篇沉积岩第二章沉积岩各论沉积岩分类

第二章沉积岩各论邵龙义讲授（1.中国矿业大学（北京）地球科学与测绘工程学院，

北京

100083）ShaoL@Petrography?Classification?Majorsub-classes?2.1.1目前流行的分类2.1Classificationofsedimentaryrocks以沉积作用方式和岩石成分把沉积岩分为三大类：碎屑岩类（Clasticrocktypes）粘土岩类（Clayrocktypes）

化学岩和生物化学岩（Chemicalandbiochemicalrocktypes）F.J.裴蒂庄（1975），塞利（1976）等，对沉积岩的分类多强调其物质来源，他们把沉积岩物质来源的差别作为沉积岩分类的基础。F.J.裴蒂庄（1975）分为：外生沉积物和内生沉积物；塞利（1976）分为：自生沉积和他生沉积；刘宝珺1980分为：陆源沉积岩、火山沉积岩和内源沉积岩。

大类

类1、自生沉积1）化学沉积：蒸发岩2）有机沉积：煤、石灰岩3）残余沉积：红土、铝土岩2、他生沉积4）陆源沉积：粘土、碎屑岩5）火山碎屑沉积：集块岩、火山角砾岩、凝灰岩塞利的沉积岩分类Classificationofsedimentaryrocks/barnes/geos435/3a_G435.ppsGrain-SizeClassificationforClasticSedimentsNameMillimetersMicrometersBoulderCobblePebbleGranuleVeryCoarseSandCoarseSandMediumSandFineSandVeryFineSandCoarseSiltMediumSiltFineSiltVeryFineSiltClay4,096256644250.0630.0310.0160.0080.00450025012562311684(modifiedfromBlatt,1982)Commonly,phi-sizesareusedforsedimentanalysisRelativeAbundancesSiltstoneandshale(clastic)~75%Sandstoneandconglomerate(clastic)~11%Limestoneanddolomite

~14%SEDIMENTARYROCKTYPES,2.1.2、Terrigenousclastics

“FromtheEarth”Terrigenousclasticsedimentaryrocksarecomposedofclastsofpre-existingrocksandminerals.Alsoreferredas:

Detrital(detachedfrompre-existingrocksbyerosionorweathering),or;

Epiclastic(derivedfromthesurface).

（外源）陆源碎屑岩沉积物（碎屑）剥蚀-搬运-沉积剥蚀区搬运区沉积区GrainSize1(mm)SedimentnameRockNameAdjectives>2GravelRuditeCobble,pebble,wellsorted,etc.0.063-2SandAreniteCoarse,medium,wellsorted,etc.<0.063MudMudstoneorLutiteSiltorclay1Forthepurposesofthisgeneralclassificationwewillassigntherockorsedimentnameshownifmorethan50%oftheparticlesareintherangeshown.Moredetailedclassificationschemeswilllimittermsonthebasisofdifferentproportionsofsedimentwithinagivengrainsize.Asimpleclassificationofterrigenousclasticrocksandsedimentisbasedonthepredominantgrainsizeofthematerial:Classificationbasedongrainsize2PyroclasticRocksBasicclassificationotbo

(onthebasisof)particlesizeBlocks(solid)andbombs(molten)(>64mm)VolcanicbrecciadepositsLapilli(2-64mm)LapillistoneAsh(<2mm)TuffAdditionalClassificationotbocompositionCrystalsLithicVitricfragments/barnes/geos435/3a_G435.pps3、内源沉积岩类

亦称内生沉积岩，组成岩石的主要物质直接来自沉积盆地的溶液或沉积场所的溶液内，是溶液中的溶解物质通过化学或生物化学作用沉淀的。内源沉积岩按其成分不同分为：

铝质岩铁质岩锰质岩磷质岩硅质岩碳酸盐岩蒸发岩可燃性有机岩等八类。2.2Terrigenousclasticrocks

2.21GeneralcharacteristicofTerrigenousclasticrocks

1、CompositionalMaturityACompositionalMaturityreflectstheweatheringprocessesinthesourceareaandthedegreeandextentofreworkingandtransportation.CompositionalMaturitycanbeexpressedbytheratioofquartz+chertgrainstofeldspars+rockfragments,thisCompositionalMaturityindexisusefulifcomparisonsbetweendifferentsandstonesarerequired.2.MaterialcompositionofTerrigenousclasticrocks

MaterialcompositionofTerrigenousclasticrocksaremainlyclasticmaterial,chemicalmaterialandmatrix.1）clasticmaterial（1)DetritalMineralGrains

Averylargenumberofdifferentmineralsmayoccurinsandsandinsandstone.themostcommondetritalmineralGrainsarequartz,feldspar,mica,heavymineralandmiscellaneousmineral.（2)LithicFragments

Thebreakdownofpre-existing,fine-tomediumigneous,metamorphicandsedimentaryrocksresultsinsand-sizedfragments.LithicFragmentaregeneratedwhenpre-existingstrataareuplifted,weatheredanderoded.2）ChemicalcementandAuthigenicMineral

Themostcommoncementaresilicaandcalcitecementation.Mineralswhichgrowcrystalsinadepositinalenvironmentarecalledauthigenicminerals.Cementation:CementingmaterialisusuallysecondarySilica(Siliceouscement),Calciumcarbonate(Carbonatecement),Ironrich(ferruginouscement)CementitselftosomeextentisthesourceofweaknessinthesedimentaryrocksBecausecementingmaterialandtheclasticsedimentsareusuallyofdifferentcomposition,leadingtoheterogeneityintheirphysicalcharacteristics.

Hencesuchrockwillnotbehavehomogeneouslyunderstress,resultingintodevelopmentofcracksorfissureswhichdevelopsincementingmaterial.IfthecementisCalciumCarbonateitisundesirable,becauseitissusceptibletodissolveinCarbondioxideinwater.However,ifcementationprocesscontinuousforlongerspanoftime.cementationwillbecomemorecomplete,whichreducetheporosityandpermeabilityintherockmassandincreasecompetence.Shapeofgrains:i.e.ifcoarsergrainsareroundedorsubroundedcementmaterialwillnothavefirmgripsuchrocksbehaveasincompetentrocks.3）Matrix

Matrix:fineinterstitialparticles.

matrixcompositiondependsupon:Sourcematerialwhattypeofrockisbeingweatheredanderoded?ThechemicalandphysicalpropertiesofthemineralsstrongeronesareatthebottomofBowensReactionSeries(e.g,Quartz).Degreeofweatheringanderosionprocessestotransportsecondarydependenceuponclimate.3.TexturesofTerrigenousclasticrocks

(1)Textures

Maturity:Chemicalandphysicalweatheringgraduallybreaksdownrocktoquartzandclayminerals.Maturityisameasureofthisprocess.Dependson:Time,Climate,TransportHistory,DepositionalEnvironment.Immature:poorlysorted,clays+mineralfragments(olivine,pyroxene,amphibole,etc.),rockfragments.Grainsareangularandvaryinsize.Mature:wellsorted,noclays,mostlymadeupofroundedquartzgrains.(2)陆源碎屑岩的结构

陆源碎屑岩的结构主要有陆源碎屑结构和泥状结构两种类型。1)陆源碎屑结构这是陆源沉积岩最主要的结构，它由碎屑颗粒和胶结物（或基质）两部分组成。岩石结构的特征取决于颗粒的结构、胶结物（或基质）的结构以及二者之间的量比和相互关系。（1)Structurecharacteristicsofclasticgrain

Structurecharacteristicsofclasticgrainincludesizeofgrain,sorting,morphology,surfacecharacteristicsandsoon.

A、SizeofgrainWealwaysusediametertomeasurethesizeofclasticgrain.Wecandividesizeofgrainasfollows：＞2mmConglomerate2—0.05mmSandstone0.05--0.005mmSiltstone＜0.005mmMudstone

Grain-SizeSortinginSandstoneVeryWellSortedWellSortedModeratelySortedPoorlySortedVeryPoorlySortedSORTINGB.sortingnormalSortingA-positive/negativeskew(正偏/负偏)%coarsefinenegativeskewpositiveskewnormalB-kurtosis（峰态）%coarsefineleptokurticplatykurticSortingC-bimodaldistributions%coarsefineROUNDNESSANDSPHERICITYOFCLASTICGRAINSHighSPHERICITYLowVeryAngularAngularSub-AngularSub-RoundedRoundedWell-RoundedROUNDNESSGrainMorphologyC-sphericityhigh medium low4)GrainFabricA-orientation-causedbywaterflowOrientation,packingandnatureofcontactsbetweengrainsHowever-thisisalsostableNote:viewfromabove4)GrainFabricB-imbrication-causedbywaterflowormassmovementOrientation,packingandnatureofcontactsbetweengrainsNote:viewfromside4)GrainFabricC-packingofgrainsOrientation,packingandnatureofcontactsbetweengrainscubicpackingrhombohedralpackingQ.Whichismoreporous?4)GrainFabricD-pointcontactsOrientation,packingandnatureofcontactsbetweengrainsImportant:trytoimaginethisin3-D4)GrainFabricE-concavo-convexcontactsOrientation,packingandnatureofcontactsbetweengrainsBut-wherehasthesilicagone???4)GrainFabricF-suturedcontactsOrientation,packingandnatureofcontactsbetweengrainsGrainMineralogyQuartzFeldsparRockFragmentsMicasClaymineralsHeavymineralsPPL-plane-polarizedlightXPL-crossedpolarsGrainMineralogy

1-QuartzRoundedquartzgrains(originalshapemoreangular)PA9-PPLGrainMineralogy

1-QuartzRoundedquartzgrainsPA9-XPLGrainMineralogy

1-QuartzSeeminglynormalroundedQuartzgrains...PA9-PPLGrainMineralogy

1-QuartzSeeminglynormalroundedQuartzgrains…areactuallypolycrystallinemanysmallersuturedgrainsPA9-XPLGrainMineralogy

1-QuartzThisquartzgraingoesintoextinctioninpoorlydefinedbandsIthasbeenstrainedunduloseextinctionPA27-XPLGrainMineralogy

2-FeldsparFeldspar-islessstablethanquartzchemicallyweatherstomicasandclaymineralsisbestpreservedinmechanically-weatheredrocksGrainMineralogy

2-FeldsparTwoorthreetypes!Potassium(K-,oralkaline)feldsparsorthoclasemicroclineCalcicfeldsparplagioclaseGrainMineralogy

2-K-FeldsparSmokey……..OrthoclaseFeldsparGrainMineralogy

2-K-FeldsparSmokey……..OrthoclaseFeldsparGrainMineralogy

2-FeldsparAK-feldsparPA27-PPLmicroclinefeldsparGrainMineralogy

2-FeldsparAK-feldsparCross-hatchtwinningPA27-XPLmicroclinefeldsparGrainMineralogy

2-FeldsparAcalcicfeldspar

BG2-PPLplagioclasefeldsparGrainMineralogy

2-FeldsparAcalcicfeldsparmultipletwinning(albite)

BG2-XPLplagioclasefeldsparBG2-XPLGrainMineralogy

2-FeldsparAK-feldsparwithmanyblebsorlamellaeofsodium-richfeldspar

perthiteBG2-XPLGrainMineralogy

2-FeldsparAcalcicfeldsparsimpletwinning(Carlsbad)

plagioclasefeldsparEXP1-PPLGrainMineralogy

3-MicaPlatysheetsilicatemineralbrown/greenpleochroisminPPLbiotitemicaEXP1-PPLGrainMineralogy

3-MicaPlatysheetsilicatemineralbrown/greenpleochroisminPPL

biotitemicaLowerpolarizerrotated90°EXP1-XPLGrainMineralogy

3-MicaPlatysheetsilicatemineralbrown/greenpleochroisminPPL

brightinterferencecoloursmuscovitemorecommonbiotitemicaR62-XPLGrainMineralogy

5-LithicFragmentsAnyreworkedfragmentsofrocke.g.cherts,mudstones,volcanics,limestones,polycrystalinequartzR62-XPLGrainMineralogy

6-MatrixGrainslessthat30µmSedimentMaturityTheconceptofmaturityrelatestotheaccumulatedprocessesofmechanicalandchemicaldegradationthathaveoccurredtoasedimentbeforedepositioni.eamaturesedimenthasbeenworkedmorethananimmaturesedimentMaturityisconsideredintermsofTEXTUREandCOMPOSITIONTexturalMaturityAtexturallymaturesedimenthasbeenrounded,sortedandhaslittlematrixTexturalMaturitySedimenttexturereflectthematurityofasediment.Mostchangesarerelatedtotransportdistance,natureofweatheringatthesiteofsedimentformationandnumberofpassesthroughtherockcycle.Changesingrainsizeandshape.IncreasingtexturalmaturityIncreasedsortingIncreasedsphericityIncreasedroundingCompositionalMaturityAsasedimentisworkedthemicaandotherweakergrainsaredestroyedMostlyquartzandalittlefeldsparisleftThemostmaturesedimentsare100%quartzMatureor?????AngulargrainsPoorlysortedLotsofmatrixTexturallyimmatureLithoclastsandothergrainsCompositionallyimmatureMatureor?????WellroundedgrainsVerywellsortedNomatrixTexturallysupermatureMainlyQzCompositionallymatureGRAINSIZEConglomerate>256-2mmSand2-0.063mmClay<0.004mmSilt0.063-0.004mmBoulder:>256mmCobble:64-256mmPebble:4-64mmGranule:2-4mmFinegravel（三）Conglomerates

Conglomeratesislithifiedgravelmadeupofroundedtosubroundedclastswhosediametersexceed2mm.Conglomeraterocksaresedimentaryrocks.Theyaremadeupoflargesedimentslikesandandpebbles.Thesedimentissolargethatpressurealonecannotholdtherocktogether;itisalsocementedtogetherwithdissolvedminerals.

京西妙峰山砾岩和角砾岩的分类

通常依砾石的圆度可把岩石分为：

砾岩（主要由次圆至圆状的砾石组成）

角砾岩（主要由棱角状砾石组成）。

按粒度可分为：

巨砾岩＞256mm；

卵石砾岩256-64mm；

粗砾岩64-16mm；

中砾岩16-4mm；

细砾岩4-2mm.

Twodistinctivevarietiesofconglomerates(andbreccias)aredefinedonthebasisoftexture:Orthoconglomerates(literally,“true”conglomerates)consistmainlyofgravel-sizedframeworkgrains.Matrix(sandorfiner)islessthan15%.So,grain-supportedframework.Paraconglomeratehaveamatrixofsandandfinerclasts.Matrixisatleast15%;mosthave50%matrixandareactuallysandstoneandmudrocksinwhichpebbles,cobblesandbouldersarescattered.粗碎屑岩类岩石的命名a)粗碎屑岩类岩石的命名按:胶结物+砾石成分+结构+基本名称。如:钙质胶结石灰岩质粗砾b)胶结物占岩石总量的10%以上，以XX质胶结作为附加修饰词。c)混入其他粒级陆源碎屑的命名，按5.3条规定的量限，以含X质、X质作为附加修饰词。d)粗碎屑岩性单一，直接参加命名;粗碎屑岩性较复杂，以其占粗碎屑总量50%以上的粗碎屑岩性作为附加修饰词;无任何一种粗碎屑岩性超过粗碎屑总量的5000，则以其量相对为主的两种粗碎屑岩性，用“一”号连接作为附加修饰词;具三种或三种以上粗碎屑岩性，其量相近并均不超过粗碎屑总量的50，则以复成分作为附加修饰词。e)命名时应予反映成因。（四）砂岩类(Sandstones)1．一般特征

粒度为2一0．063毫米的陆源碎屑含量在50％以上的沉积岩称为砂岩。砂岩的碎屑成分主要是石英、长石和岩屑三种.砂岩中的胶结物常见的有钙质、硅质、铁质等，有时还有海绿石、石膏等和泥质基质所胶结。砂岩中常见各种类型的斜层理、交错层理以及平行层理、粒序层理，波痕、冲刷痕迹、槽模、沟模和生物扰动构造等沉积构造。2．砂岩的分类(Classificationofsandstone)（1）砂岩按其颗粒大小可分为：

巨粒砂岩2～1mm粗粒砂岩1～0.5mm中粒砂岩0.5～0.25mm细粒砂岩0.25～0.05mm

砂岩成分分类的方案很多，这里采用四端元分类法。四端元分类法是以砂岩中的主要碎屑成分石英、长石、岩屑作为三端元组分划分岩石类型，再把基质也作为一个端元组分参加岩石的分类命名。首先根据基质含量将砂岩分为两类：一类称为净砂岩类；另一类称为杂砂岩类。（2）成分分类ClassificationofSandstonesMostsandstoneclassificationsarebasedonthecompositionoftherock.Dott’sclassificatonschemeisusedinmostcoursesatBrock.Itisbasedontherelativeproportionsof:Martrix

(fine-grained-<0.03mm-materialthatisassociatedwiththesandgrains).QuartzFeldsparRockfragments(sandgrainsthataremadeupcrystalsoftwoormoredifferentminerals).Pettijohn(1975沉积岩)的砂岩分类Wackes-15-75%matrix07515increasingpercentagematrixareniteswackesmudrockslithicgreywackefeldspathicgreywackeSANDSTONECLASSIFICATIONQuartz+ChertFeldsparUnstableRockFragments552525252525255050501010QuartzareniteSubarkoseSublithareniteLithicSubarkoseArkoseLithicArkoseFelspathicLithareniteLitharenite(modifiedfromMcBride,1963)Thisclassificationisbasedonthemajorcomponentofmostsandstonesandprovidesabasisforaconsistentnomenclatureforsandstones.Specifictypesofrockfragmentsmayalsobeimportantindeterminingthehistoryofthesediment.Fragmentsoflimestoneordolomitearesimplyclassedas“rockfragments”usingDott’sscheme.Suchgrainsbreakdownrapidlywithtransportsothattheirpresencesuggeststhatthesedimentwasdepositedveryclosetotheareathatitwasproduced.Thenamescanbemodifiedtoreflectothercomponentsoftherock:e.g.,Calcareousquartzarenite:aquartzarenitewithacalcitecement.1、石英(杂)砂岩；2、长石(杂)砂岩；3、岩屑(杂)砂岩；4、长石石英(杂)砂岩；5、岩屑石英(杂)砂岩；6、岩屑长石(杂)砂岩；7、长石岩屑(杂)砂岩QFR123456790753/11/11/3755025F/RF杂基>15%杂砂岩杂基<15%净砂岩FrameworkMatrixCementPoresSand(andSilt)SizeDetritalGrainsSiltandClaySizeDetritalMaterialMaterialPrecipitatedPost-Depositionally,DuringBurial.CementsFillPoresandReplaceFrameworkGrainsVoidsAmongtheAboveComponentsFOURMAJORCOMPONENTSOFSANDSTONEFOURCOMPONENTSOFSANDSTONEMATRIXFRAMEWORK(QUARTZ)FRAMEWORK(FELDSPAR)CEMENTPORENotedifferentuseof“matrix”bygeologistsandengineers0.25mmFrameworkMatrixCementPoresEngineering“matrix”Geologist’sClassification中碎屑岩（砂岩）类命名原则a)中碎屑岩类岩石的命名按:胶结物+结构+碎屑成分十基本名称。如:中粒长石石英砂岩。b)胶结物占岩石总量的10%以上，以XX质胶结作为附加修饰词。c)混入其他粒级陆源碎屑的命名，按5.3条规定的量限，以含X质、X质作为附加修饰词。d)岩屑砂岩和岩屑杂砂岩中的岩屑成分单一，直接参加命名;岩屑成分较复杂，以其占岩屑总量50%以上的岩屑成分参加命名;无任何一种岩屑成分超过岩屑总量的50%，则以其量相对为主的两种岩屑成分，用“一”号连接参加命名;具三种或三种以上岩屑成分，其量相近并均不超过岩屑总量的一半，则总称岩屑作为附加修饰词。e)石英砂岩中部分硅质胶结物，发生次生加大成为再生石英，具砂状结构，再生长式胶结，称石英岩状砂岩;胶结物已全部重结晶围绕石英颗粒呈次生加大边，称沉积石英岩。f)砂岩中若出现特殊矿物，其含量小于5%也应参加命名。如:海绿石细粒石英砂岩。

Quartzsandstone

;Arkose

;Lithicsandstone

;Greywacke;Commontypesofsandstone（五）粉砂岩Siltstones(d=0.063-0.004)Themineralogyandtexturalparametersofsiltaremoredifficulttodeterminethanforsandstonebecauseofthesmallparticlesize.Quartzi