Archaean cratonic roots, mantle shear zones and deep electrical anisotropy

THE extent to which the mantle participated in the growth and stabilization of ancient cratons is central to our understanding of the evolution of the continents 1 . The detection of seismic anisotropy beneath Precambrian North America, for example, has been interpreted as showing that strain-induce...

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Bibliographic Details
Published in:Nature (London) 1995-05, Vol.375 (6527), p.134-137
Main Authors: Mareschal, M, Kellett, R. L, Kurtz, R. D, Ludden, J. N, Ji, S, Bailey, R. C
Format: Article
Language:English
Subjects:
Anisotropy
Earth sciences
Earth, ocean, space
Electromagnetism
Evolution
Exact sciences and technology
Geology
Geophysics: general, magnetic, electric and thermic methods and properties
Humanities and Social Sciences
Internal geophysics
letter
multidisciplinary
Plate tectonics
Science
Science (multidisciplinary)
Tectonics. Structural geology. Plate tectonics
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Summary:THE extent to which the mantle participated in the growth and stabilization of ancient cratons is central to our understanding of the evolution of the continents 1 . The detection of seismic anisotropy beneath Precambrian North America, for example, has been interpreted as showing that strain-induced orientation of mantle minerals in subcontinental lithospheric mantle can preserve a record of ancient episodes of deformation 2 . Here we present mag-netotelluric measurements from the Superior Province of the Canadian shield, which reveal pronounced electrical anisotropy in the upper 100 km of the underlying mantle. We argue that this anisotropy is best explained by conducting graphite films, oriented within fractures or on grain boundaries, and associated with metasomatism of the mantle roots of major Archaean shear zones which transect the entire Superior Province. The uppermost mantle beneath the Canadian shield has therefore remained fixed to the crust and isolated from significant tectonic reworking since the late Archaean.
ISSN:0028-0836
1476-4687
DOI:10.1038/375134a0