Abstract

The Sossego iron oxide-copper-gold (IOCG) deposit is situated within the WNW-ESE-trending Canaã shear zone in the southern Copper belt, Carajás province, Brazil. The Sossego deposit consists of two major groups of orebodies (Sequeirinho-Pista-Baiano and Sossego-Curral). The Sequeirinho-Pista-Baiano orebodies are characterized by deep-emplaced magnetite-(apatite) and albite-actinolite-rich zones, whereas the Sossego-Curral orebodies have predominant potassic and chlorite alteration typical of shallow crustal levels. U-Pb (SHRIMP IIe and LA-ICPMS) geochronology on host rocks reveals Mesoarchean (3.08 Ga Xingu Complex, ca. 2.99 Ga Sequeirinho Granite and 2.97 Ga Pista felsic metavolcanic rock) and bimodal Neoarchean (ca. 2.74 Ga Sossego granophyric granite, Curral Granite and gabbronorite) units. Dating of hydrothermal monazite (U-Pb LA-MC-ICPMS) and molybdenite (Re-Os NTIMS) of the Sequeirinho-Pista orebodies rendered ages of ca. 2.71 to 2.68 Ga, while ore-related monazite of the Sossego-Curral orebodies yielded ages of ca. 1.90 to 1.88 Ga. The Neoarchean IOCG-forming events reflect coupling of ductile sinistral transpression with NNE–directed oblique shortening and Neoarchean magmatism (ca. 2.7 Ga). The shallow-emplaced Paleoproterozoic system, formed after progressive exhumation of the deep-emplaced Neoarchean IOCG deposits, coincides in age with the emplacement of 1.88 Ga A-type granites: the latter may have caused regional circulation of magmatic and externally derived fluids along crustal discontinuities, favoring copper-gold ore deposition as well as metallogenic diversity in the Carajás province (e.g., Sn, W, Au-Pd-Pt deposits).

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