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Petromagnetic Properties of Granulite-Facies rocks from the Northern North China Craton: Implications for Magnetic and Evolution of the Continental Lower Crust

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Journal of Earth Science 2013年第1期24卷 12-28页

作者：刘庆生王红才郑建平曾庆理刘青松 Institute of Geophysics & Geomatics China University of Geosciences Institute of Geomechanics Chinese Academy of Geological Sciences Faculty of Earth Sciences China University of Geosciences Paleomagnetism and Geochronology Laboratory (SKL-LE) Institute of Geology and Geophysics Chinese Academy of Sciences

This paper studies magnetic properties and composition of granulite-facies rocks of both the Neogene and Archean continental lower crust in the Neogene xenolith-bearing Hannuoba （汉诺坝） alkaline basalt and the exposed lower crustal section in the Archean Huai＇an （淮安） terrain （Wayaokou （瓦窑口）-Manjinggou （蔓菁沟） profile）, the northern North China Craton. It provides a unique oppor-tunity for a comparative study of magnetic properties and composition of both the Archean and Neogene continental lower crust. We measure magnetic parameters （susceptibility x and magnetic hysteresis parameters, such as saturation magnetization Js, saturation isothermal remanent magnetization Jrs, and intrinsic coercivity He） of eleven Hannuoba lower crustal xenoliths and nine terrain granulites from the Archean Huai＇an terrain. Results indicate that the average values of K,Js and Jrs of Archean granu- lites are 4 122×10^-6 SI, 523.1 A/m and 74.9 A/m, respectively, which are generally higher than those of granulite-facies xenoliths （1 657×10^-6 SI, 163.9 A/m and 41.9 A/m, respectively）. These two types of granulites contain ilmenite, （titano） magnetite, minor hematite and some ＂magnetic silicates＂（clinopyroxene, plagioclase and biotite）. The Mg-rich ilmenite in granulite-facies xenolith is relatively higher than that in terrain granulites. We observe a more evolved character as higher magnetic as well as lower Sr/Nd, Cr/Nd, Ni/Nd, Co/Nd and V/Nd ratios in terrain granulites. These differences in magnetic characteristics reflect their different origins and evolutions. The high magnetization of granulites in the Huai＇an terrain represents magnetic properties of the Archean continental lower crust, and low magnetization of granufite-facies xenoliths represents mag- netic properties of the Cenozoic lower crusts in the northern North China Craton.

关键词： rock and mineral magnetism magnetic mineralogy and petrology metamorphic pe-trology North China Craton

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Magnetic enhancement upon heating of environmentally polluted samples containing haematite and iron

Magnetic enhancement upon heating of environmentally pollute...

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： Chunxia Zhang,Qingsong Liu,Baochun Huang and Youliang Su Palaeomagnetism and Geochronology Laboratory of the State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics, Chinese Academy of Sciences,Beijing 100029,China.

Pollution has become an increasing problem during the last several *** magnetism provides a useful method for detecting and monitoring soil and sediment pollution. Thermomagnetic analysis is a conventional approach for identifying magnetic phases or possible thermal alterations in *** properties of samples are often enhanced after thermal treatment of environmentally polluted *** this study,we investigated the possible role of metallic iron for magnetic enhancement due to interaction between iron and haematite at elevated *** results show that synthetic samples containing both haematite and iron show significant magnetic enhancement upon heating in argon due to the neo-formation of ***,magnetite formed during heating in argon is rather stable, whereas that produced upon heating in air is oxidized to haematite at higher temperatures. We found that a small amount of iron can induce significant transformation of haematite into magnetite upon heating in ***,such a mechanism has to be considered for magnetic enhancement when conducting thermomagnetic analyses of environmentally polluted samples.

关键词： Environmental magnetism rock and mineral magnetism

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Heavy metal pollution in farmland irrigated with river water near a steel plant——magnetic and geochemical signature

Heavy metal pollution in farmland irrigated with river water...

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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： Chunxia Zhang Erwin Appel Qingqing Qiao State Key Laboratory of Litho spheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences Department of Geosciences University of Tuebingen

The presence of heavy metals(HMs) in the environment is a major threat for *** proxies provide a rapid method for assessing the degree of HM pollution in environment. We have studied farmland soil irrigated with polluted river water in the vicinity of a steel plant in Loudi city(Hunan Province,China) to test the efficiency of magnetic methods for detecting the degree of HM *** magnetic and non-magnetic(microscopic,chemical and statistical) methods were used to characterize these farmland *** magnetic concentration values were found in the upper arable soil horizon(0-20 cm),which is related to the presence of spherical～10 to 30μm sized magnetite *** spatial distribution of magnetic concentration and HM contents in the farmland soils matches with the spatial pattern of these parameters in river *** findings provide evidence that HM pollution of the farmland soil is mainly caused by irrigation with *** Zn,Pb,Cu,Cd,Co, Ni,V are well correlate with magnetic susceptibility(χ).The pollution load index(PLI) of all nine anthropogenic HMs(including also Cr and Mo) and log(χ) are significantly correlated. Using the resulting linear PLI-log(χ) function,values ofχcan serve as a convenient tool for semi-quantifying the degree of HM pollution in the uppermost～20 cm of the studied farmland *** findings suggest that magnetic methods can generally serve as a convenient tool for detecting and mapping HM pollution in farmland soil irrigated with wastewater from sites nearby heavy industrial activities.

关键词： Environmental magnetism rock and mineral magnetism Asia

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Magnetostratigraphy of the Qiliting section(SE China)and its implication for geochronology of the red soil sequences in southern China

Magnetostratigraphy of the Qiliting section(SE China)and its...

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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： Caicai Liu,~(1,2) Xinmin Xu,~3 Baoyin Yuan~1 and Chenglong Deng~1 1 Paleomagnetism and Geochronology Laboratory(SKL-LE),Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China. E-mail:cldeng@*** 2 Graduate School of the Chinese Academy of Sciences,Beijing 100039,China 3 Zhejiang Province Institute of Cultural Relics,Hangzhou 310014,China

The red soil sequences in southern and southeastern China provide important terrestrial archives of palaeoclimate and palaeoenvironment and are important sources of Palaeolithic settlements and therefore,early human *** we present detailed palaeomagnetic investigation coupled with mineral magnetic and petrographic analyses of a red soil sequence at Qiliting,southeastern *** sediments contain both strongly magnetic minerals(such as maghemite and magnetite) and weakly magnetic minerals(such as haematite and possibly goethite).Maghemite and haematite were identified as the main carriers of the natural remnant *** haematite dominates the characteristic remnant magnetisations. Palaeomagnetic findings suggest that the Qiliting sedimentary sequence recorded the early Brunhes Chron and the late Matuyama Chron,including the Jaramillo *** finding, coupled with previously published magnetostratigraphy,establishes that the red soil sequences in southern China began to accumulate no later than the Jaramillo age(i.e.～1.0 Ma). It is further suggested that the capabilities of recording magnetic polarity stratigraphy in Chinese red soil sequences are variable between areas because of different climate regimes.

关键词： Magnetostratigraphy Palaeomagnetism applied to geologic processes rock and mineral magnetism Asia

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Nature of remagnetization of Lower Triassic red beds in southwestern China

Nature of remagnetization of Lower Triassic red beds in sout...

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中国科学院地质与地球物理研究所第11届（2011年度）学术年会

作者： Chengying Liu,~(1,2) Kunpeng Ge,~(1,2) Chunxia Zhang,~1 Qingsong Liu,~1 Chenglong Deng~1 and Rixiang Zhu~1 1 State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China. 2 Graduate University of the Chinese Academy of Sciences,Beijing 100049,China

SUMMARY Widely distributed haematite-bearing red beds are an important source of palaeomagnetic field ***,unresolved issues regarding remagnetization and inclination shallowing in red beds have questioned the reliability of the palaeomagnetic results obtained from such *** this study,we investigated the remagnetization mechanism in red beds from Lower Triassic sandstones in Yunnan Province,southwestern *** results indicate that the characteristic remanent magnetizations(ChRMs) of most samples(112/125) are dominated by only one component at temperatures 80-660℃,with a mean direction of D/I= 0.9/46.6°(k = 440.2,α= 2.1°).The corresponding geomagnetic pole is 89.1°N, 331.7°E(k = 338.2,A=2.4°).This coincides with the present geomagnetic field,which is a strong indication that these ChRMs are *** rock magnetic and microscope investigations reveal that the remagnetization is due to the acquisition of a chemical remanent magnetization(CRM) carried by authigenic maghemite and *** the widespread remagnetization,about 7 per cent of the studied samples still record a magnetization that we consider to be primary that was isolated at high temperatures 610-660℃,with a mean direction of D/I = 213.3/18.6°(it = 16.0,α = 11.7°).We propose that the CRM overprinting is controlled by the overlapping degree of the unblocking temperature between the CRM carried by the authigenic haematite and the primary remanent magnetization carried by the detrital *** results further suggest that microscope investigation,rock magnetic proxies for the haematite concentration and susceptibility-temperature curves are useful methods for pre-selecting samples suitable for isolating the primary remanence at this *** linkage among the palaeomagnetic results,rock magnetic proxies and CRM remagnetization mechanism could be extended to other studies,although the detailed proxy would be different due to specific overprint process._

关键词： Remagnetization rock and mineral magnetism Asia

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A precursor to the Matuyama-Brunhes reversal in Chinese loess and its palaeomagnetic and stratigraphic significance

A precursor to the Matuyama-Brunhes reversal in Chinese loes...

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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： Chunsheng Jin Qingsong Liu Juan Cruz Larrasoaa State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences

We report high-resolution palaeomagnetic results across the lower part of S8 in the Luochuan area,northwest of China using parallel subsets samples.A palaeomagnetic anomaly with low palaeointensity and disordered magnetic direction was identified～21 ka prior to the Matuyama-Brunhes(MB) polarity reversal,and is consistent with the MB precursor observed from marine sediments and lava *** is the first convincing report of the MB precursor in terrestrial material(Chinese loess),which attests the global feature of the MB precursor. Constrained by the stratigraphic position of both the MB polarity reversal and the MB precursor, the loess unit L8 and palaeosol unit S8 of the Chinese loess sequence are undoubtedly tied to the marine isotope stages 18 and 19,*** correlation is critical for an accurate understanding of the correspondences of palaeomagnetic records between the Chinese loess and marine sediments.

关键词： Magnetic fabrics and anisotropy Palaeointensity Reversals:process,timescale,magnetostratigraphy rock and mineral magnetism

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Evaluating the environmental quality impact of the 2008 Beijing Olympic Games:magnetic monitoring of street dust in Beijing Olympic Park

Evaluating the environmental quality impact of the 2008 Beij...

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中国科学院地质与地球物理研究所第11届（2011年度）学术年会

作者： John D.A.Piper Geomagnetism Laboratory Department of Earth and Ocean SciencesUniversity of LiverpoolLiverpool L69 7ZEUK

Aggressive traffic intervention and emission control measures implemented during the 2008 Olympic Games in Beijing created a valuable case study for evaluating the effectiveness of measures for mitigating environmental pollution and protecting public *** are reported here for a suite of magnetic and non-magnetic(microscopic,chemical and statistical) methods conducted on street dust deposits and parkland soils around the Olympic Park in *** both areas magnetic grains with multidomain properties predominate;grain sizes are coarser in the heavy traffic regions and finer in the park areas with evidence for particulate steel dust input in the former *** is the major source of anthropogenic magnetic particle-induced enhancement of magnetic susceptibility in street dust;however,domestic combustion processes(mainly coal burning) are found to contribute a significant magnetic signature in the urban environment during the *** to the traffic intervention,magnetic compositions in street dust decreases significantly during the Olympic *** between magnetic parameters and heavy metal contents prove that magnetic parameters can be used as proxies for heavy metal pollution.

关键词： Environmental magnetism rock and mineral magnetism Asia

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Magnetostratigraphy of the Xihe loess-soil sequence and implication for late Neogene deformation of the West Qinling Mountains

Magnetostratigraphy of the Xihe loess-soil sequence and impl...

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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： Junyi Ge Zhengtang Guo Tao Zhan Zhengquan Yao Chenglong Deng Frank Oldfield Key Laboratory of Cenozoic Geology and Environment Institute of Geology and Geophysics Chinese Academy of Sciences Key Laboratory of Marine Sedimentology and Environmental Geology First Institute of OceanographyState Oceanic Administration State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences

The Qinling Mountain range forms an important climate barrier between southern and northern *** western part,referred to as the West Qinling,constitutes a unit of northeastern Tibetan *** uplift history of Qinling during the Neogene is still a contentious issue. Magnetostratigraphic results from the 150-m-thick Xihe loess-soil sequence(NL-Ⅵ),located on the alluvial highlands surrounding an intermontane basin from the West Qinling,indicate 17 reverse and 17 normal *** are correlative with the interval from chron C5n to chron C2Ar in the Geomagnetic Polarity *** age of the NL-VI section can thus be palaeomagnetically constrained to a period from 10.5 to 4.2 *** middle portion of the section has been affected intermittently by surface erosion *** loess is sensitive to any erosion that may have been induced by substratum deformation and tectonic uplift, this sequence indicates that the intermontane basin-ridge pattern of the West Qinling had already been formed by 10.5 Ma,thus providing suitable topographic conditions for aeolian *** timing is consistent with a significant deformation phase between～14 and 10 Ma reported for the Tibetan ***,the complete preservation of the NL-VI loess-soil sequence precludes both intense deformation of the substrate and rapid uplift of the West Qinling between 10.5 and 4.2 *** the erosion-affected portion of the NL-VI section reflects some degree of tectonic instability from 8.3 to 6.9 Ma,the intensity must have been sufficiently weak to prevent the erosion of the aeolian *** further suggest that the late Miocene growth of the Tibetan Plateau has not significantly affected the West ***,the studied NL-VI aeolian sequence provides not only independent evidence for the uplift history of the West Qinling within an accurate chronological framework,but also provides new insights into the tectonic changes on the northeastern Tibetan Plateau.

关键词： Magnetostratigraphy rock and mineral magnetism Tectonics and landscape evolution Asia

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Superparamagnetism of two modern soils from the northeastern Pampean region,Argentina and its paleoclimatic indications

Superparamagnetism of two modern soils from the northeastern...

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： José Torrent Héctor Morrás Departamento de Ciencias y Recursos Agricolas y Forestales Universidad de CordobaEdificio C4Campus de Rabanales14071 CordobaSpain Instituto de Suelos Centro de Investigacion de Recursos NaturalesINTA1618 HurlinghamBuenos AiresArgentina

The magnetic susceptibility(χ)carried by pedogenic fine-grained ferrimagnets has been widely used as paleoclimatic proxy to elucidate long-term paleoclimatic variations for wind-blown terrestrial loess/paleosol ***,the magnetic properties of the lithogenic parent material can mask the pedogenic *** this study,we systematically investigated the origin of the superparamagnetism of two modern soils from the northeastern humid Pampean region,Argentina,developed on loess materials of different mineralogical *** samples were treated with the citrate-bicarbonate-dithionite(CBD)reagent,which is known to dissolve the submicron,pedogemc ferrimagnets while leaving unaltered the coarse grained *** magnetic material accounting for the frequency-dependent magnetic susceptibility peak at about 50 K remained in the residuals and is independent of the pedogenic processes. In addition,pedogenic ferrimagnetic particles in the two soils have a magnetic signature comparable to that of the soils from the Chinese Loess *** is also suggested that theχfor the bulk samples does not seem to be a reliable paleoclimatic proxy for the Pampean soils investigated in this ***,the CBD-soluble magnetic signals could be more useful to detect paleoenvironmental variations in this *** new findings provide improved understanding of the magnetic assemblage in the Pampean loess soils and make it feasible to retrieve the paleoclimatic signals carried by the pedogenic,CBD-soluble,iron oxides after removing the effects of the lithogenic inputs.

关键词： rock and mineral magnetism

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