摘要
条带状铁建造(BIFs)中含有大量的亚铁磁性矿物,其组成及来源是认识BIF成因的重要依据。本文研究了南非巴伯顿绿岩带无花果树群(距今约32亿年)恩圭尼亚组的BIFs样品的磁学和矿物学特征。通过测量富铁层与富硅层的磁滞回线、等温剩磁获得曲线与退磁曲线、矫顽力谱分析、一阶反转曲线(FORC)、低温(20~300K)有场/无场冷却曲线以及k-T曲线、Lowrie三轴热退磁曲线,结合扫描电镜观测,揭示出研究样品中磁性矿物主要为赤铁矿和磁铁矿。基于矫顽力谱分析,富铁层中磁铁矿主要是多畴及假单畴颗粒,相对含量平均为2. 1%;赤铁矿的相对含量平均为97. 9%。富硅层中磁铁矿主要为假单畴及超顺磁性颗粒,相对含量平均为4. 6%;赤铁矿相对含量平均为95. 4%。测试样品具有Morin转变特征,转变温度介于250~260K,说明BIFs中主要为赤铁矿(0. 5~6mm)。富硅层样品出现~107K、~125K两个Verwey转变温度,表明其中可能存在生物成因和非生物成因两种类型磁铁矿。
Ferrimagnetic minerals and their origins in banded iron formations( BIFs) are contentious research topics. Here we present an integrated rock magnetic result of BIFs sample from Barberton greenstone belt( South Africa). Hysteresis loops,acquisition of saturation isothermal remanent magnetism and its back-field demagnetization curves,coercivity spectrum analysis,first-order-reversal curves( FORC), low-temperature( 20 ~ 300 K) magnetic measurements( zero-field cooling/field cooling curves), thermal demagnetization of three-component isothermal remanent magnetization curves and scanning electron microscopy observation were performed. We found that hematite and magnetite are dominated in the studied sample. The magnetite grains in the iron-rich layers are mainly multi-domain and pseudo-single-domain states with average relative content 2. 1% and the average relative content of hematite is97. 9%. In the silica-rich layer,magnetite grains mainly consist of pseudo-single-domain and superparamagnetic states with an average relative content of 4. 6% and the mean of relative content of hematite is 95. 4%. Morin transition ranging in temperature from 250 K to260 K reveal that hematite grains in BIFs is dominated by multi-domain( 0. 5 ~ 6 mm). Interestingly,the silica-rich layer displays the Verwey transition at ~ 107 K and ~ 125 K,implying presence of biogenic and abiogenic magnetite in the sample.
引文
Ahmadzadeh M,Romero C and McC loy J.2018.Magnetic analysis of commercial hematite,magnetite,and their mixtures.AIP Advances,8(5):056807
Beukes NJ.1973.Precambrian iron-formations of southern Africa.Economic Geology,68(7):960-1004
Carvallo C,Muxworthy AR and Dunlop DJ.2006.First-order reversal curve(FORC)diagrams of magnetic mixtures:Micromagnetic models and measurements.Physics of the Earth and Planetary Interiors,154(3-4):308-322
Chang L,Winklhofer M,Roberts AP,Heslop D,Florindo F,Dekkers MJ,Krijgsman W,Kodama K and Yamamoto Y.2013.Lowtemperature magnetic properties of pelagic carbonates:Oxidation of biogenic magnetite and identification of magnetosome chains.Journal of Geophysical Research:Solid Earth,118(12):6049-6065
Chang L,Heslop D,Roberts AP,Rey D and Mohamed KJ.2016a.Discrimination of biogenic and detrital magnetite through a double Verwey transition temperature.Journal of Geophysical Research:Solid Earth,121(1):3-14
Chang L,Roberts AP,Heslop D,Hayashida A,Li JH,Zhao X,Tian Wand Huang QH.2016b.Widespread occurrence of silicate-hosted magnetic mineral inclusions in marine sediments and their contribution to paleomagnetic recording.Journal of Geophysical Research:Solid Earth,121(12):8415-8431
Crosby HA,Roden EE,Johnson CM and Beard BL.2007.The mechanisms of iron isotope fractionation produced during dissimilatory Fe(Ⅲ)reduction by Shewanella putrefaciens and Geobacter sulfurreducens.Geobiology,5(2):169-189
Day R,Fuller M and Schmidt VA.1977.Hysteresis properties of titanomagnetites:Grain-size and compositional dependence.Physics of the Earth and Planetary Interiors,13(4):260-267
Deng CL,He HY,Pan YX and Zhu RX.2013.Chronology of the terrestrial Upper Cretaceous in the Songliao Basin,Northeast Asia.Palaeogeography,Palaeoclimatology,Palaeoecology,385:44-54
Dunlop DJ.1986.Hysteresis properties of magnetite and their dependence on particle size:A test of pseudo-single-domain remanence models.Journal of Geophysical Research:Solid Earth,91(B9):9569-9584
Han F,Wang FX,Li JH,Qin HF,Deng CL and Pan YX.2016.Identification of magnetic minerals in surface sediments of Miyun Lake,Beijing.Chinese Journal of Geophysics,59(8):2937-2948(in Chinese with English abstract)
Heinrichs T.1980.Lithostratigraphische Untersuchungen in der Fig Tree Gruppe des Barberton Greenstone Belt zwischen Umsoli und Lomati(Südafrika).Im Selbstverlag des Geologisch-Palontologischen Instituts der Georg-August-Universitt G9ttingen,22:118
Heimann A,Johnson CM,Beard BL,Valley JW,Roden EE,Spicuzza MJ and Beuke NJ.2010.Fe,C,and O isotope compositions of banded iron formation carbonates demonstrate a major role for dissimilatory iron reduction in~2.5Ga marine environments.Earth and Planetary Science Letters,294(1-2):8-18
Hofmann A.2005.The geochemistry of sedimentary rocks from the Fig Tree Group,Barberton greenstone belt:Implications for tectonic,hydrothermal and surface processes during Mid-Archaean times.Precambrian Research,143(1-4):23-49
James HL.1954.Sedimentary facies of iron-formation.Economic Geology,49(3):235-293
Johnson CM,Beard BL,Klein C,Beukes NJ and Roden EE.2008.Iron isotopes constrain biologic and abiologic processes in banded iron formation genesis.Geochimica et Cosmochimica Acta,72(1):151-169
Klein C.2005.Some Precambrian banded iron-formations(BIFs)from around the world:Their age,geologic setting,mineralogy,metamorphism,geochemistry,and origins.American Mineralogist,90(10):1473-1499
Kletetschka G and Wasilewski PJ.2002.Grain size limit for SDhematite.Physics of the Earth and Planetary Interiors,129(1-2):173-179
Kneller EF and Luborsky FE.1963.Particle size dependence of coercivity and remanence of single-domain particles.Journal of Applied Physics,34(3):656-658
Konhauser KO,Robbins LJ,Alessi DS,Flynn SL,Gingras MK,Martinez RE,Kappler A,Swanner ED,Li YL,Crowe SA,Planavsky NJ,Reinhard CT and Lalonde SV.2017.Phytoplankton contributions to the trace-element composition of Precambrian banded iron formations.GSA Bulletin,130(5-6):941-951
Kopp RE and Kirschvink JL.2008.The identification and biogeochemical interpretation of fossil magnetotactic bacteria.Earth-Science Reviews,86(1-4):42-61
Krüner A,Byerly GR and Lowe DR.1991.Chronology of Early Archaean granite-greenstone evolution in the Barberton Mountain Land,South Africa,based on precise dating by single zircon evaporation.Earth and Planetary Science Letters,103(1-4):41-54
Kruiver PP,Dekkers MJ and Heslop DJE.2001.Quantification of magnetic coercivity components by the analysis of acquisition curves of isothermal remanent magnetisation.Earth and Planetary ScienceLetters,189(3-4):269-276
Lan CY,Zhang LC,Zhao TP,Wang CL,Li HZ and Zhou YY.2013.Mineral and geochemical characteristics of the Tieshanmiao-type BIF-iron deposit in Wuyang region of Henan Province and its implications for ore-forming processes.Acta Petrologica Sinica,29(7):2567-2582(in Chinese with English abstract)
Li HZ,Zhai MG,Zhang LC,Yang ZJ,Kapsiotis A,Zhou YZ,He JG,Wang CL and Liang J.2014.Mineralogical and microfabric characteristics of magnetite in the Wuyang Precambrian BIFs,southern North China Craton:Implications for genesis and depositional processes of the associated BIFs.Journal of Asian Earth Sciences,94:267-281
Li YL,Konhauser KO,Cole DR and Phelps TJ.2011.Mineral ecophysiological data provide growing evidence for microbial activity in banded-iron formations.Geology,39(8):707-710
Li YL,Konhauser KO,Kappler A and Hao XL.2013.Experimental lowgrade alteration of biogenic magnetite indicates microbial involvement in generation of banded iron formations.Earth and Planetary Science Letters,361:229-237
Liu Z,Liu XM,Li PY and Mao XG.2012.The magnetic properties of the bacterial sediments in Lake Chiemsee,Germany.Quaternary Sciences,32(4):820-824(in Chinese with English abstract)
Lowe DR,Byerly GR and Heubeck C.2012.Geologic Map of the Westcentral Barberton Greenstone Belt,South Africa.Boulder,Colorado:Geological Society of America
Lowrie W.1990.Identification of ferromagnetic minerals in a rock by coercivity and unblocking temperature properties.Geophysical Research Letters,17(2):159-162
Moorbath S,O’Nions RK and Pankhurst RJ.1973.Early Archaean age for the Isua iron formation,West Greenland.Nature,245(5421):138-139
Moskowitz BM,Frankel RB and Bazylinski DA.1993.Rock magnetic criteria for the detection of biogenic magnetite.Earth and Planetary Science Letters,120(3-4):283-300
Muxworthy AR and McC lelland E.2000.Review of the low-temperature magnetic properties of magnetite from a rock magnetic perspective.Geophysical Journal International,140(1):101-114
Otake T,Wesolowski DJ,Anovitz LM,Allard LF and Ohmoto H.2010.Mechanisms of iron oxide transformations in hydrothermal systems.Geochimica et Cosmochimica Acta,74(21):6141-6156
zdemir,Dunlop DJ and BerquóTS.2008.Morin transition in hematite:Size dependence and thermal hysteresis.Geochemistry,Geophysics,Geosystems,9(10):Q10Z01
zdemirand Dunlop DJ.2014.Hysteresis and coercivity of hematite.Journal of Geophysical Research:Solid Earth,119(4):2582-2594
Pan YX,Deng CL,Liu QS,Petersen N and Zhu RX.2004.Biomineralization and magnetism of bacterial magnetosomes.Chinese Science Bulletin,49(24):2563-2568
Pan YX,Petersen N,Davila AF,Zhang LM,Winklhofer M,Liu QS,Hanzlik M and Zhu RX.2005a.The detection of bacterial magnetite in recent sediments of Lake Chiemsee(southern Germany).Earth and Planetary Science Letters,232(1-2):109-123
Pan YX,Petersen N,Winklhofer M,Davila AF,Liu QS,Frederichs T,Hanzlik M and Zhu RX.2005b.Rock magnetic properties of uncultured magnetotactic bacteria.Earth and Planetary Science Letters,237(3-4):311-325
Posth NR,Konhauser KO and Kappler A.2011.Banded iron formations.In:Reitner J and Thiel V(eds.).Encyclopedia of Geobiology.Dordrecht:Springer,92-103
Qin HF,Liu QS and Pan YX.2008.The first-order reversal curve(FORC)diagram:Theory and case study.Chinese Journal of Geophysics,51(3):743-751(in Chinese with English abstract)
Raye U,Pufahl PK,Kyser TK,Ricard E and Hiatt EE.2015.The role of sedimentology,oceanography,and alteration on theδ56Fe value of the Sokoman iron formation,Labrador Trough,Canada.Geochimica et Cosmochimica Acta,164:205-220
Roberts AP,Pike CR and Verosub KL.2000.First-order reversal curvediagrams:A new tool for characterizing the magnetic properties of natural samples.Journal of Geophysical Research:Solid Earth,105(B12):28461-28475
Roberts AP,Heslop D,Zhao X and Pike CR.2014.Understanding fine magnetic particle systems through use of first-order reversal curve diagrams.Reviews of Geophysics,52(4):557-602
Robertson DJ and France DE.1994.Discrimination of remanencecarrying minerals in mixtures,using isothermal remanent magnetisation acquisition curves.Physics of the Earth and Planetary Interiors,82(3-4):223-234
Rochette P,Fillion G,Mattéi JL and Dekkers MJ.1990.Magnetic transition at 30~34 Kelvin in pyrrhotite:Insight into a widespread occurrence of this mineral in rocks.Earth and Planetary Science Letters,98(3-4):319-328
Sun S and Li YL.2017.Microstructures,crystallography and geochemistry of magnetite in 2500 to 2200 million-year-old banded iron formations from South Africa,Western Australia and North China.Precambrian Research,298:292-305
Tadic'M,Cˇitakovi c'N,Panjan M,Stojanovi c'Z,Markovi c'D and Spasojevi c'V.2011.Synthesis,morphology,microstructure and magnetic properties of hematite submicron particles.Journal of Alloys and Compounds,509(28):7639-7944
Trendall AF.2002.The significance of iron-formation in the Precambrian stratigraphic record.In:Altermann W and Corcoran PL(eds.).Precambrian Sedimentary Environments:A Modern Approach to Ancient Depositional Systems.Oxford,UK:Blackwell Publishing Ltd.,33-66
Verwey EJW.1939.Electronic conduction of magnetite(Fe3O4)and its transition point at low temperatures.Nature,144(3642):327-328
Wang CL,Dai YP,Liu L and Zhang LC.2011.The formative age of BIFand its research methods.Acta Mineralogica Sinica,31(Suppl.1):454-456(in Chinese)
Wu WF,Li YL and Pan YX.2012.Microbial mineralization inPrecambrian banded iron formations.Chinese Journal of Geology,47(2):548-560(in Chinese)
Zhao ZH.2010.Banded iron formation and related great oxidation event.Earth Science Frontiers,17(2):1-12(in Chinese with English abstract)
韩非,王芙仙,李金华,秦华峰,邓成龙,潘永信.2016.北京密云水库表层沉积物磁性矿物的鉴别.地球物理学报,59(8):2937-2948
兰彩云,张连昌,赵太平,王长乐,李红中,周艳艳.2013.河南舞阳铁山庙式BIF铁矿的矿物学与地球化学特征及对矿床成因的指示.岩石学报,29(7):2567-2582
刘植,刘秀铭,李平原,毛学刚.2012.德国Chiemsee湖磁性细菌干湖泥的磁学性质.第四纪研究,32(4):820-824
潘永信,邓成龙,刘青松,Petersen N,朱日祥.2004.趋磁细菌磁小体的生物矿化作用和磁学性质研究进展.科学通报,49(24):2505-2510
秦华峰,刘青松,潘永信.2008.一阶反转曲线(FORC)图的原理及应用实例.地球物理学报,51(3):743-751
王长乐,代堰锫,刘利,张连昌.2011.BIF的形成时代及其研究方法.矿物学报,31(增1):454-456
吴文芳,李一良,潘永信.2012.微生物参与前寒武纪条带状铁建造沉积的研究进展.地质科学,47(2):548-560
赵振华.2010.条带状铁建造(BIF)与地球大氧化事件.地学前缘,17(2):1-12