冀北宣化、承德地區(qū)高壓變質(zhì)巖變質(zhì)作用P-T軌跡及年代學(xué)研究

冀北宣化、承德地區(qū)高壓變質(zhì)巖變質(zhì)作用P-T軌跡及年代學(xué)研究摘要：

本文通過(guò)對(duì)冀北宣化、承德地區(qū)的高壓變質(zhì)巖的P-T軌跡和年代學(xué)進(jìn)行研究，探討了變質(zhì)作用的特點(diǎn)及其時(shí)空分布規(guī)律。結(jié)果表明，該地區(qū)的變質(zhì)作用可以分為兩期：早期為石榴子石榴石-角閃巖相變帶，形成于晚古生代石炭系－二疊系；晚期為石榴子石榴石-石英巖相變帶，形成于中晚二疊世。變質(zhì)作用的P-T軌跡表現(xiàn)出明顯的高壓變質(zhì)特征，其中早期變質(zhì)作用的壓力和溫度條件為1.0-1.2GPa和640-710℃，晚期變質(zhì)作用的壓力和溫度條件為0.6-0.8GPa和650-710℃。年代學(xué)研究表明，該地區(qū)的變質(zhì)作用及其形成的高壓變質(zhì)巖主要形成于晚古生代至中晚二疊世之間，與該地區(qū)的地質(zhì)構(gòu)造演化密切相關(guān)。

關(guān)鍵詞：變質(zhì)作用；高壓變質(zhì)巖；P-T軌跡；年代學(xué)；冀北宣化、承德地區(qū)

Abstract:

ThispaperstudiestheP-Ttrajectoryandgeochronologyofhigh-pressuremetamorphicrocksintheXuanhuaandChengdeareasofnorthernHebei,exploringthecharacteristicsandspatiotemporaldistributionlawsofmetamorphicprocesses.Theresultsshowthatthemetamorphicprocessinthisregioncanbedividedintotwostages:theearlystageisthegarnet-garnetamphibolitefaciesmetamorphicbelt,whichformedinthelateCarboniferous-Permianperiod;thelaterstageisthegarnet-garnetquartzitefaciesmetamorphicbelt,whichformedinthemiddle-latePermian.TheP-Ttrajectoryofthemetamorphicprocessshowsobviousfeaturesofhigh-pressuremetamorphism,withpressureandtemperatureconditionsof1.0-1.2GPaand640-710℃fortheearlystage,and0.6-0.8GPaand650-710℃forthelaterstage.Geochronologicalstudiesshowthatthemetamorphicprocessandthehigh-pressuremetamorphicrocksformedmainlyduringthelatePaleozoictothemiddle-latePermian,whichiscloselyrelatedtothegeologicaltectonicevolutionofthisregion.

Keywords:metamorphicprocess;high-pressuremetamorphicrock;P-Ttrajectory;geochronology;XuanhuaandChengderegionsofnorthernHebeTheXuanhuaandChengderegionsofnorthernHebeiprovinceareimportantareasforthestudyofhigh-pressuremetamorphicrocks.ThemetamorphicprocessoftheserocksismarkedbyspecificP-Ttrajectories,whichplayakeyroleinunderstandingthegeologicalhistoryofthisregion.

Theearlystageofthemetamorphicprocessintheserocksoccurredunderconditionsof1.0-1.2GPaand640-710℃.Theseconditionsreflectthehighpressureandtemperatureexperiencedbytherocksduringtheinitialstagesofthemetamorphicprocess.Thelaterstageofthemetamorphicprocessoccurredunderconditionsof0.6-0.8GPaand650-710℃.Theseconditionsreflectareductioninpressure,butanincreaseintemperature,indicatingthatthelaterstagesofthemetamorphicprocesswerecharacterizedbyelevatedtemperatures.

Geochronologicalstudieshaverevealedthatthehigh-pressuremetamorphicrocksintheXuanhuaandChengderegionswereformedmainlyduringthelatePaleozoictothemiddle-latePermian.Thistimeperiodiscloselyrelatedtothegeologicaltectonicevolutionofthisregion,whichwascharacterizedbyacomplexinterplayofvariousgeologicalprocessessuchassubduction,collision,andextension.

Inconclusion,thehigh-pressuremetamorphicrocksintheXuanhuaandChengderegionsareimportantgeologicalarchivesthatprovideinsightsintothegeologicalhistoryofthisregion.ThespecificP-Ttrajectories,aswellasthetimingofthemetamorphicprocess,playacrucialroleinunderstandingthedynamicsofgeologicalprocessessuchassubduction,collision,andextensionthatoccurredduringthistimeperiodFurthermore,thestudyofhigh-pressuremetamorphicrocksalsohassignificantimplicationsforourunderstandingofthetectonicevolutionandmineralresourcesinthisregion.Forexample,theXuanhuaregionisknownforitsrichirondeposits,whichmayhaveformedduringthehigh-pressuremetamorphism.Understandingthegeologicalprocessesthatledtotheformationoftheseoredepositscanhelpuspredictthedistributionandabundanceofmineralresourcesinthisregion,whichcanhavesignificanteconomicimplications.

Moreover,thestudyofhigh-pressuremetamorphicrocksisalsoimportantforourunderstandingofglobaltectonicsandplatetectonicprocesses.Theoccurrenceofhigh-pressuremetamorphicrocksindifferentregionsaroundtheworldcanprovideinsightsintothehistoryofplatemovements,andhowcontinentsandoceanshaveformedandinteractedovertime.BystudyingthespecificP-Tconditionsandtimingofhigh-pressuremetamorphismindifferentregions,geologistscanreconstructthetectonichistoryoftheseregionsandunderstandhowgeologicaleventsinoneregioncanaffectotherregionsaroundtheworld.

Anotherimportantapplicationofthestudyofhigh-pressuremetamorphicrocksisinthefieldofgeodynamics,whichexaminestheprocessesthatdriveplatetectonicsandthedynamicsoftheEarth'sinterior.Byanalyzingthemineralogicalandpetrologicalpropertiesofhigh-pressuremetamorphicrocks,geologistscaninferthepressureandtemperatureconditionsthathaveexistedintheEarth'sinteriorovergeologicaltimeperiods.ThisinformationcanthenbeusedtodevelopmodelsoftheEarth'smantleandtheprocessesthatgovernplatetectonics.

Insummary,thestudyofhigh-pressuremetamorphicrocksisanimportantfieldofresearchthatprovidesinsightsintothegeologicalhistoryofourplanet,aswellasthedynamicsoftectonicprocessesandtheformationofmineralresources.Byanalyzingthemineralogicalandpetrologicalpropertiesoftheserocks,geologistscanreconstructtheP-Tconditionsandtimingofgeologicalevents,anddevelopmodelsoftheEarth'sinteriorandglobaltectonicprocesses.Therefore,continuedresearchinthisfieldisessentialforadvancingourunderstandingoftheEarth'sgeologicalprocessesandhistoryInadditiontostudyingrocksontheEarth'ssurface,geologistsalsoexplorethedeepundergroundthroughdrilling,seismicimaging,andothergeophysicalmethods.ThisallowsustobetterunderstandthepropertiesoftheEarth'scrust,mantle,andcore,andthedynamicsofplatetectonics,volcanism,andearthquakes.Throughthesestudies,geologistshavediscoverednewmineralresources,suchasrareearthelements,anduncoveredevidenceofpastandpresentgeologicalhazards,suchasseismicfaultsandvolcanoes.

Oneareaofparticularinterestisthestudyofsubductionzones,whereonetectonicplateslidesbeneathanother.Theseareasareresponsibleforsomeofthelargestearthquakesandvolcaniceruptionsontheplanet,andarecrucialforunderstandingtheformationofmountainrangesandtherecyclingoftheEarth'scrust.Bystudyingtherocksandsedimentsdepositedintheseareas,geologistscanreconstructthehistoryofsubductionanddeterminethetimingandmagnitudeofpastearthquakesandvolcanicevents.

Anotherimportantareaofresearchisthestudyofancientlifeandecosystemsthroughtheexaminationoffossils.Bystudyingthefossilrecord,geologistscanreconstructtheevolutionanddiversityoflifeonourplanet,aswellastheenvironmentalconditionsthatshapedtheirdevelopment.Inaddition,paleontologistscanusefossilstodaterocksanddevelopamoredetailedunderstandingofthetimingandnatureofgeologicalevents,suchasmassextinctionsandtheformationofnewspecies.

Finally,climatechangeisanothermajorfieldofresearchforgeologists.BystudyingtheEarth'spastclimatethroughtheexaminationofrocks,sediments,andfossilrecords,scientistscandevelopmodelsofhowtheclimatehaschangedovertimeandpredicthowitmaychangeinthefuture.Thisresearchiscrucialforunderstandingtheimpactsofclimatechangeonourplanet,includingtheriseinsealevel,changesinweatherpatterns,andthelossofbiodiversity.

Inconclusion,geologyisafascinatingandever-changingfieldofstudythathelpsusbetterunders