简介:近几十年来,国内外泥炭沼泽地球化学研究取得了一系列重要进展,特别是在脂类化合物和稳定同位素等方面.泥炭沼泽是一个良好的地质档案,泥炭纤维素碳、氢和氧同位素组成和比值是环境变化的综合参数,沉积脂类化合物含有反映有机质母源先质的骨架结构,这些标志物高分辨率地记录了全新世以来古气候、古植被和古环境的演变信息,在当今全球变化研究中占有相当重要的地位.本文综述了泥炭沼泽地球化学研究进展,侧重于泥炭沼泽脂类化合物和稳定同位素等标志物的地球化学研究现状和发展趋势;侧重论述了研究技术的发展、定性说明到定量分析的过渡、研究精度的提高及存在的问题,分析了这些分子标志物与植被演替、气候变迁和环境变化间的对应关系,指出了我国在该方面的薄弱之处以及需加强的领域.
简介:Tourmalineiswidespreadinthehoststrataofstrata-boundbasemetalsulphidedepositsintheDevonianmetallogenicdeistrictaroundShanyang-ZhashuiineasternQinling,Asamemberoftheschorl-draviteseries,thetourmalineischaracterizedbyMg>FeandNa>Ca,showingapparentchemicalzonationwhichrecordsthegeochemistryduringitsformationandsubsequentregionalmetamorphismandhydrothermaloverprint.Theclosesimilarityinchemicalandisotopicconstitutionsbetweenthetourmalineofthemainmetallogenicepochinthisdistrict[FeO/(FeO_MgO)=0.34-0.39andδ^11B=-7.6‰--8.8‰]andthoserelatedtomassivesulphidedepositstypicalofsubmarine(exhalative)hydrothermalsedimentation
简介:TheYushugouterrainofhigh-pressuregranulitefaciesinsouthernTianshanMountainiscomposedmainlyofanophiolitesuite.Mostselectedziroconsareroundorellipticalinshape,andsomeareoftetragonalprismwithroundedges.Thegranulometricanalysesshowthattheyarewellsortedinsedimentation.ZrO2/HfO2ratiosinzirconsrangefrom45to57.thesecharacters,togetherwiththepetrologicandgeochemicalcharactersofplagioclase-garnet-orthopyroxenitebearingzircons,indicatethattheprotolithofplagioclase-garnet-orthopyroxenitemaybederivedmainlyfromvolcanicbasesurgesedimentarydebrisinoceanicislandsandfromclaysformedbyseafloorweathering.Zirconsaresimplyofpyroclasticdebris.Theophioliteformationageof(440±18)Maandthefirst-stagemetamorphicage(amphiboliteorgranulitefacies)of(364±5)Mawereobtainedwithamethodofmultiplegrainsindifferentgroupsandamethodofconcordiaplot.TheseagesprovideimportantinformationonthetemporalandspatialoccurrenceofsouthernPaleoxoicTianshanOcean,Thesubductionrateoftheoceaniccrustandtheformationmechanismofophioliteofgranulitefacies.
简介:Phlogopite-amphibole-pyroxenitexenolithscontainedinthealkalibasic-ultrabasicsubvolcaniccomplexinLangao,shaanxiProvinece,arecomposedofdiopside,Ti-richpargasite,phlogopiteapatite,spheneandilmenite,whichhavesubsolidusmetamorphism-deformationtexturessuchastriple-points,cataclasticboundariesandkink-bands,MineralChemicalcharacteristicsshowthatthediopside,Ti-richPargasiteandphlogopitearederivedfromthemantleandaretheprioductsofmantlemetasomatism,Comparedwithnormalmantle-derivedspinel-lherzolites,thexenolithsareenrichedinTiO2,Fe2O3,CaO,Na2OandK2O,withapparentdepletioninMgO,Chondrite-normalizedREEpatternsandprimordial-mantlenormalizedtraceelementsdatashowthattheyareenrichedinREE(EspeciallyLREE)andincompatibletraceelements,Thepetropraphic,mineralogicalandpetrochemicalcharacteristicsindicatethatthexenolithsaremetasomatizedmantlexenoliths,whichofferstheevidenceformantlemetasomatismandrepresentstheanomalousmantlebeneaththeEarlyPaleozoicriftinnorthernDabaMountains,Theagentsofmantlemetasomatismareprobablyderivedfromtherisingofmantlehotplumes,Thepriocessesofmetasomatismvariedfromlimited-rangefluidmetasomatismindeepmantle(>90km)topervasivemetasomatismofsilicatemelt.
简介:ExperimentshavebeenperformedonthesystemMgO-SiO2-Cr-Oat0-2.88GPaand1100-1450℃,focusingonthestabilityofCr^2+inolivine(O1),orthopyroxene(Opx)andspinel(Sp)anditspartitioningbetweenthesephases.Analyticalreagentgradechemicals,MgO,SiO2,Cr2O3.andCrwereusedtomakestartingmixtures.ExcessCr(50%)wasthenaddedinthesemixturestoensurethattheresultantphaseswereinequilibriumwiththemetalCr.FluxofBaO+B2O3(%)wasaddedforfacilitatingexperimentalequilibriumandcrystalgrowth.Crwasusedascapsulematerial.AllphasesintheproductwereidentifiedbyX-rayandanalyzedbyelectronmicroprobe,ThecontentsofCrOinthedifferentphases(O1,OpxandSp)werecalculatedaccordingtostoichiometry.TheobtainedresultsofcalculationindicatethatCr^3+inOlandOpxisnegligible.Theexperimentalresultsshow;(a)withincreasingtemperatureanddecreasingpressure,Cr^2+solubilityinOl,OpxandSpincreases;(b)withincreasingtemperature,thepartitioningcoefficientofMgandCr^2+betweenOlandOpxdecreases,thatbetweenOpxandSpincreases,andthatbetweenOlandSpremainsalmostunchanged;(c)theeffectofpressureonallpartitioningcoefficientsisnegligible.
简介:UltrabasicrocksintheMianxian-LueyangophioliticmelangezoneincludeharzburgiteanddunitewhichexhibitLREEdepletionwithremarkablepositiveEuanomaly.ThediabasedikeswarmshowsLREEenrichmentbutslightlynegativeEuanomaly.MetamorphosedvolcanicrockscanbedividedintotwogroupsintermsoftheirREEgeochemistryandtraceelementratiosofTi/V,Th/Ta,Th/YbandTa/Yb.OneisthsMORB-typebasaltwithLREEdepletion,representingthefragmentsofoceaniccrustandimplyinganassociationoftheMORB-typeophioliteandanancientoceanbasinbetweentheQinlingandYangtzeplatesduringtheMiddlePaleozoic-EarlyMesozoicera.Theotercomprisestheisland-arcvolcanicrocksincludingtholeiiticbasaltandalargeamountofcalc-alkalineintermediate-acicvolcanicrock,whichcouldnotbethecomponentoftheancientoceaniccrustbuttheresultofmagmatismatthecontinentalmargin.ThisindicatesthattheMianxian-Lueyanglimitedoceanbasinhadundergoneawholeprocessofdevelopment,evolutionandvanishingfromDevonian-CretaceoustoPermian.AndtheQinlingareahadbeconeanindependentlithosphericmicroplate,onthesouthernsideofwhichtherewereexhibitedthetectoniccharacteristicsofactivecontinentalmarginsduringtheLatePaleozoic-EarlyMesozoic.Thatistosay.theQinlingcannotbesimplyconsideredasaresultofcollisionbetweentheYangtzeandNorthChinaplates.
简介:Basedondetailedgeologicstudy,theimportantroleofstructuringintheformationofgolddepositsintheareaisdiscussedwithspecialreferencetostructuralevolution,Syngeneticfaultingcontemporaneouswithtectonic-volcaniceventsisthoughttoberesponsibleforprovidingtheore-formingmaterialatdepth.ThelithofaciesformedbyhighlyalternatingdepositionofterrestrialandcarbonatedetritusischemicallycharacterizedbytheassemblageofAu-Sb-As,constituteingafavorablesourcebedfortheactivationandenrichmentofgold.Thisgoldsourcebedhasundergonefourmajorstagesofstructuraldeformation,accompaniedbymulti-stagedalterationandmineralization.
简介:BasedonelectronprobeanalysesofthemineralsandbulkcompositionoftheCenozoicvolcanicrocksfromYumenandHohXillithodistricts,Qinghai-Xizangplateau,theformingconditionsincludingthetemperatureandpressureofthoserocksarestudiedinthispaperAccordingtothethermodynamiccalculationresultsofmineral-meltequilibrium,thedepthoftheasthenospheresuperface(about75-130km)forthenorthernpartoftheQinghai-XizangplateauduringtheCenozoicissuggested.Finally,thispaperindicatesthattheCenozoicvolcanicrocksinthenorthernpartoftheQinghai-Xizangplateaumainlyconsistofshoshoniteseries.Theirformingtemperatureis630-1039℃andformingpressureisbetween2.3-4.0GPa.Therockswereformedintheintracontinentalorogenicbelt,ofwhichtheprimarymagmawasoriginatedfromaparticularenrichmentuppermantleandaccretedcrust-mantlebeltofdirectlyfromasthenosphericsuperfaceasaresultofpartialofpyrolite.
简介:Wateristhemostactivecomponentinallgeologicalsystems.Ithasanimportanteffectonthephysicalpropertiesofmineralsandmelts.ItalsoplaysakeyroleintheevolutionoftheEarth.Accuratethermodynamicsdataonwaterarecurrentlyconfinedtopressuresbelow1.0GPaandtemperaturesbelow900℃.PresentedinthispaperarenewdataavailableontheP-Tpropertiesofwateratpressuresupto5.0GPa,develogedfromdifferentialthermalanalysisandultrasonicwaveamplitudeanalysis.Ithasbeenfoundthattheremayexistanotherternarypointat3.0GPaandthatultrasonicwaveamplitudechangeofice-watertransitionshowstwoinflectionpointsabove2.0GPa,consistentwiththetwopeaksofdifferentialthermalcurvesabove2.0GPa.Itmaybeanewphenomenonwhichneedsfurtherstudy.
简介:Thesediment-hosteddisseminatedgolddepositsintheOinlingregionareofsedimentation-slight-metamorphicoriginsuperimposedbyhydrothermalreworkingatmoderate-lowtemperaturesandarewellcomparablewiththetypicalCarlingolddepositsintheUnitedStates.Inviewoftheconfusingconceptconcerningthe“sediment-hosted”and“Carlin-type”golddeposits,theauthorsproposethattheterm“sediment-hostedgolddeposit”shouldbeusedinabroadsensewhichencompassesatleastthefoursubtypes,i.e.,theCarlintype,themetamorphicfineclastictype,thehydrothermalsedimentarytypeandtheveintype.Inoterwords,the“Carlin-type”shouldnotbeusedasasynonymfor“sediment-hosted”butisrecommendedasasubtypeunderthegeneralcategoryof“sediment-hostedgolddeposits”