Tourmaline in a Mesoarchean pelagic hydrothermal system: Implications for the habitat of early life

Tsutomu Ota, Yuhei Aihara, Shoichi Kiyokawa, Ryoji Tanaka, Eizou Nakamura

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish
Article number105475
JournalPrecambrian Research
Volume334
DOIs
Publication statusPublished - Nov 1 2019

Fingerprint

Boron
tourmaline
hydrothermal system
boron
chert
hydrothermal fluid
habitat
RNA
Biological materials
Ribose
Fluids
organic matter
microbial activity
stratigraphic feature
dravite
boron isotope
Earth (planet)
origin of life
borate
Borates

Keywords

  • Boron
  • Early life
  • Hydrothermal system
  • Mesoarchean
  • Tourmaline

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

Cite this

Tourmaline in a Mesoarchean pelagic hydrothermal system : Implications for the habitat of early life. / Ota, Tsutomu; Aihara, Yuhei; Kiyokawa, Shoichi; Tanaka, Ryoji; Nakamura, Eizou.

In: Precambrian Research, Vol. 334, 105475, 01.11.2019.

Research output: Contribution to journalArticle

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