Distribution of and hydrographic controls on ferromanganese crusts: Tropic Seamount, Atlantic

Yeo, Isobel; Howarth, Sarah A.; Spearman, J.; Cooper, Alan K.; Crossouard, N.; Taylor, Joan E.; Turnbull, M.; Murton, Bramley J.

doi:10.1016/j.oregeorev.2019.103131

Cited by 26 publications

(10 citation statements)

References 31 publications

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“…Compared with loose sediments, transitional zone deposits experience a lower degree of mobilisation on seamount slopes. Similar observations have been presented by Yeo et al 25 . All the lithotypes in this study are shown in Fig.…”

supporting

confidence: 92%

“…Intense topographical changes on the slope, such as landslides, slope collapse and volcanic activity (which ceased in the Late Cretaceous in this case) on intraplate seamounts 10,42 , play a role in clearing deposits from seamount slopes and burying old deposits on slopes 25 . After past deposits have been removed, the seamount flank would consist exposed rock and would eventually experience build-up of new deposits.…”

Section: Resultsmentioning

confidence: 94%

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Depositional patterns constrained by slope topography changes on seamounts

Yan

Yang

et al. 2020

Sci Rep

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Slope topography is known to control the spatial distribution of deposits on intraplate seamounts; however, relatively little is known about how slope topography changes constrain those depositional patterns. In this study, we analyse data on four lithotypes found on seamount slopes, including colloidal chemical deposits comprising mainly cobalt-rich crusts, and examine the relationships between the spatial distribution of these lithotypes and current slope topography. We use these relationships to discuss depositional patterns constrained by slope topography changes. Some depositional units in drill core samples are interpreted to have resulted from past topographic changes that created the current slope topography. Two or more types of deposits that accumulated at the same location implies that the slope topography changed over time and that the depositional patterns on seamount slopes are constrained by changes in slope topography.

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supporting

confidence: 92%

Section: Resultsmentioning

confidence: 94%

Depositional patterns constrained by slope topography changes on seamounts

Yan

Yang

et al. 2020

Sci Rep

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“…Eroded botryoids of the top surface of the second generation in some samples corroborated this erosional process. Bottom currents of more than 0.2 m/s may be capable of eroding Fe-Mn crust surfaces [53]. The prevalence of columnar and mottled texture is related to a higher amount of biogenic particle input that constrains or interrupts the formation of laminations [54].…”

Section: Two Generations Of Fe-mn Crusts On Rio Grande Risementioning

confidence: 99%

Genesis and Evolution of Ferromanganese Crusts from the Summit of Rio Grande Rise, Southwest Atlantic Ocean

et al. 2020

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The Rio Grande Rise (RGR) is a large elevation in the Atlantic Ocean and known to host potential mineral resources of ferromanganese crusts (Fe–Mn), but no investigation into their general characteristics have been made in detail. Here, we investigate the chemical and mineralogical composition, growth rates and ages of initiation, and phosphatization of relatively shallow-water (650–825 m) Fe–Mn crusts dredged from the summit of RGR by using computed tomography, X-ray diffraction, 87Sr/86Sr ratios, U–Th isotopes, and various analytical techniques to determine their chemical composition. Fe–Mn crusts from RGR have two distinct generations. The older one has an estimated age of initiation around 48–55 Ma and was extensively affected by post-depositional processes under suboxic conditions resulting in phosphatization during the Miocene (from 20 to 6.8 Ma). As a result, the older generation shows characteristics of diagenetic Fe–Mn deposits, such as low Fe/Mn ratios (mean 0.52), high Mn, Ni, and Li contents and the presence of a 10 Å phyllomanganate, combined with the highest P content among crusts (up to 7.7 wt %). The younger generation is typical of hydrogenetic crusts formed under oxic conditions, with a mean Fe/Mn ratio of 0.75 and mean Co content of 0.66 wt %, and has the highest mean contents of Bi, Nb, Ni, Te, Rh, Ru, and Pt among crusts formed elsewhere. The regeneration of nutrients from local biological productivity in the water column is the main source of metals to crusts, providing mainly metals that regenerate rapidly in the water column and are made available at relatively shallow water depths (Ni, As, V, and Cd), at the expense of metals of slower regeneration (Si and Cu). Additionally, important contributions of nutrients may derive from various water masses, especially the South Atlantic Mode Water and Antarctic Intermediate Water (AAIW). Bulk Fe–Mn crusts from the summit of RGR plateau are generally depleted in metals considered of greatest economic interest in crusts like Co, REE, Mo, Te, and Zr, but are the most enriched in the critical metals Ni and Li compared to other crusts. Further investigations are warranted on Fe–Mn crusts from deeper-water depths along the RGR plateau and surrounding areas, which would less likely be affected by phosphatization.

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“…It is important to note that all samples were dredged during cruises that were not dedicated to study crusts and that sample recovery is strongly impacted by seabed and outcrop morphology. Fe-Mn crusts recovered by ROV along depth transects usually show no variation in crust thicknesses [84,85]. The two thickest crusts (GO327: 115 mm, DR11Ai: 97 mm) are situated respectively at 1820 m and 2375 m. Crust thicknesses have been measured for every sample where the right-way up was evident and for crusts with or without substrate.…”

Section: Crusts Chemical Changes With Water Depthmentioning

confidence: 99%

Origin and Composition of Ferromanganese Deposits of New Caledonia Exclusive Economic Zone

et al. 2022

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Located in the South-West Pacific, at the northern extremity of the mostly submerged Zealandia continent, the New Caledonian Exclusive Economic Zone (EEZ) covers 1,470,000 km² and includes basins, ridges and seamounts where abundant ferromanganese crusts have been observed. Several investigations have been conducted since the 1970s on the nature and composition of ferromanganese crusts from New Caledonia’s seamounts and ridges, but none have covered the entire EEZ. We present data from 104 ferromanganese crusts collected in New Caledonia’s EEZ during twelve oceanographic cruises between 1974 and 2019. Samples were analysed for mineralogy, geochemical compositions, growth rates, and through a statistical approach using correlation coefficients and factor analysis. Crust thicknesses range from 1 mm to 115 mm, with growth rates between 0.45 mm/Ma and 102 mm/Ma. Based on textures, structures, discrimination plots, and growth rates, we distinguish a group of hydrogenetic crusts containing the highest mean contents of Co (0.42 wt%), Ni (0.31 wt%), and high contents of Mo, V, W, Pb, Zn, Nb, from a group of hydrothermal and/or diagenetic deposits showing high mean contents of Mn (38.17 wt%), Ba (0.56 wt%) and low contents of other trace metals. Several samples from this later group have exceptionally high content of Ni (0.7 wt%). The data shows that crusts from the southern part of the EEZ, notably seamounts of the Loyalty Ridge and the Lord Howe Rise, present high mineral potential for prospectivity owing to high contents of valuable metals, and constitute a great target for further investigation.

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Distribution of and hydrographic controls on ferromanganese crusts: Tropic Seamount, Atlantic

Cited by 26 publications

References 31 publications

Depositional patterns constrained by slope topography changes on seamounts

Depositional patterns constrained by slope topography changes on seamounts

Genesis and Evolution of Ferromanganese Crusts from the Summit of Rio Grande Rise, Southwest Atlantic Ocean

Origin and Composition of Ferromanganese Deposits of New Caledonia Exclusive Economic Zone

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