Chen et al. (2018) developed the precision of the measurement of uranium isotope with ±0.02‰, that is much higher than ±0.10‰ for conventional uranium isotopic analyses.
The high precision enabled the authors to conduct an experiment to reveal a difference of uranium isotopic fractionation between biogenic carbonate and non-biogenic carbonate.
They revealed that the fractionation of the biogenic carbonate (0.00 to 0.09 ‰) was slightly smaller than that of non-biogenic carbonate (ca. 0.10‰).