Bulk mineralogy was determined on random powders.
Clay mineralogy was determined
by separation of the fraction of less than 2 µm with
sedimentation. Measurements were carried out on samplesthat were air-dried, ethylene glycol-solvated, and heated to
550°C (Brown 1972). Mineral abundances of samples were
determined by interpretation of XRD data. The procedure
of this method was described by Chung (1974). The error
margin of this method is approximately 10%.
Morphological and microchemical analyses were
carried out using a LEO VP-1431 scanning electron
microscope with an energy dispersive X-ray spectrometer
(SEM-EDX). Before the SEM analysis, samples were coated
with a thin film (thickness: 25 nm) of gold using a sputter
coater to make the sample conductive.