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1.
电导岩石学:原理、方法和进展 总被引：2，自引：0，他引：2
杨晓志 《中国科学:地球科学》2014,(9):1884-1900
电导岩石学是国际地学界近年来新发展起来的一门交叉性和综合性很强的学科,主要是通过高温高压实验,在有效控制温度、压强、成分和氧逸度等参数的条件下,对硅酸盐矿物的电导率进行测定,并把有关结果和地球物理学电磁探测的结果相比较,从而为正确认识地球深部的组成、结构、性质和动力学过程提供制约.根据近年来的文献报道,本文综合评述了电导岩石学研究工作的主要原理和方法,并就下地壳、上地幔、地幔过渡带、下地幔和核幔边界一些主要组成矿物电导率的实验测定进展及其对深部地球电导结构的制约进行了介绍. 相似文献
2.
我们至今仍未有一个全球电导率分布可以作为一个标准曲线来代表足够接近于全球平均值的分布曲线。大陆大地电磁法的结果显示随深度变化的电导率具有很大的分散性。其原因与地方性的性质情况有关。近年来的海洋大地电磁研究也增加了洋底电导率的可变性。这些结果表明海洋下面的地幔总的平均电导率分布与其大陆下面相对应的分布相差不大。运用日变化和磁暴时变化所做的新的工作一般都证实了以前的估计。1000公里深处的电导率约接近1s/m。1969年发生的长期变化的“颠簸”提供了重新评估下地幔电导率的资料。一致的意见是地幔底部的电导率约接近100s/m。 相似文献
3.
上地幔热结构的研究对探索地球内部物质状态和岩石圈形成演化过程,评估自然资源的存储状况,监控火山区岩浆活动从而降低自然灾害风险等有着重要的意义.本文概述了基于不同岩石物理学高温高压实验得到的上地幔矿物电导率-温度关系.通过分析并对比前人的实验结果,讨论了不同实验得到的同一矿物的电导率-温度经验关系中参数差异产生的原因.大地电磁测深法(MT)以其探测深度大,受浅部高阻体影响较小且对低阻体分辨率较高等特点,在研究壳幔电性结构、热状态和地球动力学机制中得到了广泛的应用.以MT得到的上地幔电阻率模型为基础,结合岩石物理学实验标定的矿物电导率-温度经验关系,建立上地幔的温度和熔融百分比模型,这项工作在研究上地幔热状态中起着不可或缺的作用.笔者总结并讨论了前人以MT方法获得电性结构为基础,利用电导率-温度经验关系评价上地幔热状态的应用实例,并对未来的研究工作做了展望,同时对其可行性做了评估. 相似文献
4.
《中国科学:地球科学》2017,(5)
高温高压电导率实验研究是透视地球内部结构与物质组成的一个重要窗口.百年来进行了大量地幔矿物电导率的研究,但对地幔岩石的研究却不足;进行了压力对地幔矿物电导率影响的研究,但获得的激活体积值却有正有负;进行了含水橄榄石电导率的测量,但仍存在干湿软流圈地幔之争;进行了部分熔融岩石电导率的研究,但对异常高导成因的解释却仍没有定论.因为该研究对人们认识地幔的物质组成和矿物相变,地幔的电性结构和热结构,以及洋壳俯冲和高导异常成因等地幔动力学问题有重大意义,因此,还需继续研究地幔岩石、矿物的电导率与温度、压力、氧逸度和组分等之间的关系,再结合地球物理的探测结果,构建合理的电导率-深度剖面图. 相似文献
5.
计算了对应于各个ＵＴ小时的２４个经度带的Ｓq地下感应场对外部施感场的响应函数，应用Ｓｃｈｍｕｃｋｅｒ＇ｓＡｐｐｒｏｘｉｍａｔｅＥｕｒｉｓｔｉｃ反演方法，计算了这些经度带的地下等效层及其电导率分布，得到了地壳－上地幔电导率经向分布的大致图案。对该结果的分析研究得出，全球电导率经向分布存在着极大的不均匀性，在０－４００ｋｍ深度范围内，太平洋和大西洋为低导区；欧亚大陆与美洲大陆为高导区。电导率分布特征与岩石层结构有明显的相关性：在俯冲带，低导区由海洋向大陆下插入；在大洋中脊表现为高导电性。反演结果与地震层析成像结果的比较表明，地下高电导区和低电导区的位置分别对应于地震波低速区和高速区。 相似文献
6.
《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
7.
研究由几种导体成分掺杂的混合物的整体电导率.对欧姆定律求平均,得到混合物电导率定义.对电流连续性方程求平均,得到混合物中电场增量方程.求电场增量方程在同种成分上的平均,并结合混合物电导率定义,得到混合物电导率公式.现有的三种混合物结构下电导率公式（电导率串联公式、并联公式和整体各向同性混合物电导率公式）都是混合物电导率公式的特例.进一步分析得出结论,混合物整体电导率是各成分电导率与整体电导率结构并联后的体积串联. 相似文献
8.
唐山地震与青光地磁台转换函数的时间变化 总被引：1，自引：0，他引：1
一、前言对唐山地震期间青光台的地磁短周期变化进行了分析,目的是检验在唐山地震前是否由于应力活动使地下物质的电导性质发生变化,为今后用地磁预报地震的工作探索一条途径。地球电离层、磁层外场引起的地磁短周期变化,可以反映地壳及上地幔的电磁性质-电导率的状态,或与之有关的水及热流的活动状态,这些状态可能和震前膨胀有关。本世纪初人们就用地磁短周期变化探查地壳及上地幔电导率的空间变化,研究地下 相似文献
9.
为了探讨地幔岩模型和苦橄质榴辉岩模型在上地幔存在的合理性,建立上地幔的电性结构,本文利用YJ-3000t紧装式六面顶压机和Solartron IS-1260阻抗/增益-相位分析仪,在1.0~4.0GPa、700~1150℃的条件下,采用交流阻抗谱法(频率范围10-1~106 Hz)分别测量了地幔岩和苦橄质榴辉岩的电导率.实验结果表明:随着温度的升高,地幔岩和苦橄质榴辉岩的电导率大幅增加;随着压力的增大,地幔岩的电导率略有增加,活化体积ΔV为-4.73cm3·mol-1,而苦橄质榴辉岩的电导率几乎没有变化,活化体积ΔV为-0.11cm3·mol-1;在电性方面,用苦橄质榴辉岩来表示深部的物质较为合理,地幔岩解释浅部可能更恰当,但浅部物质的分布不均匀,电导率随深度的变化主要受控于温度的影响,其次才是成分. 相似文献
10.
这篇文章给出了内蒙、甘肃、宁夏某些地区的大地电磁测深结果。这些结果显示出,在地震带内地壳和上地幔电导率分布的横向变化是很明显的,而在比较稳定的鄂尔多斯地台内电导卑分布的横向变化较小,地壳和上地幔的电导率结构比较简单。基于这些结果发现,上部地壳(10—15公里)低阻层在大震震中区较为发育,这可能与大震有关。我国西北地区已有的大地电磁测深结果显示出,莫霍面並不是一个清楚的电性分界面,而某些地区的地壳中部低阻层似乎与康拉界面相应,这就使得后者成为一个明显的电性分界面。 相似文献
11.
Kenji Ohta Kei Hirose Masahiro Ichiki Katsuya Shimizu Nagayoshi Sata Yasuo Ohishi 《Earth and Planetary Science Letters》2010,289(3-4):497-502
The electrical conductivities of natural pyrolitic mantle and MORB materials were measured at high pressure and temperature covering the entire lower mantle conditions up to 133 GPa and 2650 K. In contrast to the previous laboratory-based models, our data demonstrate that the conductivity of pyrolite does not increase monotonically but varies dramatically with depth in the lower mantle; it drops due to high-spin to low-spin transition of iron in both perovskite and ferropericlase in the mid-lower mantle and increases sharply across the perovskite to post-perovskite phase transition at the D″ layer. We also found that the MORB exhibits much higher conductivity than pyrolite. The depth–conductivity profile measured for pyrolite does not match the geomagnetic field data below about 1500-km depth, possibly suggesting the existence of large quantities of subducted MORB crust in the deep lower mantle. The observations of geomagnetic jerks suggest that the electrical conductivity may be laterally heterogeneous in the lowermost mantle with high anomaly underneath Africa and the Pacific, the same regions as large low shear-wave velocity provinces. Such conductivity and shear-wave speed anomalies are also possibly caused by the deep subduction and accumulation of dense MORB crust above the core–mantle boundary. 相似文献
12.
采用远参考道和Robust技术,处理了华北地区14个地磁台站资料,得到了相干度超过0.8的地磁测深响应函数.并将其转换为大地电磁测深的响应函数,获取了105~107 s周期范围内的视电阻率和相位.应用ρ+理论对数据进行了一致性检验和反演,结果表明417km,850km深度附近可能存在电性间断面.同时采用基于一维最光滑模型的Occam反演方法得到了300~1000km范围的地幔电性结构,并与前人在其他地区的研究结果进行了对比.发现华北地区地幔过渡带的电导率在大兴安岭—太行山重力梯度带东西两侧表现不同,重力梯度带附近及西侧台站下方过渡带深度的电导率和北美的Tucson地区相当,而华北地区东部的电导率在地幔过渡带范围高出西侧约2~5倍,这很可能和太平洋板块的俯冲有关. 相似文献
13.
Takashi Yoshino 《Surveys in Geophysics》2010,31(2):163-206
Electrical conductivity structures of the Earth’s mantle estimated from the magnetotelluric and geomagnetic deep sounding
methods generally show increase of conductivity from 10−4–10−2 to 100 S/m with increasing depth to the top of the lower mantle. Although conductivity does not vary significantly in the lower
mantle, the possible existence of a highly conductive layer has been proposed at the base of the lower mantle from geophysical
modeling. The electrical properties of mantle rocks are controlled by thermodynamic parameters such as pressure, temperature
and chemistry of the main constituent minerals. Laboratory electrical conductivity measurements of mantle minerals have been
conducted under high pressure and high temperature conditions using solid medium high-pressure apparatus. To distinguish several
charge transport mechanisms in mantle minerals, it is necessary to measure the electrical conductivity in a wider temperature
range. Although the correspondence of data has not been yet established between each laboratory, an outline tendency of electrical
conductivity of the mantle minerals is almost the same. Most of mineral phases forming the Earth’s mantle exhibit semiconductive
behavior. Dominant conduction mechanism is small polaron conduction (electron hole hopping between ferrous and ferric iron),
if these minerals contain iron. The phase transition olivine to high-pressure phases enhances the conductivity due to structural
changes. As a result, electrical conductivity increases in order of olivine, wadsleyite and ringwoodite along the adiabat
geotherm. The phase transition to post-spinel at the 660 km discontinuity further can enhance the conductivity. In the lower
mantle, the conductivity once might decrease in the middle of the lower mantle due to the iron spin transition and then abruptly
increase at the condition of the D″ layer. The impurities in the mantle minerals strongly control the formation, number and
mobility of charge carriers. Hydrogen in nominally anhydrous minerals such as olivine and high-pressure polymorphs can enhance
the conductivity by the proton conduction. However, proton conduction has lower activation enthalpy compared with small polaron
conduction, a contribution of proton conduction becomes smaller at high temperatures, corresponding to the mantle condition.
Rather high iron content in mantle minerals largely enhances the conductivity of the mantle. This review focuses on a compilation
of fairly new advances in experimental laboratory work together with their explanation. 相似文献
14.
Shun-ichiro Karato 《Earth and Planetary Science Letters》2011,301(3-4):413-423
Various methods for inferring the water distribution in Earth's mantle are reviewed including geochemical and geophysical methods. The geochemical approach using the water contents of basalts shows that the water content in the source regions of ocean island basalt is generally larger than that of the source region of mid-ocean ridge basalt, but the location of the source regions of ocean island basalts is poorly constrained. Geophysical approaches have potential of providing constraints on the spatial distribution of water but their usefulness depends critically on the sensitivity of geophysical observations to water content relative to other factors, in addition to the resolution of geophysical observations. Existing experimental data on the influence of water on seismologically observable properties and on electrical conductivity are reviewed. Frequently used seismological observations such as the anomalies in seismic wave velocities and of the topography on the mantle discontinuities are only weakly sensitive to water content but more sensitive to other factors such as the major element chemistry and temperature for a typical range of water contents. In contrast, electrical conductivity is highly sensitive to water content and only modestly sensitive to other factors such as temperature, oxygen fugacity and major element chemistry. Models of electrical conductivity–depth profiles are constructed where the influence of hydrogen and iron partitioning among coexisting minerals and of the depth variation in oxygen fugacity are incorporated. It is shown (i) that the electrical conductivity varies more than two orders of magnitude for a plausible range of water content in the mantle (~ 10 ppm wt to ~ 1 wt.%) and (ii) that if water content is constant with depth, there will be a drop in electrical conductivity at ~ 410-km. Although the resolution is not as high as seismological observations, geophysically inferred electrical conductivity distributions generally show higher conductivity in the mantle transition zone than the upper mantle, suggesting that the water content in the transition zone is higher than that in the upper mantle with some lateral variations. Implications of inferred water distribution are discussed including the possible partial melting near 410-km and its role in global water circulation. 相似文献
15.
Recent inversions of electrical profiles of the upper mantle beneath the oceans permit a variety of conductivity-depth profiles ranging from models with monotonically increasing conductivity to layered models having decreases of conductivity with depth. Laboratory data on possible mantle materials can physically explain high mantle conductivities in terms of a fluid phase (partial melt, hydrous fluid) or a good solid conductor (amorphous or graphitic carbon) and favor a profile having a high conductivity layer (HCL) underlain by a more resistive layer. 相似文献
16.
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
17.
以岩石实验中矿物的几何形态及空间分布为建模依据,以实验条件及单矿物电导率的测量结果为约束条件,用有限元数值方法模拟了不同微观结构的斜长石、辉石混合物在施加电压后电势及电流的分布情况,并计算了混合模型在不同温度条件下的电导率.研究结果显示,数值模型网格数及矿物颗粒数的选取对电导率计算结果的精度有较大影响,在体导电情况下,模型电导率因矿物比例含量和排列结构而异.当斜长石及辉石随机分布时,随着辉石含量的增加,混合模型电导率在不同温度下均有所增加,且温度越高,增加幅度越大,电导率的有限元模拟计算结果接近于有效介质渗透理论模型,且位于并、串联模型之间以及HS模型的上、下边界范围内;在斜长石及辉石含量一定的情况下,各矿物的排列分布对电导率计算结果也有一定的影响,当矿物颗粒大小接近且分布均匀时,模型中电势沿电流传导方向变化较为均匀,模拟计算得出的电导率相对较高,当矿物颗粒大小差别较大及分布不均匀时,电势分布受到一定的扰动,电导率计算结果也较低.将混合模型电导率有限元计算结果与辉长岩、辉绿岩及玄武岩实验测量结果进行比较,显示这3种岩石样品电导率与温度变化关系的斜率均与混合模型计算结果的斜率相接近,表明这些岩石在所选温度段导电机制与斜长石、辉石混合模型相似,用斜长石、辉石混合模型的电导率研究玄武岩、辉长岩及辉绿岩的导电性具有适用性.将混合模型有限元计算结果与玄武岩、辉长岩、辉绿岩覆盖区地壳大地电磁实测结果对比,发现大地电磁电导率结果位于混合模型计算结果范围内,用斜长石、辉石混合模型模拟玄武岩、辉长岩等岩石地壳具有一定的可行性. 相似文献
18.
The studies on the physical properties of minerals and rocks in combination with the work in petrology, mineralogy and geochemistry are not only a useful mean to look into the composition and structure of the earth抯 interior, but also can provide extreme… 相似文献
19.
Harve S. Waff 《Surveys in Geophysics》1980,4(1-2):31-41
This paper examines the constraint placed by electrical conductivity on physical conditions existing within the mantle. Determination of bulk electrical conductivities of multiphase materials from knowledge of individual phase conductivities and their relative fractions is discussed in the light of recent studies of the equilibrium phase geometries of partial melts. It is concluded that existing models which are based on assumed geometries offer little refinement over Hashin-Shtrikman variational bounds. The possible effects of the gravitational field on phase geometry in partial melts and the resulting conductivity anisotropy are considered. At this time it appears that minimum melt fractions can be safely estimated from a knowledge of Earth conductivity combined with laboratory data on melt and crystalline conductivities and the Hashin-Shtrikman upper bound. The question of whether or not the asthenosphere corresponds to a zone of partial melting is also addressed. 相似文献