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Sulfur isotope evidence for a Paleoarchean subseafloor biosphere, Barberton, South Africa

N. McLoughlin, E. G. Grosch, M. R. Kilburn and D. Wacey
Sulfur isotope evidence for a Paleoarchean subseafloor biosphere, Barberton, South Africa
Geology (Boulder) (September 2012) 40 (11): 1031-1034

Abstract

The Archean sub-seafloor has been proposed as an environment for the emergence of life, with septate clusters of titanite microtextures in pillow lava rims argued to be the earliest traces of microbial microboring. Here we use nanoscale secondary ion mass spectrometry (NanoSIMS) to test possible geochemical traces of life in ca. 3.45 Ga pillow lavas of the Barberton Greenstone Belt, South Africa. Sulfide inclusions in the titanite microtextures record strongly negative sulfur isotope fractionations of delta (super 34) S (sub VCDT) -39.8 per mil to -3.2 per mil (VCDT--Vienna Canyon Diablo Troilite). These represent the largest range and most negative delta (super 34) S values so far reported from the Archean, and are consistent with an early biogenic origin for the sulfides. Extensive in situ elemental mapping did not find any organic linings associated with the microtextures, despite the high spatial resolution and sensitivity of the NanoSIMS. The absence of organic linings thus excludes a key line of evidence previously used to support the biogenicity of the microtextures. In contrast, in situ sulfur isotope analysis of basalt-hosted sulfides provides an alternative approach to investigating the existence and nature of an Archean subseafloor biosphere.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 40
Serial Issue: 11
Title: Sulfur isotope evidence for a Paleoarchean subseafloor biosphere, Barberton, South Africa
Affiliation: University of Bergen, Department of Earth Science, Bergen, Norway
Pages: 1031-1034
Published: 20120904
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 31
Accession Number: 2012-086326
Categories: Isotope geochemistryStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2012290; accessed on September 13, 2012
Illustration Description: illus.
Source Medium: WWW
S35°00'00" - S22°00'00", E16°00'00" - E33°00'00"
Secondary Affiliation: University of Western Australia, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201245
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