Research Interests
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(1) Reconstructing Changes in Seawater Chemistry and Its Coevolution with Life
(2) Estimating the Composition of Ancient Martian Surface Waters
(3) Unraveling the Cretaceous–Paleogene Geological History of Southwest Japan
My research explores the evolution of surface environments on Earth and other planets through chemical signatures preserved in rocks. In particular, I use Precambrian carbonate rocks to reconstruct past seawater chemistry, redox conditions, the influence of hydrothermal activity, and the availability of elements essential for life. Through this work, I aim to clarify the relationship between ocean environments and the evolution of life. I also study carbonate minerals in the Martian meteorite ALH84001 to infer the chemical composition of ancient Martian surface waters and the chemical forms of phosphorus, seeking to understand the behavior of water and biologically essential elements in the Martian surface environment.
These studies integrate petrography, mineral assemblages, major and trace element geochemistry, and synchrotron-based analyses, with an emphasis on recovering primary environmental signals preserved in rocks. I also investigate the Cretaceous–Paleogene geological development of Southwest Japan using U–Pb dating of detrital zircon. Together, these approaches provide complementary perspectives on the history of surface environments on Earth and Mars through the geological record.
(1) Reconstructing the Evolution of Seawater Chemistry and Its Coevolution with Life
My research seeks to reconstruct ancient seawater chemistry through the geochemical characteristics of Precambrian carbonate rocks. These rocks have often undergone post-depositional modification through metamorphism and alteration, requiring careful assessment of their origins and primary chemical compositions. To address this, I reconstruct their primary compositions using geological occurrence, mineral assemblages, and major and trace element geochemistry. By evaluating their origins and depositional settings, I seek to identify the carbonate compositions that most faithfully preserve seawater chemistry at the time of deposition.
Focusing on rare earth elements and elements essential for life, I aim to constrain ancient ocean redox conditions, the influence of hydrothermal activity, and the dissolved concentrations of biologically essential elements. I then use the primary abundances of these elements in carbonate rocks to trace changes in their concentrations in seawater throughout Earth’s history and explore their relationship with the evolution of life.
[Related publications]
06. Satoshi Yoshida, et al. (2026). Constraints on bio-essential elements in the Paleoproterozoic seawater: Estimation from in situ analyses of the carbonate rocks, Francevillian Group, Gabon. Geoscience Frontiers 17, 102290, doi.org/10.1016/j.gsf.2026.102290.
05. Satoshi Yoshida, et al. (2024b). Y-Ho fractionation during basalt alteration in hydrothermal system: An implication for superchondritic Y/Ho signature recorded in Precambrian banded iron formations. Chemical Geology 670, 122421. doi.org/10.1016/j.chemgeo.2024.122421
04. Satoshi Yoshida, et al. (2024a). Depositional condition of Paleoproterozoic Francevillian carbonate rocks revisited from rare earth element contents. Geoscience Frontiers 15(3), 101771. doi.org/10.1016/j.gsf.2023.101771
03. Satoshi Yoshida, et al. (2021). Occurrence and chemical composition of the Eoarchean carbonate rocks of the Nulliak supracrustal rocks in the Saglek Block of northeastern Labrador, Canada. Island Arc 30(1), e12381. doi.org/10.1111/iar.12381
02. 吉田 聡，小宮 剛（2019）．ラブラドル・ヌリアック表成岩の炭酸塩岩の化学組成と炭質物の炭素同位体組成─地球最古の生命の痕跡と海水組成の推定─．地学雑誌 128(4)，597–623．doi:10.5026/jgeography.128.597
01. 小宮 剛，青木翔吾，吉田 聡（2018）. カナダ，ラブラドル・ヌリアック表成岩類の地質と年代 ─地球最古の表成岩とプレートテクトニクスの証拠─．地学雑誌 127(5), 683–704．doi:10.5026/jgeography.127.683
(2) Estimating the Composition of Ancient Martian Surface Waters
My research seeks to reconstruct the chemical composition of ancient Martian surface waters through the geochemical characteristics of carbonate minerals in the Martian meteorite ALH84001. One of the oldest known Martian meteorites, ALH84001 originated from the crust of early Mars and contains carbonate minerals thought to have formed through reactions with water at or near the Martian surface. These minerals may therefore preserve a record of the chemical characteristics of water on ancient Mars.
By examining the major and trace element compositions of these carbonate minerals, with particular emphasis on rare earth elements and elements essential for life, I aim to constrain the redox conditions of ancient Martian surface waters, the influence of hydrothermal activity, and the availability of biologically essential elements. I also investigate the chemical forms of phosphorus within the carbonate minerals to understand its behavior in the Martian surface environment and how elements necessary for life were retained.
[Related publications]
(3) Unraveling the Cretaceous–Paleogene Geological History of Southwest Japan
My research investigates the geological development of Southwest Japan from the Cretaceous to the Paleogene through U–Pb dating of detrital zircon. Cretaceous forearc basin deposits, exemplified by the Izumi Group, are widely distributed across Southwest Japan. In western Kyushu, at its western end, however, many questions remain about their depositional ages, sediment sources, and correlations with established stratigraphic units.
I analyze detrital zircon age spectra from Cretaceous–Paleogene sandstones on the Nagasaki Peninsula, the Nishisonogi Peninsula, and the Amakusa Islands to estimate the depositional ages and sediment sources of individual stratigraphic units. Through this work, I explore how these sandstones in western Kyushu relate to the extensive Cretaceous forearc basin deposits of Southwest Japan.
In particular, I compare zircon age spectra from these sandstones with those of contemporaneous deposits elsewhere in Southwest Japan to investigate the continuity and fragmentation of forearc basins, changes in sediment source regions, and the processes of crustal reworking at the western end of Southwest Japan during the Paleogene.
[Related publications]
01. 吉田 聡，ほか（2022）．西南日本弧白亜紀前弧盆地の西端とその後背地─長崎・西彼杵半島の上部白亜系・古第三系砂岩の砕屑性ジルコンU－Pb 年代測定─．地学雑誌 131(4)，407–422．doi:10.5026/jgeography.131.407