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- Title
Thermomagnetic properties of vivianite nodules, Lake El'gygytgyn, Northeast Russia.
- Authors
Minyuk, P. S.; Subbotnikova, T. V.; Brown, L. L.; Murdock, K. J.
- Abstract
Vivianite, a hydrated iron phosphate, is abundant in sediments of El'gygytgyn Lake, located in the Anadyr Mountains of Central Chukotka, Northeastern Russia (67°30´ N; 172°05´ E). Magnetic measurements, including weight low-field AC magnetic susceptibility, field dependent magnetic susceptibility, hysteresis parameters, temperature dependence of the saturation magnetization, as well as susceptibility in different heating media provide ample information on vivianite. 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 0.78x10-6 m⊃3 kg-1 to 1.72x10-6 m⊃3 kg-1 (average= 1.05x10-6 m⊃3 kg-1) and is higher than the susceptibility of sediments from the cold intervals. Magnetic properties of vivianite are due to product of oxidation as well as sediment and mineral inclusions. Three types of curves of high temperature dependence susceptibility of vivianite indicate different degree of oxidation and inclusions in the nodules. Vivianite acts as a reductant and reduces hematite to magnetite and suppresses the goethite-hematite transition during heating. Heating vivianite and sulfur mixture stimulate 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 produces formation of several different minerals - magnetite, monoclinic pyrrhotite, and hexagonal pyrrhotite, and make it difficult to interpret the thermomagnetic curves.
- Subjects
ELGYGYTGYN Lake (Russia); RUSSIA; THERMOMAGNETISM; VIVIANITE; LAKE sediments; HYDRATION; MAGNETIZATION; MAGNETIC susceptibility measurement
- Publication
Climate of the Past Discussions, 2012, Vol 8, Issue 5, p4989
- ISSN
1814-9324
- Publication type
Article
- DOI
10.5194/cpd-8-4989-2012