Abstract
The 10-Å clay components of sedimentary rocks (“illites”) are commonly mixtures of 100% nonexpandable illite and an ordered illite/smectite mixed-layer mineral. If the proportion of the illite/ smectite in a mixture is sufficient to produce a measurable reflection between 33–35°2θ (CuKα radiation) that is noncoincident with an illite reflection, the ratio of component layers and type of interstratification for the mixed-layer mineral can be determined. The identification technique developed in this study rests upon the following experimental findings for ordered illite/smectites of diagenetic origin: (1) the thickness of the illite layer in illite/smectites is 9.97 Å; (2) the thickness of smectite-ethylene glycol complex ranges from 16.7 to 16.9 Å; (3) illite/smectites form a continuous sequence of interstratification types—random, random/IS, IS, IS/ISII, ISII—and each type is related to a specific range of expandability.
The new technique broadens the computer simulation method developed by R. C. Reynolds and J. Hower to include those sedimentary materials which are dominated by the presence of discrete illite, are low in illite/smectite, and, as such, have been described previously only by an “illite crystallinity index.”
Резюме
10-Å глинистые компоненты осадочных пород (“иллиты”) обычно являются смесями 100% нерасширяемого иллита и упорядоченного минерала типа смешанно-слойного иллита/смектита (ИС). Отношение составляющих слоев и тип переслаивания для смешанно-слойного минерала могут быть определены, если пропорция иллита/смектита в смеси достаточна, чтобы вызвать измеряемое отра¬жение между 33–35°2θ (излучение СиКα), которое не совпадает с отражением иллита. Техника иден¬тификации, разработанная в этой статье, основывается на последовательных экспериментальных данных для упорядоченных иллитов/смектитов диагенетического происхождения: (1) толщина ил-литового слоя в иллите/смектите равна 9,97 Å; (2) толщина комплекса смектита с этиленовым гликолом изменяется в диапазоне от 16,7 до 16,9 Å; (3) иллиты/смектиты образовывают непрерывный ряд типов прослоев—беспорядочный, беспорядочный/ИС, ИС, ИС/ИСЦ, ИСП-и каждый тип связан со специфическим диапазоном расширяемости.
Эта новая техника расширяет метод компьютерного моделирования, развитый Рейнольдсом и Гоуером и включает такие осадочные материалы, в которых находится отдельный ил лит, которые имеют малые количества иллита/смектита и которые, как таковые, предварительно описывались только при помощи “индекса кристальности иллита.” [Е.G.]
Resümee
Die 10-Å Tonkomponenten von sedimentären Gesteinen (“Illite”) sind gewöhnlich Mischlingen aus 100% nicht expandierbarem Illit und einem regelmäßigen Illit/Smektit-Wechsellagerungsmineral. Wenn das Verhältnis von Illit/Smektit in einer Mischung ausreicht, um einen meßbaren Reflex zwischen 33 und 35°2θ (CuKα-Strahlung) zu erzeugen, der nicht mit einem Illitreflex zusammenfällt, dann kann das Verhältnis der Komponentenschichten und die Art der Wechsellagerung für das Wechsellagerungsmineral bestimmt werden. Die Identifikationstechnik, die in dieser Untersuchung entwickelt wurde, beruht auf den folgenden experimentellen Ergebnissen für geordnete Illit/Smektit-Wechsellagerungen diagenetischen Ursprungs: (1) Die Dicke der Illitlagen in den Illit/Smektit-Wechsellagerungen beträgt 9,97 Å; (2) die Dicke des Smektit-Äthylenglykolkomplexes reicht von 16,7–16,9 Å; (3) Illit-Smektitwechsellagerungen bilden eine kontinuierliche Abfolge von Wechsellagerungstypen—unregelmäßige, unregelmäßige/IS, IS, IS/ISII, ISII—und jeder Typ gehört zu einem bestimmten Bereich von Expandierbarkeit.
Die neue Untersuchungsmethode baut die Computersimulationsmethode aus, die von R. C. Reynolds und J. Hower entwickelt wurde, um solche sedimentären Materialien mit einzuschließen, bei denen diskreter Illit vorherrscht, die wenig Illit/Smektit enthalten, und die, als solche, früher nur durch einen “Illit-Kristallinitätsindex” beschrieben wurden. [U.W.]
Résumé
Les composés argile de 10 Å de roches sédimentaires (“illites”) sont communément des mélanges d’illite 100% non expansible et d’un minéral ordonné à couches mélangées illite/smectite. Si la proportion d’illite/smectite dans un melange est suffisante pour produire une reflection mesurable entre 33-35°2θ (radiation CuKα) qui ne coïncide pas avec une reflection illite, on peut déterminer la proportion de couches du composé et le genre d’interstratification du minéral à couches mélangées. La technique d’identification développée dans cette étude est basée sur les trouvailles expérimentales suivantes pour des illite/ smectites d’origine diagénétique: (1) l’épaisseur de la couche illite dans les illite/smectites est 9,97 Å: (2) l’épaisseur du complexe glycol smectite-éthylène s’étend de 16,7 à 16,9 Å; (3) les illite/smectites forment une séquence continuelle de types d’interstratification—au hasard, au hasard IS, IS, IS/ISII, ISII—et chaque type est apparenté à une étendue spécifique de pouvoir de dilatation.
La nouvelle technique élargit la méthode de simulation à l’ordinateur développée par R. C. Reynolds et J. Hower pour inclure les matériaux sédimentaires qui sont dominées par la présence d’illite discrète, ont un bas contenu en illite/smectite, et, en tant que tels, n’ont jusqu’à présent été décrits que par un “indexe de cristallinité d’illite.” [D.J.]
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Śrondoń, J. X-Ray Powder Diffraction Identification of Illitic Materials. Clays Clay Miner. 32, 337–349 (1984). https://doi.org/10.1346/CCMN.1984.0320501
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DOI: https://doi.org/10.1346/CCMN.1984.0320501