显微构造地质学 microstructure 中英双语复习资料Word文档下载推荐.docx

显微构造地质学 microstructure 中英双语复习资料Word文档下载推荐.docx

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isthepervasivebrittlefracturingandgranulationofrocks,generallyalongfaultsandfaultzones.Itproducesanaggregateofhighlyfracturedgrainsandrockfragmentsinamatrixofevensmaller,crushedgrains.Onceformed,suchcrushedaggregatesareabletoflowbyrepeatedfracturing,frictionalsliding,andrigid-bodyrotationofgrainsandfragments,aprocesstermedcataclasticflow.Cataclasticrocksarecharacterizedbypervasivecracksandgenerallysharp,angulargrainsandfragments.Oftensimilaratallscaleofobservation.Cataclasitefabric:

angularfragmentsofallsizes,sometransectinggrainboundaries,areembeddedinafine-grainedmatrix.Manylargerfragmentsarecrossedbyhealedfractures,alignedwithfluid-andsolidinclusions.Recrystallisedfabricofsmallnewgrainsthatgrewattheexpenseofoldgrains.Thenewgrainsshowlittlevarietyingrainsize.4.Dissolution-Precipitation溶解-沉淀Inrocksthatcontainanintegranularfluid晶间液体pressure-solutioncanoccurasdeformationmechanism.Pressure-solution:

dissolutionatgrainboundariesinagrainboundaryfluidphaseathighdifferentialstress.Pressuresolutionislocalisedwherestressinthegrainishigh,mostlywheregrainsareincontactalongsurfacesatahighangletotheinstantaneousshorteningdirectionthegrainlatticenearcontactpointsismorestronglycompressedthanelsewhere;

asaresult,materialwilldissolvenearthesecontactpointsandberedepositedatsitesoflowdifferentialstress.Alocallyhigherdensityofcrystaldefectsnearcontactpointsmayalsoenhancesolubility5.Processesofdissolutioncreep溶解蠕变（压溶作用）低温低应力低应变速率实质是coble蠕变3processes:

dissolutionatthesource,diffusionormigrationofthedissolvedmaterialalongsomepathwayreprecipitationDissolution:

Inresponsetoanapplieddifferentialstress,grainsbecomepreferentiallycorrodedalongsegmentsofgrainboundariesthatarebeingsubjectedtohighcompressivestress.Suchsegmentsincludethoseorientedathighanglestothegreatestprincipalcompressivestress

（1）andthoseinwhichrigidgrainsorobjectsimpingeononeanothertoconcentratestress.highlysolublemineralswilldissolvepreferentiallytothosewithlowersolubilities.Inimpurecarbonaterocks,forexample,calcitetypicallydissolvesmorereadilythanquartz,clays,andiron-manganeseoxides.Grainswithimpuritiesandthosewithcrystallinelatticesthathavebeensomehowdamaged,perhapsbytheworkofotherdeformationmechanisms,arelikewisemoresusceptibletodissolutionthanpristine原始的grains.溶解：

响应于施加的差异应力，晶粒优先被沿着受高压应力的晶界区段腐蚀。

这些部分包括与最大主压应力

（1）成高角度取向的部分，以及刚性颗粒或物体相互碰撞以集中应力的部分。

高度可溶的矿物质将优先溶解于溶解度较低的矿物质。

例如在不纯的碳酸盐岩中，方解石一般比石英，粘土和铁锰氧化物更容易溶解。

含有杂质的晶粒和晶格已经受到某种程度损坏的晶粒，也许是由于其他变形机制的作用，同样比原始晶粒更容易溶解。

Migrationandreprecipitation:

Assolidgrainsdissolve,theyenrichthefluidintheirconstituents,especiallynearsitesofmorerapiddissolution.Incontrast,littleornodissolutionmayoccurneargrainboundariesnormaltotheleastprincipalcompressivestress（3）.Thedifferencesindissolutionratesresultinchemicalconcentrationgradientswithinthefluid,causingdissolvedconstituentstodiffuseawayfromthedissolutionsitesandtowardsitesoflowercompressivestress.迁移和再沉淀：

由于固体颗粒溶解，它们富集成分中的流体，特别是在溶解速度更快的附近。

相反，在与最小主压应力（3）垂直的晶界附近几乎不发生溶解。

溶解速率的差异导致流体内的化学浓度梯度（实质），导致溶解成分从溶解位点扩散到较低压缩应力的位置。

比较常见的是难熔物质的两侧，周围的易溶物被溶解迁移到难熔矿物的低应力区沉淀，形成以难溶物为核晶，以易溶物为阴影的压力影构造。

Conditionofdissolutioncreep:

IntergranularfluidLowdifferentialstressLowtomoderatetemperatureSmallgrainsizefavordissolution:

Strainrateisinverselyproportionaltothecubeofthegrainsize;

hence,grain-sizereductionbydissolutionleadstoaquickeningofthepaceofdissolution,atypeofstrainsoftening.6.IntracrystallineDeformation晶内缺陷Crystalscandeforminternallywithoutbrittlefracturingbymovementofso-calledlatticedefects,aprocessknownasintracrystallinedeformationLatticedefects:

Pointdefect,linedefectsandplanardefectDislocationglide位错滑动位错滑动LineardefectintheCrystalBurgersVector:

AdislocationischaracterizedbyaBurgersvectorwhichindicatesthedirectionandminimumamountoflatticedisplacementcausedbythedislocation.通常将柏氏矢量称为位错强度，位错的许多性质如位错的能量，所受的力，应力场，位错反应等均与其有关。

它也表示出晶体滑移时原子移动的大小和方向。

位错可定义为柏氏矢量不为零的晶体缺陷，它具有连续性，不能中断于晶体内部。

其存在形态可形成一个闭合的位错环，或连接于其他位错，或终止在晶界，或露头于晶体表面。

边缘位错和螺旋位错可以互相连接成位错环Dislocationglideeasieronspecificslip-systemsdependingonP,T,fH2O,etcDislocationClimb位错攀移位错攀移Migrationofvacanciestothedislocationplanecancausetheclimbofthedislocation杂质35Theshapeofacrystalcannotbepermanentlychangedbyjustsqueezingit;

thedistancebetweenlatticepointscanonlybechangedbyaverysmallamount,leadingtoelasticdeformation.Ifstressisreleased,theoriginalshapeisrecovered.Apermanentchangeinshapecanonlybeachievedbyachangeintherelativepositionsofmoleculesoratoms.Thishappensbymovementoflat-ticedefectsthroughacrystalintheprocessofintracrys-tallinedeformation（Poirier1985;

Hull1975）.ConsiderthevacanciesinFig.3.12.Ifneighbour-ingatomsoccupythevacancysites,vacanciesaremovingthroughthecrystalandthecrystalmaychangeshapepermanently（Videos3.12a,3.12b）.Movingdislocationscanalsocauserelativedisplacementofpartsofacrystallattice.Figure3.15a（Videos3.11,3.15a）showshowmovementofadislocationdis-placespartsofcrystalswithoutactuallyseparatingonepartofthecrystalfromtheother.Dislocationscanbegeneratedinacrystalatso-calleddislocationsources.AnexampleisaFrank-Readsource（Fig.3.15b,Video3.15b）.Ductiledeformationofrocksistoalargeextentachievedthroughthemigrationofdislocationsandva-cancies.Latticedefectscancausesignificantstrainincrys-talsonlyifnewdefectsarecontinuouslycreated;

thiscanhappenatdislocationsourcesandvacancysourceswithinthecrystaloratcrystalboundaries.Intracrystallinedeformationbyglideofdislocationsaloneisknownasdislocationglide.Dislocationshaveadistinctorientationwithrespecttothecrystallatticeandcanmoveonlyinspecificcrystallographicplanesanddirections（Fig.3.11d）.Aspecificslipplanecoupledwithaslipdirec-tion（theBurgersvector）isknownasaslipsystem.Slipsys-tems（Box3.4）formineralsarenormallydeterminedbyTEM（Sect.10.2.5;

Fig.10.11）.Inmostcommonrock-formingmin-eralssuchasquartz,feldspars,calciteandolivine,severalslipsystemsofdifferentorientationcanbeactive（Sect.3.12）.ThetypeofslipsystemthatwillbeactiveinacrystaldependsFiFigg.33.1155.aaDeformationofacrystalbymovementofanedgedislocation;

thetophalfofthecrystalistranslatedoveronelatticeunittotherightasaresultofthepassageofasingledislocationfromlefttoright.Viewnormaltotheedgedislocation.OnelatticeplaneismarkedtoshowtherelativedisplacementoftheupperpartofthecrystalwithrespecttothelowerpartbbOperationofaFrank-Readdislocationsource.Ashortdislocationsegmentbetweentwoinclusionsinacrystal,withBurgersvectorintheplaneofthepaper,isdisplacedunderinfluenceofadifferentialstressinthecrystal.Thedislocationpropagatesintoakidneyshapeuntiltheendsmeetandannihilate;

adisloca-tionloopasinFig.3.11disformed,andtheremainingdislocationsegmentcanmigrateagaintoformmoredislocationloopsFiFigg.33.1166.aaDislocationblockedbyanim-purityinthecrystal.bbMigrationofvacanciestothedislocationplanecancauseclimbofthedislocationawayfromtheob-struction.ccAfterclimb,thedis-locationisnolongerblockedandcanpasstheobstruction3.4Intracr3.4IntracryystallinestallineDDeeformationformationDislocationCreep位错蠕变位错蠕变moderateTandstress蠕变creep：

在地质条件下，应变极其缓慢。

矿物中的位错有足够的时间顺序移动。

所以能在不增加应力的情况下使应变继续增加，这就是蠕变。

就像挪动很重的地毯。

应力保持一定，应变随时间不断增加的现象。

Dislocationcreep=DislocationGlide+DislocationClimb（当位错的增值引起的内应力增加（硬化）与由攀移等引起的内应力减小（恢复）之间达到动态平衡时，变形进入稳态蠕变阶段）三个阶段：

微应变阶段：

弹性应变塑性应变阶段稳态流动阶段：

应力不再增加。

结果是在矿物晶粒中产生了以位错阵列为边界的亚晶粒subgrain（而不是形成新晶粒）Unduloseextinction波状消光：

lowThighstressSubgrainboundaries亚晶界/Kink扭折:

highTlowstressSlip-System:

Aspecificslipplanecoupledwithaslipdirection（theBurgersvector）isknownasaslipsystem.Slip-system:

crystallographicdirectionandplaneinwhichthedislocationglide.DenominationusingMillerindices:

Directions:

hkl（or=allhklequivalentdirectionbysymmetry）Plane:

（hkl）（orhkl=allhklequivalentplanebysymmetry）CrystalPreferredOrientation