Boron Isotopes in the Puga Geothermal System, India, and Their Implications for the Habitat of Early Life

Luke H. Steller, Eizo Nakamura, Tsutomu Ota, Chie Sakaguchi, Mukund Sharma, Martin J. Van Kranendonk

Research output: Contribution to journalArticle

Abstract

Boron is associated with several Archean stromatolite deposits, including the tourmaline-rich Barberton stromatolites in South Africa and tourmaline-bearing pyritic laminae associated with stromatolites of the 3.48 Ga Dresser Formation in the Pilbara Craton, Australia. Boron is also a critical element in prebiotic organic chemistry, including in the formation of ribose, a crucial component in RNA. As geological evidence and advances in prebiotic chemistry are now suggesting that hot spring activity may be associated with the origins of life, an understanding of boron and its mobility and isotopic fractionation in geothermal settings may provide important insights into the setting for the origin of life. Here, we report on the boron isotopic compositions and elemental concentrations in a range of fluid, sediment, and mineral samples from the active, boron-rich Puga geothermal system in the Himalayas, India. This includes one of the lowest boron isotope values ever recorded in modern settings: diatom-rich sediments (δ11B = -41.0‰) in a multiphase fractionation system where evaporation is not the dominant form of isotope fractionation. Instead, the extreme boron isotopic fractionation is ascribed to the incorporation of tetrahedral 10B borate anions in precipitating amorphous silica. These findings expand the known limits and drivers of boron isotope fractionation, as well as provide insight into the concentration and fractionation of boron in Archean hot spring environments.

Original languageEnglish
Pages (from-to)1459-1473
Number of pages15
JournalAstrobiology
Volume19
Issue number12
DOIs
Publication statusPublished - Dec 2019

Keywords

  • Boron isotopes
  • Geochemistry
  • Hot springs
  • Origin of life

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Space and Planetary Science

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