内湿度和2MPa正应力条件下,对不同石墨含量(3,5,6和7wt%)的石英-石墨混合断层泥模拟样品开展了滑动速率介于500μm·s-1～1m·s-1的摩擦实验及相应的电导率测量,以期研究断层运动对碳分布结构的影响以及断层带电性特征对碳含量及分布的响应情况.结果显示,摩擦滑动能够显著地改变样品的电性特征(电导率大小及其各向异性).在平行滑动面方向(径向),样品电导率随着滑动位移的增加快速增加,在滑动约数十厘米之后,其电导率基本达到稳定状态;在垂直滑动面方向(轴向),样品电导率基本不随摩擦滑动速率和滑动距离而变化.SEM显微结构观测显示,摩擦滑动所引起的电导率各向异性直接反映了石墨分布结构的变化.该研究结果深化了对地震断裂带浅部电性特征的认识,为野外断层带大地电磁测深资料的解释提供了约束,同时对于了解含碳断层的力学性质和弱矿物相在剪切变形中的分布特征及其演化过程等方面也具有重要意义. 相似文献
2.
大地电磁(MT)资料显示,青藏高原地壳及地幔中普遍存在着高导层.作为大陆造山带中古洋盆岩石圈残片,蛇绿岩套的电导率测量可为了解古洋盆地区地壳及地幔的电性结构提供极其有用的信息.本研究中,我们在压力为1 GPa或3 GPa下,用交流阻抗谱法测量了采自西藏南部地区的蚀变辉长岩、玄武岩、角闪橄榄岩及方辉橄榄岩四个样品的阻抗谱,并进一步得出样品的电导率,不同样品电导率与温度之间的关系满足Arrhenius关系式.在实验温度范围内,蛇绿岩套电导率的对数logσ位于-6.0~-0.5 S/m之间,且随着温度的增高,不同样品电导率增大约4~5.5个量级.样品在未脱水的情况下,低温段的活化焓变化范围在0.4~0.6 eV之间,高温段的活化焓变化范围为1.7~2.6 eV之间.同时,我们研究了样品中结构水含量及铁含量对实验电导率的影响,验证了样品电导率与铁含量之间呈正比关系.当对样品结构水含量进行归一化后,相同温度下各样品的电导率随铁含量的增加而增大,而对样品铁含量归一化后,相同温度下各样品的电导率随样品中水含量的增加而增大.将实验电导率与藏南地区大地电磁结果进行了对比,发现本研究中各样品高温段实验电导率结果均落在大地电磁结果范围内. 相似文献
3.
地壳高导异常及各向异性成因是地学研究的热点之一,断裂带区域常呈现出高电导率特征,对于石墨富集的断裂带,石墨形态及分布对导电性的影响已经引起关注.本文利用有限元数值模拟方法,构建了石墨-石英三维模型,探讨了石墨含量、排列方式、孔隙度及温度对模型电导率的影响.结果表明,石墨连通前,温度的增加能使模型电导率显著增大,而在石墨连通后,石墨含量的增加、片状石墨沿导电方向的定向排列以及石墨直径与厚度比值的增大,均能导致模型电导率发生显著增加,孔隙度的增大则导致模型电导率减小.同时,这些参数的变化也会使模型电导率突变时的石墨含量阈值发生改变,当石墨排列方向改变时,这一阈值变化显著,对于石墨富集的一些断裂带区域,石墨定向排列可能是引起高导的一种成因. 相似文献
4.
碳是影响岩石电导率大小的一个重要因素,可能是造成龙门山断层带电导率异常的重要原因之一.为了研究不同的碳含量、矿物颗粒粒径与碳晶体结构对断层带电导率的影响,在干燥、常温、0.2~300 MPa的压力条件下实验研究了人工模拟断层泥样品(石英粉末与含碳粉末混合的样品,简称模拟样品)和采自映秀-北川断层八角庙剖面的天然断层岩样品(简称天然样品)的电导率.实验结果显示,当模拟样品中的含碳粉末连通时,电导率与碳体积率的关系符合逾渗理论模型;而含碳粉末未连通时,电导率随总孔隙度降低而指数性升高.同时模拟样品的电导率也随石英颗粒粒径的变化而发生改变.相比于模拟样品中的含碳粉末主要分布于石英颗粒支撑的孔隙中,天然样品中的碳则主要以碳膜的形式赋存在颗粒边缘,导致碳体积率相同的条件下,模拟样品的电导率小于天然样品.此外,天然样品的电导率(9×10~(-4)S·m~(-1))也要小于野外大地电磁探测的结果(0.03~0.1 S·m~(-1)).在今后的实验中还需要考虑在动态摩擦条件下对含有完整含碳结构的天然样品进行电导率的实验研究. 相似文献
5.
在压力为1.0GPa、温度为400~1 073K条件下,用交流阻抗谱法研究了采自山东泰山的黑云斜长片麻岩平行及垂直面理方向的电导率。在实验温度范围内,黑云斜长片麻岩实验样品电导率的对数值为-6.0~0.5S/m,满足Arrhenius方程。电导率在平行面理方向比垂直面理方向高出约1个数量级。平行面理方向样品电导率分别在第3轮升、降温过程中的881~1 040K之间出现1个明显的电导率突变过程,这可能与黑云母的脱水有关。在低温段,垂直及平行面理方向样品的活化焓分别为0.43和0.49eV,在高温段则分别为3.40和1.53eV。将该实验电导率结果与华东地区大地电磁结果进行对比发现,在中下地壳范围内,该实验结果部分位于大地电磁结果范围内,说明黑云斜长片麻岩可能是组成这一地区中下地壳的候选岩石之一。 相似文献
6.
7.
中地壳断层带内发现的接近静岩压力的高压流体能够合理解释汶川MS8.0级地震断层的高角度逆冲滑动, 而高压流体的产生与断层带的微裂隙愈合紧密相关.利用熔融盐固体介质三轴高温高压实验系统,我们采用含水和烘干的Carrara大理岩样品开展了微裂隙愈合实验,研究中地壳断层带内高压流体的形成条件.实验分为三类:A类、A+B类和A+B+C类,其中A阶段实验在室温条件下将样品压裂,形成一系列共轭破裂面,B阶段实验在600℃、围压700 MPa和应变速率10-6s-1条件下愈合了A阶段破碎的样品,实验样品从以碎裂变形为主向以韧性变形为主转变,C阶段实验通过快速降低轴压模拟一个扩容过程,再以相同实验条件重新加载样品,通过比较实验样品强度来检验样品的愈合程度.样品显微结构和实验样品强度表明,动态重结晶作用能够愈合微裂隙和孔隙,水能促进矿物的动态重结晶作用,较高的水含量和较大的应变有利于微裂隙和孔隙的愈合,从而有利于高压流体的形成. 相似文献
8.
国家地震局地球物理研究所 本高压容器是我国第一台10000公斤/厘米~2液体围压的三轴试验容器。容器的高压腔尺寸为φ8.5吤厘米 可放置φ2.5.5厘米的岩石样品及各种探头。它以9138油泵为侧向压力源 可产生0-10000公斤/厘米~2的围压 能模拟地壳深部30公里处的压力环境。与长江500型岩石三轴应力试验机配套使用 可进行岩石三轴压力破裂试验。容器简体采用了三层缩套配合结构 液压油进出口及电测导线的引出均在底座及大柱塞上轴向开孔 以免应力集中。上密封和下密封采用三角垫及密封环密封 引线密封采用锥塞及密封绝缘锥套密封。 相似文献
9.
《中国科学:地球科学》2016,(3)
含水矿物是地壳、地幔,尤其是俯冲带内的重要矿物.高温高压下壳幔含水矿物电导率实验研究是一个相对较新的研究方向.随着实验技术的不断进步,很多高压相含水硅酸岩矿物的电导率测定工作得以开展,在有效控制温度、压强和氧逸度等条件下,含水矿物的电导率实验数据可以对地球内部水的分布提供制约.本文介绍了已有的蛇纹石、滑石、水镁石、phase A、super hydrous phase B、phase D含水矿物在高温高压下的电导率实验研究,对各含水矿物电导率数据的有效性进行了分析,并重点介绍了电导率测试含水矿物脱水对全岩电导率的影响以及压强对含水矿物电导率的影响.在已有数据的基础上,对含水矿物的导电机制以及俯冲带的电结构进行了探讨.最后对今后的研究前景及潜在的研究领域进行了展望. 相似文献
10.
在温度750～1600 K和压力10～20 GPa条件下,借助于Kawai-5000多面顶砧高温高压设备,就位测量了(Mg0.9Fe0.1) SiO3 顽火辉石的电导率.实验结果显示,顽火辉石的电导率在高温区以小极化子机制为主,在低温区以质子导电为主,因为实验后的样品中有一定的水含量.另外,X射线衍射实验表明压力（20 GPa）诱发了顽火辉石向林伍德石的相变,这是我们首次在顽火辉石的电导率实验中观测到林伍德石含水相变,而且含水林伍德石的电导率与已有的实验结果相当一致. 相似文献
11.
12.
Geomagnetic field variations recorded by an array of magnetometers spread across the Kachchh Rift basin are reduced to a set of induction arrows as a diagnostic of lateral electrical conductivity variations. A non-uniform thin-sheet electrical conductance model is developed to account for the salient induction patterns. It indicates that the imaged conductivity anomalies can be related to the sediment-filled structural lows in between the fault bounded uplifts. It is suggested that sagging structural lows preserved the marine sediments deposited during the Mesozoic sea transgression and later developed into first order embayment basins for the deposition of sediments in association with Late Eocene transgression. Depth integrated electrical conductance helped in mapping two depo-centres: along the ENE-WSW trending Banni half-Graben bounded by the Kachchh Main fault on the south and, second, along the Vinjan depression formed in response to the subsidence between the Vigodi fault and westward extension of the Katrol Hill fault together with the westward bending of the Median High. Presence of metamorphosed graphite schist clasts in shale dominated Mesozoic sequence and/or thin films of carbon resulting from the thermal influence of Deccan activity on Carbonate-rich formations can account for the high electrical conductivity anomalies seen in the depo-centres of thick Mesozoic and Tertiary sediments. Additionally two high conductivity zones are imaged encompassing a block defined by the 2001 Bhuj earthquake and its aftershocks. In agreement with gravity, magnetic and seismic velocity signatures, aqueous fluids released by recrystallizing magmatic bodies intruded in association with Deccan trap activity account for mapped high conductivity zones. High fluid pressure in such a fractured domain, surrounding the intruded magmatic plugs, perturb the regional stress concentrations to produce frequent and low magnitude aftershocks in the shallow section of the epicentral track of the 2001 Bhuj earthquake. 相似文献
13.
Great strides have been made in understanding the upper part of the crust by in-situ logging in, and laboratory experiments on core recovered from super-deep bore-holes such as the KTB. These boreholes do not extend into the lower crust, and can contribute little to the elucidation of mechanisms that produce the high electrical conductivities that are commonly observed therein by magneto-telluric (MT) methods. Laboratory studies at simulated lower crustal conditions of temperature, pressure and saturation, on electrolyte saturated rocks thought to have been derived from the lower crust, have not been possible up until now due to their experimental difficulty. It is necessary to subject electrolyte-saturated rock samples to independently controlled confining and pore-fluid pressure, which implies that the rock be sleeved in some impermeable but deformable material, that can withstand the very high temperatures required. Metals are the only materials capable of being used, but these cause great difficulties for cell sealing and conductivity measurement. In this paper we describe recent breakthroughs in experimental work, specifically the development of two new types of sophisticated metal/ceramic seal, and a conductivity measurement technique that enables the measurement of saturated rock conductivity in the presence of a highly conducting metallic sleeve. The advances in experimental technique have enabled us to obtain data on the electrical conductivity of brine saturated basic, acidic and graphite-bearing rocks at lower crustal temperatures and raised pressures. These data have facilitated the comparison of MT derived crustal electrical conductivity profiles with profiles obtained from laboratory experiments for the first time. Initial modelling shows a good agreement between laboratory derived and MT derived profiles only if the mid-crust is composed of amphibolite pervaded by aqueous fluids, and the lower crust is composed of granulite that is saturated with aqueous fluids and/or contains interconnected grain surface films of graphite. The experimental data are consistent with a three layer crust consisting of an aqueous fluid saturated acidic uppermost layer, above an aqueous fluid saturated amphibolite mid-crust, and a granulite lowermost crust, which may or may not be saturated with aqueous fluids, but if not, requires the presence of an additional conduction mechanism such as conduction through thin graphite films. 相似文献
14.
用电磁阵列剖面法 (EMAP)、大地电磁测深方法 (MT) ,沿三河 -平谷 8级大震震源区 ,作了 31 8km长的EMAP探测和两条总长 150 0 5km共 36个点的MT探测。获得了研究范围内的地壳上地幔电性结构、高导层特征和陡变带、高导异常体、断裂展布、岩石圈结构等结果 ,为搞清地震危险区的深浅构造关系、从电性结构特征推测发震模式和预测未来强震的可能地点提供了介质电性的多种参数 相似文献
15.
本文通过对横穿海拉尔盆地的一条长约222km的北西—南东向大地电磁测深剖面数据的定性分析及二维定量反演解释,首次获得了海拉尔盆地高精度大范围的电性结构图.海拉尔盆地中-上地壳电性结构纵向上具有典型的分层特性,总体可分为四层,即低阻层-高阻层-低阻层-高阻层,而横向上又具有分块特点.海拉尔盆地边缘及内部分布的众多断裂将盆地划分为隆起与坳陷相间的格局,并发现盆地内部坳陷区也存在有小规模凸起,每一构造单元内部电性结构各具特点.海拉尔盆地中-上地壳低阻层底面最深达28km,通常在6~16km之间,但厚度变化不大,在4~10km之间,且隆起区与坳陷区底面埋深差别较大.据电性结构模型推测出两条新断裂F8和F9,且断裂F9规模较大,为基底断裂.中-上地壳的低阻层可能在一定程度上控制着海拉尔盆地内油气田的分布格局. 相似文献
16.
Hartmut Jödicke Jörn H Kruhl Christian Ballhaus Peter Giese Jürgen Untiedt 《Physics of the Earth and Planetary Interiors》2004,141(1):37-58
In order to better understand the nature of deep crustal high electrical conductivity, we studied the electrical properties of a tilted section of a former lower continental crust exposed in the Calabrian arc of the Alpine-Apennine mountain system. Geoelectric field measurements and impedance measurements on rock samples showed that these high-grade metamorphic rocks are generally highly resistive as expected for crystalline, electrolytically conducting rocks of low porosity. This holds for graphite-free metabasites as well as for metapelites which generally contain accessory, up to 3% biogenic graphite in the form of isolated grains. Clearly as an exception, a group of thin stratiform black horizons with thicknesses of 1-15 cm within the metapelitic series was detected by means of self-potential (SP) measurements. Rock samples from these horizons exhibit high, quasi-metallic bulk conductivities of up to 50 S/m (0.02 Ωm) in agreeement with up to 20% syngenetic graphite, forming a network of interconnected streaks or crack fillings. The high amount of carbon most probably originates from organic matter of Corg-rich black shales. Relative enrichment of the low mobility graphitic matter compared to the carbon content of the assumed protoliths may have been due to pressure solution and partial melting during prograde metamorphism, without major contribution of a fluid phase, resulting in isolated graphite flakes. Although enriched, graphite in this form has little effect on electrical conductivity. For the Calabrian black horizons, microscopic analyses make conceivable that, in a further decisive step, isolated graphite grains were mechanically smeared to continuous pathways during uplift by shearing, producing hereby the observed graphitic network which is needed to generate high conductivity. As Corg-rich black shales are common members of sedimentary sequences throughout the earth’s history, good conductors of this type may be expected in the continental crust at any depth depending on tectonic and metamorphic history, with the exception of magmatic protoliths. Regarding the extremely high conductivity of the meta-black shale samples containing syngenetic sheared graphite, a total thickness of a few meters of such rocks is sufficient to explain magnetotelluric high conductivity anomalies in the deep crust. 相似文献
17.
ELECTRICAL STRUCTURE OF THE 2017 MS7.0 JIUZHAIGOU EARTHQUAKE REGION AND THE EASTERN TERMINUS OF THE EAST KUNLUN FAULT 
下载免费PDF全文
下载免费PDF全文 SUN Xiang-yu ZHAN Yan ZHAO Ling-qiang CHEN Xiao-bin LI Chen-xia SUN Jian-bao HAN Jing CUI Teng-fa 《地震地质》1979,42(1):182-197
The East Kunlun Fault is a giant fault in northern Tibetan, extending eastward and a boundary between the Songpan-Ganzi block and the West Qinling orogenic zone. The East Kunlun Fault branches out into a horsetail structure which is formed by several branch faults. The 2017 Jiuzhaigou MS7.0 earthquake occurred in the horsetail structure of the East Kunlun Fault and caused huge casualties. As one of several major faults that regulate the expansion of the Tibetan plateau, the complexity of the deep extension geometry of the East Kunlun Fault has also attracted a large number of geophysical exploration studies in this area, but only a few are across the Jiuzhaigou earthquake region. Changes in pressure or slip caused by the fluid can cause changes in fault activity. The presence of fluid can cause the conductivity of the rock mass inside the fault zone to increase significantly. MT method is the most sensitive geophysical method to reflect the conductivity of the rock mass. Thus MT is often used to study the segmented structure of active fault zones. In recent years MT exploration has been carried out in several earthquake regions and the results suggest that the location of main shock and aftershocks are controlled by the resistivity structure. In order to study the deep extension characteristics of the East Kunlun Fault and the distribution of the medium properties within the fault zone, we carried out a MT exploration study across the Tazang section of the East Kunlun Fault in 2016. The profile in this study crosses the Jiuzhaigou earthquake region. Other two MT profiles that cross the Maqu section of East Kunlun Fault performed by previous researches are also collected. Phase tensor decomposition is used in this paper to analyze the dimensionality and the change in resistivity with depth. The structure of Songpan-Ganzi block is simple from deep to shallow. The structure of West Qinlin orogenic zone is complex in the east and simple in the west. The structure near the East Kunlun Fault is complex. We use 3D inversion to image the three MT profiles and obtained 3D electrical structure along three profiles. The root-mean-square misfit of inversions is 2.60 and 2.70. Our results reveal that in the tightened northwest part of the horsetail structure, the East Kunlun Fault, the Bailongjiang Fault, and the Guanggaishan-Dieshan Fault are electrical boundaries that dip to the southwest. The three faults combine in the mid-lower crust to form a "flower structure" that expands from south to north. In the southeastward spreading part of the horsetail structure, the north section of the Huya Fault is an electrical boundary that extends deep. The Tazang Fault has obvious smaller scale than the Huya Fault. The Minjiang Fault is an electrical boundary in the upper crust. The Huya Fault and the Tazang Fault form a one-side flower structure. The Bailongjiang and the Guanggaishan-Dieshan Fault form a "flower structure" that expands from south to north too. The two "flower structures" combine in the high conductivity layer of mid-lower crust. In Songpan-Ganzi block, there is a three-layer structure where the second layer is a high conductivity layer. In the West Qinling orogenic zone, there is a similar structure with the Songpan-Ganzi block, but the high conductivity layer in the West Qinling orogenic zone is shallower than the high conductivity layer in the Songpan-Ganzi block. The hypocenter of 2017 MS7.0 Jiuzhaigou earthquake is between the high and low resistivity bodies at the shallow northeastern boundary of the high conductivity layer. The low resistivity body is prone to move and deform. The high resistivity body blocked the movement of low resistivity body. Such a structure and the movement mode cause the uplift near the East Kunlun Fault. The electrical structure and rheological structure of Jiuzhaigou earthquake region suggest that the focal depth of the earthquake is less than 11km. The Huya Fault extends deeper than the Tazang Fault. The seismogenic fault of the 2017 Jiuzhaigou earthquake is the Huya Fault. The high conductivity layer is deep in the southwest and shallow in the northeast, which indicates that the northeast movement of Tibetan plateau is the cause of the 2017 Jiuzhaigou earthquake. 相似文献
18.
Anomalous geomagnetic variations have been observed at all geomagnetic stations in South India and they have earlier been attributed to ocean and crustal conductors. The spectral character of induced variations indicate that, in addition to coastal effects and channelling of currents through the Palk Straits, there is a concentration of currents in a conducting body at deeper levels in the crust or mantle.Current thinking on crustal evolution and the influence of Precambrian lineaments on tectonism and mineralisation up to recent times, provides support for the conjecture that zones of high electrical conductivity exist in the crust, which are related to tectonic and mineral influences. The Eastern Ghats and granulite terrain of South India and Sri Lanka are probably associated with such a zone of fundamental weakness in the crust. Extended graphite mineralisation along the Eastern Ghats, occurrence of economic graphite deposits near Trivandrum and in Sri Lanka and the association of alkaline and ultrabasic metallic minerals with deep faults in South India are indications of the possible chemical causes of high electrical conductivity in some regions of the crust.Similar relations between induced anomalous variations and tectonism and mineralisation in the Precambrian crystalline crust have been found in North America and Scotland. However, the regions of high electrical conductivity have not yet been mapped in detail in South India to confirm such a relationship. 相似文献
19.
近年来,随着对地震孕育背景和上地幔地球物理特性的研究,人们日益注意用地磁短周期异常来研究地壳和上地幔的电性结构。在我国继陈伯舫提出渤海地区西部地磁短周期异常并推测其下存在电导率异常后,徐文耀等人分析了甘肃东部的地磁短周期异常,也提出该区存在一东西向高导带。最近,祁贵仲等人利用渤海地区25个台站的地磁资料,进一 相似文献
20.
本文用磁场梯度法研究华北地区地幔高导层的埋藏深度.所用的 Sq 资料取自六个台站:大连、昌黎、北京、红山、泰安和西安.计算 C 值时用二次曲面法.为了解释本文的 Creal-T 曲线和|Cimag|-T 曲线,至少要假设地下是四层结构.最底层的电导率非常高,埋藏深度约为690km.中间可能有一夹层,电导率约为0.325S/m,厚约24.5km,其顶面的埋藏深度约为334km.上述结果只是初步的,其真实性还需更多的研究、证实.本区与我国东南地区的深部结构比较,差异很大,因此也需要研究其间是怎样变化过渡的. 相似文献