2:00 PM - 2:15 PM
[SCG55-02] Spatiotemporal distribution of mass accumulation rate of REE in pelagic realms of the Cenozoic ocean
Keywords:mass accumulation rate, deep-sea sediments, Pacific Ocean, REE-rich mud, seafloor mineral resources
Rare-earth elements (REE) are essential for various high-tech industries and low-carbon technologies. "REE-rich mud", or deep-sea sediments enriched in REE, is widely distributed in the eastern South and central North Pacific Ocean and has been attracting our attention as a new seafloor mineral resource [1]. Previous studies have applied independent component analysis to bulk elemental concentration datasets from sediment core samples obtained through the past scientific ocean drilling, and the source components of the REE-rich muds were revealed [2]. However, this analysis inferred the mixing relationships of source components based on the relative proportions of elements in the sediment and did not include information on the absolute amount of elemental flux deposited on the seafloor.
In this study, we constructed a new dataset of the mass accumulation rate (MAR) of each element by using the published elemental concentration dataset of deep-sea sediments in the Pacific Ocean [1] and microfossil biostratigraphy data mainly compiled from the DSDP/ODP Initial Reports [2]. By multiplying the dry bulk density of the sediment by its sedimentation rate, the mass of sediment deposited per unit time and unit area can be determined. Further multiplying this value by the bulk elemental concentration in the sediment provides the MAR of each element [3]. Since REE in REE-rich mud is primarily derived from seawater [2], we corrected the REE MAR by subtracting the REE flux due to terrigenous detritus, biogenic carbonate, and biogenic silica to estimate the REE flux from seawater. By applying this method to sediment cores from different regions and ages, as well as considering the plate motions, the spatiotemporal distribution of elemental deposition flux from the ocean to the seafloor at each age can be reconstructed.
A comparison of the spatial distribution of MAR of REE across different ages revealed that some locations exhibited high MAR of REE despite having low concentrations of REE in the bulk sediments, indicating that MAR of REE is largely controlled by the sedimentation rate of bulk sediments. In addition, because REE-rich mud can contain biogenic apatite, hydrogenous component, and hydrothermal Fe-oxyhydroxides [2], the MAR of P, Co, and Fe, which are closely related to these source components, are also investigated. The MAR of these elements also exhibited different distribution patterns from their bulk concentration distributions. In this presentation, we will visualize these MAR datasets and discuss the characteristics of their spatiotemporal distribution in the pelagic realms through the Cenozoic era.
[1] Kato et al. (2011) Nature Geoscience, 4, 535–539. [2] Yasukawa et al. (2016) Scientific Reports, 6, 29603. [3] Murray and Leinen. (1996) Geochimica et Cosmochimica Acta, 60(20), 3869-3878.
In this study, we constructed a new dataset of the mass accumulation rate (MAR) of each element by using the published elemental concentration dataset of deep-sea sediments in the Pacific Ocean [1] and microfossil biostratigraphy data mainly compiled from the DSDP/ODP Initial Reports [2]. By multiplying the dry bulk density of the sediment by its sedimentation rate, the mass of sediment deposited per unit time and unit area can be determined. Further multiplying this value by the bulk elemental concentration in the sediment provides the MAR of each element [3]. Since REE in REE-rich mud is primarily derived from seawater [2], we corrected the REE MAR by subtracting the REE flux due to terrigenous detritus, biogenic carbonate, and biogenic silica to estimate the REE flux from seawater. By applying this method to sediment cores from different regions and ages, as well as considering the plate motions, the spatiotemporal distribution of elemental deposition flux from the ocean to the seafloor at each age can be reconstructed.
A comparison of the spatial distribution of MAR of REE across different ages revealed that some locations exhibited high MAR of REE despite having low concentrations of REE in the bulk sediments, indicating that MAR of REE is largely controlled by the sedimentation rate of bulk sediments. In addition, because REE-rich mud can contain biogenic apatite, hydrogenous component, and hydrothermal Fe-oxyhydroxides [2], the MAR of P, Co, and Fe, which are closely related to these source components, are also investigated. The MAR of these elements also exhibited different distribution patterns from their bulk concentration distributions. In this presentation, we will visualize these MAR datasets and discuss the characteristics of their spatiotemporal distribution in the pelagic realms through the Cenozoic era.
[1] Kato et al. (2011) Nature Geoscience, 4, 535–539. [2] Yasukawa et al. (2016) Scientific Reports, 6, 29603. [3] Murray and Leinen. (1996) Geochimica et Cosmochimica Acta, 60(20), 3869-3878.