Significant contribution of subseafloor microparticles to the global manganese budget

Abstract

Ferromanganese minerals are widely distributed in subseafloor sediments and on the seafloor in oceanic abyssal plains. Assessing their input, formation and preservation is important for understanding the global marine manganese cycle and associated trace elements. However, the extent of ferromanganese minerals buried in subseafloor sediments remains unclear. Here we show that abundant (108–109 particles cm−3) micrometer-scale ferromanganese mineral particles (Mn-microparticles) are found in the oxic pelagic clays of the South Pacific Gyre (SPG) from the seafloor to the ~100 million-year-old sediments above the basement. Three-dimensional micro-texture, and major and trace element compositional analyses revealed that these Mn-microparticles consist of poorly crystalline ferromanganese oxides precipitating from bottom water. Based on our findings, we extrapolate that 1.5–8.8 × 1028 Mn-microparticles, accounting for 1.28–7.62 Tt of manganese, are globally present in oxic subseafloor sediments. This estimate is at least two orders of magnitude larger than the manganese budget for nodules and crusts on the seafloor. Subseafloor Mn-microparticles thus contribute significantly to the global manganese budget.

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

“…The absence of basal diffraction as well as small particle size, low crystallinity, and high Fe/Mn ratios indicate that our modern precipitates are hydrogenetic vernadite. A similar vernadite-like SAED pattern was reported in the micron-size Fe-Mn particles in deep-sea clay sediments 30 , which may have a common nature in depositional processes and environments.…”

Statistic and Isotopic Characterization of Deep‐Sea Sediments in the Western North Pacific Ocean: Implications for Genesis of the Sediment Extremely Enriched in Rare Earth Elements

“…The 206 Pb/ 204 Pb values of the samples with positive IC1 scores are within the range of the Cenozoic seawater, and those with negative IC1 scores likely correspond to the terrigenous components (Table ). A recent study demonstrated that a significant amount of “micrometer‐scale Mn‐oxide particles” (much smaller than visible micronodules that are typically identified in pelagic clay; Figure S2 in the supporting information) are present in oxic pelagic clay in the South Pacific Ocean (Uramoto et al, ). Based on the features of Fe, Mn, Co, Ni, and Cu compositions, Uramoto et al () discussed that Mn microparticles are derived primarily from hydrogenetic precipitation from bottom water.…”

Fractionation Trends and Variability of Rare Earth Elements and Selected Critical Metals in Pelagic Sediment from Abyssal Basin of NE Pacific (Clarion-Clipperton Fracture Zone)

“…Additionally, REE sources may be related to Fe-rich authigenic (diagenetic) clay minerals and admixtures of allogenic components from continental areas [14,19,30]. The REE accumulation in pelagic sediments may also be related to external influx of Fe/Mn-microparticles [31]. The REE composition and distributional patterns may be also related to high temperature hydrothermal iron oxides and aluminosilicates, products of bedrock disintegration, or endogenous (volcanoes) and exogenous (desert dust) components [32].…”

“…In addition to these features, the seafloor is characterized by a regular bathymetric pattern that consists of a system of adjacent linear groups of ridges and valleys, aligned approximately perpendicular to the boundary between the Clarion and Clipperton Fracture Zones. Distances between neighboring crests vary from 1 to 10 km, with elevations above surrounding terrain up to hundreds of meters [31]. The CCFZ ocean crust is 10.6-10.8 km thick, and is composed of two complexes: (i) tholeiitic basalts, and (ii) overlying sediment cover, with a thickness of 100 to 300 m, and age range from Late Cretaceous to Quaternary [43,52].…”