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2007 Vol. 18, No. 1

Display Method:
Balanced Cross Section for Restoration of Tectonic Evolution in the Southwest Okinawa Trough
吴时国, 倪祥龙, 郭军华
2007, 9(1)
Abstract:
Onthebasisofthemulti-channelseismicdataandtheotherdata,using2DMovesoftware,thetectonicevolutioninthreeseismicprofileswasrestoredsincePliocene.Thetectonicrestorationresultsshowthat:(1)theinitialactivecenterlayinthewestslopeandthenwastransferredtoeastandsouthviatroughcenterduringtheevolutionprocess;(2)severalmainnormalfaultscontrolledtheevolutionofthesouthernOkinawaTrough;(3)sinceLatePliocene,thesouthernOkinawaTroughhasexperiencedtwospreadingstages.TheearlyisdepressioninEarly-MiddlePleistoceneandthelateisback-arcspreadinginLatePleistoceneandHolocene,whichisinprimaryoceaniccrustspreadingstage.
Precise Timing of Caledonian Structural Deformation Chronology and Its Implications in Southeast Qilian Mountains, China
Fan Guangming* (樊光明), Lei Dongning (雷东宁)
2007, 9(1)
Abstract:
ThemiddleQilianorogenicbeltandLajishanorogenicbelt,bothofwhichwereformedintheCaledonian,strikeNW-SEdirectionacrosssoutheastQilianMountainsandtheirbasementconsistsofpre-Caledonianmetamorphicrockswithlozenge-shapedductileshearzonesinthecrystallinebasement.Thebluntanglebetweentheconjugatedductileshearzonesrangesfrom104°to114°,indicatingapproximate210°ofthemaximumprincipalstress.Theplateauagesofmuscovite40Ar/39ArobtainedfromthemylonitizedrocksintheductileshearzonesofJinshaxia-Hualong-KequemassifwithinthemiddleQilianmassifare(405.1±2.4)Maand(418.3±2.8)Ma,respectively.ThechronologydataconfirmtheformationofductileshearzonesintheCaledonianbasementmetamorphicrocksduringtheCale-donianorogeny.Furthermore,onthebasisofbasementrockstudy,precisetimingfortheclosingoftheLatePaleozoicvolcanicbasin(orisland-arcbasin)andLajishanoceanbasinisdetermined.Thisprovidesusanewinsightintotheclosingofoceanbasininthestructuralevolutionoforogenicbelt.
LA-ICP-MS U-Pb Zircon Geochronology of Basic Dikes within Maxianshan Rock Group in the Central Qilian Orogenic Belt and Its Tectonic Implications
何世平, 王洪亮, 陈隽璐, 徐学义, 张宏飞, 任光明, 余吉远
2007, 9(1)
Abstract:
Alargenumberofbasicdikes,whichindicateanimportanttectonic-magmaticeventintheeasternpartoftheCentralQilian(祁连)orogenicbelt,werefoundfromMaxianshan(马衔山)rockgroup,Yongjing(永靖)county,Gansu(甘肃)Province,China.Accordingtotheresearchonthecharacteristicsofgeologyandpetrology,thebasicdikeswarms,widelyintrudedinMaxianshanrockgroup,aredividedintotwophasesbytheauthors.U-PbisotopeofzirconsfromthebasicdikesabovetwophasesisseparatelydeterminedbyLA-ICP-MSintheKeyLaboratoryofContinentalDynamicsofNorthwestUniversity,ChinaandthecausesofformationofthezirconsarestudiedusingCLimages.Theformationageoftheearlierphaseofmetagabbrodikesis(441.1±1.4)Ma(correspondingtotheearlystageofEarlySilurian),andtheageofthemainmetamorphicperiodis(414.3±1.2)Ma(correspondingtotheearlystageofEarlyDevonian).Theformationageofthelaterphaseofdiabasedikeswarmsis(434±1.0)Ma(correspondingtothelatestageofEarlySilurian).Thecap-tured-zirconsfromdiabasedikeswarmssavedsomeinformationofmaterialinterfusionbyMaxianshanrockgroup(207Pb/206Pbapparentagesare(2325±3)–(2573±6)Ma),andsomezirconsfromdiabasedikeswarmsalsosavedimpactedinformationbytectonicthermaleventduringthelateperiodofCaledonianmovement(206Pb/238Uapparentagesare(400±2)–(429±2)Ma).Bycombiningtheresultsoftherelatedstudies,thebasicdikes withinMaxianshanrockgroupwereconsideredtobeformedinthetransferperiod,fromsubductionalorogenytowardscollisionalorogeny,whichrepresentsgeologicalrecordsofNW-SEextensionduringregionalNE-SWtowardsintensecompressionintheCentralQilianblock.
Analysis of the Ore-Controlling Structure of Ductile Shear Zone Type Gold Deposit in Southern Beishan Area, Gansu, Northwest China
陈柏林, 吴淦国, 叶德金, 刘晓春, 舒斌, 杨农
2007, 9(1)
Abstract:
Theductileshearzone-typegolddepositisakindthatboththeore-formingmechanismandore-controllingfactorsarecloselyrelatedtotheductileshearzoneanditsevolution.DuctileshearzonedevelopsinBeishanarea,GansuofNorthwestChina,anddevelopsespeciallywellinthesouthbelt.Thecontrolsoftheductileshearzoneongolddepositsareasfollows.(1)Theregionaldistributionofgolddeposits(andgoldspots)iscontrolledbytheductileshearzone.(2)Theductile-brittleshearzoneisformedintheevolutionprocessofductileshearzoneandbothareonlyore-bearingstructuresandcontroltheshape,attitude,scale,anddistributionofmineralizationzonesandore-bodies.(3)Compresso-shearductiledeformationresultsinthatthemainkindofgoldmineralizationisalteredmylonitetypeandthemainalteralizationismetasomatic.(4)Ore-bearingfracturesystemsaremainlyP-typeones,someD-typeandR-typeones,butonlyindividualR’-typeandT-typeones.(5)Dynamicdifferentiationanddynamicmetamorphichydrothermalsolutionresultingfromductiledeformationisoneofthesourcesofore-formingfluidofgoldmineralization,andthisisidenticalwiththatore-formingmaterialsaremainlyfrommetamorphicrocks,andore-formingfluidismainlycomposedofmetamorphicwater,andwiththefluidinclusionandgeo-chemicalcharacteristicsofthedeposit.(6)Thereisanegativecorrelationbetweenthegoldabundanceandsusceptibilityanisotropy(P)ofthealteredmylonitesamplesfromthedeposit,whichshowsthatthegoldmineralizationisslightlylaterthanthestructuraldeformation.Allabovefurtherexpoundtheore-formingmodeloftheductileshearzonetypeofgolddeposits.
Change of Gas Hydrate Reservoir and Its Effect on the Environment in Xisha Trough since the Last Glacial Maximum
王淑红, 颜文, 宋海斌
2007, 9(1)
Abstract:
Inthisarticle,MilkovandSassen’smodelisselectedtocalculatethethicknessofthegashydratestablezone(GHSZ)andtheamountofgashydrateintheXisha(西沙)Troughatpresentandatthelastglacialmaximum(LGM),respectively,andtheeffectsofthechangesinthebottomwatertemperatureandthesealevelonthesewerealsodiscussed.TheaveragethicknessoftheGHSZinXishaTroughisestimatedtobe287mand299mbasedontherelationshipbetweentheGHSZthicknessandthewaterdepthestablishedinthisstudyatpresentandatLGM,respectively.Then,byassumingthatthedistributedareaofgashydratesis8000km2andthatthegashydratesaturationis1.2%ofthesedimentvolume,theamountsofgashydrateareestimatedtobe~2.76×1010m3and~2.87×1010m3,andthevolumesofhydrate-boundgasesare~4.52×1012m3and~4.71×1012m3atpresentandatLGM,respectively.TheaboveresultsshowthatthethicknessofGHSZdecreaseswiththebottomwatertemperatureincreaseandincreaseswiththesealevelincrease,whereintheeffectoftheformerislargerthanthatofthelatter,thattheaveragethicknessofGHSZinXishaTroughhadbeenreducedby~12m,andthat1.9×1011m3ofmethaneisreleasedfromapproximately1.1×109m3ofgashydratesinceLGM.Thereleasedmethaneshouldhavegreatlyaffectedtheenvironment.
Types, Evolution and Pool-Controlling Significance of Pool Fluid Sources in Superimposed Basins:A Case Study from Paleozoic and Mesozoic in South China
徐思煌, 梅廉夫, 袁彩萍, 马永生, 郭彤楼
2007, 9(1)
Abstract:
Havingmultipletectonicevolutionstages,SouthChinabelongstoasuperimposedbasininnature.Mostmarinegaspoolsbecamesecondarypools.Thepoolfluidsourcesserveastheprincipalpool-controllingfactors.Onthebasisofeighttypicalpetroleumpools,thetype,evolutionintime-space,andthecontrollingofpetroleumdistributionofpoolfluidsourcesarecomprehensivelyanalyzed.Themaintypesofpoolfluidsourcesincludehydrocarbon,generatedprimarilyandsecondlyfromsourcerocks,gascrackedfromcrudeoil,gasdissolvedinwater,inorganicgas,andmixedgases.Intermsofevolution,theprimaryhydrocarbonwaspredominantpriortoIndosinian;duringIndosiniantoYenshanianthesecondarygasincludesgascrackedfromcrudeoil,gasgeneratedsecondarily,gasdissolvedinwater,andinorganicgasdominated;duringYenshaniantoHimalayanthemostfluidsourcesweremixedgases.Controlledbypoolfluidsources,thepoolswithmixedgassourcesdistributedmainlyinUpperYangtzeblock,especiallySichuan(四川)basin;thepoolswithprimaryhydrocarbonsourcesdistributedinpaleo-upliftssuchasJiangnan(江南),butmostofthesepoolsbecamefossilpools;thepoolswithsecondaryhydrocarbonsourcedistributedintheareascoveredbyCretaceousandEogeneinMiddle-LowerYangtzeblocks,andChuxiong(楚雄),Shiwandashan(十万大山),andNanpanjiang(南盘江)basins;thepoolswithinorganicgassourcemainlyformedanddistributedintensionalstructureareas.
Sedimentary Facies Models on Carbonatite in the Upper Shuaiba Member of Lower Cretaceous in Daleel Field, Oman
王锋, 姜在兴, 周丽清, 赵国良, 王林, 郑宁, 向树安
2007, 9(1)
Abstract:
TheUpperShuaibaMember(USH)isthemainforcepaybedintheDaleelfieldinnorthernOman;5layersincludingA,B,C,D,andEweredividedinprofile,andlayerDandlayerEarethemainbeds.WiththedevelopmentofexplorationintheDaleeloilfield,studyingthesedimentarysystemsabouttheirinnercompositionandthecollocationindimension,andsettingupthesedimentarymodelsintheUSHarebecomingmoreandmorenecessaryandimportanttomeetthefurtherexplorationrequirement.Basedonthedataofgeology,seism,andpaleo-biology,accordingtotheanalysismethodoncarbonatitedepositionalsystem,thelitho-faciesassemblageandsedimentaryenvironmentintheUSHwerestudied.Intershoallow-lyingsub-facies(wherethewaterdepthis10–50m)andshallowshoalsub-facies(wherethewaterdepthisnotmorethan10m)wereextinguishedinthelayerD,andstormdepositwasfoundinlayerE1,inwhichintershoallow-lyingsub-faciesalsodeveloped.Thefeatureofthesedimentarysub-faciesandthesedimentaryconditionwereanalyzed,andthesedimentarymodelwassetupinthearticle:thecarbonatiteintershoallow-lyingdevelopedundertheback-groundofopenlandinshallowsea,wherestormeventsusuallyoccurredintheLowerCretaceousinthearea.
Alteration Information Extraction by Applying Synthesis Processing Techniques to Landsat ETM+ Data: Case Study of Zhaoyuan Gold Mines, Shandong Province, China
刘福江, 吴信才, 孙华山, 郭艳
2007, 9(1)
Abstract:
Satelliteremotesensingdataareusuallyusedtoanalyzethespatialdistributionpatternofgeologicalstructuresandgenerallyserveasasignificantmeansfortheidentificationofalterationzones.BasedontheLandsatEnhancedThematicMapper(ETM+)data,whichhavebetterspectralresolution(8bands)andspatialresolution(15minPANband),thesynthesisprocessingtechniqueswerepresentedtofulfillalterationinformationextraction:datapreparation,vegetationindicesandbandratios,andexpertclassifier-basedclassification.ThesetechniqueshavebeenimplementedintheMapGIS-RSPsoftware(version1.0),developedbytheWuhanZondyCyberTechnologyCo.,Ltd,China.InthestudyareaapplicationofextractingalterationinformationintheZhaoyuan(招远)goldmines,Shandong(山东)Province,China,severalhydorthermallyalteredzones(includedtwonewsites)werefoundaftersatelliteimageryinterpretationcoupledwithfieldsurveys.Itisconcludedthatthesesynthesisprocessingtechniquesareusefulapproachesandareapplicabletoawiderangeofgold-mineralizedalterationinformationextraction.
Deformation Mechanism and Stability of a Rocky Slope
Huang Runqiu* (黄润秋), Xiao Huabo (肖华波), Ju Nengpan (巨能攀), Zhao Jianjun (赵建军)
2007, 9(1)
Abstract:
AhighslopeislocatedonthesideofthespillwayatahydropowerstationinSouthwestChina,whichhassomeweakinter-layersincliningoutwards.Partsoftheslopeshowheavyweatheringandunloading.Thereappeareddeformationandtensilecrackeitheronthesurfaceorontheafteredgeoftheslopeduringexcavation,andunderaplatform(elev.488m),twolevelsofslopescollapsedonthedownriverside.Basedontheinvestigationinsituandtheanalysisofthegeologicalstructure,theconceptualmodelofdeformationandfailuremechanismwaserectedforthisslope.Furthermore,thedeformationcharacteristicswerestudiedwithFLAC3Dnumericalsimulation.Comprehensiveanalysisshowsthatthewholedeformationoftheslopeisunloadingreboundincertaindepthscopeandthewholebodydoesnotslidealonganyweakinterlayer.Inaddition,twopartswithprominentlocaldeformationintheshallowlayeroftheslopeshowthemodelsof“creepsliding-tensilecracking”and“sliding-tensilecracking”,respectively.Basedontheaboveanalysis,thecorrespondingprojectofsupportandreinforcementisproposedtomaketheslopemorestable.
A Calculation Model for Corrosion Cracking in RC Structures
Xu Gang* (徐港), Wei Jun (卫军), Zhang Keqiang (张克强), Zhou Xiwu (周锡武)
2007, 9(1)
Abstract:
Anovelcalculationmodelisproposedaimingattheproblemofconcretecovercrackinginducedbyreinforcementcorrosion.Inthisarticle,therelationshipbetweenthecorrosiondepthofthebarandthethicknessoftherustlayerisestablished.Bydeducingtheradialdisplacementexpressionofconcrete,theformulaforcorrosiondepthandcorrosionpressurebeforecrackingisproposed.Thecrackdepthofcoverinaccordancewiththemaximumcorrosionpressureisdeduced;furthermore,thecorrosiondepthandcorrosionpressureatthecrackingtimeareobtained.Finally,thetheoreticalmodelisvalidatedbyseveralexperiments,andthecalculatedvaluesagreewellwiththeexperimentresults.
Simulation of Stress Distribution around Tunnels and Interaction between Tunnels Using an Elasto–plastic Model
Muya M S*, He Bo (何波), Wang Jingtao (王靖涛), Li Guocheng (李国成)
2007, 9(1)
Abstract:
Thisarticlepresentsacomputersimulationofstressdistributionaroundtunnelsandinteractionbetweentunnelsusinganelasto-plasticmodel.AfiniteelementmethodusingANSYSsoftwarehasbeenusedfortheanalysesofoneandtwotunnelsatdifferentoverburdendepthswithdifferentseparatingdistancesbetweenthetunnels.Theresultsofnumericalanalysesindicatethatstressdistributionandstressconcentrationaroundthetunnelsvarywiththeoverburdendepths.Itisfoundthatthecoefficientsofstressconcentrationforelasto-plasticmediumaresmallerthanthoseforelasticoneby1.9%.Furthermore,theinteractionbetweenthetwotunnelsrapidlydecreaseswiththeincreaseofseparationdistancebetweenthem.Inaddition,forquantitativelydescribingtheinteractionbetweenthetwotunnels,acriticalseparationdistanceisintroduced.Thecriticalseparationdistancesbetweenthetwotunnelsatdifferentoverburdendepthsare8m,12m,and14mrespectively.Thisfactisveryimportantandessentialforthedesignofminingtunnelsandtoensuresafetyintunnelengineering.