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Analysis on variety and characteristics of maghemite

Science China Earth Sciences 2010年第8期53卷 1153-1162页

作者： SHAW John bloemendal jan HESSE Paul ROLPH Tim Department of Earth Sciences University of Liverpool Department of Geography University of Liverpool Department of Environment and Geography Macquarie University Department of Geology University of Newcastle

Maghemite (γ-Fe2O3) is a very common mineral at the earth’s surface and also an important material for making music and video tapes. Maghemite is usually synthesized from magnetite under oxidizing conditions after a few hours or a few days below a temperature of 300°C. The magnetic property of thermal instability and the chemical action after heating is an important character for maghemite. That is, it will become hematite in certain proportion after being heated above 250°C. Maghemite is therefore actually unable to have its Curie temperature measured. But late using synthetic sample, maghemite was further found partially thermal stable with a measurable Curie temperature ~645°C. During our thermally magnetic experiments for a set of synthetic magnetite, we found that extra fined grain size (pseudo single domain (PSD) and small multi-domain (MD), mainly 1-10 μm) magnetite was formed to a completely thermally stable maghemite. This maghemite can also be produced by heating the same powder up to 700°C in an oven and keeping this temperature for 10 min, then cooling it down. When the generated maghemite by these two ways is heated from room temperature to 700°C, it shows almost fully reversible, or thermally stable. We used X-ray powder diffraction and Mssbauer spectroscopy to confirm the identity of this maghemite and compared its magnetic hysteresis, high temperature magnetization, low temperature thermal demagnetization, and low temperature susceptibility with those of the original preheated magnetite. Such quickly oxidized maghemite by heating to high temperature implies some types of maghemite formed in certain natural condition can carry a thermal remnant magnetization (TRM). Four types of maghemite were characterized and discussed according to their thermal stability. Among them, partially stable and fully thermally stable maghemite after heating should possess capability of carrying TRM. There is possibly a compensation of synthetizing maghemite between heatin

关键词： maghemite paleomagnetism environmental magnetism magnetic mineral thermal stability TRM

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Identification of Greigite in the Pliocene Sediments of Qinghai Lake and Its Geological Significance

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Acta Geologica Sinica(English Edition) 2016年第6期90卷 2261-2262页

作者： FU Chaofeng jan bloemendal QIANG Xiaoke Mimi J.HILL AN Zhisheng Key Laboratory of Western Mineral Resources and Geological Engineering Ministry of Education of ChinaChang'an University State Key Laboratory of Loess and Quaternary Geology Institute of Earth and EnvironmentCAS Geomagnetism Lab School of Environmental SciencesUniversity of Liverpool

The Qinghai Lake in North China is the largest interior plateau lake in Central Asia, and is sensitive to climate change and the environmental effects of Tibetan Plateau uplift. An almost continuous 626 m long sedimen... 详细信息

关键词： In Lake Identification of Greigite in the Pliocene Sediments of Qinghai Lake and Its Geological Significance

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Particle size separation and evidence for pedogenesis in samples from the Chinese Loess Plateau spanning the past 22 m.y.

Particle size separation and evidence for pedogenesis in sam...

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中国科学院地质与地球物理研究所2008学术年会

作者： Frank Oldfield jan bloemendal Department of Geography University of LiverpoolLiverpool L69 7ZTUK

A comparison between particle size distributions determined by laser diffraction and the pipette method confirms previous studies that point to a variable underestimate of the clay fraction using laser diffraction,relative to the values obtained by pipette *** order to yield four particle-sized fractions(8μm) for further analysis, the pipette method was used on loess and paleosol samples from sites on the Chinese Loess Plateau spanning the past 22 *** all cases,a subsidiary mode in the8μm fraction provides a basis for evaluating the relative contributions of pedogenic and detrital *** using acetic rather than hydrochloric acid for carbonate removal results in no significant loss of ferrimagnetic minerals and allows magnetic characterization of the separate fractions. This confirms the isolation of almost all the finest,pedogenic ferrimagnetic grains in the clay fraction and their negligible contribution to the magnetic properties of the coarse fractions in all the samples from early Miocene time *** similar conclusions may be drawn from previous studies of late Pleistocene samples from the east-central and extreme western parts of the Chinese Loess Plateau,we conclude that this approach provides a basis for separately characterizing eolian deposition and pedogenesis throughout the region and for the whole time span of loess accumulation.

关键词： loess pedogenesis granulometry pipette analysis magnetic properties

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The magnetic properties of loess and paleosol samples from the Chinese Loess Plateau spanning the last 22 million years

The magnetic properties of loess and paleosol samples from t...

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中国科学院地质与地球物理研究所2008学术年会

作者： Frank Oldfield jan bloemendal Department of Geography University of LiverpoolLiverpool L69 7ZTUK

Magnetic measurements(susceptibility,isothermal and anhysteretic remanence,and quotients derived from these) are presented for a suite of loess and paleosol samples from sites on the Chinese Loess *** three sites,Xifeng,Dongwan and Qinan(QA-I),together span most of the last 22 million *** results provide the first multi-parameter magnetic measurements from pre-Pleistocene loess/paleosol sequences that began accumulation in the early *** specific measurements have been corrected for carbonate concentrations which peak in the loess layers and range up to 57%.All the magnetic properties recorded indicate variability on both orbital and supra-orbital *** changing magnetic properties allow the record to be divided into a sequence of eight sample groups that broadly parallel the main supra-orbital changes in magnetic *** pre-Pleistocene parts of the record include intervals(mainly late Miocene and Pliocene) during which loess as well as paleosol layers are characterized by high values for properties such as frequency dependent susceptibility(X),usually associated with strong *** of the Miocene record prior to 8.5 Ma,with the exception of a brief interval from ca.14.4 to 15.9 Ma,shows reduced values for indicators of pedogenic ferrimagnetic concentrations in both the loess and paleosol layers,as well as a low amplitude of variability between loess and paleosol *** palaeoenvironmental imphcations of this part of the sequence are unclear since they hinge on the type of model of pedogenic magnetic mineral formation ***-field remanence measurements indicate that the coercivity of the antiferromagnetic minerals represented declined progressively throughout the whole period in both the loess and the paleosol samples,though there is no unambiguous evidence for long-term diagenetic alteration of the magnetic properties on timescales beyond the orbital ones that drive the loess/paleosol *** pr

关键词： Loess Environmental magnetism Neogene Palaeoenvironment China

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Hysteresis and thermomagnetic properties of particle-sized fractions from loess and palaeosol samples spanning 22 Myr of accumulation on the Chinese Loess Plateau

Hysteresis and thermomagnetic properties of particle-sized f...

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中国科学院地质与地球物理研究所2012年度（第12届）学术年会

作者： Qingzhen Hao Frank Oldfield jan bloemendal Zhengtang Guo Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences School of Environmental Sciences University of LiverpoolLiverpoolL69 7ZTUK

Hysteresis loop measurements and thermomagnetic experiments were carried out to characterize magnetic mineralogy and magnetic grain size in a suite of particle-size fractioned samples from the Chinese Loess Plateau,representing the main changes in magnetic properties over the last 22 Myr,We find that(1) the ferrimagnets in the detrital fractions(>8μm) younger than 14 Ma show a magnetite-type Curie temperature,whereas those older than 15 Ma have a Curie temperature slightly over 600℃owing to low-temperature oxidation.(2) The dominant ferrimagnets in the clay fractions(<2μm) are most likely to be maghemite.(3) Both the hysteresis plots and thermomagnetic experiments reinforce previous indications from low-temperature experiments that paramagnetic minerals make a major contribution to the clay fractions in all the samples considered.(4) The degree of oxidation indicated by the thermomagnetic curves is highest in the clays and next highest in the oldest coarse fractions.(5) Day plots provide limited and potentially misleading information on the differences between fine-grained pedogenic and coarse-grained detrital ferrimagnetic assemblages,even when allowance is made for the effects of hematite on the quotients *** study reinforces the view that measurements on bulk samples alone obscure critical distinctions between pedogenic and detrital components.

关键词： Environmental magnetism Magnetic and electrical properties Asia

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磁赤铁矿的几种类型与特点分析

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中国科学：地球科学 2010年第5期40卷 592-602页

作者：刘秀铭 John SHAW 蒋建中 jan bloemendal Paul HESSE Tim ROLPH 毛学刚兰州大学西部环境与气候变化研究院兰州730000 Department of Environment and Geography Macquarie University Department of Earth and Ocean Sciences University of Liverpool 浙江大学材料与化学工程学院杭州310001 Department of Geography University of Liverpool Department of Geology University of Newcastle

随着环境磁学的广泛开展和应用,最近20年来磁赤铁矿(γ-Fe2O3)被人们所日益熟悉.现在它已经被发现是一种地表十分常见的矿物,与磁铁矿常常相伴随,是氧化透水通气环境的很好指示矿物.它也是制造音乐和录像磁带的重要磁性材料,在工业有很... 详细信息

随着环境磁学的广泛开展和应用,最近20年来磁赤铁矿(γ-Fe2O3)被人们所日益熟悉.现在它已经被发现是一种地表十分常见的矿物,与磁铁矿常常相伴随,是氧化透水通气环境的很好指示矿物.它也是制造音乐和录像磁带的重要磁性材料,在工业有很广泛的用途.磁赤铁矿的人工合成一般由磁铁矿通过在低于300℃的氧化环境中加热几个小时甚至几天时间来形成.它受热不稳定而产生化学变化的磁学性质是其重要特点,即加热到250℃之后该矿物一般就会被不同程度转变成为赤铁矿.因此实际上无法测量其居里点.后来对人工合成磁赤铁矿样品研究进一步发现,该矿物受热可以部分热稳定,居里温度约为645℃.本文通过不同粒度人工磁铁矿系列样品进行热磁测量实验时发现,超细粒级(假单畴(PSD)和多畴(MD)细粒)磁铁矿在快速加热过程中,形成了完全热稳定的磁赤铁矿.而且,用同样的样品在另外加热炉中快速加热到700℃高温,并且在该温度停留10min,然后冷却下来,也可以达到相同的效果.即由此两个过程形成的磁赤铁矿,再从室温加到700℃的居里温度测量过程几乎达到百分之百可逆,即完全对热稳定性特点.我们用X衍射和穆斯堡尔谱技术来鉴定和确认加热前的磁铁矿和快速加热形成的磁赤铁矿(和赤铁矿),并且比较其磁铁矿的磁滞迴线、高温磁化强度、低温热退磁和低温磁化率特性,结果表明,这种过程通过超细磁铁矿加热快速氧化形成完全可逆具有热稳定性质的磁赤铁矿,可能暗示着在某些加热环境形成的磁赤铁矿也可能携带热剩磁.根据磁赤铁矿是否受热不稳定及其表现形式,将它详细分成4种类型探讨分析.受热后部分稳定和完全稳定的磁赤铁矿应当具备携带热剩磁的能力.人工合成磁赤铁矿的温度与其反应时间可能有个互补关系.磁赤铁受热后稳定与否可能与多种因素有关,如受纯度大小、受热温度高低和时间长短等影响,粒度大小可能也是重要因素之一.磁赤铁矿可能如同磁铁矿,也有不同粒级超顺磁(SP)、单畴(SD)和MD对应着不同的磁学特点.细粒PSD氧化的人工磁铁矿在低温磁学测量显示为Verwey转换被"抑制"的现象,其根本原因可能是,氧化后磁铁矿的内核直径实际上已经达到或者接近该矿物的SD粒径,所以它的Verwey转换显得被"抑制".

关键词：磁性矿物磁赤铁矿古地磁环境磁学热稳定性携带热剩磁

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Delayed build-up of Arctic ice sheets during 400,000-year minima in insolation variability

Delayed build-up of Arctic ice sheets during 400,000-year mi...

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中国科学院地质与地球物理研究所2012年度（第12届）学术年会

作者： Qingzhen Hao Luo Wang Frank Oldfield Shuzhen Peng Li Qin Yang Song Bing Xu Yansong Qiao jan bloemendal Zhengtang Guo Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences Key Laboratory of Tourism and Resources Environment in Universities of Shandong Taishan University Chongqing Three Gorges Institute of Paleoanthropology Grad uate University of Chinese Academy of Sciences Institute of Geomechanics Chinese Academy of Geological Sciences

Knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial may help to inform our understanding of future climate change. Unfortunately,long-term continuous records of ice-sheet variability in the Northern Hemisphere only are scarce because records of benthic O content represent an integrated signal of changes in ice volume in both polar ***,variations in Northern Hemisphere ice sheets influence the Siberian High(an atmospheric

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古环境中沉积物粒度组分分离的数学方法及其应用

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自然科学进展（国家重点实验室通讯） 2001年第3期11卷 269-276页

作者：孙东怀安芷生苏瑞侠吴锡浩王苏民孙千里 David Rea jan bloemendal 中国科学院南海海洋研究所中国科学院西安黄土与第四纪地质研究室 Department of Geological Sciences University of MichiganAnn ArborMichigan 48109-1063USA Department of Geography University of LiverpoolL69 3BXUK

陆相沉积物一般由多个粒度组分叠加组成,根据粒度分布曲线的特征可确定组分数、分布类型以及设定粒度分布函数,用设定的分布函数对实测粒度数据拟合可计算出函数的各参数,并获得各组分的百分比和分布函数,从而从数字特征上分离各组分。... 详细信息

陆相沉积物一般由多个粒度组分叠加组成,根据粒度分布曲线的特征可确定组分数、分布类型以及设定粒度分布函数,用设定的分布函数对实测粒度数据拟合可计算出函数的各参数,并获得各组分的百分比和分布函数,从而从数字特征上分离各组分。对流水和风成沉积物研究表明,河流沉积物由细粉砂级悬移组分和中砂至细砂级跃移组分叠加组成;封闭湖的碎屑沉积物主要是降水形成的地表径流搬运的细粉砂级悬移组分;风成砂由高度分选的近源跃移砂组分与细粒大气背景粉尘叠加组成;黄土由低空近源的悬移粉砂组分与高空运源悬移细粒组分叠加组成;北太平洋粉尘只有高空西风搬运的悬移细粒组分,该组分的粒度在中国沙漠、黄土高原和北太平洋的风成物中表现出一致性和成因上的内在联系,是该系统中高空悬移并分散于大气中的背景粉尘。

关键词：粒度组分分布函数沉积物组分面分比组分分离细粉砂级悬移组分近源跃移砂组分

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成壤过程中反铁磁性赤铁矿及亚铁磁性矿物生成的主控气候要素

成壤过程中反铁磁性赤铁矿及亚铁磁性矿物生成的主控气候要素

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2017中国地球科学联合学术年会

作者：高新勃郝青振旺罗 Frank Oldfield jan bloemendal 邓成龙宋杨葛俊逸吴海斌中国科学院地质与地球物理研究所 University of Liverpool 中国科学院生态环境研究中心中国科学院古脊椎动物与古人类研究所

＜正＞近些年,成壤来源的赤铁矿在进行黄土-古土壤序列所记录的古气候信息的定性和定量化研究方面受到了学术界的普遍关注。然而,关于成壤过程中控制反铁磁性赤铁矿生成的主要气候要素,目前还存在较大的争议。本次研究中,我们从黄土高...

＜正＞近些年,成壤来源的赤铁矿在进行黄土-古土壤序列所记录的古气候信息的定性和定量化研究方面受到了学术界的普遍关注。然而,关于成壤过程中控制反铁磁性赤铁矿生成的主要气候要素,目前还存在较大的争议。本次研究中,我们从黄土高原地区及其临近区域采集了179个现代土壤样品;通过重力沉降法对风化成壤来源的粘土组分和风成碎屑来源的粉砂组分进行了分离;随后分别对上述两个组分进行了系统的环境磁学测量;同时为了充分理解粘土和粉砂组分磁性矿物上的差异,我们选择

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The Role of <sup>18</sup>F-FDG-PET/CT in the Management of Patients with High-Risk Breast Cancer: Case Series and Guideline Comparison

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Advances in Molecular Imaging 2014年第3期4卷 35-41页

作者： Ben F. Bulten Marie J. de Haas Haiko J. bloemendal Adriaan J. van Overbeeke jan Paul Esser Henk J. Baarslag Lioe-Fee de Geus-Oei C. J. Rodenburg John M. H. de Klerk Department of Oncology Meander Medical Centre Amersfoort The Netherlands Department of Radiology and Nuclear Medicine Meander Medical Centre Amersfoort The Netherlands Department of Radiology and Nuclear Medicine Radboud University Medical Centre Nijmegen The Netherlands Department of Radiology Meander Medical Centre Amersfoort The Netherlands Department of Surgery Meander Medical Centre Amersfoort The Netherlands

Objectives: In grade III-IV breast cancer, dissemination of disease needs to be assessed. Until now this was done by conventional imaging (liver ultrasonography, chest X-ray and bone scintigraphy), but evidence favoring the use of FDG-PET/CT is accumulating. Methods: Patients with high-risk breast cancer, who had received conventional imaging and FDG-PET/CT, were included. Patients were staged and assigned a treatment after 1) conventional imaging and 2) FDG-PET/CT, both by a multidisciplinary oncology team. Equivocal FDG-PET/CT findings were histologically confirmed. Results: 16 patients were included (mean age 59 years). TNM-stage changed in 5 patients (31%) after FDG-PET/CT. In 3 patients (19%) unknown distant metastases were detected by FDG-PET/CT. An adjustment of treatment took place in 4 patients (25%). Conclusions: Our case series emphasizes the role of FDG-PET/CT in the staging of high-risk breast carcinoma, especially in the assessment of distant metastases. We suggest replacing conventional imaging with FDG-PET/CT.

关键词： Breast Cancer FDG-PET/CT Staging Dissemination Guidelines

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