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1、实习二沉积岩目的：1、熟悉沉积岩的层理、结构及描述方法2、认识几种碎屑岩、粘土岩和碳酸盐岩内容：1、观察并描述：砾岩、石英砂岩、长石砂岩、细砂岩、石灰岩、鲕状灰岩、竹叶状灰岩、泥灰岩等2、观察：角砾岩、岩屑砂岩、海绿石石英砂岩、黄土、豹皮状灰岩、白云质灰岩、燧石条带灰岩、板状泥灰岩等沉积岩概述SedimentaryRockWhatRocksTellUsRockTypeHowClassifiedWhatitTellsUsSedimentaryChemicalCompositionSurfaceEnvironmentGrainSizeEnergyofEnvironmentTable 1 : Rel
2、ative extent of rock types exposed at the earths surface % shale 52 sandstone 15 granite 15 limestone 7 basalt 3 others 8By studying the nature of the material in sedimentary rocks we may obtain information about the source of the sediment, the type and length of transport, and the geological enviro
3、nment in which it was deposited. In this practical, we will be examining some of the properties of sedimentary rocks.上覆压力长石石英孔隙胶结物松散沉积物压实后状态胶结成岩 一般情况下，从松散的碎屑物压实成为固结的岩石，体积可以减少50以上；细小的泥质碎屑物的压缩量就更大，可以超过70。沉积物的压缩过程所受的力主要来自上覆沉积物的静压力，因此，埋葬越深的沉积物所受的压力越大，压缩量也越大。当然，压缩量达到一定程度后沉积物便不能再被压缩。胶结作用也是成岩作用中非常重要的一环，胶结作
4、用是胶结物以不同的形式充填于沉积颗粒之间，使沉积物（尤其是碎屑物）颗粒彼此联结在一起，形成坚固的岩石的过程。Types of sediments and sedimentary rocksThere are three principle types of sedimentary rocks:1. Detrital or clastic sedimentary rocks, as described above, consist of aggregates of grains (orclasts) which have been lithified during diagenesis2. Bi
5、ogenic sedimentary rocks result from the accumulation of skeletal remains of plants oranimals. The most important types are (1) made up of calcium carbonate (calcareous) e.g. limestone, and shelly sandstone; (2) made up of silica (siliceous) e.g. chert; and (3) made up of coalified plant remains (ca
6、rbonaceous) e.g. coal.3. Chemical sedimentary rocks form from precipitation within the environment of deposition, so their composition depends on the chemical composition of the acqueous solution from which they are deposited (e.g. lake, ocean, groundwater) and chemical conditions (e.g. carbon dioxi
7、de, oxygen, pH). Common chemical precipitates include siliceous (chert), phosphatic, iron-rich, calcareous and manganiferous varieties. In addition, evaporation of saline water, especially in large marine basins, can produce large volumes of various salts, termed evaporites.Bedding or Stratification
8、AlmostAlwaysPresentinSedimentaryRocksOriginallyHorizontalTiltingbyEarthForcesLaterVariationsinConditionsofDepositionSizeofBeds(Thickness)Usually1-100CmCanRangeFromMicroscopicto50mRhythmic Layering -Alternatingparallellayershavingdifferentproperties.Sometimescausedbyseasonalchangesindeposition(Varves
9、).i.e.lakedepositswhereincoarsesedimentisdepositedinsummermonthsandfinesedimentisdepositedinthewinterwhenthesurfaceofthelakeisfrozen.Cross Bedding - Setsofbedsthatareinclinedrelativetooneanother.Thebedsareinclinedinthedirectionthatthewindorwaterwasmovingatthetimeofdeposition.Boundariesbetweensetsofc
10、rossbedsusuallyrepresentanerosionalsurface.Verycommoninbeachdeposits,sanddunes,andriverdepositedsediment.Graded Bedding-Ascurrentvelocitydecreases,firstthelargerormoredenseparticlesaredepositedfollowedbysmallerparticles.Thisresultsinbeddingshowingadecreaseingrainsizefromthebottomofthebedtothetopofth
11、ebed.Ripple Marks-Characteristicofshallowwaterdeposition.Causedbywavesorwinds.Raindrop Marks - pits (or tiny craters) created by falling rain. If present, this suggests that the sediment was exposed to the surface of the Earth.Mudcracks-resultfromthedryingoutofwetsedimentatthesurfaceoftheEarth.Thecr
12、acksformduetoshrinkageofthesedimentasitdries.Clastic Rocks 碎屑岩碎屑岩MadeofFragmentaryMaterialDepositedbyWater(MostCommon)WindGlacialActionGravityClassified by:GrainSize粒度GrainComposition成分Texture结构Sediment Sizes and Clastic Rock TypesSedimentaryrocksmadeofsilt-andclay-sizedparticlesarecollectivelycalle
13、dmudrocks,andarethemostabundantsedimentaryrocks.Rock TypeSedimentGrain SizeShaleClayless than 0.005 mmSiltstoneSilt0.005-0.05mmSandstoneSand0.05-2mmConglomerateGravel2mm +碎屑岩的观察DESCRIPTION OF DETRITAL SEDIMENTARY ROCKSSome of the important characteristics of detrital sedimentary rocks are described
14、below. It isimportant that you clearly understand the meaning of each term, and being able to describe sedimentary rocks using these terms.Grain SizeDetrital sedimentary rocks are primarily classified on the basis of their grain size. Grain size depends on the grain size of the parent material, the
15、length of transportation and the energy available during transportation.MineralsInorderofmoststabletoleaststable:Ironoxides,Aluminumoxides-suchashematiteFe2O3,andgibbsiteAl(OH)3.铁的氧化物和铝的氧化物：赤铁矿和水铝矿Quartz*石英ClayMinerals粘土矿物Muscovite*白云母AlkaliFeldspar*碱性长石Biotite*黑云母Amphiboles*角闪石Pyroxenes*辉石Ca-richpl
16、agioclase*富钙斜长石Olivine*橄榄石SortingThe sorting of a sedimentary rock is a measure of the range of grain sizes present. If the grain size is very restricted then the sedimentary rock is described as well sorted. If a wide range of grain sizes is present, then the rock is described as poorly sorted.Thed
17、egreeofuniformityofgrainsize.Particlesbecomesortedonthebasisofdensity,becauseoftheenergyofthetransportingmedium.Highenergycurrentscancarrylargerfragments.Astheenergydecreases,heavierparticlesaredepositedandlighterfragmentscontinuetobetransported.Thisresultsinsortingduetodensity.roundingDuringthetran
18、sportationprocess,grainsmaybereducedinsizeduetoabrasion.Randomabrasionresultsintheeventualroundingoffofthesharpcornersandedgesofgrains.Thus,roundingofgrainsgivesuscluestotheamountoftimeasedimenthasbeeninthetransportationcycle.Roundingisclassifiedonrelativetermsaswell.CementationAn important process
19、in the diagenesis of sediments which leads to their consolidation is cementation - the process by which a cement is added that acts as a bonding agent between grains. The cement is typically a mineral which is chemically precipitated in the pore spaces of the sediment by fluids moving through them.
20、The most common types are quartz (silica cement), calcite (carbonate cement) or iron oxide (ferruginous cement). Cement will bond both framework and matrix grains.最常见的胶结物有SiO2（硅质胶结）、氧化铁（铁质胶结）、碳酸钙（钙质胶结）等。 成岩作用中碎屑物以不同的胶结物和胶结方式固结成岩，胶结物和胶结方式可以反映碎屑物的成岩环境。碎屑岩常见的胶结物有钙质胶结、硅质胶结、铁质胶结和泥质胶结。常见的胶结方式有基底式胶结、孔隙式胶结、
21、接触式胶结和无胶结物。 ABC碎屑岩的主要胶结方式A基底式胶结B孔隙式胶结C接触式胶结碎屑岩的颜色 砾岩 由直径大于2mm的碎屑和胶结物组成，砾岩中2mm以上的碎屑物通常在50以上。砾石的成分通常为坚硬的岩石或矿物，如花岗岩、石英岩等，不同的砾岩有不同的胶结物，钙质、硅质、铁质、泥质均有。如果砾石磨圆度很差，有明显的棱角，则称为角砾岩。 砾 岩 砂岩 由直径20.1mm的碎屑物和胶结物组成，该粒级范围的碎屑物含量在50以上。砂岩的碎屑物成分以石英、长石为主，有时有白云母、暗色矿物、重矿物和岩屑。胶结物主要是钙质、硅质、铁质和粘土。以岩屑为主的砂岩称为杂砂岩或硬砂岩（以前曾称为灰瓦岩）。 砂岩G
22、raywackeAngular,ImmatureArkosesandstoneFeldspar-RichSandstoneQuartzsandstoneQuartz-Rich 粉砂岩 由直径在0.10.01mm的碎屑物和胶结物组成，且该粒级的碎屑物含量在50以上。粉砂岩的碎屑物成分多为石英，部分为长石，岩屑很少见。胶结物为钙质、铁质、硅质和粘土。粉砂岩的碎屑物颗粒较细，肉眼难于鉴别，在放大镜下可以识别。粉砂岩表面（新鲜断面）手感粗糙，很容易与泥质岩类相区别。 粉砂岩 泥质岩也经常被称为粘土质岩，是沉积岩中分布最广的一类。大部分泥质岩都是以碎屑状态从物源区以机械的形式被搬运到沉积盆地的，因此，有
23、的学者将其列入碎屑岩类。但一些泥质岩类的形成包含有化学沉积作用和生物作用。泥质岩通常含有很多的粘土矿物，如高岭石、蒙脱石、伊利石等，使得泥质岩常有一些独特的物理性质，如可塑性、烧结性、耐火性、吸附性、吸水膨胀性等都是泥质岩的一些重要特性，这些特性经常用于工农业生产。 泥质岩 页岩 最常见的泥质岩，有各种各样的颜色，具薄层状页理构造，主要由高岭石、水云母等粘土矿物组成。岩石所含成分不同，则有不同的名称，如炭质页岩、钙质页岩、铁质页岩等。致密厚层的泥质岩称为泥岩。 生物和化学沉积岩Chemical SedimentsEvaporites -Water solubleHaliteGypsumCalc
24、itePrecipitatesExample:Ca(soln)+SO4(Soln)=CaSO4GypsumLimestoneIronFormationsAlteration After depositionDolomiteBiogenic SedimentsLimestone-Shells,Reefs,Etc.Organic RemainsCoalPetroleumFossilFuelsCoalSeams,UtahCoalDelta,continentalenvironmentsCarbonizedWoodyMaterialOftenfossilizedtrees,leavespresentP
25、lantFragmentsAreOftenVisibleinCoal 碳酸盐岩主要由沉积的碳酸盐矿物（方解石、白云石、文石等）组成，主要岩石类型是灰岩和白云岩。碳酸盐岩在地壳中的分布仅次于泥质岩和砂岩，是主要的沉积岩类型，约占20左右。在我国，碳酸盐岩是主要的沉积岩类型，约占总面积的55，我国西南地区分布有大面积的碳酸盐岩，形成世界著名的喀斯特地貌。 碳酸盐岩由波浪和流水作用产生的灰岩和白云岩具有粒屑结构由原地生长的生物构成的生物灰岩、礁灰岩具有生物骨架结构由化学、生物化学作用沉淀的灰岩、白云岩，经重结晶侯具晶粒结构晶粒结构白云灰岩、交代白云岩具有残余结构或晶粒结构碳酸盐岩的结构粒屑结构颗粒颗
26、粒内碎屑砾屑、砂屑、粉屑、微晶、泥屑生物碎屑生物遗体包粒豆粒、鲕粒球粒、团块等泥晶基质泥晶基质晶粒小于0.03mm，充填于颗粒间亮晶胶结物亮晶胶结物充填于原始孔粒间的化学沉淀物胶结类型胶结类型基底式、孔隙式、接触式以及过渡碳酸盐岩的命名分类成分为主：一般采用50%几个界线若颗粒数50%叫颗粒岩命名原则是含量多的在后，少者在前内碎屑灰岩砾屑灰岩竹叶状灰岩砂屑灰岩、粉屑灰岩泥晶灰岩竹叶状灰岩竹叶状灰岩竹叶状灰岩竹叶状灰岩泥质条带状灰岩泥质条带状灰岩泥晶灰岩生物碎屑灰岩藻灰岩鲕粒灰岩鲕状灰岩白云岩 一般为灰白色，主要矿物成分是白云石和方解石，遇盐酸微弱起泡。由于构成白云岩的矿物白云石和方解石物质成分
27、和化学性质极为相似，因此灰岩和白云岩可以以任何比例构成二者的过渡类型岩石，如果白云质的含量多就称其为灰质白云岩，反之称为白云质灰岩。 描述要求颜色结构：碎屑结构构造砾屑结构砂屑结构粉砂屑结构泥质结构外观特征:表面粗糙度碎屑的大小、分选性、磨圆度、球度和矿物成分及含量胶结类型以及胶结物的成分描述要求颜色结构：粒屑结构构造砾屑结构生屑结构包粒结构泥晶结构外观特征:表面粗糙度碎屑的大小、分选性、磨圆度、成分及含量胶结类型以及胶结物的成分包粒的大小、成分及含量胶结类型及胶结物成分与5%稀盐酸反应程度实习二沉积岩目的：1、熟悉沉积岩的层理、结构及描述方法2、认识几种碎屑岩、粘土岩和碳酸盐岩内容：1、观察并描述：砾岩、石英砂岩、长石砂岩、细砂岩、石灰岩、鲕状灰岩、竹叶状灰岩、泥灰岩等2、观察：角砾岩、岩屑砂岩、海绿石石英砂岩、黄土、豹皮状灰岩、白云质灰岩、燧石条带灰岩、板状泥灰岩等
