globalchange  > 影响、适应和脆弱性
DOI: 10.1111/gbi.12186
Scopus记录号: 2-s2.0-85028250793
论文题名:
A new occurrence of ambient inclusion trails from the ~1900-million-year-old Gunflint Formation, Ontario: nanocharacterization and testing of potential formation mechanisms
作者: Wacey D.; Saunders M.; Kong C.; Kilburn M.R.
刊名: Geobiology
ISSN: 1472-4677
EISSN: 1472-4669
出版年: 2016
卷: 14, 期:5
起始页码: 440
结束页码: 456
语种: 英语
Scopus关键词: element ; chert ; chlorite ; crystal structure ; diagenesis ; grain size ; matrix ; microbial mat ; microstructure ; mineral ; organic carbon ; Proterozoic ; pyrite ; quartz ; sulfur isotope ; testing method ; thermal decomposition ; bacterium ; chemistry ; fossil ; metabolism ; microscopy ; Ontario ; river ; sediment ; spectrometry ; Bacteria ; Elements ; Fossils ; Geologic Sediments ; Microscopy ; Ontario ; Rivers ; Spectrometry, X-Ray Emission ; Current River ; United States ; Aves
Scopus学科分类: Earth and Planetary Sciences: General Earth and Planetary Sciences ; Environmental Science: General Environmental Science ; Agricultural and Biological Sciences: Ecology, Evolution, Behavior and Systematic
英文摘要: Ambient inclusion trails (AITs) are tubular microstructures thought to form when a microscopic mineral crystal is propelled through a fine-grained rock matrix. Here, we report a new occurrence of AITs from a fossilized microbial mat within the 1878-Ma Gunflint Formation, at Current River, Ontario. The AITs are 1-15 μm in diameter, have pyrite as the propelled crystal, are infilled with chlorite and have been propelled through a microquartz (chert) or chlorite matrix. AITs most commonly originate at the boundary between pyrite- and chlorite-rich laminae and chert-filled fenestrae, with pyrite crystals propelled into the fenestrae. A subset of AITs originate within the fenestrae, rooted either within the chert or within patches of chlorite. Sulphur isotope data ((34) S/(32) S) obtained in situ from AIT pyrite have a δ(34) S of -8.5 to +8.0 ‰, indicating a maximum of ~30 ‰ fractionation from Palaeoproterozoic seawater sulphate (δ(34) S ≈ +20 ‰). Organic carbon is common both at the outer margins of the fenestrae and in patches of chlorite where most AITs originate, and can be found in smaller quantities further along some AITs towards the terminal pyrite grain. We infer that pyrite crystals now found within the AITs formed via the action of heterotrophic sulphate-reducing bacteria during early diagenesis within the microbial mat, as pore waters were becoming depleted in seawater sulphate. Gases derived from this process such as CO2 and H2 S were partially trapped within the microbial mat, helping produce birds-eye fenestrae, while rapid microquartz precipitation closed porosity. We propose that propulsion of the pyrite crystals to form AITs was driven by two complementary mechanisms during burial and low-grade metamorphism: firstly, thermal decomposition of residual organic material providing CO2 , and potentially CH4 , as propulsive gases, plus organic acids to locally dissolve the microquartz matrix; and secondly, reactions involving clay minerals that potentially led to enhanced quartz solubility, plus increases in fluid and/or gas pressure during chlorite formation, with chlorite then infilling the AITs. This latter mechanism is novel and represents a possible way to generate AITs in environments lacking organic material. © 2016 John Wiley & Sons Ltd.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/85096
Appears in Collections:影响、适应和脆弱性

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作者单位: Australian Research Council Centre of Excellence for Core to Crust Fluid Systems, The University of Western Australia, Crawley, WA, Australia; Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Crawley, WA, Australia; School of Earth Sciences, University of Bristol, Bristol, UK; Electron Microscopy Unit, University of New South Wales, Kingsford, NSW, Australia

Recommended Citation:
Wacey D.,Saunders M.,Kong C.,et al. A new occurrence of ambient inclusion trails from the ~1900-million-year-old Gunflint Formation, Ontario: nanocharacterization and testing of potential formation mechanisms[J]. Geobiology,2016-01-01,14(5)
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