Vanadium isotope compositions (δ(51V)) in marine
carbonates are a potential proxy to trace global redox states of ancient
oceans. Although high-precision δ(51V) analyses are
available for many geological materials, carbonate-hosted δ(51V) data have not been reported yet due to extremely high
matrix elements and low V contents (generally below 10 μg g–1). In this study, we developed an Fe coprecipitation
method combined with an Fe column to preconcentrate V from the major
matrix elements and subsequent four-step chromatographic procedures
to further purify V in carbonates. The δ(51V) values
were measured using a sample–standard bracketing method by
MC-ICP-MS. The robustness of this method was assessed by analyzing
element-doped and matrix-spiked synthetic carbonate solutions containing
an in-house δ(51V) standard, USTC-V. The mean δ(51V) value of the synthetic carbonate solutions (0.06 ±
0.08‰; 2SD, n = 33) is in good agreement with
the recommended value of the USTC-V relative to the Oxford AA solution
(0.07 ± 0.08‰; 2SD, n = 347). In addition,
the consistency in the δ(51V) value of the igneous
carbonatite standard, COQ-1, which was processed in parallel with
the whole purification (−0.48 ± 0.04‰; 2SD, n = 3) and a four-step chromatographic procedure (−0.43
± 0.08‰; 2SD, n = 3), further validates
the robustness of our method. For the first time, we obtained δ(51V) values of four carbonate reference materials: JDo-1, −0.56
± 0.09‰ (2SD, n = 27); JLs-1, −0.61
± 0.14‰ (2SD, n = 33); GBW07217a, −0.79
± 0.09‰ (2SD, n = 6); GBW07214a, −0.51
± 0.13‰ (2SD, n = 48). The long-term
external precision of carbonate-hosted δ(51V) analyses
is better than ±0.14‰ (2SD). Our method can be applied
to measure carbonate-hosted δ(51V) to trace the evolution
in global marine redox states throughout the Earth’s history.