沉积岩石学(Sedimentary-Rocks)课件

SedimentaryRocks95%oftheEarth’svolumeisigneousandmetamorphicrocksbu75%oftheEarth’ssurfaceiscoveredbysedimentsorsedimentaryrocks.Derivedfrompre-existingrocks:1.detrital/clasticrocks:mineralgrainsorrockfragments(mechanicalorbiologicalweathering)2.chemical:dissolved&precipitatedminerals(chemicalweathering).Ex:granite:Quartz+Fs+BiotiteWeathering:Mech/bio quartzsandclaysTransport River,wind,iceDepositionBeachdeltaoceanlithification

CementedRock sandstoneshaleSedimentaryRocksEx:granite:Qtz+Caplag’Fs+BiotiteWeathering:Chem’ calciumTransport solutioninriverDepositionoceanlithification

precipitationRock limestoneTerminologyPrecipitation:oppositeofdissolve:aqueoustosolidlithification:materialsarecompactedand/orcementedtogethertoformrock.Rounded:angularfragmentsbecomerounded(&smaller)throughabrasionastheyaretransportedRoundingDeposition:ice,wind,orwaterdeposit/dropsedimentinriverbed,moraine,lake,beach,ocean,etc.Facies:adistinctsedimentorrocktypeSorting:processbywhichparticlesareseparatedaccordingtosize(&density)ClaywithclaySandwithsandGravelwithgravelWater&windareexcellentsorters,iceispoorSortingGravel Sand Silt Clay

facies

facies

facies

facieshighlowriverEnergygravellake/oceandeltabeachsandsiltclaysortedPorespace=porosity=voidsbetweenparticlesClay80%sand20%mixture5%WellsortedPorosityCompaction:weightofoverlyingsedimentcompressessediments,forceswateroutand“glues”/lithifiesmudsiltstone&shaleCementation:weatheredsilica,calciteandironoxidesdissolvedinwaterprecipitateinporespacestocement/lithifyparticlestogether.Friable:rockiseasilycrumbled(likedrycake)Fissile:rockbreakseasilyalongcloselyspacedparallellinesLikecleavageinrockFissileSedimentaryRocks1.Detrital/Clastic2.Chemical3.Biochemical1.Detrital/ClasticDetritus=solidparticlesorpre-existingrocksClastic=composedofrockfragmentsSedimentsizedescriptionrocknameGravel >2mm roundedconglomerate gravel angular breccia gravelSand1/16

–2mm(mostlyQtz)sandstoneMud<1/16mmsilt siltstone silt&claymudstone

<1/256mm clayclaystone

shaleSandstone=Sst:sandyRedsandstone:withlotsofKFs(pinkFs)=arkose

sstSiltstone:grittywithwetmudsmellShale:greasywithwetmudsmellSiltstone2.Chemical:originatefromsubstancestakenfromsolutionfromchemicalweatheringThesechemicalsareextractedfromlakeoroceanwatervia:i)precipitation(Ex;dryinglakebed)Ii)organisms(coralreef)BUTthisisabiochemicalrock!DeathValleySaltFlatsDeadSeaTextureCompositionRockNameVariescalciteCaCO3limestone/LstVariesdolomiteCaMgCO3

dolostoneCrystallinegypsumCaSO4rockgypsumCrystallinehaliteNaClrocksaltcarbonateTravertine:LstthatprecipitatesoutofhotspringsbutisrareLst:mostisbiochemicalDolostone:formsfromLstthatisalteredin:i)verysalinelagoonsii)whereLsthasbeenupliftedabovethewatertableandfreshwaterwithMgleechesthroughreplacingtheCaLst

DolostoneCaCO3CaMgCO3HClTest!BarelyfizzesFizz!!!TravertineTerracesinTurkeyEvaporites:(rockgypsumandrocksalt)precipitatefromland-lockedlakesandseaswheretheevaporationraisesthesalinitytothesaturationpoint.VerysaltywaterevaporationGypsum&halitecrystalsRockgypsum:white-pink-grey,massiveortabularcrystals,H=2,whitestreakRocksalt=halite:colourless,cubiccrystals,saltytaste,H=2-3Silvite=KCl=potash:afertilizerformedfromevaporationonvast,shallowseasinSaskatchewanGypsumGypsumThinsection3.BiochemicalTextureCompositionRockNameClastic-calciteCaCO3limestone/Lstcrystalline chalk:microscopic

coquina:shellsFine quartz chertFine- carbonC coalcrumblyLimestone:accumulationofbillionsofskeletonsofcorals,shellfi`sh,algae,etc.Originallyasaragonitewhichalterstocalcite.Forms:Massive:shellsbrokenandgroundintopowderbeforelithificationSugary=crystallineCoquina(KD)=cementedbrokenshellsChalk=soft,microscopicfossilsHCltest!Chert:forms2ways: i)silicarichwaterspercolateupthroughearthreplacingtheLstintheformofnodules,abulbousmassofchalcedony(“elephantman”) ii)organisms(sponges,diatoms)thatusesilicaforskeletonsdie;thesilicaaccumulatesontheoceanfloortoformbeddedchert(usuallygrey). Flint=blackchert Jasper=redchertChertthinsectionRadiolariansRadiolariansCoal:formintheprocess i)landplantsaccumulateinswamps,bogslowinpHandlowinO2topreven