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The Carajás Mineral Province in northern Brazil contains a variety of world-class (>100 Mt ore) iron oxide copper-gold (IOCG) deposits, including the only Archean examples of this deposit class (e.g., the Igarapé Bahia/Alemão and Salobo deposits). Tourmaline of schorldravite composition, a common gangue mineral in these deposits, precipitated shortly prior to and after the ore assemblage. A boron isotope study of texturally different tourmaline from three IOCG deposits (Igarapé Bahia, Salobo, and Sossego) using secondary ion mass spectrometry (SIMS) provides new evidence in the long-standing debate of magmatic versus non-magmatic sources for the high salinity (up to 50 wt% NaCl equiv.) of ore fl uids in these deposits. Values of δ 11 B from 14‰ to 26.5‰ for the Igarapé Bahia and Salobo deposits confi rm marine evaporite-derived brines in the ore fl uids, whereas lower δ 11 B values for the Igarapé Bahia deposit (5.8‰ to 8.8‰) suggest that these fl uids may have mixed with an isotopically different hydrothermal fl uid, or one that had a mixed boron source. More variable and isotopically lighter boron in tourmaline from the Sossego deposit (-8‰ to 11‰) is attributed to mixed sources, including light boron leached from felsic intrusive and volcanic host rocks, and heavy boron derived from marine evaporites. The boron isotope data indicate that the characteristic high salinity of the ore fl uids in the Carajás Mineral Province was acquired by the interaction of hydrothermal fl uids with marine evaporites. For IOCG deposits that contain tourmaline as a common gangue mineral, boron isotopes offer a valuable tool to constrain the high-salinity source problem, which is a critical issue in metallogenesis of IOCG deposits worldwide.

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The Paris Agreement established global ambitious targets for reducing carbon dioxide (CO 2 ) emissions, requiring the rapid and extensive development of low carbon technologies, and one of the most efficient is CO 2 geological storage. Among the deep geological formations used for CO 2 storage, the shale layers have been a new emerging field with higher efficiency because they are abundant and have a high content of organic matter that is favorable for CO 2 retention. However, one of the challenges in evaluating a location for potentials reservoirs is the adequate geological characterization and storage volume estimation. The study evaluates the Irati Formation of the Paraná Basin based on wireline logs information within Southeastern Brazil, where most stationary sources of carbon emissions are located. Three-dimensional (3D) implicit modeling techniques were applied not only for volume calculation purpose, but also in the site selection stage, generating thematic 3D models indicating thickness, depth, structures, and distance to aquifer systems. The limestones, shales, and black shales of the Irati Formation were locally grouped into six units considering the geological composition and spatial continuity. Based on the 3D model and reservoir parameters, the organic-rich shale Unit E with a theoretical capacity of 1.85 Gt is considerable for CO 2 storage. The estimated CO 2 storage capacity is promising because it is higher than the total CO 2 locally produced, and it could support the implantation of new projects in this region.