C-, Sr-isotope and Hg chemostratigraphy of Neoproterozoic cap carbonates of the Sergipano Belt, Northeastern Brazil

Mercury concentrations in carbonates of the Jacoca, Olhos D'Agua and Acauã formations are usually much higher than those observed in carbonates deposited not concomitantly with volcanic activities (<3 ng g−1). They are, in fact, similar to those in carbonates deposited during volcanic activity (e.g. Tertiary Punta Rocallosa carbonates in Chile), with concentration values between 20 and 80 ng g−1, suggesting that CO2 in the basal portion of these carbonate formations is mostly mantle-derived, accumulated in the atmosphere during Cryogenian-Ediacaran glacial events.