Phosphorites, Co-rich Mn nodules, and Fe-Mn crusts from Galicia Bank, NE Atlantic: Reflections of Cenozoic tectonics and paleoceanography

A wide variety of marine mineral deposits were recovered from 750 to 1400 m water depths on Galicia Bank, Iberian margin. Mineral deposits include: (1) carbonate fluorapatite phosphorite slabs and nodules that replaced limestone and preserved original protolith fabric. (2) Ferromanganese vernadite c...

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Bibliographic Details
Published in:Geochemistry, Geophysics, Geosystems
Main Authors: González Sanz, Francisco Javier, Somoza Losada, Luis, Hein, James R., Medialdea Cela, Teresa, León Buendía, Ricardo F., Urgorri, Victoriano, Reyes Andrés, Jesús, Martín Rubí, Juan Antonio
Format: Other/Unknown Material
Language:English
Published: American Geophysical Union 2020
Subjects:
depósito mineral
carbonato
fosforita
fosfatación
Mioceno
ferromanganeso
depósito marino
mineralización
Arctic
Depósito
Pacific
Online Access:https://hdl.handle.net/20.500.12468/400
https://doi.org/10.1002/2015GC005861
Description
Summary:A wide variety of marine mineral deposits were recovered from 750 to 1400 m water depths on Galicia Bank, Iberian margin. Mineral deposits include: (1) carbonate fluorapatite phosphorite slabs and nodules that replaced limestone and preserved original protolith fabric. (2) Ferromanganese vernadite crusts with high Mn and Fe (Mn/Fe51) contents, and thick stratabound layers consisting mainly of Mn (up to 27% MnO) and Fe (15% Fe2O3), which impregnated and replaced the phosphorite. (3) Co-rich Mn nodules are composed of romanechite and todorokite laminae. Mn-rich layers (up to 58% MnO) contain up to 1.8% Co. (4) Goethite nodules with Fe up to 67% Fe2O3 have low Mn and trace metals. We interpret this mineralization paragenesis to be related to major changes in oceanographic and tectonic regimes. Three phosphatization generations formed hardgrounds dated by 87Sr/86Sr isotopes as late Oligocene, early Miocene, and latest early Miocene. During the latest early Miocene, the hardground was fractured and breached due to regional intraplate tectonism, which was coeval with a widespread regional erosional unconformity. The stratabound layers and Co-rich manganese nodules were derived from low-temperature geothermally driven hydrothermal fluids, with fluid conduits along reactivated faults. During middle and late Miocene, the introduction of vigorous deep water flow from the Arctic generated growth of hydrogenetic ferromanganese crusts. Finally, growth of diagenetic Fe-rich nodules (late Pliocene) was promoted by the introduction of hypersaline Mediterranean Outflow Water into the Atlantic Ocean. Instituto Geológico y Minero de España, España Estación de Bioloxía Mariña da Graña, Universidade de Santiago de Compostela, España Center of Geochronology and Isotopic Geochemistry Pacific Coastal and Marine Science Center Instituto Geológico y Minero de España, España Estación de Bioloxía Marina da Graña

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