气候变化领域集成服务门户(CCPortal): Nanosized Authigenic Magnetite and Hematite Particles in Mature-Paleosol Phyllosilicates: New Evidence for a Magnetic Enhancement Mechanism in Loess Sequences of China

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DOI	10.1029/2019JB018705
	Nanosized Authigenic Magnetite and Hematite Particles in Mature-Paleosol Phyllosilicates: New Evidence for a Magnetic Enhancement Mechanism in Loess Sequences of China
	Hyodo M.; Sano T.; Matsumoto M.; Seto Y.; Bradák B.; Suzuki K.; Fukuda J.-I.; Shi M.; Yang T.
发表日期	2020
ISSN	21699313
卷号	125 期号:3
英文摘要	Magnetic enhancement of Chinese loess-paleosol sequences has been used extensively as a proxy for East Asian summer monsoon variations. However, the pedogenic magnetic particles contributing to this magnetic enhancement are difficult to extract, so it is not clear how they formed. In this study, we reveal pedogenic magnetite and hematite using electron microscopy, synchrotron radiation X-ray diffraction, and rock magnetic methods. First-order reversal curves indicate that superparamagnetic/single domain/vortex state magnetic properties dominated both loess and paleosol samples. Samples of muscovite and chlorite, which are paramagnetic, have weak spontaneous magnetization. The 1- to 10-μm-sized fraction of host silicatesis responsible for most of the magnetic enhancement of paleosols. In the paleosol fraction, we found weathered phyllosilicates (muscovite/chlorite), including many elongated submicron to a few microns authigenic magnetite and hematite particles between layers; however, few such interlayer particles were found in phyllosilicates of the loess fraction. The concentration of magnetite/hematite particles within paleosol muscovite/chlorite grains and in aggregates of phyllosilicate fragments is much higher than that of the submicron iron oxides found on silicate surfaces. Interlayer magnetite particles are dominantly prism-shaped with aspect ratios >~4. The authigenic magnetite must be mainly responsible for the spontaneous magnetization of the muscovites and chlorites and the paleosol magnetic properties. The protective silicates account for the low extraction efficiency and also the near absence of surface oxidation of pedogenic magnetite. Based on our results, we suggest that magnetite/hematite in weathered phyllosilicates contribute significantly to the magnetic enhancement of mature paleosols. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	chlorite; muscovite; pedogenic magnetic mineral; synchrotron radiation XRD; TEM/SEM; vortex state
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187922
作者单位	Research Center for Inland Seas, Kobe University, Kobe, Japan; Department of Planetology, Kobe University, Kobe, Japan; Center for Supports to Research and Education Activities, Kobe University, Kobe, Japan; Department of Earth and Planetary Materials Science, Tohoku University, Sendai, Japan; Department of Physics, Escuela Politécnica Superior, University of Burgos, Burgos, Spain; School of Ocean Sciences, China University of Geosciences, Beijing, China; School of Earth Sciences and Resources, China University of Geosciences, Beijing, China
推荐引用方式 GB/T 7714	Hyodo M.,Sano T.,Matsumoto M.,et al. Nanosized Authigenic Magnetite and Hematite Particles in Mature-Paleosol Phyllosilicates: New Evidence for a Magnetic Enhancement Mechanism in Loess Sequences of China[J],2020,125(3).
APA	Hyodo M..,Sano T..,Matsumoto M..,Seto Y..,Bradák B..,...&Yang T..(2020).Nanosized Authigenic Magnetite and Hematite Particles in Mature-Paleosol Phyllosilicates: New Evidence for a Magnetic Enhancement Mechanism in Loess Sequences of China.Journal of Geophysical Research: Solid Earth,125(3).
MLA	Hyodo M.,et al."Nanosized Authigenic Magnetite and Hematite Particles in Mature-Paleosol Phyllosilicates: New Evidence for a Magnetic Enhancement Mechanism in Loess Sequences of China".Journal of Geophysical Research: Solid Earth 125.3(2020).