Determination of ten major and trace elements in coastal placer deposits using composite flux alkali fusion-ICP-MS and analysis of their elemental associations

To address the critical national demand for securing titanium, zirconium, and hafnium resources, an enhanced alkali fusion–ICP-MS analytical method was developed using a lithium metaborate–lithium tetraborate composite flux. This method effectively overcomes the technical challenges posed by the high-salt matrix and refractory minerals commonly found in marine placer deposits from the Hainan coastal region. It enables high-throughput quantification of ten major and trace elements, including Ti, Zr, and Hf, in coastal placer deposits. Validation using certified reference materials across five concentration levels demonstrated excellent accuracy and precision, with relative errors (RE) ≤ 5.5 % and relative standard deviations (RSD) ≤ 5.1 %. The method provides a reliable solution for multi-element batch analysis of complex matrices and offers significant practical value in the assessment and development of marine mineral resources. When applied to the analysis of placer samples from the eastern coastal waters of Hainan Island, the results revealed strong positive correlations among Ti, Zr, and Hf (correlation coefficient r ≥ 0.94), as well as co-enrichment of Mn and V with the major ore-forming elements ( r = 0.77–0.85). These findings offer preliminary insights into the metallogenic mechanisms of the region. • An alkali fusion–ICP-MS method using a lithium metaborate - lithium tetraborate composite flux (mass ratio = 33:67) was developed for analyzing coastal placer deposits and complex sedimentary samples. • The incorporation of a closed-system constant-temperature oscillation-assisted digestion technique offers a safer and more effective alternative to traditional open digestion methods. • The optimized method has detection limits ranging from 0.4 to 6.6 μg/g for ten major and trace elements, lower than the requirements in relevant standards. It shows high accuracy (RE ≤ 5.5 %) and precision (RSD ≤ 5.1 %) when validated with certified reference materials. • Elemental correlation analysis reveals strong positive correlations among Ti, Zr, and Hf ( r ≥ 0.94) and synergistic enrichment of Mn and V with major ore – forming elements ( r = 0.77–0.85), providing insights into the mineralization mechanisms of coastal placer systems.