The Ce isotopic composition of the upper continental crust constraints from loess and granites

Stable isotopic composition of Cerium (Ce), a refractory, incompatible, and redox-sensitive element, provides a powerful tracer for continental weathering processes. However, the average δ 142/140 Ce value of the upper continental crust (UCC) remains poorly constrained. Here, we report Ce isotopic data of characterized upper crustal samples, including granitic rocks with distinct sources (I, A, and S-type) and loess, to constrain the Ce isotopic composition (expressed as δ 142/140 Ce relative to the NIST SRM 3110 standard) of the UCC. Despite SiO 2 contents varying from 64 % to 77 %, I and S-type granites in SE China show indistinguishable δ 142/140 Ce values (−0.018 ‰–0.057 ‰ and 0.008 ‰–0.045 ‰), while A-type granites exhibit a small but detectable variation relative to the analytical precision (±0.040 ‰). These granites have experienced fractional crystallization, but the δ 142/140 Ce values show no correlation with geochemical indices (CaO/Al 2 O 3 , Eu/Eu∗, P 2 O 5 ), and without correlation was observed with La/Sm (N) , Nb/Y, Isr and εNd(t), indicating that the influences of source heterogeneity, partial melting, and magmatic crystallization are negligible. The δ 142/140 Ce values in loess range from −0.027 ‰ to 0.073 ‰, showing limited variations. Moreover, the δ 142/140 Ce of loess shows no correlation with chemical weathering, mineral sorting, and sample locations, confirming its representativeness of the average UCC. These results show that the stable Ce isotopic composition of UCC is relatively uniform. Based on the lithology-weighted average method, the δ 142/140 Ce value of UCC is 0.017 ± 0.026 ‰.