Electrical Studies of the Crust and Upper Mantle

  1. John G. Heacock
  1. George V. Keller

Published Online: 15 MAR 2013

DOI: 10.1029/GM014p0107

The Structure and Physical Properties of the Earth's Crust

The Structure and Physical Properties of the Earth's Crust

How to Cite

Keller, G. V. (1971) Electrical Studies of the Crust and Upper Mantle, in The Structure and Physical Properties of the Earth's Crust (ed J. G. Heacock), American Geophysical Union, Washington D. C.. doi: 10.1029/GM014p0107

Author Information

  1. Department of Geophysics, Colorado School of Mines, Golden, Colorado 80401

Publication History

  1. Published Online: 15 MAR 2013
  2. Published Print: 1 JAN 1971

ISBN Information

Print ISBN: 9780875900148

Online ISBN: 9781118664049

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Keywords:

  • Crust and upper mantle;
  • Direct-current sounding;
  • Electrical conductivity;
  • Electromagnetic sounding;
  • Geomagnetic deep sounding method;
  • High-voltage direct-current (HVD);
  • Magnetotelluric soundings;
  • Schlumberger array

Summary

In recent years, there have been many efforts made to determine the profile of electrical conductivity through the crust and into the upper part of the mantle. A variety of techniques have been used, including direct-current resistivity soundings, geomagnetic deep soundings, magnetotelluric soundings, and electromagnetic soundings. As a result of the intricacies in the interpretation of the data obtained with each of the techniques, it is difficult to make generalizations about the variation in electrical conductivity in the crust from one geological province to another unless large volumes of data are considered. When such volumes are available, several consistencies in the behavior of electrical conductivity may be noted that appear to be in agreement with modem concepts of crustal mobility and plate tectonics. In tectonically active areas of the continents, most data indicate that conductivity increases to moderately high values, in the range from 0.01 to 0.1 mho/m, at depths between 50 and 100 km. In stable or nuclear continental areas, this increase is not so marked. In areas overlying subduction zones, the conductivity appears to be high through the crust and into the mantle. Where the crust is believed to be the most mobile, conductivity is highest. This increase in conductivity might be attributed to higher than normal temperatures, to the presence of higher than normal water contents, or to both factors. Either factor would also be expected to lower the viscosity of the rock in the upper mantle.