Volcanogenic features of IOCG deposits of North Carajás, Brazil, and related constraining evidence by Ana Maria Dreher, Sérgio Martini

“…The features include hosting tectonic and geological settings with coeval granitic and mafic heat sources; evidence of syndepositional faulting, exemplified by intraformational fragmental rocks; attending hydrothermal alteration represented by extensive Na-Ca, spilitic and chloritic alteration along with deposit-scale magnesian (chlorite, dalmatianite), potassic (biotite) and aluminous (andalusite, sillimanite) products; strata-bound morphology, with ore hosted in banded oxide-silicate facies iron-formations and debris flow breccia bodies located at eruptive breaks, where quiescent waning volcanic conditions favorable to ore deposition prevail; and near-deposit exhalites, for instance, oxide iron-formation, metachert and laminated quartz-amphibole-tourmaline-garnet rocks, that may extend laterally away from the deposits constituting ore-equivalent horizons. …”
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