QUANTITATIVE CLAY MINERALOGICAL ANALYSES FROM THE BULK CHEMISTRY OF SEDIMENTARY ROCKS.

Abstract

A technique suitable for computer application has been developed whereby whole rock major element analyses are corrected for X-ray detectable nonclay minerals and used to set up simultaneous equations which are solved to give clay mineral abundances. A theoretical evaluation of the approach by graphical methods enables the intrinsic errors to be very clearly assessed. Errors are minimized when SiO//2, Al//2O//3, and K//2O are used as variables but only slightly increased if total Fe//2O//3 plus MgO is substituted for SiO//2. Quartz and CO//2 content are the only data normally required which cannot be determined by X-ray fluorescence. Results compare favorably with estimates obtained by XRD and other methods, being more accurate than XRD and equally precise provided the rock does not contain clay minerals other than the kaolin group, the mica group, and chlorite. Refs.