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Magnetic viscosity of some doleritic basalts in relation to the interpretation of the oceanic magnetic anomalies
Author(s) -
Smith Brigitte M.
Publication year - 1984
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl011i003p00213
Subject(s) - basalt , geology , magnetization , remanence , dike , ridge , viscosity , geophysics , magnetic field , petrology , geochemistry , physics , paleontology , thermodynamics , quantum mechanics
The growth of induced magnetization (VIM) with time t, in a .5 Oe acquisition field, followed by subsequent decrease in zero field of the viscous remanent magnetization (VRM) with time t' was investigated, at room temperature for 5 oceanic doleritic basalts, and at temperature up to 105°C for 1 dike sample. Both VIM acquisition and VRM decay are enhanced by increasing temperature and time. However, the growth and decay do not uniformly obey a log t law on an experimental time of 2 hours. The results show that, far from the ridge axes, at the bottom of oceanic pillow layer (2A) and in the upper part of the dike layer (2B) the induced magnetization might largely dominate the remanent one, while only a small fraction of the primary TRM, corresponding to the highest blocking temperatures T B , would be preserved, the partial TRM corresponding to the lowest T B having been replaced by a viscous magnetization. Consequently, the doleritic basalts would rarely, if ever, contribute to oceanic magnetic anomalies.