Clay mineral suites of the coastal mud belt associated with the Changjiang river

Clay minerals are often used as tracers to determine the range of the dispersal pattern of the mud and to identify the source of the materials. In quantitative material tracing, it is important to evaluate the changes in the content of the tracers during transport. Preliminary analysis of the clay mineral suites of five groups of samples collected along the Changjiang sediment transport pathways over a coastal mud belt indicates that the clay mineral suite is dominated by illite, chlorite and kaolinite, without significant changes in the relative percentages of montmorillonite, illite and kaolinite after leaving the Changjaing River mouth. An exception is associated with chlorite, possibly due to hydraulic sorting of clay particles. Thus, the major clay minerals including montmorillonite, illite and kaolinite may be used in material tracing for the region. However, because there are a number of factors that may alter the clay mineral suite (e.g. estuarine and diagenetic modifications), cautions should be taken when applying a mixing model to derive quantitative estimates of material supply from different sources: 1) the clay mineral suites of the coastal mud belt may be different from those within the Changjaing River estuary, with the latter being not suitable to be used as the fingerprint; and 2) in analyzing the sediment record in cores the effect of diagenetic processes must be evaluated.