Abstract
Archean carbonate rocks hosting sulphide-sulphate (anhydrite) phases are found in association with high-grade metamorphic rocks in the Caraiba Complex (central Bahia State, Brazil). The S-bearing rocks appear in drill-core samples in association with a meta-sedimentary (marble, calc-silicate, metapelite) sequence.δ18O values (+12‰ SMOW) are similar to those found in other Precambrian carbonates. δ13C values range from −6.5 to −12‰ PBD.A model for anhydrite genesis is not obvious. Low Fe levels, isotopic data and lithologic affinities with Archean carbonate sequences suggest the possibility of an evaporitic origin. Evidence of decarboxylation reactions and local accumulations of graphite suggest the possibility of sulphide formation by sulphate reduction. In any case, the extensive rôle of Archean life systems in the Caraiba paleoenvironment is evident.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
