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1.
高温高压下地幔矿物岩石电导率影响因素研究进展 总被引：1，自引：0，他引：1
实验室高温高压条件下获得的地幔矿物岩石电导率值可以帮助获得地球内部物质组成、物质运动变化状态和解释地球物理探测资料.研究表明,电导率测量影响因素(外部因素和内部因素)控制不当将使得测量的电导率值产生较大差异.本文综述了近20年来这些影响因素对地幔矿物岩石电导率的影响程度及进展情况,电导率随着温度,铁含量和水含量的增加而增加;不含水条件下,电导率随着氧逸度和压力的增加分别增加和减小,含水条件下则恰恰相反;忽略颗粒边界的影响;测量频率和结晶方向对电导率的影响尚存在一定争议;进行电导率测量时有必要考虑系统平衡时间和样品中铁含量的流失.最后探讨了高温高压条件下电导率实验研究的不足和发展方向. 相似文献
2.
《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
3.
4.
为了建立具有普遍适用性的上地幔电性结构,本文利用Kawai-1000t压机和Solartron IS-1260阻抗/增益-相位分析仪,在4.0~14.0 GPa、873~1673 K的条件下,采用交流阻抗谱法（频率范围10-1~106Hz）测量了不含水的地幔岩电导率.实验结果显示,岩石的电导率随温度升高而大幅度的增大;在较大的温度范围内岩石的导电机制发生了变化,中低温时为小极化子导电,此时激活焓为0.94 eV （±0.13） eV,激活体积为0.11（±0.92） cm3·mol-1,高温时为和镁空穴相关的离子导电,此时激活焓为1.6~3.17 eV,激活体积为6.75（±7.43） cm3·mol-1;本次测量的电导率比低压下岩石的电导率要高,比矿物的电导率也要高.用本次的实验结果回归计算得到Fennoscandian地区的上地幔的一维电导率剖面,发现200 km以上本次实验计算的结果和大地电磁测深的电导率剖面吻合的比较好,在200 km以下本次实验得到的要比野外测量的电导率稍稍高一点,可能是因为实验过程中没有完全避免水的影响.本次的实验结果比用有效均匀介质方法计算得到的pyrolite矿物模型的电导率要高出两个数量级,这样的结果显示只用一种矿物的电导率或是几种矿物理论计算的结果有一定的不合理性. 相似文献
5.
《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
6.
介绍了地幔电性结构、地幔温度、地幔含水量等参数对地球动力学和地幔动力学过程的重要科学意义,综述了近年来利用海底电缆在该领域的主要研究进展.本文首先介绍了日本利用海底电缆探测地幔深部结构的方法原理与发展历程,然后阐述了该方法的观测方式、观测系统与仪器,综述了国际上近年来利用海底电缆在环太平洋地区海底的观测资料进行地幔一维电导率结构、三维电导率分布的研究进展.基于海底电缆的观测数据进行反演的结果表明,太平洋海域地区地球深部存在410 km,660 km的电导率不连续面,此不连续面与地震资料的波速不连续面基本一致,为地幔不连续面提供了新的地球物理证据.在根据由海底电缆观测数据反演得到的太平洋地区地球内部电导率分布基础上,综述了综合深部地震波速、岩石高温高压实验等,将电导率的分布转换为地球内部的温度场分布、推导地幔过渡带水的浓度进而转换为地幔过渡带的含水百分比(含水量)的方法技术与研究进展.研究结果表明,夏威夷和北日本海地幔过渡带电导率异常主要受温度控制,菲律宾海域地幔过渡带的电导率异常除了和温度有关外,还受含水量影响,该处地幔过渡带的含水量大约在1％左右.这些研究表明,海底电缆探测方法,在地球深部探测尤其是地幔不连续面的探测、地幔温度场分布与特征、地幔含水量等方面有重要的作用.最后,展望了海底电缆探测方法的研究与发展,这些研究方法及成果对认识中国海域地球内部机构提供一定的参考. 相似文献
7.
构成地幔的大部分名义上无水矿物,包括橄榄石及其同质异象体、辉石以及石榴石等,均可以羟基形式赋存一定量的水.水在地幔不同深度的出现不仅对一系列物理性质(包括密度、波速、熔融温度、电导率和流变强度等)有重要影响,并且对地幔的动力学行为、横向结构和成分的不均一性以及地球深部的演化过程具有重要意义.近年来,地震学研究在地幔不同深度和不同区域均发现低速带的存在,而观测到的地幔速度异常很可能与地幔中的水密切相关.高温高压矿物学利用实验和理论计算,对水是如何影响地幔主要构成矿物的弹性模量和波速进行了深入研究,并取得了大量进展.这些研究对正确理解地幔速度异常的形成机制,查明地幔中水的分布,探寻水在地球内部的迁移形式至关重要.本文针对近年来高温高压矿物学在地幔含水矿物弹性模量的研究成果进行了综述,介绍了该研究方向的进展和不足,并对未来的研究方向进行了阐述. 相似文献
8.
《中国科学:地球科学》2016,(3)
地幔深部的矿物具有显著的含水能力,含水量从几十到几万ppm(part per million)不等.由于地幔体积巨大,地球深部的水可能远大于地表水的总量.研究水在地幔矿物岩石晶体中的赋存机制及其影响是目前矿物学和地球物理学界的研究热点之一.一方面,俯冲板块向下运动,其中的蛇纹石在高温下分解,产生一系列的高含水硅酸盐矿物(如相A、粒硅镁石和斜硅镁石),这些矿物是潜在的"搬运工",将水进一步带入地幔深部,乃至转换带中;另一方面,橄榄石在转换带中的高压相(瓦兹利石和林伍德石)具有较高的储水能力,使得转换带成为了地球深部最重要的储水层,并且水也对地幔转换带的物理化学性质产生了显著影响.本文主要讨论以下两方面内容:(1)含水的硅酸盐矿物晶体结构,为微观上认识地球深部水的赋存机制和循环过程提供实验依据;(2)水对硅酸盐矿物热力学状态方程的影响,为约束地球动力学过程以及水的影响提供重要参数. 相似文献
9.
《地球物理学报》2020,(9)
为了建立具有普遍适用性的上地幔电性结构,本文利用Kawai-1000t压机和Solartron IS-1260阻抗/增益-相位分析仪,在4.0～14.0 GPa、873～1673 K的条件下,采用交流阻抗谱法(频率范围10~(-1)～10~6Hz)测量了不含水的地幔岩电导率.实验结果显示,岩石的电导率随温度升高而大幅度的增大;在较大的温度范围内岩石的导电机制发生了变化,中低温时为小极化子导电,此时激活焓为0.94 eV(±0.13)eV,激活体积为0.11(±0.92)cm~3·mol~(-1),高温时为和镁空穴相关的离子导电,此时激活焓为1.6～3.17 eV,激活体积为6.75(±7.43)cm~3·mol~(-1);本次测量的电导率比低压下岩石的电导率要高,比矿物的电导率也要高.用本次的实验结果回归计算得到Fennoscandian地区的上地幔的一维电导率剖面,发现200 km以上本次实验计算的结果和大地电磁测深的电导率剖面吻合的比较好,在200 km以下本次实验得到的要比野外测量的电导率稍稍高一点,可能是因为实验过程中没有完全避免水的影响.本次的实验结果比用有效均匀介质方法计算得到的pyrolite矿物模型的电导率要高出两个数量级,这样的结果显示只用一种矿物的电导率或是几种矿物理论计算的结果有一定的不合理性. 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.
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
12.
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
13.
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
14.
Electromagnetic Studies Of The Lithosphere And Asthenosphere 总被引：3，自引：0，他引：3
Graham Heinson 《Surveys in Geophysics》1999,20(3-4):229-255
In geodynamic models of the Earth's interior, the lithosphere and asthenosphere are defined in terms of their rheology. Lithosphere has high viscosity, and can be divided into an elastic region at temperatures below 350 °C and an anelastic region above 650 °C. Beneath the lithosphere lies the ductile asthenosphere, with one- to two-orders of magnitude lower viscosity. Asthenosphere represents the location in the mantle where the melting point (solidus) is most closely approached, and sometimes intersected. Seismic, gravity and isostatic observations provide constraints on lithosphere-asthenosphere structure in terms of shear-rigidity, density and viscosity, which are all rheological properties. In particular, seismic shear- and surface-wave analyses produce estimates of a low-velocity zone (LVZ) asthenosphere at depths comparable to the predicted rheological transitions. Heat flow measurements on the ocean floor also provide a measure of the thermal structure of the lithosphere.Electromagnetic (EM) observations provide complementary information on lithosphere-asthenosphere structure in terms of electrical conductivity. Laboratory studies of mantle minerals show that EM observations are very sensitive to the presence of melt or volatiles. A high conductivity zone (HCZ) in the upper mantle therefore represents an electrical asthenosphere (containing melt and/or volatile) that may be distinct from a rheological asthenosphere and the LVZ. Additionally, the vector propagation of EM fields in the Earth provides information on anisotropic conduction in the lithosphere and asthenosphere. In the last decade, numerous EM studies have focussed on the delineation of an HCZ in the upper mantle, and the determination of melt/volatile fractions and the dynamics of the lithosphere-asthenosphere. Such HCZs have been imaged under a variety of tectonic zones, including mid-ocean ridges and continental rifts, but Archaean shields show little evidence of an HCZ, implying that the geotherm is always below the mantle solidus. Anisotropy in the conductivity of oceanic and continental lithosphere has also been detected, but it is not clear if the HCZ is also anisotropic. Although much progress has been made, these results have raised new and interesting questions of asthenosphere melt/volatiles porosity and permeability, and lithosphere-upper mantle heterogeneity. It is likely that in the next decade EM will continue to make a significant contribution to our understanding of plate tectonic processes. 相似文献
15.
The electrical properties of rocks and minerals are controlled by thermodynamic parameters like pressure and temperature and
by the chemistry of the medium in which the charge carriers move. Four different charge transport processes can be distinguished.
Electrolytic conduction in fluid saturated porous rocks depends on petrophysical properties, such as porosity, permeability and connectivity
of the pore system, and on chemical parameters of the pore fluid like ion species, its concentration in the pore fluid and
temperature. Additionally, electrochemical interactions between water dipoles or ions and the negatively charged mineral surface
must be considered. In special geological settings electronic conduction can increase rock conductivities by several orders of magnitude if the highly conducting phases (graphite or ores)
form an interconnected network. Electronic and electrolytic conduction depend moderately on pressure and temperature changes,
while semiconduction in mineral phases forming the Earth’s mantle strongly depends on temperature and responds less significantly to pressure
changes. Olivine exhibits thermally induced semiconduction under upper mantle conditions; if pressure and temperature exceed
~ 14 GPa and 1400 °C, the phase transition olivine into spinel will further enhance the conductivity due to structural changes
from orthorhombic into cubic symmetry. The thermodynamic parameters (temperature, pressure) and oxygen fugacity control the
formation, number and mobility of charge carriers. The conductivity temperature relation follows an Arrhenius behaviour, while
oxygen fugacity controls the oxidation state of iron and thus the number of electrons acting as additional charge carriers.
In volcanic areas rock conductivities may be enhanced by the formation of partial melts under the restriction that the molten phase is interconnected. These four charge transport mechanisms must be considered
for the interpretation of geophysical field and borehole data. Laboratory data provide a reproducible and reliable database
of electrical properties of homogenous mineral phases and heterogenous rock samples. The outcome of geoelectric models can
thus be enhanced significantly. This review focuses on a compilation of fairly new advances in experimental laboratory work
together with their explanation. 相似文献
16.
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
17.
XinZhuan Guo 《中国科学:地球科学(英文版)》2016,59(4):696-706
Hydrous minerals are important water carriers in the crust and the mantle, especially in the subduction zone. With the recent development of the experimental technique, studies of the electrical conductivity of hydrous silicate minerals under controlled temperature, pressure and oxygen fugacity, have helped to constrain the water distribution in the Earth’s interior. This paper introduces high pressure and temperature experimental study of electrical conductivity measurement of hydrous minerals such as serpentine, talc, brucite, phase A, super hydrous phase B and phase D, and assesses the data quality of the above minerals. The dehydration effect and the pressure effect on the bulk conductivity of the hydrous minerals are specifically emphasized. The conduction mechanism of hydrous minerals and the electrical structure of the subduction zone are discussed based on the available conductivity data. Finally, the potential research fields of the electrical conductivity of hydrous minerals is presented. 相似文献
18.
Kiyoshi Baba 《Surveys in Geophysics》2005,26(6):701-731
This review paper presents recent research on electrical conductivity structure in various marine tectonic settings. In at
least three areas, marine electromagnetic studies for structural exploration have increasingly progressed: (1) data accumulations,
(2) technical advances both for hardware and software, and (3) interpretations based on multidisciplinary approaches. The
mid-ocean ridge system is the best-studied tectonic setting. Recent works have revealed evidence of conductive zones of hydrothermal
circulation and axial magma chambers in the crust and partial melt zones of the mid-ocean ridge basalt source in the mantle.
The role of water or dissolved hydrogen and its redistribution at mid-ocean ridges is emphasized for the conductivity pattern
of the oceanic lithosphere and asthenosphere. Regions of mantle upwelling (hotspot or plume) and downwelling (subducting slab)
are attracting attention. Evidence of heterogeneity exists not only in the crust and the upper mantle, but also in the mantle
transition zone. Electrical conductive zones frequently overlap seismic low-velocity zones, but discrepancies are also apparent.
Some studies have compared conductivity models with the results of seismic and other studies to investigate the physical properties
or processes. A new laboratory-based conductivity model for matured oceanic lithosphere and asthenosphere is proposed. It
takes account of both the water distribution in the mantle as well as the thermal structure. It explains observed conductivity
patterns in the depth range of 60–200 km. 相似文献
19.
在1.0 Pa、室温到880℃分别采用超声波透射法和阻抗谱法测量了斜长岩的纵波速度和电导率，并对实验产物进行了鉴定分析．结果表明，在680℃，由于斜长岩中的含水矿物绢云母和黝帘石发生脱水反应，岩石的纵波速度开始大幅度下降．在410℃～750℃、12～105 Hz的频率范围内，斜长岩只出现颗粒内部传导．由于脱水产生的自由水主要分布于矿物的三联点或颗粒拐角处，没有形成连通的高导性网络，因此，脱水作用不会导致斜长岩电导率显著增加，也不会改变其电传导机制．地球内部低速层和高导层的形成与演化可能具有非同步性，通过含水矿物脱水可以形成地球内部的低速层，但不一定同时形成高导层． 相似文献