The I/S-to-illite reaction in the late stage diagenesis

Lanson, Bruno; Champion, Didier

doi:10.2475/ajs.291.5.473

Cited by 105 publications

(120 citation statements)

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“…An important kinetic effect has been shown by comparing, in various sedimentary basins, the evolution of mixed-layer illite/ smectite (I/S) with the maximum temperature experienced by the sediments (Lahann, 1980;Srodon and Eberl, 1984;Velde, 1985;Velde et al, 1986;Jennings and Thompson, 1986;Freed and Peacor, 1989), and/ or with organic matter maturation (Smart and Clayton, 1985;Velde and Espitali6, 1989;Francu et al, 1989). As a result of this kinetic effect, the late stage diagenetic clay mineral assemblages in the Paris basin contain several phases* (I/S phases) with distinct, but closely related crystallographic characteristics (Lanson and Champion, 1991). Taking into account the coexistence and simultaneous evolution of randomly interstratified and ordered I/S, Velde and Vasseur (1992) proposed ' Present address: EAP-CSTJF, Laboratoire de G6ochimie Min6rale, 64018 Pau Cedex, France.…”

Section: Introductionmentioning

confidence: 99%

“…The use of a function including a shape parameter (e.g., Pearson7 or Voigt) is not recommended when fitting higher angle regions (15-50 ~ CuKa; 5,9-1.8 ~). Lanson and Champion (1991) used the decomposition program developed by Lanson (1990Lanson ( , 1992 on the 5-11 ~ CuKa (17.6-8.0 ~) range to show the simultaneous occurrence of three "illitic" phases in their Paris basin samples and to follow their evolution with burial. However, major discrepancies between the FWHM of experimental and simulated patterns, described previously by Reynolds and Hower (1970) and , do not permit the precise identification of these phases (Lanson, 1990).…”

Section: Introductionmentioning

confidence: 99%

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Decomposition of X-Ray Diffraction Patterns: A Convenient Way to Describe Complex I/S Diagenetic Evolution

Lanson

Velde

1992

Clays and clay miner.

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Abstract--Decomposition of complex X-ray diffraction profiles is used on well characterized (image analysis of transmission electron micrographs, X-ray fluorescence chemical analyses) diagenetic samples from the Paris basin. The simultaneous occurrence of three "illitic" phases (mixed-layer illite/smectite or I/S, poorly crystallized illite, and mica-like phase) is shown on the various diffraction peaks of the 2-50 ~ CuKa (44-1.8 ]k) range. However, because of theoretical and experimental constraints, it is easier to perform the decomposition routine in the 5-11 ~ CuKa (17.6-8.0 ~) range. The identification (i.e., illite content and mean coherent scattering domain size) of the various phases is performed by comparing the associated elementary peak characteristics (position, full width at half maximum intensity) with simulated X-ray patterns. When available, the characteristics obtained from the various angular regions are mutually consistent; however, the precise structures of smectite and illite end-members, on the one hand, and the structure of I/S crystallites, on the other hand, are not well known. Consequently, on some angular regions, there is a discrepancy between the characteristics obtained on experimental and calculated X-ray profiles. The definition of more realistic simulation hypotheses for I/S minerals, and for other interstratified clay minerals, would make this powerful and reliable tool to describe X-ray patterns a precise and sensitive identification tool even for complex clay parageneses.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Decomposition of X-Ray Diffraction Patterns: A Convenient Way to Describe Complex I/S Diagenetic Evolution

Lanson

Velde

1992

Clays and clay miner.

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“…The Paris Basin samples (Figure 1) have been characterized thoroughly by image analysis of transmission electron micrographs, X-ray fluorescence chemical analysis (Lanson and Champion, 1991) and decomposition of XRD profiles (Lanson and Velde, 1992). The simultaneous occurrence of three "illitic" phases (i.e., highly illitic illite/smectite mixed-layer or I/S, poorly crystallized illite and well crystallized illite) has been shown on the various diffraction peaks (001,002, 003 and 005 bands) of the 2-50~ (44 to 1.8/~) range (Lanson and Velde, 1992).…”

Section: Resultsmentioning

confidence: 99%

“…These samples are Stephanian to Permian in age, and have been extensively described by Lanson and Champion (1991 ) and Lanson and Velde (1992). An additional ten samples came from the Upper Cretaceous Niger Delta mudstones described by Velde et al (1986).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The resulting digitized data, combined with increasingly powerful computers, allow numerous calculation routines for numerical data processing to get more information out of an XRD profile. A decomposition routine, for example, enables the separation of the respective contributions of phases with distinct but closely related crystallographic characteristics from a complex XRD profile (Lanson and Champion, 1991;Righi and Meunier, 1991). In addition, quoting Klug and Alexander (1974), "Appropriate analysis of the line profile should yield such information as... the mean size of coherent crystalline domain, distribution of crystallite sizes, and the nature and extent of lattice imperfections."…”

Section: Introductionmentioning

confidence: 99%

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