本第16章泥岩
Mudrocks, which include siltstones, mudstones, mudshales, claystones, and calyshales, are the most abundant of the sedimentary rocks. They are deposited in a wide range of continental and marine environments, where they constitute entrie formantions or are interbedded with other rock types, such as sandstone and limestone.
泥岩类，是沉积岩中最常见的岩石，包括粉砂岩、泥岩、泥页岩、粘土岩和粘土页岩。其沉积环境广泛，包括大陆和海洋沉积，构成完整的岩层或是以夹层形式出现在其他类型的岩石中，如砂岩和灰岩。
Because mudrocks are typically dominated by quartz, feldspars, and caly minerals, their chemistries are usually characterized by abundant silica, alumina, and H2O.However, where mudrocks are interlayered wih carbonate rocks, as they are in the Cincinnatian Series and the Green River Formation, they contain substantial amounts of carbonate minerals. As a consequence, the chemical analyses of such mudrocks contain relatively large amounts of CaO, MgO, orboth, and substantial amounts of CO2. Among the clay minerals, smectites andkaolinite tend to occur in younger mudrocks and in smaller quantities.Bentonites, altered volcanic ash primarily composed of smectites, are an exception. Illites dominate in older mudrocks, at least in part because they are produced by diageneetic recations in which smectites are converted toillite. A variety of additional minerals occurs in mudrocks, including chlorite,zeolites,gypsum and anhydrite, pyrite and marcasite, iron oxides, apatite, and a widerange of heavy minerals such as garnet and hornblende.
由于泥岩类的典型矿物主要是石英、长石和粘土矿物，因此其化学特征通常为富含SiO2、Al2O3和H2O。然而，在泥岩和碳酸盐互层发育的地方，辛辛那提统和绿河组中的泥岩则含有大量的碳酸盐矿物。化学分析结果显示这类泥岩含有相对大量的CaO或MgO或者CaO和MgO，以及CO2。粘土矿物中，蒙脱石和高岭石在较新的泥岩中更常见, 但含量较少。膨润土、以蒙脱石为主的蚀变火山灰除外。较老的泥岩以伊利石或者至少有一部分以伊利石为主要矿物，在成岩过程中蒙脱石转化形成了伊利石。许多次要矿物包括绿泥石、沸石、石膏和硬石膏、黄铁矿和白铁矿，氧化铁、磷灰石和含量不等的重矿物，如石榴子石和普通角闪石。
The colors of mudrocks are related to their chemistry and mineralogy. Mudrocks with large amounts of organic carbon (notably kerogen and lipids) are dark gray to black.Organic carbon may total as much as 80% of the volume of some rocks, but mudrocks commonly have between 0.1 and 6% organic carbon. Pyriteor marcasitetypically occurs in the high-carbon mudrocks and these rocks are laminated,because more complex life-froms, which burrow in andbioturbate the dediment, are unable to live in the anaerobic to dysaerobic reducing envrionments in which these minerals develop.Green and light gray mudrocks typically contain one ofr more of the minerals pyrite, chlorite, and glauconite. Mudrocks with iron oxides are red to yellowand relfect either aerobic envrionments of deposition or postdepositional oxidation.
泥岩的颜色与其化学成分和矿物组成相关。含有大量有机碳(主要是油母岩和烃类)的泥岩为暗灰色到黑色。部分岩石的有机碳含量可达到80%，但是泥岩的有机碳含量通常在0.1-6%。黄铁矿或白铁矿在高碳的泥岩中较为常见，岩石为纹层状，能够在沉积物中留下潜穴和扰动构造较复杂生命形式无法在无氧到缺氧的还原条件中生存，而这又正是这些矿物形成的环境。绿色和浅灰色泥岩通常含有黄铁矿、绿泥石和海绿石中的一种或多种矿物。含有氧化铁的泥岩呈红色到黄色，指示氧化沉积环境或者沉积后的氧化环境。
Contemporary muds, the precursors of mudrocks, contain a wide variety of materials. These may include amorphous material prouduced by hydrogenous, hydrothermal, or biological precipitation; and they may include detrital minerals derived by weathering anderosion of preexisting continental or marine rocks or sediments. The source terrane may control the mineralogy of the mud, but authigentic minerals are dominant in some mudrocks. High carbon contents in mudrocks are preserved in deep, basinal anaerobic environments, but may also result form high rates of organic production or rapid burial.
现在看到的泥土是形成泥岩的原始物质，成分变化很大。可能包括由水、热液或者生物沉淀形成的非晶质物质;可能含已有的大陆或者海洋岩石或沉积物遭受风化剥蚀形成的碎屑矿物。原岩类型可能决定了泥的矿物组成，但是有些泥岩中主要是自生矿物。高碳泥岩保存在深水、无氧盆地环境，但也可能是高有机质生产率或者快速充填的结果。
Most ancient mudrocks have experienced signficant diagenesis. Illite is commonly the dominatnt mineral, but chlorites and mixed layer calys may be abundant, and quartz, feldspar, calcite, and dolomite are typical minerals that constitute most of the remainder of the mineralogy. In spite of diagenetic changes in mineralogy that may obscure the early rock histroy; the associated rocks and fossils, the chemistry, the structures, and the regional sturctural and facies realtionships allow an evalutaiton of the petrogenesis of the mudrocks.
许多古老的泥岩都经历了明显的成岩作用。伊利石通常是主要矿物，但是也可能含有丰富的绿泥石和混合层状的粘土，构成泥岩的大部分典型的残留矿物有石英、长石、方解石和白云石。虽然成岩作用使得岩石的矿物组成发生了变化，掩盖了岩石的原有面貌，但是从相关的岩石和化石、化学成分、构造、区域构造和岩相的关系上可以恢复泥岩的成岩过程。
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