Junichiro Ohta
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View article: Deep‐Sea Rare‐Earth Mineral Resources Formed in the Early Eocene Hothouse Ocean: Insights From Deep Learning‐Based Microfossil Observations
Deep‐Sea Rare‐Earth Mineral Resources Formed in the Early Eocene Hothouse Ocean: Insights From Deep Learning‐Based Microfossil Observations Open
Deep‐sea mud enriched in rare‐earth elements (REE), termed REE‐rich mud, is a promising seafloor mineral resource. Data from a decade of surveys have revealed that the mud with the highest REE concentration occurs in the pelagic realm of t…
View article: Deep-sea rare-earth mineral resources formed in the early Eocene Hothouse ocean: Insights from deep learning-based microfossil observations
Deep-sea rare-earth mineral resources formed in the early Eocene Hothouse ocean: Insights from deep learning-based microfossil observations Open
Deep-sea mud enriched in rare-earth elements (REEs), termed REE-rich mud, is a promising seafloor mineral resource. A decade of surveys has revealed that the mud with the highest REE concentration occurs in the pelagic realm of the western…
View article: Petrography and stratigraphic Os isotopic ages of ferromanganese nodules from the Northwest Pacific east of Minamitorishima Island
Petrography and stratigraphic Os isotopic ages of ferromanganese nodules from the Northwest Pacific east of Minamitorishima Island Open
The area offshore of Minamitorishima Island, Northwestern Pacific Ocean, contains large amounts of seafloor mineral resources such as ferromanganese (Fe–Mn) nodules, Fe–Mn crusts, and rare-earth element and yttrium (REY)-rich muds. In this…
View article: Applicability of Object Detection to Microfossil Research: Implications From Deep Learning Models to Detect Microfossil Fish Teeth and Denticles Using YOLO‐v7
Applicability of Object Detection to Microfossil Research: Implications From Deep Learning Models to Detect Microfossil Fish Teeth and Denticles Using YOLO‐v7 Open
Microfossils of fish teeth and denticles, referred to as ichthyoliths, provide critical information for depositional ages, paleo‐environments, and marine ecosystems, especially in pelagic realms. However, owing to their small size and rari…
View article: The Age and Origin of the Ruwai Polymetallic Skarn Deposit, Indonesia: Evidence of Cretaceous Mineralization in the Central Borneo Metallogenic Belt
The Age and Origin of the Ruwai Polymetallic Skarn Deposit, Indonesia: Evidence of Cretaceous Mineralization in the Central Borneo Metallogenic Belt Open
The Ruwai skarn deposit is the largest polymetallic skarn deposit in Borneo and is located in the Schwaner Mountains. The skarns and massive orebodies are hosted in marble of the Jurassic Ketapang Complex, which was intruded by Cretaceous …
View article: Applicability of Object Detection to Microfossil Research: Implications from Deep Learning Models to Detect Microfossil Fish Teeth and Denticles Using YOLO-v7
Applicability of Object Detection to Microfossil Research: Implications from Deep Learning Models to Detect Microfossil Fish Teeth and Denticles Using YOLO-v7 Open
Microfossils of fish teeth and denticles, termed ichthyoliths, provide critical information for depositional ages, paleo-environments and marine ecosystems, especially in pelagic realms. However, owing to their small size and rarity, it is…
View article: Compilation of the chemical composition data of pelagic clay around Minamitorishima Island in the western North Pacific Ocean
Compilation of the chemical composition data of pelagic clay around Minamitorishima Island in the western North Pacific Ocean Open
A compilation of bulk chemical composition data of pelagic clay around Minamitorishima Island in the western North Pacific Ocean. Original data were published in the cited articles (shown in Data source column). This is a supplementary dat…
View article: Compilation of the chemical composition data of pelagic clay around Minamitorishima Island in the western North Pacific Ocean
Compilation of the chemical composition data of pelagic clay around Minamitorishima Island in the western North Pacific Ocean Open
A compilation of bulk chemical composition data of pelagic clay around Minamitorishima Island in the western North Pacific Ocean. Original data were published in the cited articles (shown in Data source column). This is a supplementary dat…
View article: Study on the mineralization age of the Akenobe Sn-Cu-W polymetallic deposit in southwest Japan
Study on the mineralization age of the Akenobe Sn-Cu-W polymetallic deposit in southwest Japan Open
The northern part of Hyogo Prefecture in the southwestern Japan is a unique area having a number of large deposits that had produced various metals of industrial importance. For instance, the Nakaze deposit had been known for its extremely…
View article: Rare‐Earth Elements in Deep‐Sea Sediments in the South Pacific Gyre: Source Materials and Resource Potentials
Rare‐Earth Elements in Deep‐Sea Sediments in the South Pacific Gyre: Source Materials and Resource Potentials Open
Deep‐sea sediments enriched in rare‐earth elements and yttrium (REY) plus scandium (Sc), termed “REY‐rich mud,” have attracted attention as a possible resource for these critical industrial elements. Examples have been reported from the we…
View article: Os isotopic composition of Early Cretaceous seawater reconstructed from umber deposit in the Japanese accretionary complex
Os isotopic composition of Early Cretaceous seawater reconstructed from umber deposit in the Japanese accretionary complex Open
View article: Image datasets for training, validating and testing deep learning models to detect microfossil fish teeth and denticles called ichthyolith using YOLOv7
Image datasets for training, validating and testing deep learning models to detect microfossil fish teeth and denticles called ichthyolith using YOLOv7 Open
This repository contains datasets to train, validate and test deep learning models to detect microfossil fish teeth and denticles called "ichthyoliths". All the dataset contains images of glass slides prepared from deep-sea sediment obtain…
View article: Marine osmium isotopic composition reconstructed from the early Permian umber deposit in the Japanese accretionary complex
Marine osmium isotopic composition reconstructed from the early Permian umber deposit in the Japanese accretionary complex Open
Strata-bound ferromanganese (Fe–Mn) deposits (umbers) are thought to have formed by precipitation of Fe–Mn oxyhydroxides derived from seafloor hydrothermal activity at a mid-oceanic ridge. Fe–Mn oxyhydroxides effectively adsorb various ele…
View article: Essential processes involving REE-enrichment in biogenic apatite in deep-sea sediment decoded via multivariate statistical analyses
Essential processes involving REE-enrichment in biogenic apatite in deep-sea sediment decoded via multivariate statistical analyses Open
Deep-sea sediments highly enriched in rare-earth elements (REE), termed "REE-rich mud," have recently attracted attention as a potential mineral resource for industrially critical metals. Biogenic apatite or fish teeth and bone debris comp…
View article: Iron deposition during recovery from Late Devonian oceanic anoxia: Implications of the geochemistry of the Kawame ferromanganese deposit, Nedamo Belt, Northeast Japan
Iron deposition during recovery from Late Devonian oceanic anoxia: Implications of the geochemistry of the Kawame ferromanganese deposit, Nedamo Belt, Northeast Japan Open
The Late Devonian, during which one of the "Big Five" Phanerozoic mass extinction events occurred, was one of the most important time intervals in Earth history. Nevertheless, the paucity of deep-sea records due to subduction has hampered …
View article: Automated detection of microfossil fish teeth from slide images using combined deep learning models
Automated detection of microfossil fish teeth from slide images using combined deep learning models Open
Microfossil fish teeth, known as ichthyoliths, provide a key constraint on the depositional age and environment of deep-sea sediments, especially pelagic clays where siliceous and calcareous microfossils are rarely observed. However, tradi…
View article: Enhanced continental chemical weathering during the multiple early Eocene hyperthermals: New constraints from the southern Indian Ocean
Enhanced continental chemical weathering during the multiple early Eocene hyperthermals: New constraints from the southern Indian Ocean Open
Multiple short-term (<105 years) global warming events ("hyperthermals") occurred throughout the early Eocene. Chemical weathering of continental silicate rocks is considered to have played a key role in recovery from these transient globa…
View article: Automated detection of microfossil fish teeth from slide images using combined deep learning models
Automated detection of microfossil fish teeth from slide images using combined deep learning models Open
Microfossil fish teeth, known as ichthyoliths, provide a key constraint on the depositional age and environment of deep-sea sediments, especially pelagic clays where siliceous and calcareous microfossils are rarely observed. However, tradi…
View article: Re&#8211;Os geochemistry of altered dacitic rock at Site U1527, IODP Expedition 376: Implications for the Re cycle in intraoceanic arcs
Re–Os geochemistry of altered dacitic rock at Site U1527, IODP Expedition 376: Implications for the Re cycle in intraoceanic arcs Open
<p>The Re–Os isotopic system is a powerful tool for both geochronology and tracing various geochemical processes. Because the Os isotopic ratio (<sup>187</sup>Os/<sup>188</sup>Os) distinctly differs …
View article: Secular Variations in Provenance of Sedimentary Components in the Western North Pacific Ocean Constrained by Sr Isotopic Features of Deep‐Sea Sediments
Secular Variations in Provenance of Sedimentary Components in the Western North Pacific Ocean Constrained by Sr Isotopic Features of Deep‐Sea Sediments Open
Deep‐sea sediments around Minamitorishima Island in the western North Pacific Ocean record the depositional environment in the central to western North Pacific since the late Cretaceous. Previous studies on the bulk chemical composition of…
View article: A precise and accurate analytical method for determination of osmium isotope ratios at the 1–15 pg level by using a MC-ICP-MS equipped with sparging introduction and high-sensitivity discrete dynode-type ion-counting detectors
A precise and accurate analytical method for determination of osmium isotope ratios at the 1–15 pg level by using a MC-ICP-MS equipped with sparging introduction and high-sensitivity discrete dynode-type ion-counting detectors Open
Properly calibrated discrete dynode SEM ion-counting detectors and minimization of blank Os by an improved vial-cleaning method enables Os isotope analysis at the 1–15 pg level with high accuracy and precision.
View article: Umber as a lithified REY-rich mud in Japanese accretionary complexes and its implications for the osmium isotopic composition of Middle Cretaceous seawater
Umber as a lithified REY-rich mud in Japanese accretionary complexes and its implications for the osmium isotopic composition of Middle Cretaceous seawater Open
We report geochemical and isotopic data for umber and related greenstone samples from the Aki umber deposit in the Northern Shimanto Belt, central Shikoku, southwest Japan. The greenstone underlying the umber deposit shows a geochemical si…
View article: Re–Os geochemistry of hydrothermally altered dacitic rock in a submarine volcano at Site U1527, IODP Expedition 376: Implications for the Re cycle in intraoceanic arcs
Re–Os geochemistry of hydrothermally altered dacitic rock in a submarine volcano at Site U1527, IODP Expedition 376: Implications for the Re cycle in intraoceanic arcs Open
Despite the widespread use of Re–Os isotopes in various geoscience fields, relatively little is known about the behavior of Re and Os during fluid-mediated hydrothermal alteration of igneous rocks in the (sub)seafloor, especially in an int…
View article: Geological features and resource potential of deep-sea mud highly enriched in rare-earth elements in the Central Pacific Basin and the Penrhyn Basin
Geological features and resource potential of deep-sea mud highly enriched in rare-earth elements in the Central Pacific Basin and the Penrhyn Basin Open
Deep-sea mud enriched in rare-earth elements and yttrium (REY-rich mud) has been recognized as a new resource for REY and scandium (Sc). Recently, highly REY-rich mud with more than 2,000 ppm of REY was found in the western North Pacific O…
View article: Rapid coupling between solid earth and ice volume during the Quaternary
Rapid coupling between solid earth and ice volume during the Quaternary Open
View article: Stratigraphic Variations of Fe–Mn Micronodules and Implications for the Formation of Extremely REY-Rich Mud in the Western North Pacific Ocean
Stratigraphic Variations of Fe–Mn Micronodules and Implications for the Formation of Extremely REY-Rich Mud in the Western North Pacific Ocean Open
The origin of deep-sea sediments in the western North Pacific Ocean, which are significantly enriched in rare-earth elements and yttrium (REY), and its paleoceanographic implications have been poorly constrained. Here, we investigated stra…
View article: An improved analytical method for Re-Os isotope analysis and its application to GSJ geochemical reference materials, JCu-1 and JZn-1
An improved analytical method for Re-Os isotope analysis and its application to GSJ geochemical reference materials, JCu-1 and JZn-1 Open
<p>The Re-Os isotope system is an effective tool in geological studies, especially in radiometric dating. Since both Re and Os are highly siderophile and chalcophile elements, they tend to be concentrated in various sulfide minerals.…
View article: Stratigraphic variations in geochemistry and morphology of Fe–Mn micronodules: Implications for the formation process of extremely REY-rich mud in the western North Pacific Ocean
Stratigraphic variations in geochemistry and morphology of Fe–Mn micronodules: Implications for the formation process of extremely REY-rich mud in the western North Pacific Ocean Open
View article: Fluctuation of marine osmium isotope ratio during the Quaternary climate cycles
Fluctuation of marine osmium isotope ratio during the Quaternary climate cycles Open
FIGURES 9–12. Female head, lateral view: 9, Robertsia xylosycia; 10, Robertsia mandibularis; 11, Robertsia vaamondei; 12, Robertsia weibleni.
View article: Geochemical features of Fe-Mn micronodules in deep-sea sediments of the western North Pacific Ocean: Potential for co-product metal extraction from REY-rich mud
Geochemical features of Fe-Mn micronodules in deep-sea sediments of the western North Pacific Ocean: Potential for co-product metal extraction from REY-rich mud Open
Rare earth element and yttrium (REY)-rich mud around Minamitorishima Island, Japan, in the western North Pacific Ocean has received significant attention as a novel REY resource. In REY-rich muds, industrially critical metals such as Co, N…