Abstract: Whether geochemical mapping at different scales could obtain stable and traceable geochemical patterns and whether it could truly reflect the background values of different elements are important for testing the feasibility of the selected geochemical mapping methods. The tropical rainforest of Padang-Bengkulu area in Sumatra, Indonesia was selected for this study, and the results from geochemical mapping at the scales of 1: 1000000 (1 sample/100 km2) and 1: 250000 (1 sample/4 km2) were compared in this area. Their background values, medians, and geochemical patterns obtained are very consistent. The geochemical provinces are very similar and reproducible by different sampling densities, and the concentration centers are overlapped, which indicates that the low-density geochemical mapping can obtain stable and traceable geochemical patterns and that this method is applicable in tropical rainforest areas. The geochemical provinces delineated by the low-density geochemical mapping cover the large ore deposits and granite bodies, and truly reflect the distribution of different elements in the study area. Geochemical mapping at a larger scale could be implemented in these geochemical provinces and many local anomalies could be delineated for exploration, which thereby reduces risks in exploration and investment.

Key words: low density geochemical mapping, background value, median, geochemical pattern