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Inverse magnetic fabric in deformed limestones of the Morcles Nappe, Switzerland
Author(s) -
Ihmlé P. F.,
Hirt A. M.,
Lowrie W.,
Dietrich D.
Publication year - 1989
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/gl016i012p01383
Subject(s) - pyrrhotite , nappe , geology , remanence , magnetic susceptibility , magnetite , mineralogy , calcite , microprobe , hematite , goethite , magnetization , pyrite , chemistry , crystallography , tectonics , paleontology , physics , organic chemistry , adsorption , quantum mechanics , magnetic field
Anisotropy of magnetic susceptibility (AMS) was measured at 15 sites in deformed Helvetic limestones of the Morcles nappe in western Switzerland. Inverse magnetic fabrics, characterized by axes of maximum susceptibility subperpendicular to bedding or cleavage, were observed at four sites in the root zone of the nappe. Acquisition and thermal demagnetization of isothermal remanent magnetization show that the ferromagnetic mineralogy is dominated by pyrrhotite, with various proportions of magnetite, hematite and goethite. The matrix minerals were studied in thin section with a staining technique to distinguish different carbonates, by X‐ray texture goniometry and by microprobe analysis. Observations of AMS at room and liquid nitrogen temperatures, and of the temperature dependence of bulk susceptibility, lead to the conclusion that the inverse fabrics result from a paramagnetic component due to Fe 2+ ions in the calcite matrix.