Spectroscopic Insights Into Ferromanganese Crust Formation and Diagenesis

Abstract

Marine ferromanganese deposits, including both crusts and nodules, form in all five global ocean basins at almost every latitude (Cronan, 1977; Hein et al., 1997, 2000). Ferromanganese deposits have classically been categorized into one of three groups based on mode of formation and trace element associations: hydrogenetic deposits, diagenetic deposits, and hydrothermal deposits. Hydrogenetic ferromanganese deposits precipitate in direct contact with the water column on the surface of a substrate rock or existing crust or nodule

Enrichment Characteristics and Mechanisms of Critical Metals in Marine Fe-Mn Crusts and Nodules: A Review

“…Specifically speaking, the metal enrichments through a micro-perspective were commonly interpreted to explain how metals enrich into the layered or tunneled constituents of Fe-Mn crusts and nodules on an atomic scale [13,20,105,106]. Oceanic Fe-Mn crusts and nodules mainly consist of layered vernadite, buserite and 3-D tunneled todorokite, which are made up of octahedral MnO 6 nano-units and amorphous FeOOH that are intergrown with the Mn oxides [10,16,[107][108][109]. The MnO 6 octahedrons comprise the Mn layer and the Mn tunnel structures, and they facilitate many isomorphic substitutions through Mn 4+ or Mn 3+ replacements and exhibit many vacant sites in the structures, i.e., unfilled empty octahedrons in the layer that attracts metal fillings [13,14,105,110,111].…”

“…Hydrogenetic and diagenetic crusts and nodules have a slow growth rate, as low as 1-10 mm/Ma, which provides sufficient durations for metal enrichments; they also have the unique physical properties of low bulk density (mean of 1.3 g/cm 3 dry bulk), large specific surface area (mean of 325 m 2 g −1 ) and high porosity (mean of 60%) [2,3,[7][8][9]. Fe-Mn nodules and crusts show dominant mineralogical compositions of vernadite, birnessite, buserite, asbolan, todorokite and amorphous Fe oxyhydroxides [5,[10][11][12]. They are considered representative oceanic Fe-Mn minerals that exhibit abundant interlayers, tunnels and layers, with many vacancies for the incorporation of high amounts of metals [13][14][15][16].…”

Cobalt: A must-have element for life and livelihood

“…However, even today, Co can be found in high-temperature hydrothermal precipitates comprising the so-called Black Smoker chimneys, and from thence disperses to also precipitate in deep sea manganese–iron nodules ( 9 ). One of the mineral hosts in these nodules is the mineral green rust, or fougerite ( 10 ). Cobalt and fougerite likely precipitated, too, with the earliest banded iron formations at Isua, Greenland, although the element now mainly resides in layered sulfides thought to be precipitated then at hot springs ( 11 , 12 ).…”

Particle- and Light-Mediated Processes Control Seasonal Manganese Oxide Cycling in a Meromictic Pond

“…47 Mn K-edge XANES spectra were fit via linear combination fitting (LCF) using δ-MnO 2 , feitknechtite, and Mn(II) sorbed to microbial biomass (radiolarian) as representative Mn(IV), Mn(III), and Mn(II) standards, respectively. Mn K-edge EXAFS spectra were fit initially with a standard library containing over 30 model compounds, as done previously, 4 with final LCF reduced to combinations of δ-MnO 2 , asbolane, sodium (triclinic) birnessite, feitknechtite, and Mn(II) sorbed to biomass because this combination of standards most closely fit the data.…”

“…Manganese (Mn) oxide minerals are components of various particle and mineral deposits found in a wide range of environments, including desert rock varnish, mineral coatings within soils, and ferromanganese crusts and nodules in the ocean. , Manganese oxides are sorbents of nutrients and contaminants, including organic carbon, phosphate, and many trace metals. − Thus, the redox cycling of Mn exerts an important control on nutrient availability, with Mn itself also acting as an important micronutrient . Manganese oxides are also strong oxidants with the ability to oxidize organic carbon either through direct interactions or indirectly via microbial respiration .…”