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QuarterlyThe IRM

Summer 2018, Vol. 28 No.2

Michael VolkDario BilardelloMike Jackson

Institute for Rock Magnetismmvolk@umn.edu

cont’d. on pg. 8...

ISSN: 2152-1972

Inside...Current Articles 2... and more throughout!

Inthefirstinstallmentofthisshortseriesofarticlesonmagnetic tests,wediscussedusingstrongmagneticfields to better understand the magnetic domain stateand/orparticlesizesofasample.Inthissecondinstall-ment,wewill describe theuseofweakfieldmagneti-zationsandsusceptibilities,aswellasusefulratiosandbiplotsthatcanhelptocharacterizegrainsizeordomainstate. Many of the magnetizations and properties de-scribed are of extremelywidespread use and have be-comethe“breadandbutter”ofrock-magneticresearchandsomeapplicationsofrock-magnetisminparticular.Otherproperties,ontheotherhand,arenotascommonandrequireinstrumentationthatisnotasreadilyavail-able, and have therefore remainedmore unfamiliar tosome,despitetheusefulinformationtheymayprovide. Thedisciplineofenvironmentalmagnetismfirstandforemost has incredibly benefited from advances inrock-magnetism,andmanyof the testsandproceduresdescribedhereweredevisedforenvironmentalapplica-tions.Thesamegoesforpaleointensityandotherareasofresearch.Otherdisciplines,however,havesometimedisplayed some hysteresis (#magnetistjoke, see IRMQ22(4))andhavemaintainedamoresimplisticapproach.Asisthecase,natureiscomplex,andsoismagneticre-search,sowithoutfurtheradoweintroducethelowfieldtests.

MagneticSusceptibility Measurementofmagneticsusceptibility,k= M / H,initsmostgeneral(andcommon)form,probablyinvolvestheweakestfieldapplicationthatwillcometomindtomostpaleo-androck-magnetists.Magneticsusceptibil-ity ismost commonlymeasured infields of ~200-300A/mor less [footnote: thecurrentgenerationofmulti-functionKappabridges operates atACfield intensitiesfrom2A/muptoamaximumof700A/m;theMagnon

VFSMrangeis20-400A/m;olderKappabridgeshadafixedfieldstrengthof300A/m],whichdonot(gener-ally)causeirreversiblemagnetizations,andthereforeisawidelyappliednon-destructivetechniquetocharacterizeaspecimen’smagneticresponse. Themagneticbehaviorof anymaterial is subdivid-ed into diamagnetic, paramagnetic and ferromagnetic(ferrimagnetic and antiferromagnetic) components andtherefore,whenimmersedinasteadyfield,thedifferentmineralspresentwillcontributepositivelyornegativelytothebulkmagneticsusceptibilityofthespecimen.Thegeneralassumption is that ironoxideshave largersus-ceptibilities than other diamagnetic and paramagneticminerals thatmake up the “non-magneticmatrix” andtherefore, theferrimagneticmineralswilldominate thesusceptibilityresponse.Whethertheassumptioniscor-rectornot,magneticsusceptibilityisastronglyconcen-tration-dependent property, and is often referred to as“bulk”susceptibility. Bulk susceptibility, as other magnetic properties,canbenormalizedbythevolumeorbythemass,whichsometimes introduces minor confusion when dealing

Magnetic tests and characterization protocols: mineralogy and grain size / domain state Part II: isothermal weak field tests

Figure1.TheACfieldvarieswithtimeasH = H0cos(ωt).Themagneticresponsemaylagbehind,e.g.duetoviscosity:M = M0cos(ωt-δ),whereδisthephaselag,whichis15°inthisexample.Thiscanbedecomposedintoin-phase(“real”)andout-of-phase(“imaginary”or“quadrature”)components:M = M'cos(ωt)+M" sin(ωt),wheretan(δ)=M"/M'and(M0)

2 = M'2+M"2.

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0 45 90 135 180 225 270 315 360M/M

0 ωt (degrees)

totalin-phase

quadrature

2

Current ArticlesAlistofcurrentresearcharticlesdealingwithvarioustopicsinthephysicsandchemistryofmagnetismisaregularfeatureoftheIRMQuarterly.Articlespublishedinfamiliargeologyandgeophysicsjournalsareincluded;specialemphasisisgiventocurrentarticlesfromphysics,chemistry,andmaterials-sciencejournals.Most are taken from ISIWeb ofKnowledge, afterwhichtheyaresubjectedtoProcrusteancullingforthisnews-letter.Anextensive reference listofarticles (primarilyaboutrock magnetism, the physics and chemistry of magnetism,andsomepaleomagnetism)iscontinuallyupdatedattheIRM.Thislist,withmorethan10,000references,isavailablefreeofcharge.Yourcontributionsbothto thelistandtotheCurrentArticlessectionoftheIRMQuarterlyarealwayswelcome.

ArcheomagnetismAidona,E.,G.S.Polymeris,P.Camps,D.Kondopoulou,N.

Ioannidis, andK.Raptis (2018),Archaeomagnetic versusluminescencemethods:thecaseofanEarlyByzantinece-ramic workshop in Thessaloniki, Greece,ArchaeologicalandAnthropologicalSciences,10(4),725-741.

Jordanova,N.,D. Jordanova,M.Kostadinova-Avramova,D.Lesigyarski, V. Nikolov, G. Katsarov, and K. Bacvarov(2018),AMineralMagneticApproachtoDeterminePaleo-Firing Temperatures in the Neolithic Settlement Site ofMursalevo-Deveboaz(SWBulgaria),JournalofGeophysi-calResearch-SolidEarth,123(4),2522-2538.

Juarez-Rodriguez,O.,D.Argote-Espino,M.Santos-Ramirez,andP.Lopez-Garcia(2018),PortableXRFanalysisfortheidentificationofrawmaterialsoftheRedJaguarsculpturein Chichen Itza, Mexico, Quaternary International, 483,148-159.

Kitahara,Y.,Y.Yamamoto,M.Ohno,Y.Kuwahara,S.Kam-eda,andT.Hatakeyama(2018),Archeointensityestimatesofatenth-centurykiln:firstapplicationoftheTsunakawa-Shawpaleointensitymethod toarcheological relics,EarthPlanetsandSpace,70.

Stillinger,M.D.,J.M.Feinberg,E.Ben-Yosef,R.Shaar,J.W.Hardin,andJ.A.Blakely(2018),ARejoinderontheValueofArchaeomagneticDatingIntegrativeMethodologyIstheKey toAddressingLevantine IronAgeChronology,NearEasternArchaeology,81(2),141-144.

BiomagnetismAmor,M.,etal.(2018),Ironuptakeandmagnetitebiominer-

alizationinthemagnetotacticbacteriumMagnetospirillummagneticumstrainAMB-1:Anironisotopestudy,Geochi-micaEtCosmochimicaActa,232,225-243.

Environmental magnetism and ClimateAo,H.,M.J.Dekkers,A.P.Roberts,E.J.Rohling,Z.S.An,

X.D.Liu,Z.X.Jiang,X.K.Qiang,Y.Xu,andH.Chang(2018),Mineralmagneticrecordof theMiocene-PlioceneclimatetransitionontheChineseLoessPlateau,NorthChi-na,QuaternaryResearch,89(3),619-628.

Ghazala,H.H.,I.M.Ibraheem,M.Haggag,andM.Lamees(2018),Anintegratedapproach toevaluate thepossibilityofurbandevelopment aroundSohagGovernorate,Egypt,usingpotentialfielddata,ArabianJournalofGeosciences,11(9).

Ghorbanzadeh,N.,R.Kumar,S.H.Lee,H.S.Park, andB.H.Jeon(2018),ImpactofShewanellaoneidensisonheavymetalsremobilizationunderreductiveconditionsinsoilof

Guilan Province, Iran, Geosciences Journal, 22(3), 423-432.

Goman,M.,A.Joyce,S.Lund,C.Pearson,W.Guerra,D.Dale,D.E.Hammond, andA. J.Celestian (2018),Preliminaryresults from LagunaMinucua: a potentially annually re-solvedrecordofclimateandenvironmentalchangeforthepastsimilarto5000yearsintheMixtecaAltaofOaxaca,Mexico,QuaternaryInternational,469,85-95.

Guo,X.L.,S.K.Banerjee,R.H.Wang,G.Y.Zhao,H.Song,B.Lu,Q.Li,andX.M.Liu(2018),WhymagnetiteisnottheonlyindicatorofpastrainfallintheChineseLoessPlateau?,GeophysicalJournalInternational,213(3),2128-2137.

Jia,J.,H.Lu,Y.J.Wang,andD.S.Xia(2018),VariationsintheIronMineralogyofaLoessSectioninTajikistanDur-ingtheMid-PleistoceneandLatePleistocene:Implicationsfor theClimaticEvolution inCentralAsia,GeochemistryGeophysicsGeosystems,19(4),1244-1258.

Lang,X.G.,J.T.Chen,H.Cui,L.Man,K.J.Huang,Y.Fu,C.M.Zhou,andB.Shen(2018),Cycliccoldclimatedur-ingtheNantuoGlaciation:EvidencefromtheCryogenianNantuoFormationintheYangtzeBlock,SouthChina,Pre-cambrianResearch,310,243-255.

Letsch,D.,S.J.E.Large,M.W.Buechi,W.Winkler,andA.vonQuadt (2018), Ediacaran glaciations of thewestAf-ricanCraton -Evidence fromMorocco,PrecambrianRe-search,310,17-38.

Li,Z.J.,F.Wang,X.Wang,B.F.Li,andF.H.Chen(2018),A multi-proxy climatic record from the central TenggerDesert, southernMongolian Plateau: Implications for thearidificationofinnerAsiasincethelatePliocene,JournalofAsianEarthSciences,160,27-37.

Li,M.K., et al. (2018), InfluenceofSeaLevelChange andCentennial East Asian Monsoon Variations on NorthernSouth China Sea Sediments Over the Past 36 kyr, Geo-chemistryGeophysicsGeosystems,19(5),1674-1689.

Lu,Y.,X.M.Fang,O.Friedrich,andC.H.Song(2018),Char-acteristicgrain-size component -Auseful process-relatedparameter for grain-size analysis of lacustrine clastics?,QuaternaryInternational,479,90-99.

Mejia-Echeverry,D.,M.A.E.Chaparro,J.F.Duque-Trujillo,and J. D. Restrepo (2018),An environmentalmagnetismapproach to assess impacts of land-derived sediment dis-turbancesoncoralreefecosystems(Cartagena,Colombia),MarinePollutionBulletin,131,441-452.

Pang,H.L.,B.T.Pan,E.Garzanti,H.S.Gao,X.Zhao,andD.B.Chen(2018),MineralogyandgeochemistryofmodernYellowRiver sediments: Implications forweathering andprovenance,ChemicalGeology,488,76-86.

Park,C.K.,andG.C.Lee(2018),RockMagneticApproachesUsedonDeep-seaSediments in theNortheasternEquato-rialPacific,OceanScienceJournal,53(2),369-380.

Shi, J.Y., Z. J. Jin,Q.Y.Liu,Z.K.Huang, andY.Q.Hao(2018),Terrestrialsedimentaryresponsestoastronomicallyforcedclimatechangesduring theEarlyPaleogene in theBohaiBayBasin,easternChina,PalaeogeographyPalaeo-climatologyPalaeoecology,502,1-12.

Vingiani,S.,E.DiIorio,C.Colombo,andF.Terribile(2018),IntegratedstudyofRedMediterraneansoilsfromSouthernItaly,Catena,168,129-140.

Wang,J.,Z.Chen,Q.Z.Gao,R.Grapes,Z.L.Peng,andG.N.Chen(2018),LatePleistoceneloess-likedepositsinthecoastalareaofsouthChina,Catena,167,305-318.

Weber,M.E.,etal.(2018),200,000yearsofmonsoonalhis-tory recordedon the lowerBengalFan - strong responseto insolation forcing,Global and PlanetaryChange, 166,107-119.

Zhang,Q.,Q.S.Liu,J.H.Li,andY.B.Sun(2018),AnInte-

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gratedStudyoftheEolianDustinPelagicSedimentsFromtheNorthPacificOceanBasedonEnvironmentalMagne-tism,TransmissionElectronMicroscopy,andDiffuseRe-flectanceSpectroscopy,JournalofGeophysicalResearch-SolidEarth,123(5),3358-3376.

Extraterrestrial and Planetary MagnetismChareev,D.A.,N.S.Bezaeva,andE.Khakhalova(2018),Syn-

thesisandcharacterizationofsinglecrystalsofmonoclinicpyrrhotite:possibleimplicationsforextraterrestrialmagne-tism,Meteoritics&PlanetaryScience,53,6359-6359.

Cordier, C., B. Baecker, U. Ott, L. Folco, and M. Trieloff(2018),Anewtypeofoxidizedandpre-irradiatedmicrome-teorite,GeochimicaEtCosmochimicaActa,233,135-158.

Day,J.M.D.,J.Maria-Benavides,F.M.McCubbin,andR.A.Zeigler(2018),Thepotentialformetalcontaminationdur-ingApollolunarsamplecuration,Meteoritics&PlanetaryScience,53(6),1283-1291.

Hausrath, E.M., D.W.Ming,T. S. Peretyazhko, and E. B.Rampe(2018),Reactivetransportandmassbalancemodel-ingoftheStimsonsedimentaryformationandalteredfrac-ture zones constrain diagenetic conditions atGale crater,Mars,EarthandPlanetaryScienceLetters,491,1-10.

Lorand,J.P.,S.Pont,V.Chevrier,A.Luguet,B.Zanda,andR.Hewins(2018),Petrogenesisofmartiansulfides in theChassignymeteorite,AmericanMineralogist,103(6),872-885.

Melero-Asensio,I.,J.Ormo,E.Sturkell,G.Stockmann,andJ.Mansfeld (2018),Geophysical signatureofMalingen, theminorcrateroftheLockne-Malingendoubletimpactstruc-ture,Meteoritics&PlanetaryScience,53(7),1456-1475.

Morrison, S.M., et al. (2018),Crystal chemistry ofmartianmineralsfromBradburyLandingthroughNaukluftPlateau,Galecrater,Mars,AmericanMineralogist,103(6),857-871.

Morrison,S.M.,etal.(2018),Relationshipsbetweenunit-cellparametersandcompositionforrock-formingmineralsonEarth, Mars, and other extraterrestrial bodies, AmericanMineralogist,103(6),848-856.

Oran,R.,B.P.Weiss,andO.Cohen(2018),Werechondritesmagnetizedby theearlysolarwind?,EarthandPlanetaryScienceLetters,492,222-231.

Scheinberg,A.L.,K.M.Soderlund,andL.T.Elkins-Tanton(2018),Abasalmagmaoceandynamotoexplaintheearlylunarmagneticfield,EarthandPlanetaryScienceLetters,492,144-151.

Thomas, P., M. Grott, A. Morschhauser, and F. Vervelidou(2018), Paleopole Reconstruction of Martian MagneticFieldAnomalies,JournalofGeophysicalResearch-Planets,123(5),1140-1155.

Fundamental Rock and Mineral MagnetismAnettsungla,V.Rino,andS.Kumar(2018),RedoxCondition,

NatureandTectono-magmaticEnvironmentofGranitoidsandGranitegneissesfromtheKarbiAnglongHills,North-east India: Constraints fromMagnetic Susceptibility andBiotiteGeochemistry,JournaloftheGeologicalSocietyofIndia,91(5),601-612.

Conbhuii,P.O.,W.Williams,K.Fabian,P.Ridley,L.Nagy,andA.R.Muxworthy(2018),MERRILL:MicromagneticEarth Related Robust Interpreted Language Laboratory,GeochemistryGeophysicsGeosystems,19(4),1080-1106.

deGroot,L.V.,K.Fabian,A.Beguin,P.Reith,A.Barnhoorn,and H. Hilgenkamp (2018), Determining Individual Par-ticleMagnetizationsinAssemblagesofMicrograins,Geo-physicalResearchLetters,45(7),2995-3000.

Delefortrie, S., D. Hanssens, and P. De Smedt (2018), Low

signal-to-noiseFDEMin-phasedata:Practicalpotentialformagneticsusceptibilitymodelling,JournalofAppliedGeo-physics,152,17-25.

Harrison,R.J.,J.Muraszko,D.Heslop,I.Lascu,A.R.Mux-worthy,andA.P.Roberts(2018),AnImprovedAlgorithmforUnmixingFirst-OrderReversalCurveDiagramsUsingPrincipalComponentAnalysis,GeochemistryGeophysicsGeosystems,19(5),1595-1610.

He,X.L.,H.B.Li, L. Zhang,H.Wang,C.L.Ge,Y.Cao,M.K.Bai,C.L.Li,X.Z.Ye,andS.Han(2018),Mineraland chemical response to low magnetic susceptibility ofthefaultgougefromtheGuanxian-AnxianfaultzoneandfaultcreepsettingintheLongmenShan,ChineseJournalofGeophysics-ChineseEdition,61(5),1782-1796.

Kontny,A.,andB.Reznik(2018),Effectofpost-shockanneal-ingonmagneticpropertiesofshockedmagnetite,Meteorit-ics&PlanetaryScience,53,6285-6285.

Kontny, A., B. Reznik, A. Boubnov, J. Gottlicher, and R.Steininger(2018),PostshockThermallyInducedTransfor-mationsinExperimentallyShockedMagnetite,Geochem-istryGeophysicsGeosystems,19(3),921-931.

Makaroglu,O.,M.N.Cagatay,N.R.Nowaczyk,L.J.Pesonen,andN.Orbay (2018),Discrimination ofHolocene tephraunitsinLakeVanusingmineralmagneticanalysis,Quater-naryInternational,486,44-56.

McEnroe, S.A., P. Robinson, N. Church, andM. Purucker(2018), Magnetism at Depth: A View from an AncientContinentalSubductionandCollisionZone,GeochemistryGeophysicsGeosystems,19(4),1123-1147.

Pensa,A.,L.Capra,G.Giordano,andS.Corrado(2018),Em-placement temperature estimation of the 2015 dome col-lapseofVolcandeColimaaskeyproxyforflowdynamicsof confined and unconfined pyroclastic density currents,Journal of Volcanology and Geothermal Research, 357,321-338.

Roberts,A.P.,L.Tauxe,D.Heslop,X.Zhao,andZ.X.Jiang(2018),ACriticalAppraisalofthe"Day"Diagram,JournalofGeophysicalResearch-SolidEarth,123(4),2618-2644.

Till,J.L.,andN.Nowaczyk(2018),Authigenicmagnetitefor-mationfromgoethiteandhematiteandchemicalremanentmagnetization acquisition, Geophysical Journal Interna-tional,213(3),1818-1831.

Vasquez,C.A.,F.F.Sapienza,A.Somacal,andS.Y.Fazzito(2018), Anhysteretic remanent magnetization: model ofgrainsizedistributionofsphericalmagnetitegrains,StudiaGeophysicaEtGeodaetica,62(2),339-351.

Zhang,L.,H.B.Li,Z.M.Sun,Y.M.Chou,Y.Cao,H.Wang,X.Z.Ye,andX.L.He(2018),Rockmagneticevidencefortheseismogenicsettingof largeearthquakes in theLong-menShanfaultzone,ChineseJournalofGeophysics-Chi-neseEdition,61(5),1715-1727.

Geomagnetism, Paleointensity and Records of the Geomag-netic Field

Balbas,A.M.,A.A.P.Koppers,P.U.Clark,R.S.Coe,B.T.Reilly,J.S.Stoner,andK.Konrad(2018),Millennial-ScaleInstabilityintheGeomagneticFieldPriortotheMatuyama-BrunhesReversal,GeochemistryGeophysicsGeosystems,19(3),952-967.

Bolzan, M. J.A., C. M. Denardini, andA. Tardelli (2018),Comparison of H component geomagnetic field time se-riesobtainedatdifferentsitesoverSouthAmerica,AnnalesGeophysicae,36(3),937-943.

Channell,J.E.T.,D.A.Hodell,S.J.Crowhurst,L.C.Skinner,andR.Muscheler(2018),Relativepaleointensity(RPI)inthelatestPleistocene(10-45ka)andimplicationsfordegla-cialatmosphericradiocarbon,QuaternaryScienceReviews,

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191,57-72.Cromwell,G.,C.L.Johnson,L.Tauxe,C.G.Constable,and

N.A.Jarboe(2018),PSV10:AGlobalDataSetfor0-10MaTime-Averaged Field and PaleosecularVariation Studies,GeochemistryGeophysicsGeosystems,19(5),1533-1558.

deOliveira,W.P.,D.R.Franco,D.Brandt,M.Ernesto,C.F.D.Neto,X.X.Zhao,F.B.V.deFreitas,andR.S.Martins(2018),BehaviorofthePaleosecularVariationDuringthePermian-CarboniferousReversedSuperchronandCompar-isonstotheLowReversalFrequencyIntervalsSincePre-cambrian Times, Geochemistry Geophysics Geosystems,19(4),1035-1048.

Evans,M.E.,andA.R.Muxworthy(2018),Are-appraisaloftheproposedrapidMatuyama-Brunhesgeomagneticrever-salintheSulmonaBasin,Italy,GeophysicalJournalInter-national,213(3),1744-1750.

Gogorza,C.S.G.,M.A.Irurzun,M.J.Orgeira,P.Palermo,andM.Llera(2018),AcontinuousLateHolocenepaleose-cularvariationrecordfromCarmenLake(TierradelFuego,Argentina), Physics of the Earth and Planetary Interiors,280,40-52.

Goguitchaichvili,A.,R.G.Ruiz,F.J.Pavon-Carrasco,J.J.M.Contreras,A.M.S.Arechalde,andJ.Urrutia-Fucugauchi(2018),LastthreemillenniaEarth'sMagneticfieldstrengthinMesoamerica and southernUnitedStates: Implicationsingeomagnetismandarchaeology,PhysicsoftheEarthandPlanetaryInteriors,279,79-91.

Greve,A.,andG.M.Turner(2018),Newandrevisedpalaeo-magneticsecularvariationrecordsfrompost-glacialvolca-nicmaterialsinNewZealand(vol269,pg1,2017),PhysicsoftheEarthandPlanetaryInteriors,279,92-94.

Kim,W.,S.J.Doh,andY.Yu(2018),ReliablepaleointensitydeterminationsfromLateCretaceousvolcanicrocksinKo-reawithconstraintofthermochemicalalteration,PhysicsoftheEarthandPlanetaryInteriors,279,47-56.

Liu,J.B.,N.R.Nowaczyk,U.Frank,andH.W.Arz(2018),A20-15kahigh-resolutionpaleomagneticsecularvariationrecordfromBlackSeasediments-noevidenceforthe'Hi-linaPaliexcursion'?,EarthandPlanetaryScienceLetters,492,174-185.

Molinek, F. R., andD. Bilardello (2018),Application of anAnisotropy-Based Correction to Relative PaleointensityEstimates of Experimentally Deposited Sediments, Geo-chemistryGeophysicsGeosystems,19(3),882-900.

Panovska, S., C. G. Constable, and M. C. Brown (2018),GlobalandRegionalAssessmentsofPaleosecularVariationActivityOver thePast100ka,GeochemistryGeophysicsGeosystems,19(5),1559-1580.

Sanchez-Moreno, E. M., M. Calvo-Rathert, A. Goguitchai-chvili,G.T.Vashakidze, andV.A.Lebedev (2018),Evi-denceofUnusualGeomagneticRegimesRecordedinPlio-PleistoceneVolcanicSequencesfromtheLesserCaucasus(Southern Georgia), Geochemistry Geophysics Geosys-tems,19(5),1429-1446.

Sprain,C.J.,N.L.Swanson-Hysell,L.M.Fairchild,andK.Gaastra (2018),A field like today's? The strength of thegeomagneticfield1.1billionyearsago,GeophysicalJour-nalInternational,213(3),1969-1983.

Xu,Y.C.,Z.Y.Yang,Y.B.Tong,andX.Q.Jing(2018),Pa-leomagnetic Secular Variation Constraints on the RapidEruption of the Emeishan Continental Flood Basalts inSouthwestern China and Northern Vietnam, Journal ofGeophysicalResearch-SolidEarth,123(4),2597-2617.

Magnetic Fabrics and AnisotropyBiedermann,A.R.(2018),Magneticanisotropyinsinglecrys-

tals: a review.Geosciences8(8),DOI:10.3390/geoscienc-

es8080302Canon-Tapia,E.,andM.I.B.Raposo(2018),Anisotropyof

magneticsusceptibilityofsilicicrocksfromquarriesinthevicinityofSaoMarcos,RioGrandedoSul,SouthBrazil:Implicationsforemplacementmechanisms,JournalofVol-canologyandGeothermalResearch,355,165-180.

Chatterjee,S.,S.Mondal,P.Paul,andP.Das(2018),Palaeo-currentandenvironmentalimplicationsfromanisotropyofmagneticsusceptibility(AMS):acasestudyfromTalchirandBarakarformations,RaniganjBasin,WestBengal,In-dia,ArabianJournalofGeosciences,11(11).

Guimaraes, L. F.,M. I. B. Raposo,V.A. Janasi, E. Canon-Tapia,andL.A.Polo(2018),AnAMSstudyofdifferentsilicicunitsfromthesouthernParana-EtendekaMagmaticProvince in Brazil: Implications for the identification offlowdirectionsand localsources,JournalofVolcanologyandGeothermalResearch,355,304-318.

Hrouda, F., M. Chadima, and J. Jezek (2018), Anisotropyof susceptibility in rockswhich aremagnetically nonlin-eareven in lowfields,Geophysical Journal International,213(3),1792-1803.

Hrouda,F.,M.Chadima,J.Jezek,andJ.Kadlec(2018),An-isotropiesofin-phase,out-of-phase,andfrequency-depen-dentsusceptibilitiesinthreeloess/palaeosolprofilesintheCzechRepublic;methodologicalimplications,StudiaGeo-physicaEtGeodaetica,62(2),272-290.

Nke,B.E.B.,T.Njanko,M.A.Mamtani,E.Njonfang,andP. Rochette (2018), Kinematic evolution of the MbakopPan-African granitoids (western Cameroon domain): AnintegratedAMSandEBSDapproach,JournalofStructuralGeology,111,42-63.

Oliva-Urcia,B.,I.Gil-Pena,R.Soto,J.M.Samso,B.Antolin,andE.L.Pueyo(2018),Newinsightsintoasymmetricfold-ingbymeansoftheanisotropyofmagneticsusceptibility,VariscanandPyreneanfolds(SWPyrenees),StudiaGeo-physicaEtGeodaetica,62(2),291-322.

Terrinha, P., E. L. Pueyo,A.Aranguren, J. C.Kullberg,M.C.Kullberg,A.Casas-Sainz,andM.D.Azevedo (2018),GravimetricandmagneticfabricstudyoftheSintraIgne-ous complex: laccolith-plug emplacement in theWesternIberianpassivemargin,InternationalJournalofEarthSci-ences,107(5),1807-1833.

Mineralogy, Petrology, Mineral Physics and Chemistry Czaja,A.D.,M.J.VanKranendonk,B.L.Beard,andC.M.

Johnson (2018),Amultistage origin forNeoarchean lay-ered hematite-magnetite iron formation from the WeldRange,YilgarnCraton,WesternAustralia,ChemicalGeol-ogy,488,125-137.

Eslami,A.,S.Arai,M.Miura,andM.A.Mackizadeh(2018),Metallogenyoftheperidotite-hostedmagnetiteoresoftheNainophiolite,CentralIran:ImplicationsforFeconcentra-tionprocessesduringmulti-episodicserpentinization,OreGeologyReviews,95,680-694.

Farley,K.A. (2018),Heliumdiffusion parameters of hema-titefromasingle-diffusion-domaincrystal,GeochimicaEtCosmochimicaActa,231,117-129.

Gahlan,H.A.,M.K.Azer,andP.D.Asimow(2018),Ontherelativetimingoflistwaeniteformationandchromianspi-nel equilibration in serpentinites,AmericanMineralogist,103(7),1087-1102.

Liang,Z.,Y.Xiao,J.Thakurta,B.X.Su,C.Chen,Y.Bai,andP.A.Sakyi(2018),ExsolutionLamellaeinOlivineGrainsofDuniteUnitsfromDifferentTypesofMafic-UltramaficComplexes,ActaGeologicaSinica-EnglishEdition,92(2),586-599.

Mei,W.,X.B.Lu,X.D.Wang,M.R. Jiang,X. J. Fan, S.

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"Beforethebreakup,andafterthebreakup":1858illustrationsof Pangea byAntonio Snider-Pellegrini, from "La Créationet ses mystères dévoilés" ("Creation and its Mysteries Un-veiled".)

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cont’d. from pg. 1...

with theunitsofmeasure,orat least imposesdefiningtwo “different” susceptibilities. Because of the weakfieldsused, itmakessense to report these inA/m,andthereforesusceptibilitymeasurementswillinvolvemag-neticmoment(Am2)dividedbyfield(A/m),whichwillthenbeequaltom3.Normalizingbyvolume(m3inSI),willresultindimensionlesssusceptibility,referredtoask,whichusersoftenreportas“SIunit”,or,becauseofthegenerallysmallvalues,μSI(=10-6SI).However,notallrocks(orspecimens)havecomparabledensities,andvolume-normalizedsusceptibilitiesoftenreflectvariabledegreesofcompactionaswellasdifferencesinconcen-tration.Forthisreason,andbecauseitisgenerallyeasiertogetaccuratemeasurementsofmass thanofvolume,susceptibility(likeotherconcentration-dependentprop-erties) is commonlymass-normalized. Whenmass isusedasanormalizer(kginSI),thebulksusceptibilityisthenreferredtoasmasssusceptibilityχ,inm3/kg.Assumingthesusceptibilityresponseisdominatedbytheferromagneticfraction,susceptibilityismostoftenusedasamagneticconcentrationparameter,whichmakesita valuable normalizer to remove the concentration-de-pendencefromothermagneticproperties(morebelow). Theaboveisvalidinsteady(DC)magneticfields,forwhichkorχaresimplerealnumbers.However,changing(AForAC)fieldsmaycausedelayedresponses,makingtheACsusceptibilityingeneralacomplexquantity:k= k’ - iωk”,wherek’isthein-phaseresponseofMtoanoscillatingfieldH0 e

iωt andk”isthe90˚out-of-phase(orquadrature)response(Fig.1). The delayed response and corresponding out-of-phasesusceptibilitycanarisefromthreedifferentphysi-cal mechanisms (see IRMQ 13(4)): (1) magnetic vis-cositywithrelaxationtimescomparabletotheACfieldreversalinterval;(2)irreversiblemagnetizationchanges(low-field hysteresis) driven by theAC field; and (3)productionofelectricaleddycurrentsbytheACfieldinelectricallyconductivematerials.Eachofthesemecha-nismsissignificantonlyforarestrictedrangeofmate-rials. Viscosityonmillisecond timescales is generallyonlyimportantforfineSDparticles,neartheSPbound-ary. Low-field hysteresis has been documented onlyin multidomain pyrrhotite, hematite and intermediatecompositiontitanomagnetites,wherespontaneousmag-netizationisnottoolargeandwall-pinningenergiesare

comparabletoexternal-fieldinteraction(Zeeman)ener-gies.Conductivityisonlylargeenoughtomatterinmet-als,graphiteandsomesulfideminerals,inthefrequencyrangecommonlyusedforsusceptibilitymeasurements.Quadraturesusceptibilityk”isthereforealmostalwaysmuchsmallerthanin-phasesusceptibilityk’.Butwhenitissignificantinmagnitude,itprovidesimportantinfor-mationaboutthemagnetic(and/orconductive)mineralassemblage. ForverysmallSD(“viscoussuperparamagnetic”orVSP)grains,k”andthefrequencydependenceofk’(fre-quencyf= ω/2π)arecloselyrelatedtoviscouschangesofMrwithtime t(Néel,1949;MullinsandTite,1973;ShcherbakovandFabian,2005;Egli,2009).Ausefulre-lationforrecognizingthermalrelaxationistheso-called“π/2” law: χ”[viscosity]= -(π/2)(δχ’/δlnf),which applies topopulations of VSP particles with a range of particlesizes/shapesorthermalactivationenergies. Thesebehaviorsallowforgrainsizeapplicationsofmagneticsusceptibility:atsmallSDgrainsizesthesus-ceptibilityincreasesasthesuperparamagneticthresholdisapproached,andsmallrotationsofthegrainmomentsin response to thefieldgiveway tocomplete thermal-ly-assisted moment reversals (e.g. Stacey & Banerjee1974). Since superparamagnetic properties are charac-terizedbyashortrelaxationtimeτ,theapparentsuscep-tibilityofgrains thataresuperparamagneticatDCandlowAFfieldswilldecreasestronglyatfrequencies,f>l/τ. Whilemagnetite susceptibility is independentofH0 uptothemaximumACfieldsavailableinmostinstru-ments(afewhundredA/morμT),Clark(1984)andlaterWorm (1991) discovered low-field amplitude depen-dencefor thesusceptibilityofpyrrhotite; this isduetolow-fieldhysteresis,andisaccompaniedbyanincreaseinquadraturesusceptibility.Wormetal.(1993)alsode-termined that pyrrhotite (depending on grain size) ex-hibitsfrequency-dependentsusceptibilityinsufficientlyhighfrequencies(>1kHz),duetoinductionofeddycur-rents.Roomtemperaturedependenceonfieldamplitude(H0)andfrequency(f)canthusbeusedasindicationforcoarse-grainedpyrrhotite(Fig.2).Jackson et al. (1998) observed field amplitude-depen-dence for Ti-magnetite for both in-phase (χ’) and outof phase (χ”) susceptibility, and determined that (a) χ’

Figure2.Wormetal.(1993).Comparisonoffrequencydependence(a,b)inphaseandoutofphasesusceptibilitiesofpyrrhotite(a)andmagnetite(b).c)showscomparisonoffielddependence(f=2kHz)inphasesusceptibilityofpyrrhotiteore,whereSE09haslarger(mm-sized)crystalsthanSE7,andmagnetite.Notethatthefielddependenceincreaseswithgrainsize.

9

decreases and (b) χ”/χ’ increases with increasing Ti-substitution (Fig. 3). With decreasing spontaneousmagnetization,thesusceptibilitydropsbelowthe“self-demagnetization limit”of1/N(whereN is thedemag-netizingfactor)thatischaracteristicofMDparticlesofhigh-intensitymagneticphases. A useful parameter to quantify frequency-depen-dence,forexampleforenvironmentalapplications,isthepercent frequency-dependenceofmagneticsusceptibil-ityχ,

χfd%=(χlf-χhf)/χlfx100

Whereχlfandχhfarealowandhighfrequencyvalues,re-spectively,thataretypicallyanorderofmagnitudeapart.Thedifferenceχlf-χhfiszeroforSDgrains,andincreasesforSPgrains(e.g.Oldfieldetal.,2009).

ARM Anhysteretic remanentmagnetization (ARM) is ac-quiredinthepresenceofastrongalternatingfield(AF)thatdecayswithtime,andaweaksteady(DC)field.Thesteadyfieldproducesabiasinwhatwouldotherwisebean effective demagnetization process. The role of therandomizingAF isanalogous to thatof temperature in

thermal demagnetization or remanence acquisition,overcominganisotropyenergybarriers in themagneticparticles, and allowing the netmoment of the popula-tiontoequilibratewiththeambientsteadyfield.Thus,despitetheuseofstrongalternatingfields,ARMiscon-sideredtobeaweak-fieldremanence,withanintensitygenerallyproportionaltothebiasfield,typicallyontheorderoftheEarth’sfieldorlittlehigher(~50μT-200μT,or equivalently, 40 - 160A/m), and anorientationgenerallyparalleltoit(intheabsenceofanisotropy,orifappliedalonganeasy-axisofmagnetization).Therapid-ityofARMs(at leastcomparedtoa laboratoryTRM),jointlywith itsmagnetizationeffectivenessandtheca-pabilityofmodernmagnetometerstoapplytheseinline,makesthemextremelyuseful.

Mineral Frequency (Hz)- dependency

Field (HAC)- de-pendency

References

SPgrains χ’, χ” χ’, χ” MullinsandTite(1973)

Pyrrhotite χ’, χ” χ’, χ” Worm(1991);Wormetal.(1993);Volketal.(2018)

Mgt Moskowitzetal.(1998);Ozdemiretal.(2009)

MDmgt χ', χ" χ’, χ” Moskowitzetal.(1998);Ozdemiretal.(2009)

Ti-mgt χ', χ" Moskowitzetal.(1998);Jacksonetal.(1998)

Hmt RockMagneticBestiary

Weak/strong field testsAFdemagnetizationspectra,theLowrieFullerTest Lowrie andFuller (1971) devised a test thatwouldhelpdistinguishbetweenremanencescarriedbySDorMDgrains.Initsoriginalform,theycomparedtheAFdemagnetizationspectraoftheoriginalNRM,oraweakfieldTRM,withthespectraofanIRM.BecausethistestremovestheNRM,analternativepro-tocolwasproposedundertheassumptionthatanARMisanadequateanaloguetotheTRM(Dunlopetal.,1973).The basic idea is that, if theweak-fieldTRM ismoreeasilyAFdemagnetizedthanthestrongfieldSIRM,thesampleisinapredominantlyMDstate.IftheoppositeistruethesampleismoreSD(Fig.4).FollowingJohn-sonetal.(1975),mostapplicationsoftheLowrie-FullertesthavesubstitutedARMforTRMastheweak-fieldre-manence.Ineithercase,thetesthasuncertaintheoreti-calfoundations(e.g.DunlopandÖzdemir1997),andisbasedsolelyonexperimentalobservations.Thetest’sva-

Figure3.In-phasesusceptibilityk’asafunctionofACfieldamplitudeforsynthetictitanomagnetites:a)single-crystalspheres,exhibitingtheself-demagnetizationlimit(N=⅓, k=3SI);b)irregularpolycrystals.

Summaryofknownmagneticsusceptibilityobservationsfordifferentmineralsandgrainsizes:f(Hz)isfrequencydependence;f(H)isamplitudedependence;χ’ is in-phase susceptibility; χ” is out of phase susceptibility.Entries in boldindicatewheretheeffectismostpronounced.

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liditywasseriouslyquestionedwhenitwasdiscoveredthatsometrulyMDsamples(>100µm)showedSDlikebehavior(Heideretal.1992).Thiswasattributedtothelowinternalstressofthesesamples.Thus,thetestmaybeusedtodeterminethedomainstate,ifthegrainscon-tainenoughdefectsfordomainwallstobepinned.How-ever,DunlopandÖzdemir (1997)noted that the sameinformationcanberetrievedfromtheshapeoftheTRMdemagnetizationspectraalone.WhileMDgrainsshowanexponentialdecayoftheremanence,aninitialplateauinremanenceat lowAF-fieldscan indicateamoreSDbehavior(Fig.5).

Magnetic Ratios and biparametric plotsBanerjee-KingPlot Ausefulgrain-sizedependentpropertyistheanhys-teretic susceptibility (χARM,unitsofm

3/kg, anddefinedastheratiooftheARMmagnetization,inAm2/kg,tothebiasDCfields, inA/m),which is highest for particlesin the stable SD (SSD) size range, decreasing slowlywithincreasinggrainsizeandrapidlyfallingtozeroforsmallergrains (i.e. towardsSPsizes,EgliandLowrie,002)(Fig.6)). Similarly,thelow-fieldsusceptibility(χLF)ishighestforparticlesizesattheupperendoftheSPrange,anddecreases (not necessarily monotonically) through theSSDandlargersizes(Fig.7aandb). TheBanerjee-Kingplot(Banerjeeetal.,1981;Kingetal.,1982) tries toquantify theconcentrationandef-fective grain size of magnetic carriers, or variationsin the ratio of coarse tofine grain-sizes, by construct-ingabiplotofanhystereticsusceptibility (χARM)versuslow-field susceptibility (χLF) (e.g.,Fig8a).Byplottingthese twoconcentration-andsizedependentpropertiesagainsteachother,itispossibletoobtainanestimateofmagnetiteconcentrationandparticlesize(Fig8b,Kingetal.,1982).Thetechniquehasbeensuccessfullyusedto distinguish climatic/environmental events in lakecoresfromMinnesota(Banerjeeetal.,1981;Kingetal.,1982).

Figure4.NRM/IRMAFdemagnetizationplotsofFulleretal.(1988).Intheleft-handpaneldemagnetizationdataofalteredlavacarryingsecondarymag-netization are shownas a functionofAFfield: other than thefirst step, theIRMoveralldemagnetizesmorereadilythantheNRM,suggestingSD-likebe-havior.Ontheright-handpanelPermianlavasfromNewZealandshowfasterdemagnetizationofanIRM,suggestingMD-likebehavior.

DatafromtheTivaCanyonsamples(IRMQ14.3and16.1)beautifullyillustratetheabilityoftheplottotrackgrain size changes in a sample setwith approximatelyconstant (titano)magnetite concentration (Fig. 9, left),whileatthesametimepointingtosomesignificantca-veats. For one, the calibrationdoes not extendbelow100nm,somanyoftheTivaCanyonsamplesare“offthegrid”.Nanoparticlepopulationsintroduceanambi-guity:withlowratiosofχARM/χLF,theyplotinthelowerrightportionofthediagramalongwithhigherconcentra-tionsofMDparticles.Anothercaveathastodowiththeabsolutesizecalibration;sizedpowdersaredifficult todisperseeffectivelyinanonmagneticmatrix,andinter-particleinteractionsarenotoriousforsuppressingARMacquisition (e.g., Sugiura, 1979; Dunlop & Ozdemir1997§11.4).Asaresult,innon-interactingpopulationssuchastheTivaCanyonsamples,χARMismuchhigherforeachgrainsizethanitwasinthecorrespondingcali-brationsamples(Fig.9,right).

Figure5.Lowrie-Fullertestsforsamplesfrombasalticflows.a)anex-ponentialdecayoftheremanenceistypicalofMDgrains,despitetheIRMdemagnetizingmorerapidlythantheNRMorARM,contrarilytoLowrieandFuller’s(1971)initialassumption;b)aninitialplateau(orhump)isindicativeofSD-likebehavior,asistheIRMdemagnetizingmorerapidlythantheNRMorARM.

Figure6.χARMasafunctionofgrain-sizeforacollectionofdata(EgliandLowrie,2002.)

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Figure7.Grain-sizedependentpropertiesintheTivaCanyontuff(Tilletal.,2011);magneticparticlesizeincreasessystem-aticallyupwardfromthebaseoftheflow.Thepeakinχ0(=χLF)markstheSP-SSDtransition;thepeaksinχARMandinMrs/Ms marktheupperendoftheSSDrange.ThesizerangedoesnotincludeMDparticles.

χARM/SIRM Assumingasingle(magnetite)remanencecarrier,theχARM/SIRMratio,whereSIRMisthesaturationisother-malremanentmagnetizationimpartedinafieldof1T,reflects someaspect of theparticle-sizedistributionofthe remanence carriers. Because both of these are re-manentmagnetizations,SPparticleshaveno influenceon the ratio. χARMdecreasesmore rapidly thanSIRMwithincreasinggrainsize,sotheratiodecreasescontinu-ouslyfromSDthroughthePSDandMDsizeranges.Insampleswith awide range of particle sizes, the χARM/SIRMratioisrelatedtotheproportionoffinergrainsin

Figure8.Calibrationdata(left)forsizedmagnetitepowdersdispersedat~1%concentrationinanonmagneticmatrix,andresultantsize-con-centrationgrid(right),fromKingetal1982.

thepopulation(Maher,1988).Highervaluessometimesexceed2x10-3m/A,indicatingdominancebySDgrains(e.g.Oldfieldetal.,2003;EgliandLowrie,2002).

ARM/SIRMversusDCfield Sugiura(1979)utilizedARMacquisition(normalizedtoSIRM)versusDCfieldtoquantifymagneticinterac-tions: PSD particles (sample 6 in Fig. 10) haveARMacquisitionthatismorelinearandplotsatlowervaluesofARM/SIRMthanSDparticles(sample1inFig.10).Sugiura(1979)thereforeproposedtousetheshapeandslopeofthecurvestoquantifymagneticinteractions.Thetechniquewassuccessivelyutilizedbyanumberofauthorsondifferent applications (e.g.DunlopandOz-demir,1997;EgliandLowrie2002;Egli2006onSD;Moskowitzetal.,1993;Tilletal.,2011).

Mrs/MsvsχARM/Mrs Lascuetal.(2010)proposedamethod,whichallowsforthequantificationofseveralmagneticparametersofasedimentatonce.TheyuseMsasaproxyforthetotalferrimagneticconcentrationofasample.Further,simi-larlytotheDayetal.(1977)plot,theirapproachutilizesthe remanenceratio toestimate thedomainstate. TheratioχARM/Mrsissensitivetobothdomainstate(Maher,2007;Egli2006)andtomagnetostaticinteractions(Su-giura1979).TheuseofχARMasawaytoquantifyinter-actionswasexperimentallyvalidated:highlyinteractingsingledomainmagnetiteintheteethofchitons(marinemolluscs),showlowχARM,whilewellseparatedparticlesofsimilarsizehavemuchhighervalues.Finally,there-manence ratio is plotted against the χARM/Mrs ratio.BycreatingsyntheticmixturesofMD,PSD,andSDmag-netitesLascuetal.(2010)wereabletocalculatemixinglinesthatcorrespondwellwiththeexperimentaldata.

OtherBiplots Oldfield et al. (2009) describe other ratios that areusefultoquantifymagneticgrain-sizewithintheSD-SP

Figure9.(left)Banerjee-KingplotoftheTivaCanyontuffsamples(Tilletal.,2011), illustratingtheprogressionfor increasingparticlesizes(smaller thanMD)withapproximatelyconstantconcentration.Symbolcolorsandshapessignifystratigraphicheight,andthusgrainsizeofthemagneticparticles(cffig7).Distinctpeaksoccuralongeachaxisatdomainstatethresholds.(right)thegrain-sizecalibrationlines(diametersinμm)fromtheoriginalstudiesyieldgrossunderestimatesof theSD-PSDsizes,andoverestimatesof theSP-SDsizes,probablybecauseinteractionsdepressedtheχARMvaluesofthecali-brationsamples.

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Figure10.Sugiura1979.ARMacquisitionasafunctionofbiasfield (wherePARMdenotesARM(H)/SIRM).Particle interac-tions increase from specimens 1 (SD particles) to 6 (PSD).ARMacquisitionbecomesmorelinearasARMdecreases.size range: χARM/χlf increaseswithmagnetic grain-size,providedthatthemeangrain-sizeiswithinorbelowthestable single domain (SD) size range (i.e. grain diam-eters less than~0.1μm(Maher,1988;Oldfield,1994,2007); χARM/χfd increases with increased grain-sizewithintheSPtoSDsizeranges(Oldfield,1994,2007).Plottingonequantityversustheotherresultsinausefulbi(logarithmic)plotthathelpsconstrainthefinermagnet-icgrains.Figure12showssuchaplotforloess/paleosolssamplesfromtheChineseloessplateau,soils,andlakeand marine sediments containing biogenic magnetite.StableSDgrain-sizesplottotheupperrightandgrain-sizedecreasestowardstheorigin.

χARM/IRM100mTversusχfd% MaherandThompson(1992)utilizedabivariateplottoalsoquantifymagneticgranulometryofloessandpa-

Figure11.Lascuetal.2010modelwithendmemberpopula-tionscomprisedofMD,PSD,SD, interactingSD (ISD)anduniaxial noninteractingSD (UNISD) populations, aswell asmixtures of these endmembers, distinguished in a bivariateplot.

leosolsamples.Ontheordinateaxis,theχARM/IRM100mT ratio increases for decreasinggrain-sizes, fromMD toSD.χfd%increaseswithdecreasinggrain-size,reachingamaximumattheSD/SPthreshold.Notethatthesamplesusedcontainedhematite,andarethereforeoffsetwithre-specttopuremagnetitepowders(whichinturnarelikelyoffsettowardslowerχARM/IRM100mTbecauseofparticlesclumping…)(Fig.13).

MagneticMineralogytests Attemptstodeterminethemagneticmineralogyfromcombinationsofthemagneticpropertiesdescribedhereandinthepreviousinstallmentofthisseriesofarticleson rock-magnetic tests (IRMQ27 (4)) have been per-formedbyqualitativelyevaluatingbiplotsandchoosingappropriate ratios. Following Thompson and Oldfield(1986), Peters and Thompson (1998) plot the ratio ofSIRM/χlf(unitsofA/m)versusacoarseestimateofco-ercivityofremanenceBcr(unitsofmT)(Fig.14a).Theplotdefinessomewhatoverlappingdistributionsfordif-ferentminerals,aroundwhichtheauthorsdrewirregularpolygons inanattempt todefine theoccurrenceof thedifferent mineralogies (not shown). To better separatethe distribution of pyrrhotite from those ofmagnetite,titanomagnetiteandgreigite,theyplotSIRM/χlfversusARM40mT/SARM(wheretheSARMwasacquiredin99mTfields,andbothARMsusingabiasfieldof0.1mT).TheARMimpartedover40mTwaschosenbecauseitwas empirically determined by the authors that it bestseparatedthetwomineralgroups(Fig.14b).Likewise,theyplotteda100mTbackfieldIRMoverSIRMration(IRM-100mT/SIRM) versus ARM40mT/SARM to furtherdistinguishgreigitefrommagnetite,titanomagnetiteandpyrrhotite(Fig.14c).Peters and Dekkers (2003) subsequently extended the

Figure12.Bi-logarithmicplotofχARM/χlfversusχARM/χfd. Both ratios increase fromSP to stableSDgrain-sizes (Oldfield etal.,2009).

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Figure13.χARM/IRM100mTratioversusχfd%(MaherandThompson,1992)forsamplesfromtheChineseLoessPlateau(containingmagnetiteandhematite),andpuremagnetitepowdersofdifferentsizes.

workofThompsonandOldfield(1986),andprovidingadditionaldata fromothermagneticminerals (goethiteandmaghemite) they regenerated the plot of SIRM/χlf(which they refer to as σRS, units ofA/m) versus co-ercivityofremanence(Bcr,unitsofmT).Forthelatter,however,theyusedthemeancoercivitydistributionde-rived from theunmixingof an IRMacquisitioncurve,which they refer to as (B0)CR’, insteadof theBcr deter-minedfromaback-fieldcurve(Fig.15). Inafutureinstallmentwewillpresentrock-magnetictestsperformedasafunctionoftemperature.Weleaveyou with a summary table of the symbols and the SIunits ofmeasure for the low-fieldmagnetic propertiesdescribedinthisarticle(onthenextpage).

ReferencesBanerjee, S.K., King, J.W., and J. Marvin (1981).A rapid

method for magnetic granulometry with applications toenvironmentalstudies.Geophys.Res.Lett.,8,4,333-336.

Cisowski,S.,J.Dunn,M.Fuller,andP.J.Wasilewski(1990).NRM:IRM(s)demagnetizationplotsofintrusiverocksandtheoriginofthetheirNRM,Tectonophys.,184,35–54.

Clark, D.A. (1984). Hysteresis properties of sized dispersedmonoclinicpyrrhotitegrains.Geophys.Res.Lett.,11,173-176.

Day,R.,Fuller,M.,andV.A.Schmidt,V.A.(1977).Hysteresispropertiesoftitanomagnetites:Grain-sizeandcomposition-aldependence.Phys.EarthPlanet.Int.,13,260-267.

Dunlop,D.J.(1973).Superparamagneticandsingle-domain-threshold sizes inmagnetite. J.Geophys.Res., 78, 7602-7613.

Dunlop,D.J.andÖ.Özdemir(1997).RockMagnetism:Fun-damentalsandfrontiers.CambridgeStudiesinMagnetism,CambridgeUniversityPress,Cambridge,573pp.

Egli, R. (2006).Theoretical considerations on the anhys-teretic remanent magnetization of interacting particleswith uniaxial anisotropy, J.Geophys.Res., 111,B12S18,doi:10.1029/2006JB004577.

Egli, R. (2009). Magnetic susceptibility measurements as afunctionoftemeperatureandfreqeuncyI:inversiontheory.Geophys.J.Int.(2009)177,395–420.

Egli,R.,andW.Lowrie(2002).Anhystereticremanentmag-netizationoffinemagneticparticles,J.Geophys.Res.,107,

Figure14. a)SIRM/χLF versus coercivityof remanenceBcrfor a collection ofmagneticminerals ; b) SIRM/χLF versusARM40mT/SARMempiricallydeterminedtoseparatethedistri-butionofpyrrhotitefromthoseofmagnetite, titanomagnetiteandgreigite;c)ARM40mT/SARMtofurtherdistinguishgreigitefrom magnetite, titanomagnetite and pyrrhotite (Peters andThompson,1998).

Figure15.SIRM/χLFversuscoercivityofremanenceBcrforacollectionofmagneticminerals(PetersandDekkers2003).

A)

B)

C)

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B10,doi:10.1029/2001JB000671.Fuller,M.,S.Cisowski,M.Hart,R.Haston,andE.Schmidtke

(1988).NRM:IRM(s)demagnetizationplots;anaidtotheinterpretationofnaturalremanentmagnetization,Geophys.Res.Lett.,15,518–521

Fuller,M.,T.Kidane,andJ.Ali(2002).AFdemagnetizationcharacteristics of NRM, compared with anhysteretic andsaturation isothermal remanence:anaid in the interpreta-tionofNRM,Phys.Chem.Earth,27(25-31),1169-1177

Heider,F.,Dunlop,D.J.,aandH.C.Soffel (1992).Low-tem-perature and alternating field demagnetization of satura-tionremanenceandthermoremanenceinmagnetitegrains(0.037umto5mm).J.Geophys.Res.,97,9371-9381.

Jackson,M.J.,Moskowitz,B.M.,Rosenbaum,J.,andC.Kis-sel(1998).Field-dependenceofACsusceptibilityintitano-magnetites.Earth.Planet.Sci.Lett.,157,129-139.

Johnson,H.P.Lowrie,W., andD.V.Kent (1975).Stabilityofanhysteretic remanent magnetization in fine and coarsemagnetiteandmaghemiteparticles.Geophys.J.Roy.As-tron.Soc.,41,1-10.

King,J.W.,Banerjee,S.K.,Marvin,J.,andÖ.Özdemir(1983).Acomparisonofdifferentmagneticmethodsfordetermin-ing the relative grain size of magnetite in natural soils:someresultsfromlakesediments.Earth.Planet.Sci.Lett.,59,404-419.

Lascu,I.,Banerjee,S.K.,andT.S.Berquo(2010).Quantifyingthe concentration of ferrimagnetic particles in sedimentsusing rockmagneticmethods.Geochem.,Geophys,Geo-syst.,11,Q08Z19,doi:10.1029/2010GC003182.

Lowrie,W., and M. Fuller (1971). On the alternating fielddemagnetization characteristics of multidomain thermo-remanentmagnetizationinmagnetite.J.Geophys.Res.,76,6339-6349.

Maher, B.A. (1988).Magnetic properties of some syntheticsub-micronmagnetites.Geophys.J.Roy.Astr.Soc.94,83-96.

Maher, B.A. (2007). Environmental magnetism and climatechange.ContemporaryPhysics,48,5,247-274.

MaherB.A,ThompsonR(1992)PaleoclimaticsignificanceofthemineralmagneticrecordoftheChineseloessandpaleo-sols.QuaternaryResearch37:155-170

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byB.A.MaherandR.Thompson (CambridgeUniversityPress,Cambridge,1999).

Moskowitz,B.M.,R.B.Frankel,andD.A.Bazylinski(1993).Rockmagneticcriteriaforthedetectionofbiogenicmag-netite,EarthPlanet.Sci.Lett.,120,283–300,doi:10.1016/0012-821X(93)90245-5.

Moskowitz,B.M.,Jackson,M.J.,andKissel,C.(1998).Low-temperaturemagnetic behavior of titanomagnetites.EarthPlanet.Sci.Lett.,157,141–149.

Mullins, C.E., and M.S. Tite (1973), Magnetic viscosity,quadrature susceptibility, and frequency dependence ofsusceptibilityinsingle-domainassembliesofmagnetiteandmaghemite.J.Geophys.Res.,78,804–809.

Néel,L.(1949).Theoriedutrainagemagnetiquedesferromag-netiquesengrainsfinsavecapplicationsauxterrescuites.Ann.Peophys.,5,99-136.

Oldfield,F.(1994).Towardthediscriminationoffine-grainedferrimagnetsbymagneticmeasurementsinlakeandnear-shoremarinesediments.J.Geophys.Res.,99,9045–9050.

Oldfield, F. (2007). Sources of fine-grainedmagneticminer-alsinsediments:aproblemrevisited.Holocene,17,1265–1271.

Oldfield,F.,Asioli,A.,Accorsi,C.A.,Mercuri,A.M.,Juggins,S.,Langone,L.,Rolph,T.,Trincardi,F.,Wolff,G.,Gibbs,Z.,Vigliotti,L.,Frignani,M.,vanderPost,K.andBranch,N.(2003).AhighresolutionlateHolocenepalaeo-environ-mentalrecordfromthecentralAdriaticSea.Quatern.Sci.Rev.,22,319–342.

Oldfield,F.,Hao,Q.,Bloemendal,J.,Gibbs-Eggar,Z,Patil,S.,Guo,Z.(2009).Linksbetweenbulksedimentparticlesizeandmagneticgrain-size:generalobservationsandimplica-tions forChinese loessstudies.Sedimentology,56,2091-2106,doi:10.1111/j.1365-3091.2009.01071.x.

Özdemir,Ö.,Moskowitz,B.,andJackson,M.(2009).Frequen-cy andfield dependent susceptibility ofmagnetite at lowtemperature.EarthPlanetsSpace,61,125-131.

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Peters, C., and M. J. Dekkers (2003), Selected room tem-peraturemagneticparametersasafunctionofmineralogy,concentration and grain size, Physics and Chemistry ofthe Earth, PartsA/B/C, 28(16), 659-667, doi: https://doi.

Property UnitsVolumesusceptibility,k Dimensionless(typicallyexpressedasμSI=

10-6SI)Masssusceptibility, χ m3/kgIn-phasesusceptibility,k’ or χ’ μSIorm3/kgOutofphasesusceptibility,k” or χ” μSIorm3/kgFrequencydependentsusceptibility,kfd or χfd μSIorm3/kgPercentfrequencydependentsusceptibility,kfd% or χfd%

Dimensionless

Lowfrequencysusceptibility,klf or χlf μSIorm3/kgHighfrequencysusceptibility,khf or χhf μSIorm3/kgLowfieldsusceptibility,kLF or χLF μSIorm3/kgHighfieldsusceptibility,kHF or χHF μSIorm3/kgAnhystereticRemanentMagnetization,ARM Am2/kgSusceptibilityofARM,χARM μSIorm3/kgSummaryofmagneticproperties,symbolsandunitscoveredinthisarticle.

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Quarterly The IRM QuarterlyispublishedfourtimesayearbythestaffoftheIRM.Ifyouorsomeoneyouknowwouldliketobeonourmailinglist,ifyouhavesomethingyouwouldliketocontribute(e.g.,titlesplusabstractsofpapersinpress),orifyouhaveanysuggestionstoimprovethenewsletter,pleasenotifytheeditor:

Dario BilardelloInstituteforRockMagnetismDepartmentofEarthSciencesUniversityofMinnesota150JohnTTateHall116ChurchStreetSEMinneapolis,MN55455-0128phone:(612)624-5274e-mail:dario@umn.eduwww.irm.umn.edu

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The Institute for Rock Magnetismisdedi-catedtoprovidingstate-of-the-artfacilitiesandtechnicalexpertisefreeofchargetoanyinterestedresearcherwhoappliesandisac-ceptedasaVisitingFellow.Shortproposalsareacceptedsemi-annuallyinspringandfallforworktobedoneina10-dayperiodduringthefollowinghalfyear.Shorter,lessformalvisitsarearrangedonanindividualbasisthroughtheFacilitiesManager. The IRMstaffconsistsofSubir Baner-jee,Professor/FoundingDirector;Bruce Moskowitz,Professor/Director;Joshua Feinberg,AssistantProfessor/AssociateDirector;Mike Jackson, Peat Sølheid andDario Bilardello,StaffScientists. FundingfortheIRMisprovidedbytheNational Science Foundation, the W. M. Keck Foundation,andthe University of Minnesota.

The IRM

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