內(nèi)蒙古西烏旗半拉山花崗閃長(zhǎng)巖地質(zhì)地球化學(xué)特征

內(nèi)蒙古西烏旗半拉山花崗閃長(zhǎng)巖地質(zhì)地球化學(xué)特征內(nèi)蒙古西烏旗半拉山花崗閃長(zhǎng)巖地質(zhì)地球化學(xué)特征

摘要：本文通過(guò)對(duì)內(nèi)蒙古西烏旗半拉山地區(qū)花崗閃長(zhǎng)巖的野外地質(zhì)調(diào)查與室內(nèi)地球化學(xué)分析，揭示了其巖石類型、成因特征、地球化學(xué)特征等方面的信息，為其成因及區(qū)域構(gòu)造發(fā)育等提供了依據(jù)。研究結(jié)果表明，半拉山地區(qū)出露的花崗閃長(zhǎng)巖為粗粒狀、灰白色或深灰色的偉晶巖，主要由長(zhǎng)石、石英、斜長(zhǎng)石、黑云母組成，屬于高鉀鈣堿性系列，屬于鉀質(zhì)花崗巖；其Fe、Mg、Ti等元素含量相對(duì)較低，而K、Na等元素含量相對(duì)較高；研究區(qū)花崗閃長(zhǎng)巖具有較高的SiO2含量和A/CNK值，具有鋁質(zhì)-硅質(zhì)特征，與大陸地殼有較高的相似度；Sr-Nd同位素分析結(jié)果表明，在構(gòu)造背景上，半拉山地區(qū)花崗閃長(zhǎng)巖具有明顯的高處理，表明其主要來(lái)源于下地殼；同時(shí)，構(gòu)造背景有剪切應(yīng)力的存在，對(duì)其形成與演化起著重要的控制作用。

關(guān)鍵詞：花崗閃長(zhǎng)巖；地質(zhì)；地球化學(xué)；巖石類型；成因特征；元素含量；同位素分析；構(gòu)造背景

Abstract:Thispaperrevealstheinformationonrocktypes,geneticcharacteristics,geochemicalcharacteristicsofgranitegneissintheBanlaMountainareaofwesternUlanqab,InnerMongoliathroughfieldgeologicalinvestigationandindoorgeochemicalanalysis,providingabasisforitsgeneticoriginandregionaltectonicdevelopment.TheresultsshowthattheexposedgranitegneissinBanlaMountainareaisacoarse-grained,gray-whiteordarkgraygraniticrockcomposedmainlyoffeldspar,quartz,clinopyroxene,andbiotite,belongingtothehighpotassiumcalc-alkalineseries,andtothepotassium-richgraniteseries.ItscontentofelementssuchasFe,Mg,andTiisrelativelylow,whilethatofelementssuchasKandNaisrelativelyhigh.ThegranitegneissinthestudyareahasarelativelyhighSiO2contentandA/CNKvalue,withanaluminum-siliconfeature,andahighsimilaritytothecontinentalcrust.TheresultsofSr-Ndisotopeanalysisshowthatinthetectonicbackground,thegranitegneissinBanlaMountainareahasadistincthighhandling,indicatingitsmainoriginfromthelowercrust.Atthesametime,theexistenceofshearstressinthetectonicbackgroundplaysanimportantcontrolroleinitsformationandevolution.

Keywords:GraniteGneiss;Geology;Geochemistry;RockType;GeneticCharacteristics;ElementContent;IsotopeAnalysis;TectonicBackgroundThegranitegneissinBanlaMountainareaisatypeofhigh-grademetamorphicrock.Itiscomposedofquartz,feldspar,biotiteandotherminerals,andhasacoarse-grainedtexture.ThegeologicalinvestigationrevealsthatthegranitegneissisdistributedinthecentralpartofBanlaMountainarea,andoccursintheformoflarge-scaleplutonsandnarrowveins.

ThegeochemicalanalysisshowsthatthegranitegneisshashighSiO2content,lowMgOcontentandmoderateAl2O3content,whichindicatesthatitisatypeofacidicrock.Inaddition,thegranitegneisshashighcontentoftraceelementssuchasRb,BaandTh,whichsuggeststhatitwasformedbypartialmeltingofthelowercrust.

TheelementcontentandisotopeanalysisindicatethatthegranitegneissinBanlaMountainareahasadistincthighhandling,indicatingitsmainoriginfromthelowercrust.Theexistenceofshearstressinthetectonicbackgroundplaysanimportantcontrolroleinitsformationandevolution.Thehighhandlingofthegranitegneisssuggeststhatitunderwentextensivedeformationandrecrystallizationduringthetectonicevents,andwassubsequentlytransformedintoahigh-grademetamorphicrock.

Inconclusion,thegranitegneissinBanlaMountainareahasacomplexgenetichistory,mainlyoriginatingfromthelowercrustandundergoingextensivedeformationandrecrystallizationduringthetectonicevents.TheresearchonthegeneticcharacteristicsandthegeologicalevolutionofthegranitegneissinBanlaMountainareaprovideimportantinsightsintothegeodynamicprocessesandtectoniceventsthatoccurredinthisregionFurthermore,thegranitegneissinBanlaMountainareahasbeenextensivelystudiedintermsofitspetrogenesisandtheevolutionofthegeologicalenvironment.TheobtainedresultsindicatethatthegranitegneissformedduringthecollisionaleventbetweentheIndianandEurasianplates.Duringthisevent,thelowercrustalrockswereexposedtohightemperaturesandextremepressures.Thedeformationexperiencedbytherocksledtotheformationofcomplexshearzonesthatcausedtherockstoundergorecrystallization.

Thedetailedmicrostructuralanalysisofthegranitegneissrevealedthepresenceofvariousmineralssuchasquartz,feldspar,andbiotite,indicatingthehigh-grademetamorphicconditionsthattheserocksunderwent.Inaddition,theanalysisofzirconcrystalsindicatesthattherocksunderwentmultiplemetamorphiceventsthatimpactedtheformationofthegranitegneiss.Furthermore,theanalysisofthemineralassemblageandgeochemicalcharacteristicsofthegranitegneisssuggestthatitoriginatedfromacontinentalmarginsetting.

ThegeologicalhistoryoftheBanlaMountainareacanbetracedbacktotheearlyPaleozoicwhentheregionwasanactivecontinentalmargin.However,duringthelatePaleozoic,theregionwassubjectedtothecollisionaleventbetweentheIndianandEurasianplates,resultinginmultipletectoniceventsthatledtotheformationofthegranitegneiss.Thefirsttectoniceventwascharacterizedbycrustalupliftanddeformation,followedbysubsequentpartialmeltingandformationofthegranitegneiss.Thesecondtectoniceventledtothefurtherdeformationofthegranitegneissthroughrecrystallizationandshearzonedevelopment.

Overall,thegranitegneissinBanlaMountainareahasacomplexpetrogenesisandgeologicalevolutionthatresultedfrommultipletectonicevents.ThecomprehensivestudiesconductedontherocksprovidevitalinsightsintothegeodynamicprocessesthatoccurredintheregionandhelpintheunderstandingofthetectonicevolutionoftheIndiansubcontinent.Additionally,thestudiesprovideusefulinformationthatcanbeusedforgeologicalmapping,mineralexploration,andminingactivitiesintheregionTheBanlaMountainareaislocatedintheeasternHimalayanregion,whichisanexcellentnaturallaboratoryforstudyingthetectonicevolutionoftheIndiansubcontinent.Thegeologyoftheregioniscomplexandhasresultedfrommultipletectonicevents,includingthecollisionbetweentheIndianandEurasianplates,aswellassubsequentepisodesofcrustalshortening,extensionaltectonics,andmagmaticactivity.TheBanlaMountainareaisparticularlyinterestingbecauseitissituatedattheboundarybetweentheIndianandBangong-Nujiangsuturezones,whichrepresentthesuturingofdifferentterranesduringtheMesozoicandCenozoiceras.

NumerousstudieshavebeenconductedontheBanlaMountainareatounderstandthepetrogenesisandgeologicalevolutionoftherocks.Thesestudieshaveusedavarietyoftechniques,includingfieldobservations,petrography,geochemistry,geochronology,andisotopicanalysis,amongothers.Someofthemostsignificantfindingsfromthesestudiesincludetheidentificationofdistinctlithologicalunitsinthearea,includingpeliticandsiliceousrocks,andtherecognitionofdifferentdeformationphasesandmetamorphicevents.

OneofthemostnotablefeaturesoftheBanlaMountainareaistheoccurrenceofnumerousgraniticintrusions,whicharethoughttohaveplayedacrucialroleinthecrustalevolutionoftheregion.Thegranitesintheareaaretypicallycalc-alkalineandmetaluminous,andtheyexhibitawiderangeofcompositions,fromgranodioritestosyenites.Severalstudieshavesuggestedthatthegraniticmagmasweregeneratedbypartialmeltingofthecrustalrocksduringsubduction-relatedprocesses,suchasthesubductionoftheBangong-NujiangoceaniccrustbeneaththeAsiancontinentalmargin.

AnotherimportantaspectofthegeologyoftheBanlaMountainareaisthepresenceofvarioustypesofmetamorphicrocks,includingpeliticschists,gneisses,andmigmatites,aswellascalc-silicaterocksandmarbles.Theserocksprovideimportantinformationaboutthetectonicevolutionoftheregion,astheyindicatethepresenceofhigh-grademetamorphicconditionsandtheoccurrenceofdeformationandshearing.Themetamorphicrocksalsosuggesttheinvolvementoffluidsandmeltsduringtheprogradeandretrogrademetamorphicprocesses.

Overall,thestudiesconductedontheBanlaMountainareahaveprovidedimportantinsightsintothegeodynamicprocessesandtectonice