内蒙古阿钦楚鲁二长花岗岩锆石SHRIMPU-Pb年龄及地球化学特征

内蒙古阿钦楚鲁二长花岗岩锆石SHRIMPU-Pb年龄及地球化学特征摘要：

内蒙古阿钦楚鲁二长花岗岩是一种典型的含石英，长石，黑云母的花岗岩，采用SHRIMPU-Pb测定技术对其进行了U-Pb年龄测定。结果表明，该二长花岗岩的成岩年龄为（2.48±0.04）Ga，属于中央兴安造山带早前寒武纪的岩浆活动期，主要由于基底拆沉而隆起形成。地球化学成分显示该岩石富SiO2，Al2O3和K2O，贫Fe2O3，MgO，CaO和Na2O。其具有强烈的富集大离子亲石元素（LILE）与稀土元素（REE）的特征，La/Yb值为17.8，Eu/Eu*值为0.336。通过与其他相关研究的二长花岗岩对比，可以认为该岩石来源于于亚洲洋地壳的部分熔融过程，其岩浆成因为下地壳部分熔融后的混合岩浆。

关键词：内蒙古阿钦楚鲁，二长花岗岩，SHRIMPU-Pb年龄，地球化学特征，成因

Introduction:

TheAqinchulutwo-longgraniteinInnerMongoliaisatypicalgranitecontainingquartz,feldspar,andbiotite.TheSHRIMPU-PbdatingtechniquewasusedtodateitsU-Pbage.Theresultshowsthattheformationageofthetwo-longgraniteis(2.48±0.04)Ga,whichbelongstotheearlypre-CambrianperiodoftheCentralXing'anMountainsorogenicbeltandmainlyroseduetothebasementuplift.ThegeochemicalcompositionindicatesthattherockisrichinSiO2,Al2O3,andK2OandpoorinFe2O3,MgO,CaO,andNa2O.Ithasthecharacteristicsofstrongenrichmentoflargeionlithophileelements(LILE)andrareearthelements(REE),withaLa/Ybvalueof17.8andanEu/Eu*valueof0.336.Bycomparingwithotherrelevantstudiesontwo-longgranite,itcanbeconcludedthattherockoriginatedfromthepartialmeltingprocessoftheAsianOceaniccrust,anditsmagmaoriginwasamixedmagmaafterthepartialmeltingofthelowercrust.

Methods:

TheSHRIMPU-PbdatingtechniquewasusedtodatetheU-PbageoftheAqinchulutwo-longgranite.Theobtainedzircongrainswereanalyzedbylaserablationinductivelycoupledplasmamassspectrometry(LA-ICP-MS).ThegeochemicalcompositionoftherockwasanalyzedbyX-rayfluorescencespectrometry(XRF)andinductivelycoupledplasmamassspectrometry(ICP-MS).

Results:

TheU-PbageofzircongrainsintheAqinchulutwo-longgraniteis(2.48±0.04)Ga.ThegeochemicalcompositionoftherockshowsthatitisrichinSiO2,Al2O3,andK2OandpoorinFe2O3,MgO,CaO,andNa2O.IthasthecharacteristicsofstrongenrichmentofLILEandREE,withaLa/Ybvalueof17.8andanEu/Eu*valueof0.336.

Discussion:

TheformationageoftheAqinchulutwo-longgraniteisconsistentwiththeearlypre-CambrianperiodoftheCentralXing'anMountainsorogenicbelt.Itsgeochemicalcompositionindicatesthatitwasformedbyamixedmagmaafterthepartialmeltingofthelowercrust.TheoriginofthemagmaisthepartialmeltingprocessoftheAsianOceaniccrust.ThecharacteristicsofenrichedLILEandREEareconsistentwiththecharacteristicsofpartialmeltingofthelowercrust.

Conclusion:

TheAqinchulutwo-longgraniteinInnerMongoliahasanU-Pbageof(2.48±0.04)GaandshowsthecharacteristicsofenrichedSiO2,Al2O3,andK2OanddepletedFe2O3,MgO,CaO,andNa2O.ItsorigincanbeattributedtothepartialmeltingprocessoftheAsianOceaniccrust,andthemixedmagmaformedafterthepartialmeltingofthelowercrust.TheAqinchulutwo-longgraniteisanimportantrocktypeintheCentralXing'anMountainsorogenicbelt,anditsgeochronologyandgeochemicalcharacteristicsprovidevaluableinsightsintothetectonicandmagmaticevolutionoftheregion.Theearlypre-Cambrianperiodwasacriticaltectonicperiodintheevolutionoftheregion,asitmarkedthetransitionfromancientcratonizationtotheformationofthefirstmodern-styleorogenicbelts.

ThegeochemicalcharacteristicsoftheAqinchulutwo-longgraniteshowthatitisatypicalI-typegranite,whichisformedbyapartialmeltingprocessofthelowercrust.ThesegranitesarecharacterizedbyhighSiO2andK2O,lowMgOandCaO,andstrongenrichmentofLILEandREE,whichareconsistentwiththecharacteristicsofpartialmeltingofthelowercrust.

Inadditiontoprovidinginsightsintothetectonicandmagmaticevolutionoftheregion,theAqinchulutwo-longgranitealsohassignificanteconomicpotential.Theenrichmentofrareearthelementsinthegranitesuggeststhatitmaybeapotentialsourceofthesevaluableminerals.Rareearthelementsarecriticalcomponentsofmanymoderntechnologies,includinggreenenergy,defensesystems,andconsumerelectronics.TheexplorationandexploitationofrareearthelementsintheAqinchulutwo-longgranitecouldhaveimportanteconomicandstrategicimplications.

Inconclusion,theAqinchulutwo-longgraniteinInnerMongoliaisanimportantrocktypethatprovidesvaluableinsightsintothetectonicandmagmaticevolutionoftheCentralXing'anMountainsorogenicbelt.Itsgeochemicalcharacteristicssuggestthatitwasformedbyapartialmeltingprocessofthelowercrustandmayhavesignificanteconomicpotentialasasourceofrareearthelements.TheAqinchulutwo-longgranitealsoplaysacrucialroleinthereconstructionofthetectonichistoryoftheCentralXing'anMountains.Thegraniteintrudedduringtheearlypre-Cambrianperiod,whichwasacriticaltimewhentheancientblockscollidedandassembledtoformthefirstorogenicbelts.Theintrusionofthegraniteindicatesanactivetectonicenvironmentandmayhavecontributedtotheformationoftheorogenicbelt.

ThegeochemicalcharacteristicsoftheAqinchulutwo-longgranitealsosuggestthatitexperiencedacrystalfractionationprocessduringitsformation.Thisprocesscanresultintheseparationofmineralsandelements,leadingtotheenrichmentofcertainelementssuchasrareearthelements.Therareearthelementsinthegraniteoccurasaccessoryminerals,mainlyintheformofmonaziteandallanite.Thesemineralscanbeextractedusingmodernminingtechniquesandprocessedforvariousapplications.

ThepotentialeconomicandstrategicsignificanceoftheAqinchulutwo-longgranitehasattractedattentionfrombothacademiaandindustry.Severalexplorationandminingprojectshavebeenconductedonthegranite,andsignificantrareearthelementdepositshavebeendiscovered.Thedevelopmentofthesedepositscouldmeettheincreasingdemandforrareearthelementsandreducetherelianceonimportsfromothercountries.

Inconclusion,theAqinchulutwo-longgraniteinInnerMongoliaisavaluablerocktypethatprovidesimportantinsightsintothetectonicandmagmaticevolutionoftheCentralXing'anMountainsregion.Itsgeochemicalcharacteristicssuggestthepotentialforrareearthelementexplorationandextraction,whichcouldhavesignificanteconomicandstrategicimplications.Theongoingexplorationanddevelopmentofthegranitewillcontinuetocontributetotheunderstandingoftheregion'sgeologicalandeconomicsignificance.Furthermore,theAqinchulutwo-longgraniteisalsoofscientificinterestduetoitsuniquemineralassemblagesandtextures.Thegranitecontainsavarietyofminerals,includingfeldspars,quartz,biotite,andamphibole,eachwithdistinctcrystalstructuresthatreflecttheirgrowthconditions.Thetexturesofthegranite,suchasitsporphyriticandgranitictextures,suggestacomplexanddynamicevolutionhistory.

TheAqinchulutwo-longgranitealsocontainsxenoliths,orpiecesofsurroundingrockthatwereincorporatedintothegraniteduringitsformation.Thesexenolithsprovideimportantinformationonthecompositionandstructureofthepre-existingrocks,aswellasthepressureandtemperatureconditionsduringthegranite'sformation.

StudyingtheAqinchulutwo-longgraniteanditssurroundingrocksiscrucialforunderstandingthegeologicalhistoryoftheCentralXing'anMountainsandthebroaderregion.Thetectonicandmagmaticprocessesthatformedthegranitearepartofalargersystemofplateboundaries,subductionzones,andcollisioneventsthathaveshapedtheEarth'scontinentsovergeologicaltime.ByunderstandingtheseprocessesandtheireffectsontherocksandmineralsthatmakeuptheEarth'scrust,wecanbetterunderstandtheevolutionofourplanetasawhole.

Insummary,theAqinchulutwo-longgraniteinInnerMongoliaisacomplexandintriguingrocktypethathassignificantgeological,economic,andscientificimplications.Itscomposition,textures,andmineralassemblagesprovideimportantinformationonthetectonicandmagmaticprocessesthat