内蒙古基东方辉橄榄岩的成因及其温压条件

内蒙古基东方辉橄榄岩的成因及其温压条件内蒙古基东方辉橄榄岩的成因及其温压条件

摘要：

基东方辉橄榄岩位于内蒙古阿拉善盟境内，是一种古老的岩石类型，其研究对于探究早期地球的演化过程具有重要意义。本文通过对该橄榄岩的矿物组成、物相学特征、化学特征等方面进行了综合研究，探讨了其成因机制及温压条件。结果表明，基东方辉橄榄岩的形成与深部的岩浆活动以及后期的变质作用密切相关，主要经历了橄榄岩形成、逆掩断裂的发育、HP-UHP变质的过程。在岩浆晶体化过程中，高压和高温作用下使橄榄石和钠长石在对流岩浆中不断析出，最终形成了橄榄岩。后期的逆掩断裂使其隆起到地表，经历了低压变质作用，造成了基东方辉橄榄岩成分特异性以及矿物形态学及化学成分的改变，使之发生了UHP变化。

关键词：基东方辉橄榄岩；成因机制；温压条件；岩浆晶体化；变质作用；低压变质作用；UHP变化

Abstract:

JidongfanghuiPeridotiteisanancientrocktypelocatedinAlxaregionofInnerMongolia.Itsstudyisofgreatsignificanceforexploringtheevolutionprocessoftheearlyearth.Inthispaper,thecomprehensivestudyofmineralcomposition,phasepetrology,chemicalcharacteristicsandotheraspectsoftheperidotiteisconductedtoexploreitsgenesismechanismandtemperature-pressureconditions.TheresultsshowthattheformationofJidongfanghuiperidotiteiscloselyrelatedtothedeepmagmaticactivityandlatermetamorphicaction,mainlyexperiencingtheprocessofperidotiteformation,thedevelopmentofthrustfault,HP-UHPmetamorphism.Intheprocessofmagmaticcrystallization,olivineandsodiumfeldsparareconstantlyprecipitatedintheconvectionmagmaunderhighpressureandhightemperaturetofinallyformolivinerock.Laterthrustfaultupliftedittothesurface,experiencinglow-pressuremetamorphism,resultinginthespecificityofJidongfanghuiperidotitecomposition,andchangesinmineralogyandchemicalcomposition,causingUHPchanges.

Keywords:Jidongfanghuiperidotite;genesismechanism;temperature-pressureconditions;magmaticcrystallization;metamorphicaction;low-pressuremetamorphism;UHPchangesTheformationoftheJidongfanghuiperidotiteisbelievedtohaveoccurredthroughacombinationofmagmaticcrystallizationandmetamorphicactionunderhigh-pressureandhigh-temperatureconditions.Themagma,whichwasrichinmagnesiumandiron,intrudedintotheEarth'smantleandunderwentcrystallizationtoformtheperidotiterock.

Theperidotiterock,overtime,wassubjectedtointensepressuresandtemperatures,leadingtotheformationofolivine-richlayers.Thehigh-pressureconditionsunderwhichtheperidotitewasformedcausedittohaveadistinctchemicalcompositionandmineralogy.

Later,theperidotitewasupliftedtothesurfacethroughthrustfaulting,andthisprocessledtolow-pressuremetamorphism,whichcausedchangesinthemineralogyandchemicalcompositionoftherock.TheJidongfanghuiperidotiteunderwentthismetamorphicaction,resultinginUltra-High-Pressure(UHP)changes.

Inconclusion,thegenesismechanismofJidongfanghuiperidotiteiscomplexandinvolvedvariousgeologicalprocessesthatoccurredoveralongperiodoftime.Thecombinationofmagmaticcrystallizationandmetamorphicactionunderhigh-pressureandhigh-temperatureconditions,followedbylow-pressuremetamorphism,contributedtotheformationofthisuniquerockwithitsdistinctmineralogicalandchemicalcharacteristicsTheJidongfanghuiperidotitehasplayedanimportantroleinstudyingplatetectonicsandmantleprocesses.ItprovidessignificantinformationforreconstructingthegeodynamicevolutionofthedeepEarth.

Thehigh-pressureandhigh-temperatureconditionsthatformedtheJidongfanghuiperidotitewereinfluencedbyseveralprocessesthatoccurredovertime.ThemagmaticprocessplayedamajorroleinthegenesisoftheJidongfanghuiperidotite.Themagmafromthemantlerockdifferentiated,andtheultramaficminerals,particularlyolivine,accumulatedintheJidongfanghuiperidotite.Theintrusionofmagmacausedtheperidotitetomeltpartially,andtheresultantmeltsolidifiedintotheorthopyroxene-bearingwehrliteenclosedbytheperidotite.

MetamorphicrecrystallizationthatoccurredduringsubductionfurthermodifiedtheJidongfanghuiperidotite.SubductionoccurredduringtheearlyhistoryoftheXing'anMassifwhentheJidongfanghuiperidotitewasburiedunderathickpileofsediments.Thesedimentsandperidotiteweretransportedtodepthbysubductionatdifferenttimes.Theintensepressureandtemperatureconditionsresultedinthedevelopmentofpargasiticamphiboleandphlogopiteintheperidotite.Italsoledtopartialmeltingoftheperidotite,whichproducedasmallamountofeclogite.

Duringexhumation,theJidongfanghuiperidotiteunderwentlow-pressuremetamorphismthatfurthermodifiedtherock.ThelaststageofmetamorphismoccurredduringtheCenozoicEra,whichwascharacterizedbyretrogrademetamorphism.Retrogrademetamorphismoccurredunderlow-pressureconditionswhentheJidongfanghuiperidotitewasupliftedtoitspresentposition.Themetamorphicrecrystallizationresultedintheformationoftremoliteandcalciteveinsintheperidotite.

Insummary,theJidongfanghuiperidotiteformedasaresultofdifferentgeologicalprocesses,includingmagmaticcrystallization,subduction,andlow-pressuremetamorphism.TheseprocessesleftauniquemineralogicalandchemicalimprintthatprovidescrucialinformationaboutthegeodynamicevolutionofthedeepEarth.StudyingtheJidongfanghuiperidotitewillcontinuetoprovidevaluableinsightsintomantleprocessesovertimeInadditiontothegeologicalprocessesthatformedtheJidongfanghuiperidotite,thestudyofthisrockcanalsoshedlightonenvironmentalandsocietalconcerns.Onesuchconcernistheoccurrenceofasbestos,agroupofsixnaturallyoccurringmineralfibersthatareknowntocauselungcancerandotherrespiratoryillnesseswheninhaled.Tremolite,oneofthemineralsfoundintheJidongfanghuiperidotiteveins,isatypeofasbestos.

Understandingtheformationanddistributionofasbestos-bearingrocksisimportantforassessingtheriskofasbestosexposureanddevelopingstrategiestomitigateit.Althoughasbestosusehasbeenlargelybannedinmanycountries,therearestillmillionsofpeopleworldwidewhoareexposedtoasbestosfibersintheworkplaceorthroughenvironmentalexposure.ThepresenceofasbestosintheJidongfanghuiperidotitehighlightstheneedforcontinuedresearchonthehealtheffectsofasbestosandeffectivewaystopreventexposure.

Beyondthehealthimplicationsofasbestos,theJidongfanghuiperidotitealsohaspotentialeconomicsignificance.Asmentionedearlier,peridotiteisarocktypethatisoftenassociatedwithdiamonddeposits.AlthoughnodiamondhasbeenfoundintheJidongfanghuiperidotitetodate,thepresenceofkimberlitemagmaandeclogitexenolithsinthesurroundingareassuggeststhattheremaybediamond-bearingrocksnearby.

Thediscoveryofnewdiamonddepositscouldhavesignificanteconomicbenefitsforthelocalcommunityandthewidersociety.Diamondsareusedinavarietyofindustrialapplicationsandarealsohighlyvaluedfortheiruseinjewelry.Theexplorationandminingofdiamonddeposits,however,needstobedoneresponsiblytominimizetheenvironmentalandsocialimpacts.

Inconclusion,theJidongfanghuiperidotiteisafascinatingrockthatoffersinsightsintothegeologicalhistoryoftheEarth,thehealth