Early clay diagenesis in gulf coast sediments : New insights from XRD profile modeling
McCarty, Douglas K. (Chevron ETC)
Sakharov, Boris A. (Russian Academy of Science. Geological Institute)
Drits, Victor A. (Russian Academy of Science. Geological Institute)

Data:	2008
Resum:	Samples from different depths in the Oligocene Frio formation (offshore Gulf of Mexico) were studied by X-ry diffraction (XRD), thermal analyses, and scanning electron microscopy. The experimental XRD patterns recorded from oriented and ethylene glycol (EG) solvated clay fractions of the samples were similar to those typical of random, mixed-layered illite-smectite (R0 I-S). The experimental XRD patterns recorded in air-dried (AD) and EG states were simulated using three different models. One of them corresponds to R0 I-S for which thickness and content of the interstratified layers were determined by the Środoń technique. The second model is represented by a single homogeneous I-S in which illite and smectite layers are interstratified with a tendency to segregation. The expandability of the segregated I-S model varies from 48% to 75% without any rational relationship between the smectite layer content and depth. The third model assumes that the clay fraction is a physical mixture of smectite and an R0 I-S. In this model the I-S contains 65% illite and 35% smectite layers independent of depth, whereas the smectite content varies from 28% to 63%. This model has consistently smaller profile factors, R, for both EG and AD XRD scans compared with the R values determined for the other two models. The mineralogical association, volcanic origin, narrow stratigraphic interval (427 m), and low maximum temperature (42°C) of the studied Frio Formation are considered. These features are completely consistent with the two-phase model and so the segregation model must be rejected. An authigenic origin of the pure smectite and an alternative detrital or authigenic origin of the R0 I-S are discussed.
Drets:	Aquest material està protegit per drets d'autor i/o drets afins. Podeu utilitzar aquest material en funció del que permet la legislació de drets d'autor i drets afins d'aplicació al vostre cas. Per a d'altres usos heu d'obtenir permís del(s) titular(s) de drets.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Diagenesis ; Gulf Coast ; Illite-Smectite ; Frio Formation ; Smectite
Publicat a:	Clays and Clay Minerals, Vol. 56, Núm. 3 (2008) , p. 359-379, ISSN 1552-8367

DOI: 10.1346/CCMN.2008.0560306

21 p, 2.0 MB  Accés restringit a la UAB

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