Reconstruction of palaeothermal conditions in a passive margin using illite-smectite mixed-layer series (BA1 scientific deep drill-hole, Ardeche, France)

Renac, Christophe; Meunier, A.

doi:10.1180/claymin.1995.030.2.03

Cited by 14 publications

(11 citation statements)

References 13 publications

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“…Renac (1994) has done very detailed mineralogical work on a series of shale samples from a deep drill hole (Balazuc 1) in southeastern France. As reported in Renac & Meunier (1995), the sequence covers a 400 m interval of 20 Ma depositional history at 200 Ma. The depth is currently 1170-1540 m but an estimated 1.5 km of sediments has been eroded from the top of the series.…”

Section: Mineralogical and K-ar Relations In Diagenetically Altered Smentioning

confidence: 74%

Smectite to illite conversion and K-Ar ages

Velde

Renac²

1996

Clay miner.

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Interpretation of K-Ar determinations of the apparent age of crystallization of diagenetic potassic layer silicates should take into account the current ideas concerning the smectite to illite conversion of clay minerals. These minerals are the major K-bearing neogenic phases in sedimentary rocks and, therefore, it is important to keep in mind their origin and tile pathway of their evolution. Another important contributor to K and Ar content are detrital minerals which are not considered in detail in this paper. The radiogenic Ar retained by diagenetic illitic clay minerals (illite and illite-smectite interstratified minerals with a low smectite content) will be a function of: (1) the amount Ar lost through the destruction of mixed-layer and small grained iUitic material dissolved to produce new, larger, illite-rich crystals; and (2) the amount of Ar produced and retained in the growing, stable illite mineral grains. Hence the K/Ar ratios in diagenetic illites depend on several variables. In samples where the detrital contribution is small, when the illite growth reaction is rapid, i. e. occurring over a short period of time, the accumulated radiogenic Ar can be used to date the geologic event which caused this crystal growth. However, if the process occurs over a significant period of time, as is usually the case in shales, the age deduced by radiogenic Ar content will indicate the changes in mineralogy and grain-sizes of the different participating phases. These changes will be the result of time and temperature variables of the sedimentation and burial of the samples studied. The radiogenic Ar accumulated will reflect a sequence of mineral changes over a period of time.The K-Ar dating of potassic sedimentary minerals has been pursued for some time now, with reasonable results especially when the minerals were formed rapidly such as in glauconite genesis. In smectite/illite mineral mixtures, the results are often more than ambiguous. The greatest number of cases where different layers in a continuous depositional series (diagenesis) are dated show a significant decrease in apparent age as the sedimentary age increases

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Section: Mineralogical and K-ar Relations In Diagenetically Altered Smentioning

confidence: 74%

Smectite to illite conversion and K-Ar ages

Velde

Renac²

1996

Clay miner.

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“…The development of kinetic models of vitrinite reflectance evolution based on viable chemical principles provide a powerful tool for thermal modeling (Larter 1989;Sweeney and Burnham 1990). Other studies dealing with changes in clay mineralogy in sedimentary rocks have tried to use mineral indicators to constrain the thermal history of sedimentary basins (Kfibler 1973;Hoffman and Hower 1979;Smart and Clayton 1985;Pollastro and Barker 1986;Kisch 1987;Pearson and Small 1988;Pollastro 1993;Renac and Meunier 1995).…”

Section: Introductionmentioning

confidence: 99%

Clay Mineral Diagenesis and Thermal History of the Thonex Well, Western Swiss Molasse Basin

Schegg

Leu²

1996

Clays and clay miner.

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Abstract--Results are presented of a diagenetic study from the 1300 m thick Oligocene Molasse deposits penetrated by the Th6nex geothermal exploration well (Geneva, Switzerland). The x-ray diffraction (XRD) studies of fine-grained rocks indicate the following diagenetic changes: a decrease of illite/smectite (US) expandability from approximately 90% to 30% with depth, a decrease of the amount of US in the clay mineral fraction, and the appearance of corrensite at depths >750 m. The transition from random US to ordered I/S occurs at the base of the Th6nex well (1200 to 1300 m) and is associated with a coal rank of about 0.7% Rr (mean random vitrinite reflectance) corresponding to paleotemperatures of 110 to 115 ~ Corrensite appears at a vitrinite reflectance value of 0.6% Rr and a corresponding paleotemperature of 100 ~ The amount of post-Molasse erosion is estimated to be approximately 2 km. Thermal history modeling of the Th6nex well suggests maximum paleotemperatures of 80 to 115 ~ and an average paleogeothermal gradient of 27 ~ during Late Miocene maximum burial conditions.

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“…The use of several elementary peaks to characterize a single phase must be supported by evidence from additional analyses (such as scatter of individual particle composition or scatter of the particle size and thickness). This case is common in late-stage diagenesis; for example, where illitic US coexists with pure illite having very variable CSDS (Lanson and Champion 1991;Lanson and Velde 1992;Renac and Meunier 1995;Varajao and Meunier 1995;Lanson and Meunier 1995;Lanson et al 1996). In this case, the CSDS distribution is usually fitted with 2 distinct elementary peaks related to "poorly crystallized" and "well-crystallized" illites (Lanson and Meunier 1995).…”

Section: Prospectsmentioning

confidence: 99%

“…For example, a decomposition routine is now widely used to separate the respective contributions of partially overlapping peaks due to phases with distinct but closely related crystallographic characteristics from a complex XRD profile (Howard and Preston 1989;Jones 1989;Lanson and Champion 1991;Righi and Meunier 1991;Stern et al 1991;Bouchet et al 1992;Lanson and Besson 1992;Drits et al 1993;Robinson and Bevins 1994;Renac and Meunier 1995;Righi et al 1995;Lanson et al 1996). In this paper, the word "phase" describes a population of particles whose characteristics (such as size or chemical composition) vary about a mean value.…”

Section: Introductionmentioning

confidence: 99%

“…The decomposition procedure may be used to characterize any clay assemblage, and is especially useful for complex ones such as those from soils (Righi and Meunier 1991;Righi et al 1993;Righi et al 1995). It is also suitable for the study of relative variation within a series of samples whose compositions lie between identified end members (Lanson and Champion 1991;Lanson and Besson 1992;Renac and Meunier 1995;Varajao and Meunier 1995;.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Decomposition of Experimental X-Ray Diffraction Patterns (Profile Fitting): A Convenient Way to Study Clay Minerals

Lanson

1997

Clays and clay miner.

214

141

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Abstract--This paper thoroughly describes the decomposition procedure, using the example of DE-COMPXR (Lanson 1990). The steps of the decomposition procedure are: 1) preliminary data processing; 2) decomposition; 3) validation of results; and 4) use of the results. The use of decomposition is restricted to the separation of contributions from various phases. The effect of preliminary data processing steps (data smoothing, background stripping) on profile shape is shown to be limited and their implementation is detailed. Potential experimental limitations such as peak symmetry, experimental reproducibility or discrimination are equally minor. A logical decomposition process starts from the definition of the angular range to be fitted, proceeds with the determination of the number of elementary peaks to be fitted and ends with the check for results consistency.Numerical data processing is a powerful tool for the accurate identification of monophases, because of the additional parameters available to constrain XRD profile simulation. Ultimately, however, the match over the whole angular range of both the experimental and the simulated patterns remains the only valid way to characterize the phases present in the sample. Additionally, the decomposition procedure permits both the identification of complex clay mineral assemblages and the characterization of their evolution. This step constrains, and may help to determine, the reaction mechanisms of a transformation; and, as a consequence, to characterize and to model the kinetics of this transformation.

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Reconstruction of palaeothermal conditions in a passive margin using illite-smectite mixed-layer series (BA1 scientific deep drill-hole, Ardeche, France)

Cited by 14 publications

References 13 publications

Smectite to illite conversion and K-Ar ages

Smectite to illite conversion and K-Ar ages

Clay Mineral Diagenesis and Thermal History of the Thonex Well, Western Swiss Molasse Basin

Decomposition of Experimental X-Ray Diffraction Patterns (Profile Fitting): A Convenient Way to Study Clay Minerals

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