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下扬子地区若干上地幔橄榄岩的显微构造研究.docx

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下扬子地区若干上地幔橄榄岩的显微构造研究 Title:MicrostructuralAnalysisofUpperMantlePeridotitesintheLowerYangtzeRegion Introduction TheEarth'suppermantleplaysacrucialroleinthedynamicsandevolutionofthelithosphere.Understandingthemicrostructuralcharacteristicsofmantleperidotitesoffersvaluableinsightsintothegeologicalprocessesthatoccuratgreatdepths.Inthisstudy,weaimtoinvestigatethemicrostructuralfeaturesofuppermantleperidotitesintheLowerYangtzeregion,sheddinglightontheirformationmechanismsandtectonicimplications. Methods Toachieveourresearchobjectives,wecollectedrepresentativesamplesofuppermantleperidotitesfromseverallocationsintheLowerYangtzeregion.Thesesamplesweresubsequentlypreparedforpetrographicanalysis,includingthinsectioningandpolishing,torevealthemicrostructuraldetails.Fordefinitivemicrostructuralexamination,transmittedandreflectedlightmicroscopy,scanningelectronmicroscopy(SEM),andelectronbackscatterdiffraction(EBSD)wereemployed.High-resolutionimagingtechniquesallowedfortheidentificationofvariousmicrostructuralfeatures,suchasfoliation,grainboundaries,andmineralcompositions. ResultsandDiscussion ThemicrostructuralanalysisoftheuppermantleperidotitesintheLowerYangtzeregionrevealedseveralimportantfindings.Firstly,foliationpatternswereobservedinthesamples,indicatingthepresenceofdeformationandshearingprocesses.Thealignmentofmineralgrainssuggestedaprogressivedeformationsequence,suggestingahistoryoftectonicevents.Secondly,grainboundariesexhibitedgrainsizevariations,suggestingrecrystallizationprocessesandtheinfluenceofmelt-rockinteractions.Theseobservationspointtowardsdynamicmetamorphismandpartialmeltingoccurringathightemperaturesandpressures.Additionally,thepresenceofmicrofracturesandmineralinclusionsincertainsamplesindicatethepossibilityoffluidinfiltrationandreaction-inducedcracking. Themineralcompositionswithintheperidotitesampleswerefoundtobedominatedbyolivine,pyroxenes,andspinel.Olivinegrainsexhibitedvariousdegreesoffabricdevelopment,asrevealedbyEBSDanalysis.Thecrystallographicpreferre