Composition and Origin of Ferromanganese Crusts from Equatorial Western Pacific Seamounts |
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| Authors: | WANG Guozhi;JANSA Luba;CHU Fengyou;ZOU Can;SUN Guosheng;State |
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| Institution: | WANG Guozhi;JANSA Luba;CHU Fengyou;ZOU Can;SUN Guosheng;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology;Department of Earth Sciences, Dalhousie University;Key Laboratory for Geosciences,State Oceanic Administration;Chengdu University of Technology;College of Earth Sciences, Jilin University; |
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| Abstract: | In the equatorial western Pacific, iron-manganese oxyhydroxide crusts(Fe-Mn crusts) and nodules form on basaltic seamounts and on the top of drowned carbonate platform guyots that have been swept free of pelagic sediments. To date, the Fe-Mn crusts have been considered to be almost exclusively of abiotic origin. However, it has recently been suggested that these crusts may be a result of biomineralization. Although the Fe-Mn crust textures in the equatorial western Pacific are similar to those constructed by bacteria and algae, and biomarkers also document the existence of bacteria and algae dispersed within the Fe-Mn crusts, the precipitation, accumulation and distribution of elements, such as Fe, Mn, Ni and Co in Fe-Mn crusts are not controlled by microbial activity. Bacteria and algae are only physically incorporated into the crusts when dead plankton settle on the ocean floor and are trapped on the crust surface. Geochemical evidence suggests a hydrogenous origin of Fe-Mn crusts in the equatorial western Pacific, thus verifying a process for Fe-Mn crusts that involves the precipitation of colloidal phases from seawater followed by extensive scavenging of dissolved trace metals into the mineral phase during crust formation. |
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