Environmental mechanism of magnetic susceptibility changes of lacustrine sediments from Lake Hulun, China |
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Authors: | HU Shouyun WANG Sumin Erwin Appel JI Lei |
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Institution: | (1) Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 210008 Nanjing, China;(2) Institut für Geologie und Pal?ontologie, Universit?t Tübingen, 72076 Tübingen, Germany |
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Abstract: | The changes of magnetic susceptibility(κ) are correlated with those of corresponding sedimentological, geochemical, mineralogical and biological results, which verifies
thatκ can be taken as one of the environmental proxies. However, usually the exact origin of magnetic signal is poorly understood,
and is difficult to relate with the environmental evolution. Magnetic properties of material derived from the catchment and
sedimentary environment may affect the accumulation, preservation, or authigenesis and diagenesis of magnetic minerals. In
the Lake Hulun region in Inner Mongolia, it is found that muddy sediments, deposited during high water level period (corresponding
to humid climate), have comparatively highκ values. In contrast, the sandy sediments, deposited during low water level period (corresponding to arid climate), have lowκ values. Detailed rock magnetic investigation confirms that detrital magnetite derived from volcanic rocks in the catchment
exists in both muddy and sandy sediments. During high water level period, secondary ferrimagnetic iron sulphide was produced
in muddy sediments under relatively reductive conditions. Ferrimagnetic iron sulphide, coexisting with detrital magnetite,
predominates the magnetic properties of muddy sediments, resulting in increasingκ. This paper reveals the significance of authigenic ferrimagnetic iron sulphide produced after sediment deposition. |
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Keywords: | lacustrine sediment magnetic susceptibility environmental magnetism ferrimagnetic iron sulphide Lake Hulun |
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