ANALYSIS AND MAPPING OF GEOCHEMICAL ANOMALIES WITH DIRECTIONAL CATCHMENT BASIN

Stream sediment geochemistry, used for almost 50 years worldwide, is a very robust, successful mineral exploration technique. We present a new method of directional catchment-based stream sediment geochemical anomalies analysis and mapping, including: (1)automatic extraction of directional catchment basins with GIS technique; (2) Analysis and mapping of geochemical anomalies with directional catchment basin. The term directional catchment basin as used here is restricted to represent the boundary of the catchment or the water parting disjoint at the outlet of catchment basin, with the advantage showing the drainage direction and the catchment area. The arrangements and combinations of catchment basins with drainage direction will provide information on geological structure, such as lineament and circular structures, which controlled the distribution of the geochemical anomalies. Otherwise, indicating drainage directions within the drainage basin is important to the provenance studies of geochemical anomalies. The automatic extraction method of directional catchment basins with GIS technique consists of the following steps: (1)Convert the catchment basin polygons to catchment basin boundary polylines and keep the attributes; (2)Get the point of intersection of the catchment basin boundary polylines and the stream networks polylines; (3)Clip the catchment basin boundary polylines with appropriate length on both sides of the point of intersection, so get the directional catchment basin, which keep the attributes of catchment basin polygons. We test this technique with heavy mineral geochemical data in dexing ore cluster area, Jiangxi province, China.