內蒙古伊敏地區(qū)侏羅紀流紋巖地球化學特征及其地質意義

內蒙古伊敏地區(qū)侏羅紀流紋巖地球化學特征及其地質意義摘要

伊敏地區(qū)位于內蒙古自治區(qū)西北部，地處西伯利亞克拉通東緣，侏羅系是該地區(qū)主要地層，出露有豐富的流紋巖。本文通過對伊敏地區(qū)侏羅系流紋巖進行地球化學分析，探究其地球化學特征及其地質意義。

研究結果表明，伊敏地區(qū)侏羅系流紋巖主要由玄武巖和安山巖組成，具有低K_2O、高Na_2O和SiO_2含量的特點；稀土元素配分模式呈現(xiàn)輕稀土元素富集、重稀土元素虧損的形式，具有典型的弱過鋁質巖石特征；富集大離子親石元素K、Ba、Sr、Rb，虧損高場強元素Nb、Ta、Ti、P。

結合區(qū)域構造背景、巖石成因類型等方面考慮，伊敏地區(qū)侏羅系流紋巖為弱過鋁質堿性玄武巖系列巖石，屬于古特提斯洋俯沖作用的產物，具有重要的構造背景和沉積環(huán)境意義。

關鍵詞：伊敏地區(qū)；侏羅系；流紋巖；地球化學特征；地質意義

Abstract

TheEmeenareaislocatedinthenorthwestofInnerMongoliaAutonomousRegionandissituatedalongtheeasternmarginoftheSiberiancraton.Jurassicstrataarethemaingeologicalformationsinthisregion,andthereareabundantrhyolitesexposed.Inthispaper,thegeochemicalcharacteristicsandgeologicalsignificanceofJurassicrhyolitesintheEmeenareawereexploredthroughthegeochemicalanalysis.

TheresultsshowthattheJurassicrhyolitesintheEmeenareaaremainlycomposedofbasaltandandesite,withlowK_2O,highNa_2O,andSiO_2contents.Thedistributionpatternofrareearthelementsshowslightrareearthelementenrichmentandheavyrareearthelementdepletion,whichhavetypicalweaklyperaluminouscharacteristics.TheyareenrichedinlargeionlithophileelementsK,Ba,Sr,andRb,anddepletedinhighfieldstrengthelementsNb,Ta,Ti,andP.

Consideringtheregionaltectonicbackgroundandpetrogenesistypes,theJurassicrhyolitesintheEmeenareaareweaklyperaluminousalkalinebasalticrockseries,whicharetheproductsofthesubductionofthePaleo-TethysOcean,andhaveimportanttectonicbackgroundandsedimentaryenvironmentsignificance.

Keywords:Emeenarea;Jurassicstrata;rhyolite;geochemicalcharacteristics;geologicalsignificancTheEmeenareaislocatedinthewesternpartofInnerMongolia,China,andisknownforitsJurassicstrata,whichcontainasignificantamountofrhyolites.Thegeochemicalcharacteristicsoftheserhyoliteshavebeenextensivelystudied,revealingimportantinsightsintothetectonicbackgroundandpetrogenesisofthearea.

Basedonthegeochemicaldata,theJurassicrhyolitesintheEmeenareaareweaklyperaluminousalkalinebasalticrockseries,whichimpliesthattheyareformedasaresultofthesubductionofthePaleo-TethysOcean.Furthermore,therhyolitesdisplayevidenceoffractionalcrystallizationandassimilationofcrustalmaterials,whichsuggeststhattheywereformedthroughmagmaticdifferentiationandassimilationprocesses.

Intermsofelementalcomposition,therhyolitesintheEmeenareaareenrichedinK,Rb,andBa,whicharetypicallyassociatedwiththesubductionofoceaniclithosphere.Thisenrichmentisconsistentwiththetectonicsettingofthearea,whichisinaregionthatexperiencedsubductionduringtheJurassicperiod.Conversely,therhyolitesaredepletedinhighfieldstrengthelementssuchasNb,Ta,Ti,andP,suggestingthattheseelementswereremovedfromthemagmabyfractionalcrystallizationorassimilation.

Overall,thegeochemicalcharacteristicsoftheJurassicrhyolitesintheEmeenareaprovideimportantinsightsintothetectonicbackgroundandpetrogenesisoftheregion.TheysuggestthattheareawassubjecttosubductionduringtheJurassicperiod,whichresultedintheformationoftherhyolitesthroughmagmaticdifferentiationandassimilationprocesses.ThesefindingshavesignificantgeologicalsignificanceandcanhelptofurtherourunderstandingofthegeologicalhistoryofInnerMongoliaFurthermore,thegeochemicalcharacteristicsoftheJurassicrhyolitessuggestthattheyweregeneratedinacontinentalmarginsettingratherthanatypicalislandarcenvironment.Thisisevidencedbythehighlevelsofpotassium,aluminum,andsilica,whicharetypicalofcontinentalcrust.Inaddition,therhyoliteshavebeenidentifiedasmetaluminousorweaklyperaluminous,indicatingthatthemagmawaslikelycontaminatedandenrichedbyinteractionwithcontinentalcrust.

TheageoftheJurassicrhyolitesintheEmeenareaissignificantbecauseithelpstoshedlightonthetectonicevolutionofInnerMongoliaduringthisperiod.TheJurassicwasatimeofsignificanttectonicactivityintheregion,withtheopeningoftheMongol-OkhotskOceanandtheinitiationofconvergenttectonicsalongthenorthernmarginofChina.ThediscoveryoftheJurassicrhyolitesprovidesevidencethatsubductionwasoccurringduringthistime,makingitanimportantperiodforunderstandingthetectonichistoryoftheregion.

Inadditiontotheirtectonicsignificance,theJurassicrhyolitesalsohavepotentialeconomicsignificance.TheEmeenareaisknowntocontainsignificantmineraldeposits,includinggold,silver,copper,andlead-zinc.TherhyolitesthatwereformedduringtheJurassicperiodmayhaveplayedaroleintheformationofthesedeposits,makingthemausefultargetformineralexploration.

Overall,thegeochemicalcharacteristicsoftheJurassicrhyolitesintheEmeenareaprovideimportantinsightsintothetectonicandmagmaticprocessesthatwereoccurringinInnerMongoliaduringtheJurassicperiod.Theiridentificationascontinentalmarginrhyolitessuggeststhattheregionwassubjecttosubductionduringthistime,whichhasimplicationsforourunderstandingoftheevolutionofnorthernChina.Additionally,thepotentialeconomicsignificanceoftheserhyolitesmakesthemavaluabletargetforfuturemineralexplorationintheregionThediscoveryoftherhyolitesintheEmeenareahasimplicationsnotonlyforourunderstandingofthegeologyofnorthernChinaduringtheJurassicperiodbutalsoforfuturemineralexploration.Rhyolitesareknownfortheirpotentialtohostmetallicmineralssuchasgold,silver,copper,andlead,makingthemeconomicallysignificant.

TheidentificationoftheEmeenrhyolitesascontinentalmarginrhyolitessuggeststhattheywereformedinasubductionzonesetting.Subductionoccurswhenonetectonicplateisforcedunderneathanotherplate,causingittomeltandformmagma.Thismagmacanrisetothesurfaceandsolidifyasvolcanicrocks,suchasrhyolites.

ThesubductionofthetectonicplatesintheregionduringtheJurassicperiodhadimportantimplicationsfortheevolutionofnorthernChina.Subductioncancausetheformationofislandarcs,whicharechainsofvolcanicislandsthatformattheboundarybetweentwotectonicplates.ThesubductionoftheplatesinnorthernChinamayhaveledtotheformationofsuchislandarcs,whichcouldhaveplayedanimportantroleinthedevelopmentoftheregion'sgeologyandmineralresources.

ThepotentialeconomicsignificanceoftheEmeenrhyolitesmakesthemanimportanttargetforfuturemineralexplorationintheregion.Rhyolitesareknowntohostmetallicminerals,andtheEmeenrhyolitescouldbenoexcepti