FIG. 13. ¹⁸O vs. ¹³C diagram showing the field for carbonates from the Igarapé Bahia Fe oxide Cu-Au-(U-REE) deposit (Oliveira et al., 1998; Tazava, 1999) compared to carbonates from carbonatites, freshwater limestone, marine limestone, and the Olympic Dam deposit. The data are consistent with an association with alkaline rocks. Modified after Oreskes and Einaudi (1992).