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Summary: Journal of the Geological Society, London, Vol. 149, 1992, pp. 373-381, 10 figs, 4 tables. Printed in Northern Ireland
Geophysical investigation of the HonningsvHg igneous complex,
Scandinavian Caledonides
T.H.TORSVIK', 0. OLESEN',A.TRENCH's4,T. B . ANDERSEN2,
H. J . WALDERHAUG3 & M.A.SMETHURST'
'Geological Survey of Norway, PB 3006 Lade N-7002 Trondheim, Norway
21nstitute of Geology, University of Oslo, PB 1047 0316 Blindern, Oslo 3, Norway
'Institute of Solid Earth Geophysics, University of Bergen N-5014 Bergen, Norway
4Present address: Department of Geology, University of Western Australia, Nedlands, Perth, 6009, Australia
Abstract: The Honningsvag igneous complex within the Magerery nappe, northern Norway, has marked
magnetic and gravimetric signatures. Palaeomagnetic studies reveal a Siluro-Devonian (Scandian) dual-
polarity remanence (NEand up-SW and down; mean declination = 045", inclination = -38" and ag5=
8.4"). Rock-magnetic and petrological studies indicate a puremagnetite host for the remanent magnetiz-
ation component. Magnetic-fabric ellipsoids delineate D1 and D2 Scandian structures affecting the area,
and demonstrate an internal reclined fold-structure of the Honningsvig igneous complex. Forward-
modelling demonstrates that a short-wavelength, positive aeromagnetic anomaly (c. 700nT) over the
northwestern part of the complex is associated with an area of reverse remanent polarity(SW and down).
Conversely, areas of normal remanence polarity (NE and upmost common) areassociated with magnetic
'lows' or 'quiet' zones. The gravity field in the vicinity of the complex displays a symmetrical positive
anomaly of approximately 200 g.u. (wavelength 15 km). This can be attributed to a density contrast of
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