Samarium-Neodymium and Rubidium-Strontium Isotopic Dating of Veined REE Mineralization for the Bayan Obo REE-Nb-Fe Deposit, Northern China

The Bayan Obo REE-Nb-Fe deposit in Inner Mongolia, China, consists of later REE-mineralizing fluorocarbonate veins cutting the earlier banded and massive ores in the deposit. Samarium-neodymium dating using the minerals including huanghoite and rubidium-strontium dating using single-grain biotites both from the later veins show concordant isochrons corresponding to 442 +/- 42 Ma (2 sigma uncertainty) and 459 +/- 41 Ma, respectively. The isochron ages suggest that the later REE vein mineralization took place during the middle Paleozoic at Bayan Obo, consistent with geological observations and age data previously reported.