Randomly Interstratified Serpentine/Chlorite: Its Detection and Quantification by Powder X-ray Diffraction Methods

R. C. Reynolds Jr.1, M. P. DiStefano2 and R. W. Lahann2
1 Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755
2 Exploration Research Division, Conoco Inc., P.O. Box 1267 Ponca City, Oklahoma 74603

Abstract: X-ray diffraction studies of the pore-lining chloritic mineral from the Tuscaloosa Formation disclose a marked pattern of odd-order line broadening for the 001 to the 00,16 reflections. The odd-order peaks are approximately twice as broad as the even orders after correction for instrumental broadening effects. These results are consistent with a randomly interstratified 7-Å/14-Å structure, which is most likely serpentine/chlorite. Quantitative analysis of line broadening and model calculations indicate that the serpentine/chlorite contains 7% serpentine layers.

A simplified method is proposed for quantifying randomly interstratified serpentine/chlorite. Residual line broadening (βr) is obtained from the half-height widths of uncorrected diffraction profiles for the 004 and 005 “chlorite” reflections by means of the following: β r = ( β 005 1.25 − β 004 1.25 ) 1 1.25 . Percent serpentine in the random interstratification is computed from the empirical expression %S=−0.51+24.27 β r , which is valid from about 1 to 20 percent serpentine.

Key Words: Interstratification • Mixed-layered • Serpentine/chlorite • Tuscaloosa • X-ray diffraction line broadening

Clays and Clay Minerals; June 1992 v. 40; no. 3; p. 262-267; DOI: 10.1346/CCMN.1992.0400302
© 1992, The Clay Minerals Society
Clay Minerals Society (www.clays.org)