Neoarchean A-type granitoids from Carajás province (Brazil): New insights from geochemistry, geochronology and microstructural analysis

On the origin of oldest Iron-Oxide-Copper-Gold (IOCG) deposits at the transition from Archean drip to plate tectonics

“…Comparison of empirical melting relations with modelled P-T conditions in the lithosphere during extension indicates that large volumes of magma may be produced by decompressional partial melting of melt-metasomatized mantle during the earliest stages of extension in localized rift basins [39,40]. These melts would pond at the base of the Itacaiúnas shear belt and ascend to generate the ma c-ultrama c rocks of the CMP and the Carajás basin, while the heat transferred by such underplating would favour melting at the base of the previous TTG proto-continent, yielding coeval syn-kinematic [20] A-type granites with ancient Hf-isotope signatures. Transport of the Cu and REE to into IOCG mineralization is commonly attained by chloride complexes [41,42].…”

“…represented by TTG-greenstone belt associations, with minor sanukitoids and K-rich granitoids [17,18,19,20]; ii) the Carajás basin composed of a meta-volcanosedimentary sequence, including thick Superior-type BIFs coeval with the intrusion of A-type granitoids and layered ma cultrama c complexes (2.78-2.72 Ga), alkaline high-K intrusions (c. 2.56 Ga) and younger low-grade siliciclastic cover rocks [21,22]; and iii) widespread Paleoproterozoic (c. 1.88 Ga) A-type intrusions [23] (Fig. 1).…”

“…The dome-and-keel terrane is bound to the north by a high-to low grade 200-km wide anastomosing set of E-W to ESE-WNW strike-slip shear zones and faults (Itacaiúnas shear belt) developed around 2.85 Ga. This shear belt was later reactivated by sinistral motion at the time of development of Carajás basin at 2.78-2.72 Ga, accompanied by the intrusion of syn-kinematic A-type granites [20,28,29].…”

“…They have been affected by intense proximal K-Fe and distal Na-Ca hydrothermal alteration with late-stage chlorite and carbonates, associated with hypersaline uids (250°-570°C) and late sulphide deposition with different sul dation states [30]. Geochronology points to two main IOCG mineralization events at 2.75-2.68 Ga and 2.62-2.50 Ga [31], the rst associated with reactivated regional shear zones and syn-kinematic intrusions of A-type granitoids [20] and the later to a second reactivation stage accompanied by minor alkaline high-K granitoids [32].…”

Integrated Geochemical Assessment of Soils and Stream Sediments to Evaluate Source-Sink Relationships and Background Variations in the Parauapebas River Basin, Eastern Amazon

“…Rio Maria-Sapucaia-Canaã dos Carajás domains (RM-S-CC): It is restricted to the south of PB (Figure 1d), and is composed essentially of Mesoarchean tonalitetrondhjemite-granodiorite (TTG) series associated with greenstone belt sequences and calc-alkaline granites to tonalites and sanukitoids [25][26][27][28]. Neoarchean A-type like granitoids, charnockitic rocks, mafic-ultramafic bodies, and Paleoproterozoic anorogenic granites crosscut the Mesoarchean units [25,[29][30][31][32][33].…”