Geochemical multifractal distribution patterns in sediments from ordered streams

For geochemical exploration, the stream sediment survey is of great importance for the delineation of geochemical anomalies and the distribution patterns of chemical elements are critical for anomaly recognition and mineral resource assessment. To study the distribution patterns of elements, we collected 7113 stream sediment samples along stream networks with seven orders from an area in the Qulong region of Tibet in southwest China where numerous polymetallic Cu deposits have been found. Thirteen elements, including Cu, Ag, As, Au, Ba, Bi, Hg, Mo, Pb, Sb, Sn, Zn, and W, were measured in each sample. The distribution patterns of the element concentrations are represented by multifractal spectrum estimated by the method of moments and characterized by six quantitative multifractal parameters. The multifractalities and inhomogeneity of the elements grow stronger as the elements transported from the main streams to the streams of order 1. Our study shows that the Cu anomalies delineated by the multifractal inverse distance weighted interpolation analysis correspond from streams of order 1 to streams of order 5, which indicates the self-similarity of geochemical variables. These results strongly suggested that the multifractal model and the multifractal parameters might be useful in estimating other stream sediments' properties and studying the geochemical dynamic transport behaviors of elements in stream sediments, which also might be extended to study the physical and chemical properties of soils from different horizons and other kinds of media at different scales as well.