Metallogenetic systems associated with granitoid magmatism in the Amazonian Craton: An overview of the present level of understanding and exploration significance

Abstract

The Amazonian Craton hosts world-class metallogenic provinces with a wide range of styles of primary precious, rare, base metal, and placer deposits. This paper provides a synthesis of the geological database with regard to granitoid magmatic suites, spatio temporal distribution, tectonic settings, and the nature of selected mineral deposits. The Archean Carajas Mineral Province comprises greenstone belts (3.04 2.97 Ga), metavolcanic-sedimentary units (2.76-2.74 Ga), granitoids (3.07-2.84 Ga) formed in a magmatic arc and syn-collisional setting, post-orogenic A(2)-type granites as well as gabbros (ca. 2.74 Ga), and anorogenic granites (1.88 Ga). Archean iron oxide-Cu-Au (IOCG) deposits were synchronous or later than bimodal magmatism (2.74-2.70 Ga). Paleoproterozoic IOCG deposits, emplaced at shallow-crustal levels, are enriched with Nb-Y-Sn-Be-U. The latter, as well as Sn-W and Au-EGP deposits are coeval with ca. 1.88 Ga A(2)-type granites. The Tapajos Mineral Province includes a low-grade meta-volcano-sedimentary sequence (2.01 Ga), tonalites to granites (2.0-1.87 Ga), two talc-alkaline volcanic sequences (2.0-1.95 Ga to 1.89-1.87 Ga) and A-type rhyolites and granites (1.88 Ga). The talc-alkaline volcanic rocks host epithermal Au and base metal mineralization, whereas Cu-Au and Cu-Mo +/- Au porphyry-type mineralization is associated with sub-volcanic felsic rocks, formed in two continental magmatic arcs related to an accretionary event, resulting from an Andean-type northwards subduction. The Alta Floresta Gold Province consists of Paleoproterozoic plutono-volcanic sequences (1.98-1.75 Ga), generated in ocean ocean orogenies. Disseminated and vein-type Au +/- Cu and Au + base metal deposits are hosted by calc-alkaline I-type granitic intrusions (1.98 Ga, 1.90 Ga, and 1.87 Ga) and quartz-feldspar porphyries (ca. 1.77 Ga). Timing of the gold deposits has been constrained between 1.78 Ga and 1.77 Ga and linked to post-collisional Juruena arc felsic magmatism (e.g., Colider and Teles Pires suites). The Transamazonas Province corresponds to a N-S-trending orogenic belt, consolidated during the Trans amazonian cycle (2.26-1.95 Ga), comprising the Lourenco, Amapa, Carecuru, Bacaja, and Santana do Araguaia tectonic domains. They show a protracted tectonic evolution, and are host to the pre-, syn-, and post-orogenic to anorogenic granitic magmatism. Gold mineralization associated with magmatic events is still unclear. Greisen and pegmatite Sn-Nb-Ta deposits are related to 1.84 to 1.75 Ga late-orogenic to anorogenic A-type granites. The Pitinga Tin Province includes the Madeira Sn-Nb-Ta-F deposit, Sn-greisens and Sn-episyenites. These are associated with A-type granites of the Madeira Suite (1.84 -1.82 Ga), which occur within a cauldron complex (Iricoume Group). The A-type magmatism evolved from a post-collisional extension, towards a within-plate setting. The hydrothermal processes (400 degrees C 100 degrees C) resulted in albitization and formation of disseminated cryolite, pyrochlore columbitization, and formation of a massive cryolite deposit in the core of the Madeira deposit. The Rondonia Tin Province hosts rare-metal (Ta, Nb, Be) and Sn-W mineralization, which is associated with the Sao Lourenco-Caripunas (131-1.30 Ga), related to the post-collisional stage of the Rondonia San Ignacio Province (1.56-1.30 Ga), and to the Santa Clara (1.08-1.07 Ga) and Younger Granites of Rondonia (0.99-0.97 Ga) A type granites. The latter are linked to the evolution of the Sunsas-Aguapel Province (1.20-0.95 Ga). Rare metal polymetallic deposits are associated with late stage peraluminous granites, mainly as greisen, quartz vein, and pegmatite types. (C) 2015 Elsevier Ltd. All rights reserved.