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2007 Vol. 18, No. 4

Display Method:
Geochemistry Characteristics of Sediment and Provenance Relations of Sediments in Core NT1 of the South Yellow Sea
王红霞, 张宪军, 蓝先洪, 张志珣, 林振宏, 赵广涛
2007, 9(4)
Abstract:
ThecontributionofsubstancefromYellowRiver,YangtzeRiver,andKoreanriverstothesedimentationofYellowSeaisstudiedthroughgeochemicalanalysisandthroughcharacterizationofthesourceofthesubstanceaboutsedimentfromCoreNT1amongthelutaceousareainCentralSouthYellowSea.TheresearchfindsoutthatthesedimentinCoreNT1mainlycomesfromYangtzeRiverandYellowRiver,thesedimentbetween0–7.70minupperCoreNT1mainlybelongstoYangtzeRiversource;thesedimentsbetween7.70–16.60mand42.0–54.80minmiddleCoreNT1aremainlyfromYellowRiver,the26mthicksedimentinterlayerinitmainlycomesfromYangtzeRiver;andthesedimentbetween54.80–69.76minthebottomofCoreNT1ismainlyfromYangtzeRiver.TheresultsdemonstratethatYangtzeRiverhasbeenplayingamainroleinthelutaceousareaintheCentralSouthYellowSeasinceearlyLatePleistocene,andYellowRiverstartedtoinfluencethecontinentalsedimentationofYellowSeafromearlyWarmGlaciationoflateLatePleistocene.
The Effects of Applying the Association of Al, K, and Sn in Stream Sediments for Gold Exploration in Different Landscapes
He Jinzhong* (何进忠), Yao Shuzhen (姚书振)
2007, 9(4)
Abstract:
Geochemicaldataofalteredwallrocksareimportantforthemetallogenicprognosisofhydrothermalgolddeposits.IndicatorelementsofalteredwallrockssuchasK,Al,As,Sb,andHghavebeensuccessfullyusedtoassessgoldanomaliesinlithogeochemicalsurvey.However,suchresearcheshaverarelybeendoneinstreamsedimentsurveyfortheexplorationofgoldfromvariouslandscapes.OnthebasisofthegeochemicalanalysisofalteredwallrocksofgolddepositsinthecolddesertareasofGansu(甘肃)ProvinceinNorthwestChina,itisfoundthatthecombinationofAl,K,andSncouldserveasanimportantindicatorofhydrothermalgolddepositsandcanbeusedtoevaluatethemetallogenicprospectiveofgoldanomaliesinstreamsediments.Morestudiesperformedinthecoldgrasslandareasandthemoderate-lowreliefmountainousareasshowedthat,bothweakandstronggeochemicalanomaliescanbeextracted,ifstrictlyabidingbythewaysofcalculationandadditionofthebinaryvaluesoftheindicatorelementswithequalweight,andthisprovidesthesounddelineationofmetallogenicperspectiveareas.
Experimental Verification and Research for the Distortion in the Integrated Frequency Responses of the High-Pressure Sealed Cabin and Magnetic Field Sensor
Deng Ming* (邓明), Wei Wenbo (魏文博), Jin Sheng (金胜), Ye Gaofeng (叶高峰), Zhang Qisheng (张启升), Jing Jian’en (景建恩)
2007, 9(4)
Abstract:
Althoughmagnetotelluricsoundingmethodappliedtothelandisadvanced,therearemanydifficultieswhenitisappliedtomarineenvironment,oneofwhichishowtolaymagneticfieldsensorsdowntotheseafloortocompletemeasurements.Toprotectthemagneticfieldsensorsfromintenseerosionandhighpressure,suitablehigh-pressuresealedcabinsmustbedesignedtoloadthem.Fortheconsiderationofmagneticmeasurementandmarineoperation,thesealedpressurecabinshouldbenonmagneticandtransportable.Amongalloptionalmaterials,LC4super-hardaluminumalloyhasthehighestperformanceofprice/qualityratiotomakethesealedpressurecabin.However,itdoesnotmeanthatthehigh-pressuresealedcabinmadeusingLC4willbeperfectinperformance.Infact,becauseofitsweakmagnetism,thepressurecabinmadeusingLC4hasdistortingeffectonfrequencyresponsesofthemagneticfieldsensorssealedinit.Thisdistortingeffectdoesnotaffecttheuseofthemagneticfieldsensor,butifwewanttoeliminateitseffect,weshouldstudyitbyexperimentalmeasurements.Inourexperimenttests,frequencysweepmagneticfieldasexcitationsignalwasused,andthenresponsesofthemagneticfieldsensorbeforeandafterbeingloadedintothehigh-pressuresealedcabinweremeasured.Finally,normalizedabnormalcurvesforthefrequencyresponseswereobtained,throughwhichwecouldshowhowthehigh-pressuresealedcabinproduceseffectsontheresponsesofthemagneticfieldsensor.Experimentalresultssuggestthattheresponsedistortioninducedbythesealedpressurecabinappearsonmid-andhigh-frequencyareas.Usingexperimentalresultsasstandardizationdata,thefrequencyresponsescollectedfromseafloormagnetotelluricmeasurementscanbecorrectedtorestorerealinformationabouttheseafloorfieldsource.
High Precision Time Domain Forward Modeling for Crosshole Electromagnetic Tomography
林树海, 赵立英
2007, 9(4)
Abstract:
Toimprovetheresolutionofcrossholeelectromagnetictomography,highprecisionofforwardmodelingisnecessary.Apseudo-spectraltimedomain(PSTD)forwardmodelingwasusedtosimulateelectromagneticwavepropagationbetweentwoboreholes.ThePSTDalgorithmisbasedonthefinitedifferencetimedomain(FDTD)methodandusesthefastFouriertransform(FFT)algorithmforspatialderivativesinMaxwell’sequations.BesideshavingthestrongpointoftheFDTDmethod,thecalculationprecisionofthePSTDalgorithmishigherthanthatoftheFDTDmethodunderthesamecalculationcondition.TheforwardmodelingusingthePSTDmethodwillplayanimportantroleinenhancingtheresolutionofcrossholeelectromagnetictomography.
Electrical Structure and Fault Features of Crust and Upper Mantle beneath the Western Margin of the Qinghai-Tibet Plateau: Evidence from the Magnetotelluric Survey along Zhada-Quanshui Lake Profile
Jin Sheng* (金胜), Ye Gaofeng (叶高峰), Wei Wenbo (魏文博), Deng Ming (邓明), Jing Jian’en (景建恩)
2007, 9(4)
Abstract:
Themagnetotelluric(MT)surveyalongtheZhada(札达)-Quanshui(泉水)LakeprofileonthewesternmarginoftheQinghai(青海)-TibetplateaushowsthatthestudyareaisdividedintothreetectonicprovincesbytheYalungTsangpoandBangong(班公)-Nujiang(怒江)sutures.FromsouthtonorththesearetheHimalayanterrane,Gangdiseterrane,andQiangtang(羌塘)terrane.Forthestudyarea,therearewidespreadhigh-conductivitylayersinthemidandlowercrust,thetoplayersofwhichfluctuateintensively.Thehigh-conductivitylayerwithintheGangdiseterraneisdeeperthanthosewithintheQiangtangterraneandtheHimalayaterrane,andthedeepesthigh-conductivitylayeristothesouthoftheBangong-Nujiangsuture.Thetopsurfaceofthehigh-conductivitylayerinthesouthoftheBangong-Nujiangsutureisabout20kmlowerthanthatinthenorthofit.Thehigh-conductivitylayerwithintheGangdiseterranedipstowardnorthandtherearetwohigh-conductivitylayerswithinthecrustofthesouthernQiangtangterrane.Intheuppercrustalongtheprofile,therearegroupsoflateralelectricalgradientzonesordistortionzonesofdifferentscalesandoccurrenceindicatingthedistributionoffaultsandsuturesalongtheprofile.Accordingtotheelectricalstructure,thestructuralcharacteristicsandspacedistributionoftheYalungTsangposuture,Bangong-Nujiangsuture,andthemajorfaultsofLongmucuo(龙木错)andGeerzangbuareinferred.
Research of the Conductive Structure of Crust and the Upper Mantle beneath the South-Central Tibetan Plateau
叶高峰, 金胜, 魏文博
2007, 9(4)
Abstract:
Withthesuper-widebandmagnetotelluricsoundingdataoftheJilong(吉隆)-Cuoqin(措勤)profile(namedline800)whichwascompletedin2001andtheDingri(定日)-Cuomai(措迈)profile(namedline900)whichwascompletedin2004,weobtainedthestrikedirectionofeachMTstationbystrikeanalysis,thentracedprofilesthatwereperpendiculartothemainstrikedirection,andfinallyobtainedtheresistivitymodelofeachprofilebynonlinearconjugategradients(NLCG)inversion.Withthesetwomodels,wedescribedtheresistivitystructurefeaturesofthecrustandtheuppermantleofthecenter-southernTibetanplateauanditsrelationshipwithYalungTsangposuture:theuppercrustoftheresearchareaisaresistivelayerwithresistivityvaluerangeof200–3000Ω·m.Thedepthofitsbottomsurfaceisabout15–20kmgenerally,butthebottomsurfaceofresistivelayerisdeeperinthemiddleofthesetwoprofiles.Atline900,itisabout30kmdeep,andevenatline800,itisabout38kmdeep.Thereisagradientbeltofresistivityatthedepthof15–45km,andaconductivelayerisbeneathitwithresistivityevenlessthan5Ω·m.Thisconductivelayeriscomposedofindividualconductivebodies,andatthesouthoftheYalungTsangposuture,theconductivebodiesaresmallerwiththicknessabout10kmandleantothenorthslightly.However,atthenorthoftheYalungTsangposuture,theconductivebodiesarelargerwiththicknessabout30kmandalsoleantothenorthslightly.Relatively,theconductivebodiesofline900arethinnerthanthoseofline800,andthedepthofthebottomsurfaceofline900isalsoshallower.Atlast,afteranalyzingtheeffectfactorstotheresistivityofrocks,itwasconcludedthattheveryconductivelayerwascausedbypartialmeltorconnectivewaterinrocks.Itsuggeststhatthemiddleandlowercrustofthecenter-southernTibetanplateauisverythick,hot,flabby,andwaxy.
Application of Reservoir Seismic Inversion to the Damintun Sag in the Liaohe Oilfield
Duan Yunqing (段云卿), Wang Yanchun* (王彦春), Qin Tian (覃天), Yang Wenjun (杨文军), Gao Haiyan (高海燕)
2007, 9(4)
Abstract:
AccordingtothespecialgeologicconditionsoftheDamintun(大民屯)sagintheLiaohe(辽河)basin,withacomplexstructureandrapidlateralchangeofthininterbeds,thetechniqueoflogging-constraintseismicinversionbasedonprestackhigh-resolutionseismicdatawasusedinthedescriptionofoil-gasreservoirs.Reservoirseismicinversioncaneffectivelyidentifyundergroundcomplexgeologicstructuresandseismicanomalousreflectionvolumesandquantitativelypredictthedistributionofsandstonesinspaceandtheirvariantlawincombinationwithlithologicinterpretation.Thisworkstudiesthewaveimpedanceinversionofhigh-resolutionprestackseismicdata,andloggingmulti-attributedatainversion,andappliesthesemethodstotheDamintunsag.Asaresult,theverticalresolutionofreservoirpredictionisraised,abilityofidentifyingthin-interbedsandbodiesisenhanced,reliabilityofreservoirpredictionisimproved,andfavorablelithologictrapsofthisareaarefurtherconfirmed.Theseeffectsareofsignificanceintheexplorationofhiddenhydrocarbonsinthisoilfield.
The Offset-Domain Prestack Depth Migration with Optimal Separable Approximation
张致付, 刘春园, 张春涛, 孟小红
2007, 9(4)
Abstract:
Theoffset-domainprestackdepthmigrationwithoptimalseparableapproximation,basedonthedoublesquarerootequation,isusedtoimagecomplexmediawithlargeandrapidvelocityvariations.Themethoddownwardcontinuesthesourceandthereceiverwavefieldssimultaneously.ThemixeddomainalgorithmwithforwardFourierandinverseFouriertransformisusedtoconstructthedoublesquarerootequationwavefieldextrapolationoperator.Thisoperatorseparatesvariablesinthewavenumberdomainandvariablesinthespacedomain.Thephaseoperationisimplementedinthewavenumberdomain,whereasthetimedelayforlateralvelocityvariationiscorrectedinthespacedomain.Themigrationalgorithmisefficientsincetheseismicdataarenotcomputedshotbyshot.ThedatasettestoftheMarmousimodelindicatesthattheoffset-domainmigrationprovidesasatisfiedseismicmigrationsectiononwhichcomplexgeologicstructuresareimagedinmediawithlargeandrapidlateralvelocityvariations.
A Study on the Classification and Well-Logging Identification of Eclogite in the Main Hole of Chinese Continental Scientific Drilling Project
Jing Jian’en* (景建恩), Wei Wenbo (魏文博), Jin Sheng (金胜), Ye Gaofeng (叶高峰), Deng Ming (邓明)
2007, 9(4)
Abstract:
Eclogite,oneoftheimportantlithologiesinthemainholeoftheChineseContinentalScientificDrilling(CCSD)Project,existsabovethedepthof3245mandhasdistinctiveresponsesofgamma-ray,compensatingdensityandneutronwell-logging,andsoon.Inthisstudy,accordingtothediversitiesofmineralsandchemicalcomponentsandwell-loggingresponses,eclogitesareclassifiedfromthreeaspectsoforigin,contentofoxygen,andsub-mineral.Westudiedtheloggingidentificationmethodforeclogitesub-classesbasedonmulti-elementstatisticsandreconstructed11kindsofeclogite.Asaresult,eclogitescanbedividedinto6typesusingwelllogs.Inthelightofthisrecognition,theeclogiteinthemainholeisdividedinto20sections,andthedistributioncharactersofallsub-classesofeclogiteareanalyzed,whichwillprovideimportantdataforgeologicalresearchofCCSD.
A Preliminary Study on Paleomagnetism and Rock Magnetism of Eclogite from the Maobei Area
孟小红, 余钦范, 郭友钊, 周姚秀
2007, 9(4)
Abstract:
Apreliminarystudyofpaleomagnetismandrockmagnetismhasbeendoneon55eclogitesamplescollectedfromtheChineseContinentalScientificDrilling(CCSD)siteattheMaobei(毛北)area,Donghai(东海)County,Jiangsu(江苏)Province.Alsotheisothermalremanence,hysteresisloop,magneticfabric,thermalsusceptibilityweremeasured,andanalysesweremadebyelectron-probeandscanningelectricmicroscopeonsomesamplessynchronously.Theresultindicatesthattherearetwogroupsofstableremanence,thenormalandreversedmagnetization.Theremanenceorientationsare:D=94.3o,I=-29.1oandD=273.7o,I=15.4o,respectively.Themagnetizationintensityandthedensityofthesampleswhichcarrythenormalmagnetizationareverydifferentfromthosebearingreversedmagnetization.Themagneticanisotropyisweak,andtheminimumaxisishardlydetermined.TheisothermalremanenceandthehysteresisloopshowthatthemagneticcarriersoftheeclogitearelikelySD(singledomain)andPSD(pseudo-singledomain)magnetite.Accordingtothemagneticproperty,thecauseofformationofmagneticcarriers,themechanismoftheremanence,andthesignificanceforthetectonicsarediscussed.