Spectroscopic Approach for Investigating the Status and Mobility of Ti in Kaolinitic Materials

Nathalie Malengreau1, *, Jean-Pierre Muller1, 2 and Georges Calas1
1 Laboratoire de Minéralogie-Cristallographie, URA CNRS 09 Universités de Paris 6 et 7, 4 Place Jussieu, 75 252 Paris Cedex 05, France
2 O.R.S.T.O.M., Département T.O.A. 213 Rue La Fayette, 75 480 Paris Cedex 10, France
* Present address: Dr. Nathalie Malengreau, ESPM-ESD, University of California, 108 Hilgard Hall, Berkeley, California 94720.

Abstract: The form under which Ti occurs in kaolinitic materials from various environments has been investigated using second derivative diffuse reflectance spectroscopy. The position of the absorption edge may be used as a diagnostic band to determine Ti-phases (anatase, futile, Ti-gels). Ti-oxides may be detected in kaolins, down to 0.1 wt. % TiO2. Diffuse reflectance spectra show the presence of Ti-gel-like phases occluded in sedimentary kaolinite particles. These phases, which record conditions at the time of kaolinite growth, constitute the first direct evidence of Ti mobility at the scale of mineral assemblages and question the substitution of Ti for Al in kaolinite. The nature of the Ti-oxides associated with kaolinite particles gives some constraints on the temperature conditions of hydrothermal kaolins, the evolution of sedimentary kaolin during basin diagenesis and the source of parental material in soil kaolins.

Key Words: Diffuse reflectance spectroscopy • Kaolins • Ti-mobility • Ti-status

Clays and Clay Minerals; October 1995 v. 43; no. 5; p. 615-621; DOI: 10.1346/CCMN.1995.0430511
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)