Abstract
ABSTRACT The Lomagundi-Jatuli Event (LJE) is a significant positive δ13Ccarb anomaly in Paleoproterozoic carbonates globally. In the northeast São Francisco Craton (SFC), this event is documented in phosphorous (P)-rich marbles, along with subordinate graphite schists and iron formations, located in the Tanque Novo-Ipirá Complex (TNIC), Jacurici Valley (JV) and Rio Salitre Complex (RSC). Although the TNIC, JV, and RSC share comparable geological, geochronological, and mineralization characteristics, their connection and phosphogenic ties to the LJE are still uncertain. By combining new and reviewed C and O isotopes, cerium (Ce) anomalies relative to an array of rare earth elements, and yttrium (REY), we aim to constrain the paleoenvironmental conditions governing the phosphogenesis in the northeast SFC and its cause-and-effect relationship with the LJE. The Ce anomalies between 0.12 and 0.67 reveal a connection between the TNIC, JV, and RSC marbles and an oxic-suboxic shallow ocean influenced by detritus inflow. The remaining dataset links the carbonate protoliths to a continental margin of a paleocean and continental rift. Additionally, The positive δ13C excursions in the marbles, ranging from 5. 38 to 9.69‰, in conjunction with available geochronological data, indicate a maximum deposition age within 2.20 and 2.02 Ga. Our results indicate that the carbonate protoliths in the TNIC, JV, and RSC were deposited in similar paleoenvironmental conditions during the Paleoproterozoic. During this time, factors such as elevated oxygen levels, oceanic primary paleoproductivity, and organic matter burial played a crucial role in determining P supply, precipitation, and accumulation. These factors ultimately led to the positive δ13C excursions observed in the SFC, which are consistent with marine carbonates found around the world towards the end of the LJE.
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