Comment on Evaporitic carbonates in the pre-salt of Santos Basin-Genesis and tectonic implications

Based on petrography, mineralogy, facies analysis and geochemical data Farias et al. (2019) suggested that syndepositional hydrothermal fluids generated in part by mantle serpentinisation and seepage of brines through the Walvis Ridge-Rio Grande Rise sourced the South Atlantic basins, which resulted in the deposition of the Barra Velha carbonates in the Santos Basin, focus of their study. However, they seek support for this hypothesis in clumped isotope data, which does not unequivocally provide evidence for this interpretation. Furthermore, they presented significantly radiogenic Sr-87/Sr-86 data, which in turn do not give support for the inference of significant mantle-derived fluid sources. Therefore, their hypotheses should be carefully reconsidered.

Automated summary

The study suggests that sediments in the South Atlantic basins may have been influenced by hydrothermal fluids, but the current evidence is not sufficient to definitively support this hypothesis, therefore further scrutiny is needed.