Metallogenesis of the orosirian epithermal coringa gold-silver (Cu-Pb-Zn) deposit, southeastern Tapajós mineral Province, Amazonian craton, Brazil

Gold in Paleoproterozoic (2.1 to 1.77 Ga) Continental Magmatic Arcs at the Tapajós and Juruena Mineral Provinces (Amazonian Craton, Brazil): A New Frontier for the Exploration of Epithermal–Porphyry and Related Deposits

“…HS = Field of high-sulfidation hydrothermal fluids; LS = Low-sulfidation fluids, and T = Alunite of the 1.87 Ga Tapajós high-sulfidation fluid. Data source: [this paper, [8,15,20,35,62,76,100,101]]. Nine 40 Ar-39 Ar spectra for alunite yield ages between 1869 ± 2 Ma and 1846 ± 2 Ma.…”

“…Adularia-sericite (Figure 4H), argillic, and carbonate alteration zones represent the Au-Ag-(Cu-Pb-Zn) mineralization locus. A hematite-chlorite alteration was considered a proximal halo by [35,104] or a distal alteration [104].…”

“…Ore zones include stockworks, sulfide-quartz veins controlled by brittle structures, commonly with comb, banded, crustiform, colloform, and brecciated textures, rare massive sulfide zones, and disseminated sulfides [26]. The main ore minerals are pyrite (Figure 4I), chalcopyrite, Fe-poor sphalerite, galena (Figure 4J), native silver, and gold, electrum (27 to 30% Ag; [35]), and minor digenite, bornite, argentite, tennantite, and secondary covellite and acanthite [26]. The gold content in veins decreases in-depth and outwards rhyolitic domes, similar to observed in typical epithermal veins [106].…”

“…Aqueous and aqueous-carbonic fluids have been interpreted as of meteoric and magmatic origin, respectively (Figure 6A) [35]. The oxygen isotope composition of fluids in equilibrium with quartz, sericite, and calcite (δ 18 O H2O = −1.8 to 9.8‰, at 400 to 234 • C) points to mixing between magmatic and meteoric fluids [35] (Figure 5A). The δD H2O values (−92‰) estimated from the sericite could reflect vapor influence or extensive magma degassing.…”

“…The discovery of a well-preserved high-sulfidation epithermal gold mineralization associated with 1.88 Ga calc-alkaline volcanic rocks by Rio Tinto company [12][13][14][15][16] and porphyry-like gold systems [17][18][19][20] opened the possibility for the occurrence of large Paleoproterozoic gold and Cu-Mo deposits in both provinces, as proposed by [21]. In the following years, due to academic research and mineral exploration programs, several epithermal (low-, intermediate-and high-sulfidation) occurrences related to calc-alkalic and alkalic porphyry-like mineralization, sometimes with Au, Cu or Mo, were identified in both provinces [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. This expands the perspectives for the existence of magmatichydrothermal high-grade epithermal and large porphyry-like deposits.…”