Comprehensive Sr-Nd Isotopic Analysis of Deep Sea Ferro-manganese Oxide Reference Materials by ID-TIMS and MC-ICP-MS

Strontium and Neodymium isotopes of deep-sea ferro-manganese （Fe-Mn） oxides are valuable geochemical fingerprints to identify metal sources and reconstruct their formation processes. However， the reference materials for deep-sea Fe-Mn oxides Sr and Nd isotope analysis have not been systematically investigated， which hinders the comparison of data quality across different laboratories. Here， we measured Rb， Sr， Sm， and Nd mass fractions and Sr-Nd isotope ratios of five powdered Fe-Mn nodule and crust reference materials， including manganese nodules GBW07295-07296 （GSPN-2～3） and cobalt-rich crusts GBW07337-07339 （GSMC-1～3） from China using isotope dissolution thermal ionization mass spectrometry （ID-TIMS）. The Sr-Nd isotopic homogeneity of NOD-A-1 and NOD-P-1 from the United States Geological Survey （USGS）， as well as JMn-1 from the Geological Survey of Japan （GSJ）， is also re-examined in this study. With a sample size of 50 mg， the internal precision on Sr-Nd isotope ratios of eight reference materials is better than 10 ppm （2SE）， and external precision of ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd is less than 30 ppm （2SD）. This study systematically reports Sr-Nd isotopic data of five Chinese reference materials for the first time， providing a new database for geochemical evaluation of Sr-Nd system in Fe-Mn oxide reference materials.