Formation of micro-spherulitic barite in association with organic matter within sulfidized stromatolites of the 3.48 billion-year-old Dresser Formation, Pilbara Craton.

Autor: Baumgartner RJ; Australian Centre for Astrobiology, School of Biological, Earth and Environmental Sciences, The University of New South Wales, Kensington, NSW, Australia.; Mineral Resources, Commonwealth Scientific and Industrial Research Organization, Kensington, WA, Australia., Van Kranendonk MJ; Australian Centre for Astrobiology, School of Biological, Earth and Environmental Sciences, The University of New South Wales, Kensington, NSW, Australia., Fiorentini ML; School of Earth Sciences, The University of Western Australia, Perth, WA, Australia., Pagès A; Department of Water and Environmental Regulation, Joondalup, WA, Australia., Wacey D; Centre for Microscopy, Characterization and Analysis, The University of Western Australia, Perth, WA, Australia., Kong C; Electron Microscopy Unit, The University of New South Wales, Kensington, NSW, Australia., Saunders M; Centre for Microscopy, Characterization and Analysis, The University of Western Australia, Perth, WA, Australia., Ryan C; Mineral Resources, Commonwealth Scientific and Industrial Research Organization, Melbourne, Vic., Australia.
Jazyk: angličtina
Zdroj: Geobiology [Geobiology] 2020 Jul; Vol. 18 (4), pp. 415-425. Date of Electronic Publication: 2020 May 02.
DOI: 10.1111/gbi.12392
Abstrakt: The shallow marine and subaerial sedimentary and hydrothermal rocks of the ~3.48 billion-year-old Dresser Formation are host to some of Earth's oldest stromatolites and microbial remains. This study reports on texturally distinctive, spherulitic barite micro-mineralization that occur in association with primary, autochthonous organic matter within exceptionally preserved, strongly sulfidized stromatolite samples obtained from drill cores. Spherulitic barite micro-mineralization within the sulfidized stromatolites generally forms submicron-scale aggregates that show gradations from hollow to densely crystallized, irregular to partially radiating crystalline interiors. Several barite micro-spherulites show thin outer shells. Within stromatolites, barite micro-spherulites are intimately associated with petrographically earliest dolomite and nano-porous pyrite enriched in organic matter, the latter of which is a possible biosignature assemblage that hosts microbial remains. Barite spherulites are also observed within layered barite in proximity to stromatolite layers, where they are overgrown by compositionally distinct (Sr-rich), coarsely crystalline barite that may have been sourced from hydrothermal veins at depth. Micro-spherulitic barite, such as reported here, is not known from hydrothermal systems that exceed the upper temperature limit for life. Rather, barite with near-identical morphology and micro-texture is known from zones of high bio-productivity under low-temperature conditions in the modern oceans, where microbial activity and/or organic matter of degrading biomass controls the formation of spherulitic aggregates. Hence, the presence of micro-spherulitic barite in the organic matter-bearing Dresser Formation sulfidized stromatolites lend further support for a biogenic origin of these unusual, exceptionally well-preserved, and very ancient microbialites.
(© 2020 John Wiley & Sons Ltd.)
Databáze: MEDLINE
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