The Santa Lúcia Cu-Au deposit, Carajás Mineral Province, Brazil: a Neoarchean (2.68 Ga) member of the granite-related copper-gold systems of Carajás

The Santa Lucia copper-gold deposit lies in the southeastern portion of the Carajas Mineral Province, along NW-SE splays of the Carajas Fault. The deposit is hosted by a rhyolitic subvolcanic rock, which is crosscut by pegmatite intrusions. The paragenetic evolution at Santa Lucia encompasses an early stage of chlorite alteration, followed by potassic alteration with microcline, greisenization (quartz-muscovite-tourmaline), copper-gold ore precipitation, and late sericite and hematite vein formation/fracture infill. Copper mineralization is dominantly represented by chalcopyrite-sphalerite-pyrrhotite-pentlandite-pyrite breccias, which are spatially associated with greisen alteration and characterized by the enrichment of light rare earth elements (LREE), Ni, Co, and Cr. The alteration types, mineralization styles, and ore assemblage suggest that the Santa Lucia deposit could represent a member of the Paleoproterozoic (ca. 1.88 Ga) granite-related copper-gold systems of Carajas (e.g., the Breves and Estrela deposits). However, the in situ U-Pb analyses of ore-related monazite yield a weighted average 207Pb/206Pb age of 2688 ± 27 Ma, thereby constraining the timing of mineralization at Santa Lucia to the Neoarchean. Moreover, tourmaline from the pegmatite and within the ore zones has a range of δ11B values from − 3.7 to − 0.6‰, therefore linked to a magmatic boron source. Collectively, these results indicate that the Santa Lucia deposit is the first reduced magmatic-hydrothermal, iron oxide–poor system formed in the Neoarchean, coeval with the 2.72–2.68 Ga metallogenic event responsible for the genesis of important iron oxide copper-gold (IOCG) deposits in the Carajas Mineral Province.