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A strong angular dependence of magnetic properties of magnetosome chains:Implications for rock magnetism and paleomagnetism

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A strong angular dependence of magnetic properties of magnet...

Intensified tectonic deformation and uplift of the Altyn Tagh range recorded by rock magnetism and growth strata studies of the western Qaidam Basin, NE Tibetan Plateau

中国科学院地质与地球物理研究所2013年度（第13届）学术年会

作者： Jinhua Li Kunpeng Ge Yongxin Pan Wyn Williams Qingsong Liu Huafeng Qin Paleomagnetism and Geochronology Laboratory Key Laboratory of Earth's Deep InteriorInstitute of Geology and GeophysicsChinese Academy of Sciences China-France Biomineralization and Nano-Structure Laboratory Chinese Academy of Sciences Paleomagnetism and Geochronology Laboratory Institute of Geology and GeophysicsChinese Academy of Sciences

[1]Single-domain magnetite particles produced by magnetotactic bacteria(magnetosomes) and aligned in chains are of great interest in the biosciences and ***,we investigated angular variation of magnetic properties of aligned Magnetospirillum magneticum AMB-1 cells,each of which contains one single fragmental chain of *** measurements at increasing angles from the chain direction,we observed that(i) the hysteresis loop gradually changes from nearly rectangular to a ramplike shape(e.g.,B and remanence decrease),(ii) the acquisition and demagnetization curves of IRM shift toward higher fields(e.g.,B increases),and(iii) the FORC diagram shifts toward higher coercivity fields (e.g.,B increases).For low-temperature results,compared to unoriented samples,the samples containing aligned chains have a much lower remanence loss of field-cooled(δ) and zero-field-cooled (δ) remanence upon warming through the Verwey transition,higherδ-ratio(δ=δ/δ) for the measurement parallel to the chain direction,and lowerδ-ratio,largerδ andδ values for the perpendicular *** simulations confirm the experimental observations and reveal that the magnetization reversal of magnetosome chain appears to be noncoherent at low angles and coherent at high *** simulations also demonstrate that the angular dependence of magnetic properties is related to the dispersion degree of individual chains,indicating that effects of anisotropy need to be accounted for when using rock magnetism to identify magnetosomes or magnetofossils once they have been preserved in aligned ***,this study experimentally demonstrates an empirical correspondence of the parameter B to B rather than B,at least for magnetite chains with strong shape *** suggests FORC analysis is a good discriminant of magnetofossils in sediments and rocks.

关键词： magnetosome chain magnetic property angular dependence magnetic anisotropy rock magnetism paleomagnetism.

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Intensified tectonic deformation and uplift of the Altyn Tag...

rock magnetic properties of a loess-paleosol couple along an N-S transect in the Chinese Loess Plateau

2015中国地球科学联合学术年会

作者： Tao Zhang Wenxia Han Xiaomin Fang Weilin Zhang Chunhui Song Maodu Yan Key Laboratory of Continental Collision and Plateau Uplift Institute of Tibetan Plateau Research CAS Key Laboratory of Salt Lake Resources and Chemistry Qinghai Institute of Salt Lakes Chinese Academy of Sciences CAS Center for Excellence in Tibetan Plateau Earth Sciences School of Earth Sciences & Key Laboratory of Western China’s Mineral Resources of Gansu Province

The Altyn Tagh range is the tectonically and geographically northern edge of the Tibetan Plateau,precise dating of its activities is essential for understanding the possible mechanisms of the Tibetan Plateau uplift and its effects on climate *** the framework of basin-mountain coupling,both magnetic susceptibility and rock magnetic research were carried out on the Late Cenozoic sediments of the Honggouzi section（7-5 Ma）in the western Qaidam *** study attempts to find out the evolution history of tectonic and climatic changes and to detect their interactions in the Altyn Tagh *** results showed that magnetic susceptibility records kept relatively low and stable values before0Ma,and rapidly increased since0 *** rock magnetic results revealed that paramagnetic minerals,maghemite and hematite have been dominated during the early periods（>10 Ma）in the Honggouzi section,and were replaced by magnetite and maghemite after that time.A detailed comparison of magnetic susceptibility records in the Honggouzi section with tectonic and climate records from the study areas and surrounding regions were also carried *** with sedimentary facies,lithology and angular unconformity in the sequence,as well as seismostratigraphy data,paleocurrent study,provenance and conceptual models analyses,we argue that the0 Ma shift in the HGZ section might be caused by the uplift of the Altyn Tagh range during that time.

关键词： rock magnetism growth strata tectonic uplift Altyn Tagh range Qaidam Basin

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Science China Earth Sciences 2001年第12期44卷 1099-1109页

作者：郭斌朱日祥白立新 FlorindoFabio Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China Beijing Seismology Bureau Beijing China Instituto Nazionale di Geofisica Roma Italy

We have conducted detailed rock magnetic experiments on samples from loess unit 8 (L8) and paleosol unit 8 (S8) in Jingbian, Yichuan and Duanjiapo loess sections along an N-S transect in the Chinese Loess Plateau. Major rock magnetic results are as follows: (i) An increase of high field susceptibility (χh) in the same level of loess or paleosol from north to south is observed, suggesting an enhancement of pedogenesis. (ii) The low field susceptibility(χL) in loess unit L8 is almost the same in three sections. In contrast, the χL of paleosol unit S8 in Yichuan is highest, and the χL of Duanjiapo is lower than that in Yichuan section, suggesting that there is not correlation between the χL and the degree of pedogenesis in loess-paleosols. (iii) With the increasing of χL, both the contents of the superparamagnetic (SP) and the ferrimagnetic grains in loess-paleosol increase, however, the enhancement of magnetic susceptibility is probably dependent more on the increase of the ferrimagnetic concentration than on a change in the grain size. (iv) The content of the maghemite in loess unit 8 increases from the northern to the southern part of the Chinese Loess Plateau, and is positively correlated with the pedogenesis of the loess.

关键词： loess-paleosol rock magnetism paleoclimate

Paleomagnetic results from Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane, Tibet, China, and their tectonic implications

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Science China Earth Sciences 2017年第1期60卷 124-134页

作者： YANG XingFeng CHENG Xin ZHOU YaNan MA Lun ZHANG XiaoDong YAN ZhaoSheng PENG XiMing SU HaiLun WU HanNing Department of Geology and State Key Laboratory of Continental Dynamics Northwest University Xi 'an 710069 China

Results of a systematic paleomagnetic study are reported based on Late Carboniferous to Early Permian sedimentary rocks on the north slope of the Tanggula Mountains, in the northern Qiangtang terrane （NQT）, Tibet, China. Data revealed that magnetic minerals in limestone samples from the Zarigen Formation （CP^z）are primarily composed of magnetite, while those in sandstone samples from the Nuoribagaribao Formation （Pnr） are dominated by hematite alone, or hematite and magnetite in combination. Progressive thermal, or alternating field, demagnetization allowed us to isolate a stable high temperature component （HTC） in 127 specimens from 16 sites which successfully passed the conglomerate test, consistent with primary remnance. The tilt-corrected mean direction for Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane is D°=30.2°, Is=-40.9°, ks=269.0, a95=2.3°, N=16, which yields a corresponding paleomagnetic pole at 25.7°N, 241.5°E （alp/rim=2.8°/1.7°）, and a paleolatitude of 23.4°S. Our results, together with previously reported paleomagnetic data, indicate that：（1） the NQT in Tibet, China, was located at a low latitude in the southern hemisphere, and may have belonged to the northern margin of Gondwana during the Late Carboniferous to Early Permian; （2） the Paleo-Tethys Ocean was large during the Late Carboniferous to Early Permian, and （3） the NQT subsequently moved rapidly northwards, perhaps related to the fact that the Paleo-Tethys Ocean was rapidly contracting from the Late Permian to Late Triassic while the Bangong Lake-Nujiang Ocean, the northern branch of the Neo-Tethys Ocean, expanded rapidly during this time.

关键词： Northem Qiangtang terrane Late Carboniferous Early Permian rock magnetism Conglomerate test Paleomagnetic pole

Magnetic properties and paleoclimatic implications of loess-paleosol sequences of Czech Republic

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Science China Earth Sciences 2001年第5期44卷 385-394页

作者：朱日祥石采东 V.Suchy A.Zeman 郭斌潘永信 Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China Institute of Geology Czech Academy of Sciences Prague Czech Republic

Detailed rock magnetic investigations and X-ray diffraction (XRD) were carried out on loess-paleosol sequences of the last interglacial-glacial at Znojmo section in Czech Republic. The results indicate that pedogenesis causes susceptibility enhancement in the paleosols, which is similar to that observed in the Chinese Loess Plateau. κ-T curves, IRM, and XRD show that magnetite is the dominant magnetic mineral in the loess-paleosol sequences at the Znojmo section, while maghemite, hematite, and pyrite/pyrrhotite are minor minerals. Measurements of anisotropy of magnetic susceptibility (AMS) indicate that the magnetic lineation is smaller than the foliation. The susceptibility ellipsoids are oblate and the directions of the maximum principal axes (κmax) are distributed randomly, and cannot be used to determine the paleo-wind direction.

关键词： Czech Republic loess rock magnetism paleoclimate.

Reliability of Relative Paleointensity Recorded in Chinese Loess-Paleosol Sediments

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Acta Geologica Sinica(English Edition) 2012年第5期86卷 1276-1288页

作者： YANG Tianshui LI Haiyan WU Huaichun YANG Zhenyu ZHANG Shihong HYODO Masayuki State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China School of the Earth Sciences and Resources China University of GeosciencesBeijing 100083China School of Ocean Sciences and Resources China University of GeosciencesBeijing 100083China Institute of Geomechanics Chinese Academy of Geological SciencesBeijing 100081China Research Center for Inland Seas Kobe UniversityKobe 657-8501Japan

A detailed paleomagnetic and rock-magnetic investigation spanning loess L7 to paleosol S8 has been carried out at the Baoji and Xifeng sections. Results of anisotropy of magnetic susceptibility confirm that the studied loess-paleosol sediments retain primary sedimentary fabrics. Stepwise thermal demagnetization shows that two well-defined magnetization components can be isolated from both loess and paleosol specimens. A low-temperature component, isolated between 100°C and 200°C, is consistent with the present geomagnetic field direction, and a high-temperature component, isolated between 200-300°C and 620-680°C, includes clearly normal and reversed polarities. Isothermal remanent magnetization and thermomagnetic analyses indicate that characteristic remanent magnetization is mainly carried by magnetite and hematite. The Day plot, together with the stratigraphic variations of rock-magnetic parameters, shows that the uniformity of magnetic mineralogy and grain size fulfills the criteria for relative paleointensity （RPI） studies. RPI records have been constructed using natural remanent magnetization （NRM） intensity after thermal demagnetization at 300°C normalized by low-frequency magnetic susceptibility （NRM 300 /χ）. The results show that the RPI record from the Baoji section, where pedogenesis is quite weak, is compatible with the stacked PISO-1500 paleointensity record, suggesting that it might reflect the paleointensity variation of the geomagnetic field. The RPI record from the Xifeng section, where pedogenesis is rather strong, indicates a clear dissimilarity with the stacked PISO-1500 paleointensity record, implying that it does not reflect the paleointensity variation of the geomagnetic field. Our new results show that the NRM 300 /χ from the strongly pedogenetic paleosols does not completely eliminate the pedogenetic （climatic） influence, so it might be unsuitable for a reliable paleointensity study.

关键词： Chinese loess pedogenesis relative paleointensity rock magnetism geomagnetic field

Magnetic characterization and paleoclimatic significances of late Pliocene-early Pleistocene sediments at site 882A,northwestern Pacific Ocean

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Science China Earth Sciences 2012年第2期55卷 323-331页

作者： JIANG ZhaoXia LIU QingSong State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing100029China Graduate University of Chinese Academy of Sciences Beijing 100049China

Aeolian dust, a primary terrigenous component of ocean sediments, has been widely used to reconstruct the paleoclimatic evolution because its transported distance, grain size and concentration are sensitive to climate changes. To further characterize the aeolian dust, the deposits at site Ocean Drilling Program (ODP) 882A in northwestern Pacific Ocean are divided into four grain-size fractions (64 μm) using the gravitative differentiation method. Detailed rock magnetism results show that magnetite and hematite are dominant magnetic minerals for the dust components. In addition, the aeolian dust (64 μm) contributes little to the magnetic enhancement of the sediments at 2.73 Ma. These new results greatly improve our understanding of paleoenvironmental evolution during late Pliocene-early Pleistocene in this area.

关键词： eolian dust sediment rock magnetism magnetite hematite ODP site 882A the major glaciation in the Northern Hemisphere

Determination of the heating efficiency of magnetotactic bacteria in alternating magnetic field

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Journal of Oceanology and Limnology 2021年第6期39卷 2116-2126页

作者： Tongwei ZHANG Huangtao XU Jia LIU Yongxin PAN Changqian CAO Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsInnovation Academy for Earth ScienceChinese Academy of SciencesBeijing 100029China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China France-China Joint Laboratory for Evolution and Development of Magnetotactic Multicellular Organisms Chinese Academy of SciencesBeijing 100029China

Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell ***,the detailed magnetic hyperthermia properties and optimum heat production conditions of MTB cells are still poorly understood due to lack of standard measuring *** specific absorption rate(SAR)of MTB cells is often measured by home-made equipment at a limited frequency and magnetic field *** this study,we have used a commercial standard system to implement a comprehensive study of the hyperthermic response of Magnetospirillum gryphiswaldense MSR-1 strain under 7 frequencies of 144-764 kHz,and 8 field amplitudes between 10 and 45 kA/*** measurement results prove that the SAR of MTB cells increases with magnetic field frequency and amplitude within a certain *** combination with the magnetic measurements,it is determined that the magnetic hyperthermia mechanism of MTB mainly follows the principle of hysteresis loss,and the heat efficiency of MTB cells in alternating magnetic field are mainly aff ected by three parameters of hysteresis loop,saturation magnetisation,saturation remanent magnetisation,and *** when we culture MTB in LA-2 medium containing sodium nitrate as source of nitrogen,the SAR of MTB LA-2 cells with magnetosomes arranged in chains can be as high as 4925.6 W/g(in this work,all SARs are calculated with iron mass)under 764 kHz and 30 kA/m,which is 7.5 times than current commercial magnetic particles within similar size range.

关键词： magnetotactic bacteria(MTB) hyperthermia rock magnetism alternating magnetic field(AMF)

Identification of greigite in lake sediments and its magnetic significance

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Science China Earth Sciences 2002年第1期45卷 81-87页

作者：胡守云 E.Appel V.Hoffmann W.Schmahl Nanjing Institute of Geography & Limnology Chinese Academy of Sciences Nanjing China Institut für Geologie und Paläontologie Universität Tübingen Germany Institut für Mineralogie Ruhr-Universtität Bochum Germany

Detailed rock magnetic investigations and mineralogical analysis were conducted on lacustrine sediments recovered from Zoigê Basin, eastern Tibetan Plateau. Greigite, with fine and homogenous grain size, is found as a main magnetic carrier, which is suspected to be of biochemical origin. In contrast to some reports, greigite within the sediments is not oxidized even after exposure to air for a few years, which could be due to the fact that greigite is sealed by silicate.

关键词： greigite lacustrine sediments rock magnetism X-ray diffraction SEM