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Behavior of oceanic crustal magnetization at high temperatures: Viscous magnetization and the marine magnetic anomaly source layer
Author(s) -
Bowles Julie A.,
Johnson H. Paul
Publication year - 1999
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 - 10.1029/1999gl900541
Subject(s) - geology , magnetization , basalt , dike , magnetic anomaly , remanence , gabbro , geophysics , demagnetizing field , oceanic crust , crust , rock magnetism , petrology , geochemistry , magnetic field , seismology , subduction , physics , quantum mechanics , tectonics
Although the source layer for marine magnetic anomalies has been assumed to be the extrusive basalts of uppermost ocean crust, recent studies indicate that lower crustal rocks may also contribute. Because the temperature at which magnetization of crustal rocks achieves long‐term stability is crucial to any source layer contribution, we undertook high‐temperature VRM (viscous remanent magnetization) experiments on samples of basalt, dike and gabbroic sections. Samples were heated at temperature intervals up to T c , while a magnetic field was applied for periods between 6 hours and 28 days. Results show that the dike and gabbro samples achieve maximum VRM acquisition near 250°C, well below the T c of 580°C. The basalt sample shows a peak at 68°C, also well below T c . Results of this pilot study indicate that the critical isotherm for stable magnetization acquisition is defined by the VRM behavior of the specific crustal section.