QUANTITATIVE MEASUREMENT OF CHLORITE IN THE CHINESE LOESS BY SEQUENTIAL EXTRACTION METHOD

Chlorite is an important kind of Fe-bearing minerals and clay minerals of the Quaternary and Tertiary loess sediments in the Chinese loess plateau, weathering of which during the interglacial times produced an increase of pedogenetic iron oxide minerals and thus enhanced magnetic susceptibility signal in paleosol. However, because the absolute concentration of chlorite is hard to be determined quantitatively by XRD, its chemical weathering rate and climate implications are largely unexplored. In this study, a new chemical method is established to quantitatively measure the absolute concentration of chlorite in the Chinese loess. The method includes three sequential extraction steps. First, use acetic acid to dissolve the carbonates in samples; second, eliminate the free iron oxides by citrate - bicarbonate - dithionite (CBD) method; finally, use HCl to dissolve chlorite at 80 centigrade, and then make chemical analyses of the resulting solution by ICP-AES and solid residues by XRF. This method is also suitable for quantitative measurement of iron-rich chlorite mineral in other type sediment, soils and rocks.