Celadonite and its transformation to smectite in an Entisol at Red

Abstract--A green, Lithic Torriorthent soil derived from a celadonite-rich, ydrothermaUy altered basalt immediately north of the Mojave Desert region in southern California was studied to investigate he fate of the celadonite in a pedogenic weathering environment. Celadonite was found to be disseminated in the highly altered rock matrix with cristobalite, chalcedony, and stilbite. X-ray powder diffraction (XRD) showed the soil material to contain celadonite having a d(060) value of 1.510 A, indicative of its di-octahedral nature. Very little smectite was detected in the parent material, whereas Fe-rich smectite was found to be abundant inthe soil. The Fe-smectite and celadonite were identified as the sole components of the green-colored clay fraction (<2 t~m) of all soil horizons. The soil clay showed asingle d(060) value of 1.507/~, indicating that the smectite was also dioctahedral nd that its b-dimension was the same as that of the celadonite. M6ssbauer spectroscopy showed that he chemical environments of Fe in the rock-matrix celadonite and in the smectite-rich soil clay were also nearly identical. These data strongly suggest a simple transformation f the celadonite to an Fe-rich smectite during soil formation. Supporting evidence for this transformation was obtained by artificial weathering of celadonite, using sodium tetraphenyl boron to extract interlayer K. The intensity of the 001 XRD peak (at 10.1 7t) of celadonite was greatly reduced after the treatment and a peak at 14.4 A, absent in the pattern of th