Les illites du bassin oligocène de Salins (Cantal)

Abstract

Description géologique du bassin oligocène de Salins (Cantal) et étude du mode de formation des différentes sortes de sédiments argileux, à base de kaolinite, d'illite et de montmorillonite qui s'y rencontrent. Discussion de la composition chimique de la série illite˗glauconie. Résultats de l'examen des courbes thermo˗pondérales, des spectres de rayons X et de l'observation au microscope électronique des principaux types.

Constraints on the Genesis of Ferrian Illite and Aluminum-Rich Glauconite: Potential Impact on Sedimentology and Isotopic Studies

“…D and H) Lack of relation between tetrahedrally coordinated aluminum and divalent cations indicates that charge disequilibrium during Al-for-Fe substitution is neutralized by loss of potassium and not by the Al-Si substitution at tetrahedral sites. Glauconite Fe-rich illite Al-rich glauconite Gabis, 1963Jung, 1954Kossovskaya and Dritts, 1970Berg-Madsen, 1982Dasgupta et al, 1990Guimaraes et al, 2000Ireland et al, 1983 This study Keller, 1958Odin and Matter, 1981Odom, 1976Thompson and Hower, 1975Porrenga, 1968 Mg) / VI Al value. The 1.49 value is the one from the reference material, e.g., the least modifi ed glauconitic mineral (AM-04A).…”

“…aluminum content is of diagenetic origin (Dasgupta et al 1990, Guimaraes et al 2000, Ireland et al 1983. Some iron-rich illite has a similar composition, but its formation is related to hypersaline or fl uvial environments (Dasgupta et al 1990, Gabis 1963, Hay et al 1991, Jung 1954, Kossovskaya & Drits 1970, Parry & Reeves 1966, Porrenga 1968). This is not the case for the Anse Maranda Formation (Longuépée & Cousineau 2005).…”

Clay Sedimentology

“…Almost excIusively iIIitic minerals also occur in some ancient lakes devoid of noticeable volcanic activity, as for instance in Oligocene lakes of the Massif Central, France (e.g., Jung 1954, Gabis 1963; see 4.1.2). Almost excIusively iIIitic minerals also occur in some ancient lakes devoid of noticeable volcanic activity, as for instance in Oligocene lakes of the Massif Central, France (e.g., Jung 1954, Gabis 1963; see 4.1.2).…”

The Variability of Micaceous Minerals in Sedimentary Rocks

“…There were only occasional finds of hydromicas of a composition intermediate between glauconites and illites, known under the names "illites ferriques" or "illites ferrif2res (JUNG, 1954;GABIS, 1963), "glauconitic mica" (KELLER, 1958;PARRY and REEVES, 1966) and "glauconitic illite" (PORRENGA, 1968).…”

“…1, 2, 3 show crystallo-chemical peculiarities of micaceous minerals of various types. One of the most expressive parameters that enabled to distinguish between various types of micaceous minerals proved to be the Fe3+ content in octahedral positons of the structure (JUNG, 1954). Depending on the index Fe3+/(Fe3+ + A13+), changes of tetrahedral, octahedral and total layer charges were analyzed.…”