Modern precipitation of hydrogenetic ferromanganese minerals during on-site 15-year exposure tests

Abstract

Redox-sensitive metallic elements, Mn and fe, are oxidized in deep sea waters and form abundant ferromanganese crusts and nodules on the world's ocean floors at ultraslow rates of growth. This process of oxidation and the mechanism of precipitation are yet unknown. in this paper, the results of the first successful, long-term, on-site experiment of mineral precipitation that ascertains modern, ongoing hydrogenetic deposition of oxide materials from normal seawaters at water depths of 900-4500 m of geologically active and inactive environments are presented. We succeeded in the insitu precipitation experiment on the sea floor and characterized the precipitates using high-resolution and submicron-scale chemical, mineralogical, and structural analyses. The installed artificial plates of glass, ceramics, and plastic yielded spread-out particles of sizes varying from one to a few micrometers in diameter, of coccoid-like irregular shapes, with a maximum of 1,000-10,000 individual particles/ mm 2 /year after 12-15 years of exposure. The results indicated a continuous substantial growth of the hydrogenetic minerals if both Mn and fe are supplied to the bottom waters. the mineralogical, chemical, and structural properties of the precipitates are similar to those of the natural precipitates on the seabed that are made up of hydrogenetic ferromanganese crusts and nodules, together with settling sediments, suspended hydrothermal particles, or microbial precipitates from cultivated Mnoxidizing bacteria. our work presents new realistic insight into proposed genetic models of marine hydrogenetic ferromanganese deposits in modern diverse ocean environments.

Late Summer Peak and Scavenging-Dominant Metal Fluxes in Particulate Export Near a Seamount in the Western North Pacific Subtropical Gyre

“…This similarity supports the newly proposed model that continuous Mn oxidation occurs even within the oxygen minimum zone (OMZ) such that particulate Fe-Mn oxide forms piled ferromanganese crusts and nodules (Usui et al, 2017). Recently, Usui et al (2020) presented evidence of ongoing precipitation of Fe-Mn oxide particles (a few micrometers in diameter) from normal seawater at 900-4,500 m depth based on in situ 15-years exposure tests. Such particulate precipitates could be a common source of Mn for both cobalt-rich crusts and sinking particles.…”

Manganese enrichment of polymetallic oceanic nodules via selective leaching process for energy storage applications

“…Therefore, it is important to understand and explore the prospects of deep seabed mining, which is gaining increasing popularity globally, especially in India. The ocean floor bears resources with high concentrations of metals, like manganese nodules, which are rock concretions formed by concentric layers of Fe and Mn hydroxides, and are characterized by high concentrations of metals, such as Cu 1%, Ni 1.2%, Co 0.1%, Fe 5.5%, Li, Mo, Te, Ti, Li, rare earths, and Mn 2,5–7 ( the latter being the most abundant with an average content of around 24%) 8 . Mining the deep sea bed is advantageous because of significantly reduced overload charges, as they are strictly two‐dimensional, 1,3 whereas significant amounts of surcharges are applied to land‐based mining, as it is exploited in a three‐dimensional way.…”

Possibilities and Limitations of the Use of Seafloor Photographs for Estimating Polymetallic Nodule Resources—Case Study from IOM Area, Pacific Ocean

“…Polymetallic marine nodules are an attractive metal source due to the scarcity of high-grade metals in onshore deposits [33]. Nodules contain large variety of metals such as: Cu, Ni, Co, Li, Mo, Te, Ti, Y, Pt, Zn, Zr, Ge, REEs, and Mn [30][31][32][33][34][35][36].…”