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| Titel |
High-temperature thermomagnetic properties of vivianite nodules, Lake El'gygytgyn, Northeast Russia |
| VerfasserIn |
P. S. Minyuk, T. V. Subbotnikova, L. L. Brown, K. J. Murdock |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 9, no. 1 ; Nr. 9, no. 1 (2013-02-19), S.433-446 |
| Datensatznummer |
250017447
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| Publikation (Nr.) |
 copernicus.org/cp-9-433-2013.pdf |
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| Zusammenfassung |
| Vivianite, a hydrated iron phosphate, is abundant in sediments of Lake
El'gygytgyn, located in the Anadyr Mountains of central Chukotka,
northeastern Russia (67°30′ N, 172°05′ E). Magnetic
measurements, including mass-specific low-field AC magnetic susceptibility,
field-dependent magnetic susceptibility, hysteresis parameters, temperature
dependence of the induced magnetization, as well as susceptibility in
different heating media, provide ample information on vivianite nodules.
Electron microprobe analyses, electron microscopy and energy dispersive
spectroscopy were used to identify diagnostic minerals. Vivianite nodules are
abundant in both sediments of cold (anoxic) and warm (oxic) stages. Magnetic
susceptibility of the nodules varies from
0.78 × 10−6 m3 kg−1 to 1.72 × 10−6
m3 kg−1 (average = 1.05 × 10−6 m3 kg−1)
and is higher than the susceptibility of sediments from the cold intervals.
Magnetic properties of vivianite are due to the respective product of
oxidation as well as sediment and mineral inclusions. Three types of curves
for high-temperature dependent susceptibility of vivianite indicate different
degrees of oxidation and inclusions in the nodules. Vivianite acts as a
reductant and reduces hematite to magnetite and masks the goethite–hematite
transition during heating. Heating vivianite and sulfur mixtures stimulates
the formation of monoclinic pyrrhotite. An additive of arsenic inhibits the
formation of magnetite prior to its Curie temperature. Heating selective
vivianite and pyrite mixtures leads to formation of several different
minerals – magnetite, monoclinic pyrrhotite, and hexagonal pyrrhotite, and
makes it difficult to interpret the thermomagnetic curves. |
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