Variation of Electrical Conductivity With Depth by the Magneto‐telluric Method

Niblett, E. R.; Sayn-Wittgenstein, Catherine

doi:10.1190/1.1438799

Cited by 117 publications

(46 citation statements)

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“…This approach is based on the maximum resistivity values for a depth of 200 km using the Niblett-Bostick transformation (e.g. Niblett and Sayn-Wittgenstein, 1960;Bostick, 1977). Coloured circles on top show kimberlite locations (red= diamondiferous, green= non-diamondiferous, and white= not defined or unknown.…”

Section: Discussionmentioning

confidence: 99%

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

Weckmann

2011

Surv Geophys

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The African continent inherits a long history of continental accretion and breakup. The stage of "making" a continent goes back to the Archean, when the first continental masses formed cratons which mostly remained stable ever since. Subsequent collision of weaker continental masses was followed by several extension and compression episodes that resulted in the formation of supercontinents. After the assemblage of Gondwana, a period of predominantly "breaking" , i.e. the breakup of supercontinents, took over. The modern day African continent exhibits different types of margins; continental rifting occurs side by side with recent collision. Since the late 1960's Magnetotelluric (MT) experiments have played an important role in studies of the electrical conductivity structure of Africa. The early results significantly shaped the MT community's understanding of continental scale conductivity belts and basic characteristics of cratons and mobile belts on both crustal and lithospheric mantle scale for some decades. Modern MT studies in Africa have generally supported earlier results with high resistivities observed on cratons and low resistivities observed across mobile belts. Advances in instrumentation, data processing and interpretation resulted in higher resolution images of the lithosphere which in consequence induce an improved understanding of tectonic processes and geological prerequisites for the occurrence of natural resources. The high electrical conductivity of mobile belts and their relation to reactivated fault and detachment zones were often interpreted to characterize mobile belts as tectonic weak zones, which can accommodate stress and constitute zones along which continents can break. Recent breaking of the African continent can be studied on land across the East African rift; however, the lack of amphibian MT experiments across today's margins does not allow for good resolution of remnants of continental break-up processes. Naturally, the regions and the focus of the MT studies in Africa are diverse, but they all contribute to the story of making and breaking a continent.

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Section: Discussionmentioning

confidence: 99%

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

Weckmann

2011

Surv Geophys

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“…The MT work was carried out by field parties from the Observatory's Division of Geomagnetism in Ottawa and Victoria. Apart from the stations discussed in this paper, the map includes the early GDS profile of Hyndman (1963), the permanent magnetic observatories in this area (Victoria, Newport, Meanook), and the MT stations at Meanook (Niblett and Sayn-Wittgenstein, 1960), Vulcan (Vozoff and Ellis, 1966), and Victoria (Carer and Auld, 1968). Other MT stations in Alberta are not shown, mainly because their period range was inadequate for upper mantle resolution.…”

Section: Introductionmentioning

confidence: 99%

Electrical Conductivity Structure in Western Canada and Petrological Interpretation

Caner

1970

J. geomagn. geoelec

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An integrated approach using both geomagnetic depth-sounding (GDS) and magnetotellurics (MT) is applied to the determination of the electrical conductivity structure in western Canada; 42 GDS stations and 6 broad-band MT stations are used. These data are combined with other geophysical information to provide self-consistent petrological models. Excluding geochemically improbable solutions, it can be shown that: a) temperatures at depth 35km must be at least 750C in the entire western region (eastwards extent undefined); b) in a smaller, sharply defined, region (eastern boundary within about +50 km of the Rocky Mountain Trench) the lower crust and possibly uppermost 10-25km of the mantle are hydrated, probably with partial melting.

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“…A criterion used in selecting magnetic events was that the vertical cDmponent must be less than the horizontal component. The use Df the strong inequality of Niblett and Sayn-Wittgenstein (1960) that the vertical be much less than the horizontal component, would have left too few examples in the periDd examined. Short period events also usually had a significant vertical component which could arise from the land-sea cDnductivity distribution as well as an inhomDgeneous source field.…”

Section: Discussionmentioning

confidence: 99%

Magneto-telluric results from Scott Base

Gill

1971

New Zealand Journal of Geology and Geophysics

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The amplitude ratio E/B for the earth current and magnetic variations at Scott Base has been determined over the period range of 30s to 30,000s. The distortion of the electric field by the land and sea in the neighbourhood of Scott Base is estimated and an equivalent E/B curve is derived for a horizontally uniform medium. A magnetotelluric interpretation of this curve gives the thickness of the poorly conducting outer layer of the earth as 100 km, but other evidence suggests that this is an underestimate.

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Variation of Electrical Conductivity With Depth by the Magneto‐telluric Method

Cited by 117 publications

References 0 publications

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

Electrical Conductivity Structure in Western Canada and Petrological Interpretation

Magneto-telluric results from Scott Base

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