Preparation of Geochemical Reference Materials of Stream Sediments

In order to meet the needs of regional geochemical survey and mineral exploration, 15 reference materials of stream sediment were prepared as 6 of total 15 were duplicates for previous reference materials, 9 were new developed reference materials sampled from special landscape of forest, swamp and desert on northern China. Based on the requirements of regional geochemical survey, the size fractions for samples from froest-swamp, desert and mountain-hillyground area were 2.0-0.22 mm, 4.76-0.90 mm and less than 0.22 mm, respectively. The samples were heated in oven at 110 ℃ for 24 h after being dried down at lab. Then, the samples were crushed and the 99% final sizes were less than 0.074 mm by large-scale high Al porcelain ball mill. The good homogeneous was tested by wavelength dispersion X-ray fluorescence spectrum with F values were less than the critical value and RSDs were less than 4%. The RSDs of most elements were less than 3% and that of P, Mn, Ti, Fe₂O₃ and K₂O were less than 1%.The stability was tested by 4 times analysis during 2 years and there was no significant change for all results. Fifteen certified laboratories in China participated to analysis about 72 components by suing high precision analytical method based on ISO guideline 35 and guideline for national first grade reference material preparation. The certified values(some were reference values) and RSD were presented for 72 components for 15 stream sediments reference materials. The new prepared geochemical reference materials enhanced greatly the previous system of stream sediments reference materials.