Language：English   Publishing type：Research paper (scientific journal)  

The characteristic behavior of magnetic remanence correlated with mineralogical textures and composition was observed using low-temperature magnetometry, microscopy, and chemical analysis of three isocubanite samples collected from hydrothermal deposits in the Okinawa Trough and a sample transformed from natural cubanite via heating. Both zero-field remanence acquired at 5 K and field cooling remanence acquired at 300–5 K of all samples sharply decreased with increasing temperature at approximately 100 K. In addition, low-temperature cycling of isothermal remanence at 300 K exhibited a transition at approximately 100 K; remanence increased with decreasing temperature and vice versa. The intensity of remanence at low temperature and sharpness of the transition varied across samples with different compositions and microscopic textures, that is, the presence or absence of chalcopyrite lamellae and their widths. The sample obtained from a hydrothermal chimney, in which the magnetic transition was most clearly observed, was also subjected to X-ray diffraction, Mössbauer spectroscopy, electrical resistivity, and magnetic hysteresis measurements. The obtained results were generally consistent with those reported previously for unnamed mineral CuFe3S4 with an ordered cation arrangement. The low-temperature magnetic behavior of isocubanite possibly depends on the degree of cation ordering and can be regarded as an indicator of chemical composition and cooling history. Therefore, low-temperature magnetometry is useful for the detection of isocubanite and a potentially powerful technique for the prompt estimation of its composition and texture, contributing to our understanding of the formation process of hydrothermal deposits.

DOI： https://doi.org/10.1007/s00269-023-01264-3

Repository Public URL： https://hdl.handle.net/2324/7236433

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2138/am-2020-7153

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1186/s40623-018-0945-y

Repository Public URL： https://hdl.handle.net/2324/7236436

Publisher：Geophysical Research Letters  

The movement history of boulders is crucial for the reconstruction of paleo-tsunamis. We report findings from viscous remanent magnetization studies of the boulders on Tongatapu Island, aiming to reconstruct their reworkings. Two boulders exhibited viscous remanence, whereas two larger boulders lacked viscous components but exhibited stable remanence. Both the viscous and stable components deviated from the geomagnetic field direction. These observations indicate that: (a) the boulders with a viscous component were reworked before the latest event, which could have reworked all boulders, and (b) the magnitude of the latest event was larger than that of an earlier event. The reworked timing indicated that the event occurred between 3,000 years ago and the fifteenth century. The difference in the wave height required to move boulders on the eastern and western coasts suggests that the source of the earlier tsunami was likely an eruption due to volcanoes along the Tonga Ridge.

DOI： 10.1029/2024GL110932

Web of Science

Scopus

Language：English   Publisher：Springer  

Single silicate crystals hosting tiny magnetic inclusions are remarkable targets to study the paleointensities of the Earth and extraterrestrial samples. Since the pioneering work done in late 1990s, paleointensity studies using various silicate minerals such as feldspar, quartz, zircon, pyroxene, and olivine with magnetic inclusions trapped during grain growth or exsolved from the host phase have been reported. It has been shown that some single crystals have the ability to record paleomagnetic information as reliable or more reliable than the whole rock, by direct comparison of the obtained paleointensity estimate from single crystal and the whole-rock sample or the magnetic observatory data. Various rock-magnetic studies also support the fidelity of these crystals. Here, we provide a brief review of the rock-magnetic characteristics of the single crystals, the mineralogical background of the hosting silicates, and experimental procedures developed to obtain reliable data from magnetically weak samples with distinctive rock-magnetic features. We also overview the studies on paleointensity and related topics on various terrestrial and extraterrestrial samples published mainly after the comprehensive reviews in late 2000s. The present review covers the advantages as well as the limitations and caveats of paleointensity studies using single crystal samples and will help readers who wish to utilize this technique in their research.

DOI： 10.1186/s40623-024-01994-w

Web of Science

Scopus

CiNii Research

Event date： 2024.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：立川市  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東北大学   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：相模原市立産業会館・けやき会館   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.6

Language：English   Presentation type：Oral presentation (general)  

Venue：San Francisco   Country：United States  

Language：English   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

Single silicate crystals hosting tiny magnetic inclusions are remarkable targets to study the paleointensities of the Earth and extraterrestrial samples. Since the pioneering work done in late 1990s, paleointensity studies using various silicate minerals such as feldspar, quartz, zircon, pyroxene, and olivine with magnetic inclusions trapped during grain growth or exsolved from the host phase have been reported. It has been shown that some single crystals have the ability to record paleomagnetic information as reliable or more reliable than the whole rock, by direct comparison of the obtained paleointensity estimate from single crystal and the whole-rock sample or the magnetic observatory data. Various rock-magnetic studies also support the fidelity of these crystals. Here, we provide a brief review of the rock-magnetic characteristics of the single crystals, the mineralogical background of the hosting silicates, and experimental procedures developed to obtain reliable data from magnetically weak samples with distinctive rock-magnetic features. We also overview the studies on paleointensity and related topics on various terrestrial and extraterrestrial samples published mainly after the comprehensive reviews in late 2000s. The present review covers the advantages as well as the limitations and caveats of paleointensity studies using single crystal samples and will help readers who wish to utilize this technique in their research.

DOI： https://doi.org/10.1186/s40623-024-01994-w

Repository Public URL： https://hdl.handle.net/2324/7236439

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Audience：General,　Scientific,　Company,　Civic organization,　Governmental agency

Type：Lecture

Audience：General,　Scientific,　Company,　Civic organization,　Governmental agency

Type：Lecture