Barite-hosted Ba isotope compositions (δ¹³⁸Ba) have been advocated as a novel proxy to trace marine export productivity. However, barites in sediments could be re-dissolved under the sulfate-deficient anoxic conditions, raising the uncertainty on the application of barite-hosted δ¹³⁸Ba. Thus, it is necessary to investigate diagenetic effects on δ¹³⁸Ba in barites. Here, we present δ¹³⁸Ba data, together with the published Sr and S isotope data, in diagenetic barites that are hosted in the black shales of the Lower Cambrian Yurtus Formation in Tarim Basin, NW China.
The δ¹³⁸Ba values vary from -0.15‰ to 0.50‰, with an average of 0.17±0.29‰. The significantly elevated δ³⁴S values (56.8–76.4‰) suggest that the barite-sulfate may have experienced enhanced microbial sulfate reduction without renewal. The lack of the relationship between δ¹³⁸Ba and δ³⁴S, however, suggests the renewal of Ba in pore waters. Considering the positive correlation between the δ¹³⁸Ba and ⁸⁷Sr/⁸⁶Sr ratios (0.7083 to 0.7090), we proposed that the Ba in pore waters could be modified by the penecontemporaneous seawater that weakly interacted with the host fine-grained siliciclastic sediments.
 

Diagenetic Effect,barites,Ba isotope composition