Carajas Mineral Province - Example of metallogeny of a rift above a cratonic lithospheric keel

摘要

The Caraj ' as Mineral Province (CMP) is located on the southeastern margin of the Amazonian Craton, in northern Brazil. It is the largest producer of high-grade iron ore and a major world supplier of copper, nickel, manganese and gold. This article presents the CMP as a product of oblique rift evolution (2.76-2.06 Ga) controlled by the Canaa similar to and Cinzento strike slip system. The Caraj ' as rift is hosted in the tonalite-trondhjemite-granodiorite (TTG)greenstone Rio Maria terrains (3.0-2.85 Ga). It overlies a subcratonic lithospheric mantle (SCLM) keel as indicated by seismic tomography and is filled by the Caraj ' as plutonic-volcanic sedimentary sequences (CPVSS) that host the CMP. The rifting stage (Gra similar to o Par ' a Group) began with intense tholeiitic fissure volcanism with basalt and rhyolite flows, coeval intrusions of alkali granites and mafic-ultramafic bodies, BIFs, shales and restricted tuff beds. The Azul and ' Aguas Claras Formations consist mainly of shales and sandstones deposited during the sag stage. The calc-alkaline signature of the Gra similar to o Par ' a metavolcanic rocks was demonstrated to reflect the composition of the melted TTG basement. The high magnesium and platinum-group elements (PGE) contents of Puma and Onca mafic-ultramafic complexes indicate extensive partial fusion, conditions that are indicative of a plume origin. We are proposing that CMP's IOCG deposits were formed from saline carbonate fluids exsolved from deep-seated metasomatic mantellic magmas (MMM), channelled and concentrated along jogs and step-overs in strike-slip fault systems in the Caraj ' as rift. The CMP comprises three main ore-forming stages: (1) a plume stage, ca. 2.76-2.73 Ga, creating supergiant exhalative sedimentary biogenic Fe deposits (Serra Norte, Serra sul and Serra Leste), syngenetic exhalative Cu-Au-Zn (Pojuca deposit), exhalative Mn (Antonio Vicente), Ni-PGE-reef deposits in a magma mixing zone of layered intrusions (e.g. Luanga deposit), and Siqueirinho IOCG deposit; (2) a metasome stage including crustal extension and mantle flash melting (60-100 km depth), ca. 2.68-2.50 Ga, forming the most important IOCG deposits like Salobo, Alema similar to o and Igarape ' Bahia. and (3) a sag stage, ca. 2.68-2.06 Ga, with sedimentary Mn deposited in a redox-controlled stratified oceanic environment. The deposits related to granitic intrusion, ca. 1.88 Ga, with Cu-(Au-Mo-W-Sn) greisen (Breves deposit) and Cu-(Au-Mo-F) veins (Gameleira and Alvo 118 deposits) are associated with the A-type magmatism that affected the entire central Amazonian Craton. These deposits are, in contrast, related to an intracratonic silicic large igneous province (SLIP) and have no relation to the Archean Caraj ' as cratonic lithosphere keel rift evolution. The CMP is directly related to the thinning of the lithosphere above a mantle plume, beneath a sub-continental lithospheric mantle (SCLM) keel.