�ber einen Keuperton von Zaisersweiher bei Maulbronn

142

Abstract--Burial diagenetic reactions of di-and trioctahedral clay minerals were compared in Brazilian offshore, basinal sediment sequences of Cretaceous age. Originally dioctahedral smectite-rich shales of three basins --Potiguar, Ceara, and llha de Santana --exhibited the classical smectite-to-illite burial pattern. Trioctahedral clay-rich shales and trioctahedral clay-mineral cements in sandstones, however, showed a burial sequence of saponite to mixed-layer chlorite/saponite with progressive increase in the percentage of chlorite layers with increasing burial depth.The change from disordered to ordered interstratifications of chlorite/saponite occurred in the temperature range 60%-70~ at a vitrinite reflectance value of about 0.65. These values are lower than those found for the ordering of illite/smectite clays. Increasing substitution of Al for Si in tetrahedral sites, followed by fixation of interlayer hydroxide sheets was found to be the major chemical change promoting transformation of saponite to chlorite via corrensite.

Section: Trioctahedral Clay Diagenesismentioning

confidence: 99%

“…The term corrensite was proposed by Lippmann (1954) to describe a mixed-layer clay mineral with a regular alternation of chlorite and swelling chlorite. The term has subsequently been employed to describe a variety of regularly interstratified chlorite and expandable clays.…”

Section: Trioctahedral Clay Diagenesismentioning

confidence: 99%

Comparisons Between the Diagenesis of Dioctahedral and Trioctahedral Smectite, Brazilian Offshore Basins

Chang

Mackenzie

Schoonmaker

1986

142

“…In the present paper the name tosudite will be used in the more general sense to include both the di/di and the di/trioctahedral clays as well as intermediate forms. originally used to indicate a regularly interstratified chlorite/swelling chlorite (Lippmann, 1954). Li-tosudite is a tosudite that contains lithium in the interlayer hydroxyl sheet.…”

Section: Terminologymentioning

confidence: 99%

Reaction Series for Dioctahedral Smectites

Eberl

1978

Abstract--Several dioctahedral clay minerals are related through reaction series. These series can be produced hydrothermally from beidellite gel and montmorillonite by making simple changes in interlayer and solution chemistry. The series are:gel-K-beidellite-random illite/smectite-K-rectorite-illite; K-montmorillonite-K-rectorite-illite; Na-montmorillonite or beidellite-Na-rectorite-paragonite; Li-montmorillonite-Li-tosudite-Li-rectorite-cookeite(?); Mg-montmorillonite-Mg-rectorite-tosu dite-sudoite(?); Ca-montmorillonite-Ca-rectorite-margarite(?); AI-Ca-montmorillonite-kaolinite/smectite-kaolinite (150~ AI-Ca-montmorillonite-pyrophyllite/smectite-pyrophyllite (320~ Assuming stability for the mixed-layer phases, paragenesis is a function of P, T, and X conditions. If the phases are considered to be metastable, paragenesis is a function of the speed and path of reaction.

“…Lippmann (1954) gave the name corrensite to one of these materials and defined it as a regular 1:1 interstratified trioctahedral chlorite/ swelling chlorite mineral. He subsequently referred to the swelling component as vermiculite (Lippmann, 1956), and later as "expandable layers" (Lippman, 1957, 1976, Lippmann and Johns, 1969.…”

Section: Introductionmentioning

confidence: 99%

“…He subsequently referred to the swelling component as vermiculite (Lippmann, 1956), and later as "expandable layers" (Lippman, 1957, 1976, Lippmann and Johns, 1969. The existence of a "chlorite/swelling layer interstratification" is now generally accepted, hut the swelling component is still not well characterized, mainly because of its variable behavior in standard solvatation and heating treatments (Lippmann, 1954(Lippmann, , 1956(Lippmann, , 1976Bradley and Weaver, 1956;Earley et al, 1956;Sudo and Kodama, 1957;Alietti, 1957aAlietti, , 1957bMartin Vivaldi and MacEwan, 1960;Sugiura, 1962;Almonet al, 1976;April, 1980;Churchman, 1980). The XRD features of this material can be summarized as follows: the untreated material gives rise to a reflection at 29-31 /~; after the sample is treated with ethylene glycol, this reflection expands to 31-33 /k; after the sample is heated to 550~ the reflection collapses to 23-28 /~ (Bailey et al, 1982).…”

Section: Introductionmentioning

confidence: 99%

Crystal Chemistry of Corrensite: A Review

Brigatti¹,

Poppi

1984

Abstract--Statistical analyses of chemical data from the literature of corrensite minerals suggest a large compositional variability, more evident in octahedral than in tetrahedral coordination. Mg occupies 40-80% of the octahedral sites, with A1 and Fe 2+ making up the remainder. Approximately 15-30% of the tetrahedral sites are filled by A1. Despite this compositional variability, distinct fields for the several types of mixed-layer trioctahedral chlorite/trioctahedral swelling layer are not apparent. Statistical analyses of the composition of corrensite compared with saponite, vermiculite, and chlorite suggest that corrensite is an intermediate between trioctahedral chlorite and trioctahedral smectite. If Fe/(Fe + Mg) > 50%, chlorite alone is favored, but with increasing Mg, chlorite appears to transform into corrensite and then, by iron oxidation, into trioctahedral smectite. Despite the chemical variability between corrensite, chlorite, and saponite, corrensite appears chemically to be a well-defined species. On the other hand, corrensite cannot be characterized chemically on the basis of its swelling component. Thus, the current definition of corrensite as a regular 1:1 interstratification of trioctahedral chlorite and either trioctahedral smectite or vermiculite is appropriate.