Fróðskaparrit - 01.01.1982, Page 49

Some Magnetotelluric Measurements on the Faeroe Islands 57
explained as a change of composition (see fig. 6), but we do
not here attempt to make a petrological interpretation.
The effect of partial melting on the upper mantle would
reduce the resistivity level, but the high sub-moho velocity
(Bott et al. 1974) found beneath the Faeroe Islands, does not
support this possibility. Also, the presence of a low resistivity
layer at the crust-mantle boundary found beneath Iceland
(Beblo and Bjørnsson, 1979) is not observed in our measure-
ments.
The results obtained for the high frequencies suggest pore
fluids as the main factor in controlling the resistivities at the
upper crust, but the few data and the 2- and 3-dimensionality
of the crust make interpretation very doubtful.
Acknowledgment: One of the authors (PHN) wants to thank
for support by a grant from Statens Naturvidenskabelige
Forskningsrád.
REFERENCES
Beblo, M. and A. Bjørnsson, 1978. Magnetotelluric investigation of the
lower crust and upper mantle beneath Iceland. J. Geophysics 45, 1—16.
Bott, M. H. P., P. H. Nielsen, and ]. Sunderland, 1976. Converted P-waves
originating at the continental margin between the Iceland-Faeroe Ridge
and the Faeroe Block. Geophys. J. R. astr. Soc. 44, 229—238.
Bott, M. H. P., ]. Sunderland, P. ]. Smith, U. Casten, and S. Saxov, 1974.
Evidence for continental crust beneath the Faeroe Islands. Nature 248,
202—204.
Haak, V., 1980. Relations between electrical conductivity and petrological
parameters of the crust and upper mantle. Geophysical Surveys 4, 57—69.
]ones, A. G., 1980. Geomagnetic Induction Studies in Scandinavia.
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Rasmussen, ]. and A. Noe-Nygdrd, 1969. Beskrivelse til Geologisk kort
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Rasmussen, T., P.H. Nielsen, L.B. Pedersen, 1981. Magnetotelluric mea-
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versity of Aarhus.
Weidelt, P., 1979. Principles of plane wave inversion. Lecture notes from
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physics, August 20—31, 1979.
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