Tracing Fluid Sources for the Salobo and Igarape Bahia Deposits: Implications for the Genesis of the Iron Oxide Copper-Gold Deposits in the Carajas Province, Brazil

Autor(es)

de Melo, Gustavo H. C. ^[1] ; Monteiro, Lena V. S. ^[2] ; Xavier, Roberto P. ^[3] ; Moreto, Carolina P. N. ^[3] ; Santiago, Erika ^[2]

Afiliação do(s) autor(es)

^[1] Fed Univ Ouro Preto UFOP, Dept Geol, Morro Cruzeiro Campus Morro Cruzeiro S-N, BR-35400000 Ouro Preto, MG - Brazil

^[2] Univ Sao Paulo, Inst Geosci, Rua Lago 562, BR-05508080 Sao Paulo, SP - Brazil

^[3] Univ Estadual Campinas, UNICAMP, Inst Geosci, R Joao Pandia Calogeras 51, BR-13083870 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: ECONOMIC GEOLOGY; v. 114, n. 4, p. 697-718, JUN 2019.
• Citações Web of Science: 0

Resumo

The Salobo and Igarape Bahia iron oxide copper-gold (IOCG) deposits stand out as economically important deposits in the Carajas Province. Whereas granitoids and gneisses host the Neoarchean Salobo deposit, the Igarape Bahia deposit occurs in volcanic rocks and associated sedimentary sequences. Paragenetic evolution of the IOCG alteration-mineralization evidences higher temperature conditions at Salobo (almandine-grunerite-biotite-magnetite) than at Igarape Bahia (tourmaline-carbonate-magnetite-chlorite). At Salobo, iron enrichment at 565 degrees +/- 50 degrees C was accompanied by hydrothermal fluids with magmatic or metamorphic compositions, as evidenced by grunerite (delta O-18(H2O) = 7.20-8.50 parts per thousand, delta D-H2O = -25.33 to -16.01 parts per thousand), garnet ((delta O-18(H2O) = 7.10-9.70 parts per thousand), and tourmaline ((delta O-18(H2O) = 5.07-7.37 parts per thousand, (delta D-H2O = -32.13 to + 11.60 parts per thousand). Fluids associated with potassic alteration at 565 degrees +/- 50 degrees C also have a typical magmatic/metamorphic composition, indicated by biotite (delta O-18(H2O) = 7.23-8.03 parts per thousand, delta D-H2O = -40.94 to -25.94 parts per thousand) and quartz (delta O-18(H2O) = 7.52 parts per thousand). Sulfur isotope signatures for chalcopyrite (0.81-1.28 parts per thousand) and bornite (-0.37 to + 1.63 parts per thousand) suggest a magmatic sulfur source at Salobo. For the Igarape Bahia deposit, fluids associated with tourmaline display magmatic or metamorphic signatures (delta O-18(H2O) = 5.07-7.37 parts per thousand, delta D-H2O = -34.02 to -19.74%, at 330 degrees +/- 50 degrees C), but those associated with calcite (delta O-18(H2O) = 1.68-3.10 parts per thousand, 330 degrees +/- 50 degrees C) and chlorite (delta O-18(H2O) = 1.92-3.20 parts per thousand, delta D-H2O = -57.36 to -21.34 parts per thousand, 255 degrees +/- 50 degrees C) evidence the input of O-18-depleted fluids. delta O-13(H2O) values (-9.32 to -4.93 parts per thousand) for fluids in equilibrium with calcite also imply magmatic sources. Our data indicate that the main source of the ore-forming fluids for Salobo was derived from exsolved magmatic brines associated with crystallization of the coeval ca. 2.5 Ga granites. In contrast, though the early fluids at Igarape Bahia were also magmatic-hydrothermal, the influx of O-18-depleted formation water was prominent during the later stages of ore genesis. (AU)

• Processo FAPESP: 16/13162-7 - Evolução geoquímica e isotópica de sistemas cupríferos neoarqueanos e paleoproterozoicos da Província Carajás, PA
• Beneficiário: Roberto Perez Xavier
• Modalidade de apoio: Auxílio à Pesquisa - Regular