Open AccessMagnetic Mineralogy and Petrophysical Properties of Ultramafic Rocks: Consequences for Crustal Magnetism
Author(s) -
Maat Geertje W.,
McEnroe Suzanne A.,
Church Nathan S.,
Larsen Rune B.
Publication year - 2019
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2018gc008132
Subject(s) - geology , petrophysics , ultramafic rock , rock magnetism , geochemistry , magnetism , petrology , mineralogy , magnetization , magnetic field , condensed matter physics , geotechnical engineering , porosity , physics , quantum mechanics , remanence
Magnetic properties from the Reinfjord Ultramafic Complex, in northern Norway, which formed as part of a deep magmatic conduit system, have been investigated to determine the magnetic signature of ultramafic rocks now exposed at the surface and deeper in the lower crust. The dominant carriers in these ultramafic rocks are a chrome‐spinel with Fe‐rich exsolution blebs and exsolution lamellae of magnetite in clinopyroxene. Except locally, in a fault zone and in discrete small fractures, these rocks show only minor to no alteration. We infer that the magnetic oxides characterized here are representative of pristine magnetic carriers in similar rocks deeper in the crust. These oxides can be stable in lower crustal, possibly upper mantle, depths when temperatures are below the Curie temperature of magnetite, taking into account pressure effects. These ultramafic rocks are candidates for potential sources of long‐wavelength anomalies.