Crust and upper mantle electrical conductivity beneath the Yellowstone Hotspot Track

Geology ◽  
2012 ◽  
Vol 40 (5) ◽  
pp. 447-450 ◽  
Author(s):  
A. Kelbert ◽  
G. D. Egbert ◽  
C. deGroot-Hedlin
Keyword(s):  
Electrical Conductivity ◽  
Upper Mantle ◽  
Crust And Upper Mantle ◽  
Yellowstone Hotspot

scholarly journals Geoelectric heterogeneities of the Kerch iron ore basin

2021 ◽  
Vol 43 (5) ◽  
pp. 165-180
Author(s):  
I. Yu. Nikolaev ◽  
T. K. Burakhovych ◽  
A. M. Kushnir ◽  
Ye. M. Sheremet
Keyword(s):  
Electrical Conductivity ◽  
Upper Mantle ◽  
Iron Ore ◽  
Earth’S Crust ◽  
Crust And Upper Mantle ◽  
Near Surface ◽  
Low Resistivity ◽  
Kerch Peninsula ◽  
Mud Volcanism ◽  
Earth's Crust

The three-dimensional geoelectric model of the Earth’s crust and upper mantle of the Kerch Peninsula has been built for the first time based on the results of experimental observations of the Earth’s low-frequency electromagnetic field, carried out in 2007—2013 by the Institutes of the National Academy of Sciences of Ukraine. Its physical and geological interpretation and detailing of the near-surface part were carried out according to the data of the audiomagnetotelluric sounding method to study the deep structure of the Kerch iron ore basin. To the east of the Korsak-Feodosiya fault along the southern part of the Indolo-Kuban trough (in the north of the South Kerch and almost under the entire North Kerch zones), a low-resistance anomaly (ρ=1 Ohm∙m) was found at depths from 2.5 km to 12 km about 20 km wide. Its eastern part is located in the consolidated Earth’s crust and is galvanically connected with surface sedimentary strata, while the western part is completely in sedimentary deposits. The anomaly covers the territory of the Kerch iron ore basin and occurrences of mud volcanism. The characteristics of the upper part of the layered section of the Kerch Peninsula in the interval of the first hundreds of meters were obtained from the results of one-dimensional inversion of the audiomagnetotelluric sounding data (frequency range 8—4000 Hz). It is shown that the first 15 m of the section, corresponding to Quaternary deposits, have resistivity values up to 1 Ohm∙m. Below, in the Neogene sediments, the electrical resistance increases to values of 5 Ohm∙m and more. Both horizontally and vertically, the distribution of resistivity values has a variable character, manifesting as a thin-layered structure with low resistivity values. Possibly, such areas have a direct connection with the channel for transporting hummock material and gases. A connection is assumed between the low-resistivity thin-layered near-surface areas, a deep anomaly of electrical conductivity in the upper part of the Earth’s crust, and the likely high electrical conductivity of rocks at the depths of the upper mantle with iron ore deposits, as well as the manifestation of mud volcanism. The heterogeneity of the crustal and mantle highly conductive layers may indicate a high permeability of the contact zones for deep fluids.

Electrical Conductivity Structure of the Crust and Upper Mantle Beneath the Rhenish Massif

1983 ◽  
pp. 288-302 ◽  
Author(s):  
H. Jödicke ◽  
J. Untiedt ◽  
W. Olgemann ◽  
L. Schulte ◽  
V. Wagenitz
Keyword(s):  
Electrical Conductivity ◽  
Upper Mantle ◽  
Rhenish Massif ◽  
Crust And Upper Mantle ◽  
Conductivity Structure

Electrical conductivity of omphacite and garnet in eclogite: implications for water recycling in the mantle

2020 ◽  
Author(s):  
Hanyong Liu ◽  
Xiaozhi Yang
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Deep Water ◽  
Upper Mantle ◽  
Critical Role ◽  
High Resistivity ◽  
Water Recycling ◽  
Structural Water ◽  
Crust And Upper Mantle ◽  
Water Contents

<p>Eclogite is an important constituent of subduction slabs and plays a critical role in transporting surface materials (e.g., water) into the deep Earth. Eclogite consists mainly of omphacite and garnet. Although nominally anhydrous, omphacite and garnet contain some amount of structural water (OH) in the lattice, which is up to >1500 ppm wt. H<sub>2</sub>O. This is virtually the highest content in nominally anhydrous minerals (NAMs) derived from the crust and upper mantle (Ingrin and Skogby, 2000). The electrical property of NAMs is very sensitive to water content and a small amount of water could dramatically enhance the conductivity. Thus, laboratory measured conductivity data of omphacite and garnet may help to understand the deep water recycling by eclogitized slab.</p><p>In this study, we have systemically determined the conductivity of omphacite and garnet with different water contents. The experiments were carried out at 350-800 °C, 1 GPa (note that the effect of pressure itself on conductivity is very small) and Ni-NiO buffered conditions. The data show that the conductivity of both omphacite and garnet increases with water content or temperature. The bulk conductivity is then modeled for different mineral compositions and water contents over a range of conditions (Liu et al., 2019). In combination with the geophysically documented high resistivity of the crustal part in deep subducted slabs, we suggest that the water content in omphacite and garnet in the deep-subducted eclogites should not be high at mantle depths. This provides new insights into the deep water recycling by subducted eclogites.</p><p> </p><p><strong>References:</strong></p><p>Ingrin, J., and Skogby, H., 2000, Hydrogen in nominally anhydrous upper-mantle minerals: Concentration levels and implications: European Journal of Mineralogy, 12, 543–570.</p><p>Liu, H., Zhu, Q., and Yang, X., 2019, Electrical conductivity of OH-bearing omphacite and garnet in eclogite: the quantitative dependence on water content: Contributions to Mineralogy and Petrology, 174, doi:10.1007/s00410-019-1593-3.</p><p></p><p></p><p></p><p></p>

scholarly journals The response of the local geomagnetic field to geodynamic processes during the preparation of the 1988 Spitak earthquake

2020 ◽  
Author(s):  
А.Г. Григорян ◽  
Д.А. Лиходеев
Keyword(s):  
Electrical Conductivity ◽  
Physical Properties ◽  
Upper Mantle ◽  
Geomagnetic Field ◽  
Power Plants ◽  
External Source ◽  
Crust And Upper Mantle ◽  
Strong Earthquakes ◽  
The Earth ◽  
Geodynamic Processes

Актуальность работы. Изучение изменений локального геомагнитного поля с целью выявления предвестников сильных землетрясений, особенно в сейсмоактивных регионах, где расположены большие города и объекты особо важного значения (АЭС, водохранилище и т.п.) остается одной из главных задач современной науки. В разных странах мира, используя магнитометрические методы, проводятся исследования по поиску предвестников сильных землетрясений. Цель. Однако, за первую половину XX века, несмотря на отдельные попытки ученых Японии и других стран, серьезных результатов достичь не удалось. Установлено, что с развитием геодинамических процессов в земной коре, особенно при подготовке сильных землетрясений, происходят изменения в магнитных свойствах горных пород (электропроводности, диэлектрической и магнитной проницаемости). Геомагнитные вариации, создаваемые внешним источником, несут в себе важную информацию об изменениях в физических свойствах в земной коры и верхней мантии, а так же позволяют оценить эти изменения. Методы. Представлена методика, которая позволяет с помощью изучения вариаций локального геомагнитного поля, создаваемых внешним источником, выявить изменения в электропроводности на разных глубинах земной коры и верхней мантии, связанные с развитием геодинамических процессов. С этой целью использован расчетный параметр N(A), который является отношением амплитуд вариаций геомагнитного поля внешнего происхождения, измеренных синхронно на разных парах станций. Изучены вариации с периодами 1025, 3060 минут и Sq-вариации. Метод применяется в низкоширотных областях Земли, где вариации переменного геомагнитного поля хорошо выделяются. Результаты. Используя предлагаемую методику, на территории Армении были выявлены аномальные изменения локального отклика геомагнитного поля перед Парванийским 1986 г. (М5,4) и Спитакским 1988 г. (М7,0) землетрясениями. Предполагается, что причинами изменений в физических свойств геологической среды в частности электропроводности, являются дегазация Земли и вертикальная фильтрация флюидов в верхние слои земной коры Relevance. The study of local geomagnetic field changes in order to identify harbingers of strong earthquakes, especially in seismically active regions where large cities and especially important objects (nuclear power plants, a storage reservoir, etc.) are located remains one of the main tasks of modern science. In different countries studies are being conducted to search for precursors of strong earthquakes, using magnetometric methods. Aim. However, for the first half of the 20th century, despite some attempts by scientists from Japan and other countries, no serious results were obtained. It has been established that with the progress of geodynamic processes in the earths crust, especially during the preparation of strong earthquakes, changes in the magnetic properties of rocks (electrical conductivity, dielectric and magnetic permeability) occur. However, geomagnetic variations created by an external source carry important information about changes in physical properties, in particular, electrical conductivity in the earths crust to the upper mantle, and make it possible to evaluate these changes. Methods. A technique that allows to identify changes in electrical conductivity at different depths of the earths crust and upper mantle associated with the development of the geodynamic process, using the study of local geomagnetic field variations created by an external source, is presented. For this purpose, parameter N(A), which is the ratio of the amplitudes of variations of the geomagnetic field of external origin, measured synchronously at different pairs of stations, was used. Variations with periods of 10-25, 30-60 minutes and Sq-variations were studied. The method is used in low latitude areas of the Earth, where variations of the variable geomagnetic field stand out well. Results. Anomalous changes in the local geomagnetic field were revealed in Armenia before the Parvania 1986 (M 5.4) and Spitak 1988 (M 7.0) earthquakes, using the proposed methodology. It is assumed that the causes of changes in the physical properties of the geological environment, in particular, electrical conductivity, are most likely to be the degassing of the Earth and the vertical filtration of fluids into the upper layers of the earths crust

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