Tourmaline B-isotopes fingerprint marine evaporites as the source of high-salinity ore fluids in iron oxide copper-gold deposits, Carajás Mineral Province (Brazil)

Abstract

Research Article| September 01, 2008 Tourmaline B-isotopes fingerprint marine evaporites as the source of high-salinity ore fluids in iron oxide copper-gold deposits, Carajás Mineral Province (Brazil) Roberto Perez Xavier; Roberto Perez Xavier * 11Departamento de Geologia e Recursos Naturais, Instituto de Geociências, Universidade Estadual de Campinas, 13083-970 Campinas (SP), Brazil *E-mail: xavier@ige.unicamp.br. Search for other works by this author on: GSW Google Scholar Michael Wiedenbeck; Michael Wiedenbeck 22GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany Search for other works by this author on: GSW Google Scholar Robert B. Trumbull; Robert B. Trumbull 22GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany Search for other works by this author on: GSW Google Scholar Ana M. Dreher; Ana M. Dreher 33Companhia de Pesquisa de Recursos Minerais/Serviço Geológico do Brasil, Av. Pasteur 404, 22290-240 Rio de Janeiro (RJ), Brazil Search for other works by this author on: GSW Google Scholar Lena V.S. Monteiro; Lena V.S. Monteiro 11Departamento de Geologia e Recursos Naturais, Instituto de Geociências, Universidade Estadual de Campinas, 13083-970 Campinas (SP), Brazil Search for other works by this author on: GSW Google Scholar Dieter Rhede; Dieter Rhede 22GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany Search for other works by this author on: GSW Google Scholar Carlos E.G. de Araújo; Carlos E.G. de Araújo 11Departamento de Geologia e Recursos Naturais, Instituto de Geociências, Universidade Estadual de Campinas, 13083-970 Campinas (SP), Brazil Search for other works by this author on: GSW Google Scholar Ignacio Torresi Ignacio Torresi 11Departamento de Geologia e Recursos Naturais, Instituto de Geociências, Universidade Estadual de Campinas, 13083-970 Campinas (SP), Brazil Search for other works by this author on: GSW Google Scholar Geology (2008) 36 (9): 743–746. https://doi.org/10.1130/G24841A.1 Article history received: 02 Mar 2008 rev-recd: 16 May 2008 accepted: 10 Jun 2008 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Roberto Perez Xavier, Michael Wiedenbeck, Robert B. Trumbull, Ana M. Dreher, Lena V.S. Monteiro, Dieter Rhede, Carlos E.G. de Araújo, Ignacio Torresi; Tourmaline B-isotopes fingerprint marine evaporites as the source of high-salinity ore fluids in iron oxide copper-gold deposits, Carajás Mineral Province (Brazil). Geology 2008;; 36 (9): 743–746. doi: https://doi.org/10.1130/G24841A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Carajás Mineral Province in northern Brazil contains a variety of world-class (>100 Mt ore) iron oxide copper-gold (IOCG) deposits, including the only Archean examples of this deposit class (e.g., the Igarapé Bahia/Alemão and Salobo deposits). Tourmaline of schorl-dravite composition, a common gangue mineral in these deposits, precipitated shortly prior to and after the ore assemblage. A boron isotope study of texturally different tourmaline from three IOCG deposits (Igarapé Bahia, Salobo, and Sossego) using secondary ion mass spectrometry (SIMS) provides new evidence in the long-standing debate of magmatic versus non-magmatic sources for the high salinity (up to 50 wt% NaCl equiv.) of ore fluids in these deposits. Values of δ11B from 14‰ to 26.5‰ for the Igarapé Bahia and Salobo deposits confirm marine evaporite–derived brines in the ore fluids, whereas lower δ11B values for the Igarapé Bahia deposit (5.8‰ to 8.8‰) suggest that these fluids may have mixed with an isotopically different hydrothermal fluid, or one that had a mixed boron source. More variable and isotopically lighter boron in tourmaline from the Sossego deposit (−8‰ to 11‰) is attributed to mixed sources, including light boron leached from felsic intrusive and volcanic host rocks, and heavy boron derived from marine evaporites. The boron isotope data indicate that the characteristic high salinity of the ore fluids in the Carajás Mineral Province was acquired by the interaction of hydrothermal fluids with marine evaporites. For IOCG deposits that contain tourmaline as a common gangue mineral, boron isotopes offer a valuable tool to constrain the high-salinity source problem, which is a critical issue in metallogenesis of IOCG deposits worldwide. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.