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Metalliferous deposits from the Apennine ophiolites: Mesozoic equivalents of modern deposits from oceanic spreading centers

1976; Geological Society of America; Volume: 87; Issue: 1 Linguagem: Inglês

10.1130/0016-7606(1976)87 2.0.co;2

1943-2674

Enrico Bonatti, Marco Zerbi, Robert W. Kay, H. Rydell,

Geology and Paleoclimatology Research

Research Article| January 01, 1976 Metalliferous deposits from the Apennine ophiolites: Mesozoic equivalents of modern deposits from oceanic spreading centers ENRICO BONATTI; ENRICO BONATTI 1Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar MARCO ZERBI; MARCO ZERBI 2Istituto di Petrografia, Università di Parma, Parma, Italy Search for other works by this author on: GSW Google Scholar ROBERT KAY; ROBERT KAY 1Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar HAROLD RYDELL HAROLD RYDELL 3Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida 33146 Search for other works by this author on: GSW Google Scholar Author and Article Information ENRICO BONATTI 1Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 MARCO ZERBI 2Istituto di Petrografia, Università di Parma, Parma, Italy ROBERT KAY 1Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 HAROLD RYDELL 3Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida 33146 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1976) 87 (1): 83–94. https://doi.org/10.1130/0016-7606(1976)87 2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation ENRICO BONATTI, MARCO ZERBI, ROBERT KAY, HAROLD RYDELL; Metalliferous deposits from the Apennine ophiolites: Mesozoic equivalents of modern deposits from oceanic spreading centers. GSA Bulletin 1976;; 87 (1): 83–94. doi: https://doi.org/10.1130/0016-7606(1976)87 2.0.CO;2 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 SocietyGSA Bulletin Search Advanced Search Abstract Northern Apennines ophiolite complexes, consisting of peridotite-gabbro-basalt assemblages overlain by chert of Late Jurassic age, are probably fragments of oceanic crust created at a Mesozoic spreading center. Metalliferous sedimentary deposits are found at the base of the chert formation, close to the basalt-chert contact. The main mineral component of these deposits is braunite; the deposits are rich in Mn and contain less than 1 percent Fe; no equivalent Fe-rich sedimentary rocks have been observed. The geochemistry of the minor transition metals, of the rare-earth elements, Ba, U, and Th in these deposits, as well as their stratigraphic position, indicate that they are not similar to "hydrogenous" ferromanganese deposits from modern oceans; they instead show affinities to metalliferous deposits of hydrothermal origin associated with modern spreading centers. Fe-Cu-Zn-sulfide deposits are common in basalt of the Apennine ophiolite and are often close to the metalliferous sedimentary rocks. The metalliferous sedimentary rocks and the metal sulfide mineralizations probably originated as a result of the mobilization of metals from basalt during circulation of thermal waters in the basaltic-gabbroic crust close to a Mesozoic spreading center. Upper mantle volatiles may have provided additional metals to the thermal waters. The sulfide deposits formed during the subbottom convective circulation, whereas the manganiferous sediment originated from precipitation of the metals after discharge of the thermal solutions through the sea floor. Extensive metal fractionation may have occurred during the sub-bottom circulation, especially during deposition of the sulfide phases; the lack of Fe in the metalliferous sedimentary rocks may be due to such fractionation. This model can be applied to associations of sulfide ore and metalliferous sedimentary deposits in other ophiolitic complexes of various ages and to metallogenesis in modern spreading centers. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.