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ID 57034
著者
Ota, Tsutomu Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University ORCID Kaken ID
Aihara, Yuhei Department of Earth and Planetary Sciences, Kyushu University
Kiyokawa, Shoichi Department of Earth and Planetary Sciences, Kyushu University
Tanaka, Ryoji Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University ORCID Kaken ID publons
Nakamura, Eizo The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Kaken ID
抄録
The RNA World hypothesis requires the synthesis of RNA to allow the emergence of life on Earth. Hydrothermal systems have been proposed as potential candidates for constructing complex biomolecules. However, in order to successfully form RNA, it is necessary to stabilize ribose, a RNA carbohydrate component. Borate has been found to stabilize ribose. Therefore, boron rich hydrothermal systems are important environments concerning the origin of life on Earth.
The 3.2-Ga Dixon Island Formation of the West Pilbara Superterrane, Western Australia, is a volcano-sedimentary sequence. The Formation represents a Mesoarchean pelagic hydrothermal system, which formed adjacent to an immature island arc. Fine-grained tourmaline, in addition to biogenic carbonaceous matter and spherulitic and tubular bacteriomorphs, are found in black chert. A boron-rich environment was responsible for the formation of these deposits. To explore the implications of such a boron enriched environment on microbial activity, modes of occurrence and chemical compositions of the tourmaline were examined.
The tourmaline is schorl or dravite of the alkali tourmaline group and the boron isotope compositions range in δ11B from -7.3 to +2.6‰. The tourmaline occurs in microcrystalline quartz matrix of black chert veins that cross cut a volcanic unit and also in a bedded black chert, which overlays the volcanic unit. The volcanic unit contains highly altered zones with hydrothermal veins. The associated lithologic and stratigraphic features suggest that the black chert veins were the conduits for upward moving hydrothermal fluids, which reached the sea floor. Subsequently, the volcanic unit was covered by organic matter-rich cherty sediments that in part were fed, and/or altered, by the hydrothermal fluids.
These results suggest that the origin of boron enrichment to form Dixon Island tourmaline is not the associated sedimentary mineral assemblage, which includes diagenetic clay, low-grade metamorphic mica, and organic matter. Instead, the tourmaline was directly precipitated from hydrothermal fluid, enriched in boron. Furthermore, the hydrothermal fluids had already concentrated the boron, in the Mesoarchean pelagic system, prior to the apex of organic matter production and microbial activity. Our findings support a hypothesis that the boron-enriched hydrothermal environment aided the survival and evolution of early life.
キーワード
Mesoarchean
Hydrothermal system
Early life
Boron
Tourmaline
備考
This fulltext will be available in Nov 2021
発行日
2019-11
出版物タイトル
Precambrian Research
334巻
出版者
Elsevier
開始ページ
105475
ISSN
03019268
NCID
AA00780095
資料タイプ
学術雑誌論文
言語
English
OAI-PMH Set
岡山大学
論文のバージョン
author
DOI
Web of Science KeyUT
関連URL
isVersionOf https://doi.org/10.1016/j.precamres.2019.105475
Citation
Tsutomu Ota, Yuhei Aihara, Shoichi Kiyokawa, Ryoji Tanaka, Eizo Nakamura, Tourmaline in a Mesoarchean pelagic hydrothermal system: Implications for the habitat of early life, Precambrian Research, Volume 334, 2019, 105475, ISSN 0301-9268, https://doi.org/10.1016/j.precamres.2019.105475.
助成機関名
日本学術振興会
助成番号
26257211