Chemostratigraphy of deep-sea sediments in the western North Pacific Ocean: Implications for genesis of mud highly enriched in rare-earth elements and yttrium

Tanaka, Erika; Nakamura, Kozo; Yasukawa, Kazutaka; Mimura, Kazuhide; Fujinaga, Koichiro; Iijima, Koichi; Nozaki, Tatsuo; Kato, Yasuhiro

doi:10.1016/j.oregeorev.2020.103392

Cited by 58 publications

(149 citation statements)

References 39 publications

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“…A 187 Os/ 188 Os excursion in this core was interpreted as the late Eocene excursion (Nozaki et al 2019), as well as in a nearby core KR13-02 PC05 (Ohta et al 2020). Geochemical and magnetic correlations confirmed that they are in the same stratigraphic position (Tanaka et al 2020;Yamazaki et al 2020).…”

Section: Methodsmentioning

confidence: 62%

“…In both cores, the 187 Os/ 188 Os excursions roughly coincide with the high concentrations (> 2000 ppm) of rareearth elements and yttrium (REY), labeled as the 1st REY peak (Iijima et al 2016;Tanaka et al 2020). REY in pelagic clay are mainly carried by fish debris consisting of biogenic apatite (Kashiwabara et al 2014(Kashiwabara et al , 2018Yasukawa et al 2016), especially in this region (Takaya et al 2018;Yasukawa et al 2019).…”

Section: Methodsmentioning

confidence: 80%

“…Gray symbols show data with MAD > 15°, which are not plotted in c and d. f Variation of total REY content(Iijima et al, 2016). On the right are chemostratigraphic Units ofTanaka et al (2020)…”

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confidence: 99%

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Magnetostratigraphic evidence for post-depositional distortion of osmium isotopic records in pelagic clay and its implications for mineral flux estimates

Usui

Yamazaki

2021

Earth Planets Space

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Chemical stratigraphy is useful for dating deep-sea sediments, which sometimes lack radiometric or biostratigraphic constraints. Oxic pelagic clay contains Fe–Mn oxyhydroxides that can retain seawater 187Os/188Os values, and its age can be estimated by fitting the isotopic ratios to the seawater 187Os/188Os curve. On the other hand, the stability of Fe–Mn oxyhydroxides is sensitive to redox change, and it is not clear whether the original 187Os/188Os values are always preserved in sediments. However, due to the lack of independent age constraints, the reliability of 187Os/188Os ages of pelagic clay has never been tested. Here we report inconsistency between magnetostratigraphic and 187Os/188Os ages in pelagic clay around Minamitorishima Island. In a ~ 5-m-thick interval, previous studies correlated 187Os/188Os data to a brief (< 1 million years) isotopic excursion in the late Eocene. Paleomagnetic measurements revealed at least 12 polarity zones in the interval, indicating a > 2.9–6.9 million years duration. Quartz and feldspars content showed that while the paleomagnetic chronology gives reasonable eolian flux estimates, the 187Os/188Os chronology leads to unrealistically high values. These results suggest that the low 187Os/188Os signal has diffused from an original thin layer to the current ~ 5-m interval, causing an underestimate of the deposition duration. The preservation of the polarity patterns indicates that a mechanical mixing such as bioturbation cannot be the main process for the diffusion, so diagenetic redistribution of Fe–Mn oxyhydroxides and associated Os may be responsible. The paleomagnetic chronology presented here also demands reconsiderations of the timing, accumulation rate, and origins of the high content of rare-earth elements and yttrium in pelagic clay around Minamitorishima Island.

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Section: Methodsmentioning

confidence: 62%

Section: Methodsmentioning

confidence: 80%

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Magnetostratigraphic evidence for post-depositional distortion of osmium isotopic records in pelagic clay and its implications for mineral flux estimates

Usui

Yamazaki

2021

Earth Planets Space

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“…A 187 Os/ 188 Os excursion in this core was interpreted as the late Eocene excursion (Nozaki et al 2019), as well as in a nearby core KR13-02 PC05 (Ohta et al, 2020). Geochemical and magnetic correlations con rmed that they are in the same stratigraphic position (Tanaka et al 2020;Yamazaki et al 2020).…”

Section: Methodsmentioning

confidence: 81%

Magnetostratigraphic Evidence for Post-Depositional Distortion of Osmium Isotopic Records in Pelagic Clay and Its Implications for Mineral Flux Estimates

Usui

Yamazaki

2020

Preprint

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Chemical stratigraphy is useful for dating deep sea sediments which sometimes lack radiometric or biostratigraphic constraints. Oxic pelagic clay contains Fe-Mn oxyhydroxides that can retain seawater 187Os/188Os values, and its age can be estimated by fitting the isotopic ratios to the seawater 187Os/188Os curve. On the other hand, the stability of Fe-Mn oxyhydroxides is sensitive to redox change, and it is not clear whether the original 187Os/188Os values are always preserved in sediments. However, due to the lack of independent age constraints, the reliability of 187Os/188Os ages of pelagic clay have never been tested. Here we report inconsistency between magnetostratigraphic and 187Os/188Os ages in pelagic clay around Minamitorishima Island. In a ~ 5 m thick interval, previous studies correlated 187Os/188Os data to a brief (< 2 million years) isotopic excursion in the late Eocene. Paleomagnetic measurements revealed at least 12 polarity zones in the interval, indicating a > 3.3–7.4 million years duration. Quartz and feldspars content showed that while the paleomagnetic chronology gives reasonable eolian flux estimates, the 187Os/188Os chronology leads unrealistically high values. These results suggest that the low 187Os/188Os signal has diffused from an original thin layer to the current ~ 5 m interval, causing an underestimate of the deposition duration. The preservation of the polarity patterns indicates that a mechanical mixing such as bioturbation cannot be the main process for the diffusion, so diagenetic re-distribution of Fe-Mn oxyhydroxides and associated Os may be responsible. The paleomagnetic chronology presented here also demands reconsiderations of the timing, accumulation rate, and origins of the high content of rare-earth elements and yttrium in pelagic clay around Minamitorishima Island.

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“…REY-rich deep-sea sediments were first discovered in the central North Pacific and southwestern Pacific [4], and subsequently reported across most of the Pacific, Indian, and Atlantic oceans (Figure 1) [3,[6][7][8][9]. At present, deep-sea sediments in the western Pacific have the greatest resource potential, with the REY content (ΣREY) in the enrichment layer as high as 7974 ppm off Minamitorishima Island [1,3,6,9]. [1,3,4,[6][7][8][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Mechanism and Influencing Factors of REY Enrichment in Deep-Sea Sediments

et al. 2021

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Deep-sea sediments with high contents of rare-earth elements and yttrium (REY) are expected to serve as a potential resource for REY, which have recently been proved to be mainly contributed by phosphate component. Studies have shown that the carriers of REY in deep-sea sediments include aluminosilicate, Fe-Mn oxyhydroxides, and phosphate components. The ∑REY of the phosphate component is 1–2 orders of magnitude higher than those of the other two carriers, expressed as ∑REY = 0.001 × [Al2O3] − 0.002 × [MnO] + 0.056 × [P2O5] − 32. The sediment P2O5 content of 1.5% explains 89.1% of the total variance of the sediment ∑REY content. According to global data, P has a stronger positive correlation with ∑REY compared with Mn, Fe, Al, etc.; 45.5% of samples have a P2O5 content of less than 0.25%, and ∑REY of not higher than 400 ppm. The ∑REY of the phosphate component reaches n × 104 ppm, much higher than that of marine phosphorites and lower than that of REY-phosphate minerals, which are called REY-rich phosphates in this study. The results of microscopic observation and separation by grain size indicate that the REY-rich phosphate component is mainly composed of bioapatite. When ∑REY > 2000 ppm, the average CaO/P2O5 ratio of the samples is 1.55, indicating that the phosphate composition is between carbonate fluoroapatite and hydroxyfluorapatite. According to a knowledge map of sediment elements, the phosphate component is mainly composed of P, Ca, Sr, REY, Sc, U, and Th, and its chemical composition is relatively stable. The phosphate component has a negative Ce anomaly and positive Y anomaly, and a REY pattern similar to that of marine phosphorites and seawater. After the early diagenesis process (biogeochemistry, adsorption, desorption, transformation, and migration), the REY enrichment in the phosphate component is completed near the seawater/sediment interface. In the process of REY enrichment, the precipitation and enrichment of P is critical. According to current research progress, the REY enrichment is the result of comprehensive factors, including low sedimentation rate, high ∑REY of the bottom seawater, a non-carbonate depositional environment, oxidation conditions, and certain bottom current conditions.

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Chemostratigraphy of deep-sea sediments in the western North Pacific Ocean: Implications for genesis of mud highly enriched in rare-earth elements and yttrium

Cited by 58 publications

References 39 publications

Magnetostratigraphic evidence for post-depositional distortion of osmium isotopic records in pelagic clay and its implications for mineral flux estimates

Magnetostratigraphic evidence for post-depositional distortion of osmium isotopic records in pelagic clay and its implications for mineral flux estimates

Magnetostratigraphic Evidence for Post-Depositional Distortion of Osmium Isotopic Records in Pelagic Clay and Its Implications for Mineral Flux Estimates

Mechanism and Influencing Factors of REY Enrichment in Deep-Sea Sediments

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