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| Titel |
Quantifying gyroremanent magnetization in greigite-bearing sediments |
| VerfasserIn |
Karl Fabian, Thomas Frederichs |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055550
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| Zusammenfassung |
| The occurence of a gyroremanent magnetization (GRM) in sediments typically
indicates the presence of greigite (Fe3S4). It is commonly observed that during AF
demagnetization of greigite-bearing sediments the NRM first decreases and then
apparently increases again at higher demagnetization levels (> 40Â mT) due to
the generation of a gyroremanent component. To diminish this effect the NRM
components may be measured repeatedly after demagnetization of each single direction.
This method has been implemented in the automated 2G cryogenic magnetometer
at the University of Bremen, such that NRM demagnetization at each field step
results in three magnetization vector-measurements, one after demagnetizing in
X-direction, one after demagnetization in Y -direction and one after demagnetization
in Z-direction. In addition to the combined GRM-free NRM, consisting of the
x-component of the 1st, the y-component of the 2nd, and z-component of the third
measurement as described by Dankers and Zijderveld (1981), these data contain six
off-diagonal measurements for each demagnetization step. Based on data from
ODP sites 911a and 910c a new method is tested to quantify the intensity of the
gyroremanence by making use of these additional measurements. By describing
the coercivity spectrum of GRM compared to the AF spectrum of the NRM we
attempt to assess whether the NRM contains fractions less influenced by possible
deflections due to GRM, and to estimate the total effect of greigite upon the NRM. |
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