Development of Five Stream Sediment Certified Reference Materials for Geochemical Surveys in Arid Desert Areas of North China

Certified reference materials (CRMs) play a pivotal yet frequently overlooked function in mineral exploration. Effective exploration requires CRMs that closely match the geological background. With the full launch of a new round of prospecting strategic breakthrough actions, large-scale regional geochemical surveys will be conducted around the main metallogenic zones in China. Currently, there is a notable shortage of CRMs specifically designed for the arid desert regions of northern China, which have huge mineralization potential. To address this gap and meet analysis and testing needs for stream sediment samples, five stream sediment CRMs have been developed for these arid desert areas. These CRMs represent diverse geological settings: a regional background area, a Ni-polymetallic mining area, a Cu mining area, a Cu-Pb-Zn polymetallic mining area, and a Cu-Fe mining area. The development process strictly followed the requirements outlined in the ISO series of international standards for CRMs. The candidate materials were prepared in accordance with these standards, involving procedures such as impurity removal, drying, multi-stage milling, and homogenization prior to packaging. Homogeneity and stability were evaluated using 30 randomly selected units per candidate, and the results demonstrated excellent performance in both aspects. For characterization, 13 authoritative laboratories collaborated to determine the concentrations of 73 components using validated measurement techniques. Through statistical measurement and rigorous uncertainty assessment, it was confirmed that these materials meet all requirements for CRMs. These new CRMs are recommended for property value assignment, instrument calibration, quality control, and proficiency testing in regional geochemical surveys and mineral exploration.