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Geochemistry of Pyrite from Diamictites of the Boolgeeda Iron Formation, Western Australia with Implications for the GOE and Paleoproterozoic Ice Ages☆

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Geochemistry of Pyrite from Diamictites of the Boolgeeda Iron Formation, Western Australia with Implications for the GOE and Paleoproterozoic Ice Ages☆ Chemical Geology 362 (2013) 131–142 Contents lists available at ScienceDirect Chemical Geology journal homepage: www.elsevier.com/locate/chemgeo Geochemistry of pyrite from diamictites of the Boolgeeda Iron Formation, Western Australia with implications for the GOE and Paleoproterozoic ice ages☆ Elizabeth D. Swanner a,1, Andrey Bekker b, Ernesto Pecoits c,KurtO.Konhauserc, Nicole L. Cates a, Stephen J. Mojzsis a,d,e,⁎ a Department of Geological Sciences, University of Colorado, UCB 399, 2200 Colorado Avenue, Boulder, CO 80309-0399, USA b Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada c Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada d Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Budapest, Budaorsi ut 45, H-1112, Hungary e Laboratoire de Géologie de Lyon, Ecole Normale Supérieure de Lyon and Université Claude Bernard Lyon 1, CNRS UMR 5276, 46 Allée d’Italie, 69007 Lyon, France article info abstract Article history: Sediments of the ca. 2400 Ma Turee Creek Group of Western Australia are coincident with the oxygenation of Accepted 29 July 2013 Earth's surface associated with the ‘Great Oxidation Event’ (GOE). Diamictite within the Boolgeeda Iron Forma- Available online 6 August 2013 tion from the Boundary Ridge section at the Duck Creek Syncline was previously correlated to the glaciogenic sediments of the Meteorite Bore Member of the Turee Creek Group at the Hardey Syncline (Martin, 1999). The Keywords: Meteorite Bore Member is considered correlative and time-equivalent with the Paleoproterozoic glacial Pyrite diamictites of the 2.45–2.22 Ga Huronian Supergroup in North America. If the diamictite units at Boundary Sulfur isotopes Paleoproterozoic glaciations Ridge correspond to worldwide Paleoproterozoic glaciations, they should also record the disappearance of Atmospheric oxygen mass independently fractionated (MIF) sulfur. Triple S-isotope compositions for pyrites from the Boundary Ridge sections were measured in situ by a multi-collector ion microprobe and yielded both mass dependently fractionated (MDF) and MIF sulfur isotope values (Δ33Svaluesfrom−0.44 to +6.27‰). Trace element hetero- geneities are indicated by measurements at multiple spatial scales within rounded pyrites in the Boundary Ridge section, consistent with multiple generations of pyrite that incorporated sulfur processed in an anoxic atmo- sphere. A compilation of S-isotope data from pyrite in the Boundary Ridge diamictites analyzed in this study and previous work (Williford et al., 2011)defines multiple δ34Svs.δ33S arrays, consistent with an origin of detri- tal pyrite from the underlying Hamersley and Fortescue groups. Sulfides in a shale unit from the Boundary Ridge section plot along the terrestrial fractionation line but still retain positive MIF-S. This and detrital pyrite suggest low atmospheric oxygen immediately before the initiation of Paleoproterozoic Ice Ages. This data is inconsistent with a correlation to glacially-influenced successions within the North American Huronian Supergroup, in which the MIF-S signal permanently disappears. The diamictites at the Duck Creek Syncline are older than the Meteorite Bore Member because their stratigraphic position is within the Boolgeeda Iron Formation that underlies the Turee Creek Group, which is separated from the Meteorite Bore Member by nearly 1000 m of the Kungarra shale at the Hardey Syncline. © 2013 Elsevier B.V. All rights reserved. 1. Introduction and geological setting The principal geochemical indicators used to probe conditions for marine pyrite (FeS2) formation in the Archean and Paleoproterozoic Abbreviations: GOE, Great Oxidation Event; MIF, mass independent fractionation; are multiple sulfur isotopes (32S, 33S, 34Sand36S), iron isotopes (typically MDF, mass dependent fractionation; TFL, terrestrial fractionation line; MSR, microbial sul- 54 56 57 58 fate reduction; IF, iron formation. Fe and Fe; although Fe and Fe have been also used), and variable ☆ Dedication: To the memory of our mentor and friend, H.D. Holland. trace metal concentrations (Ni, Co, and other transition metals). The ⁎ Corresponding author at: Department of Geological Sciences, University of Colorado, Archean Eon (ca. 3850 to 2500 Ma) affords special opportunities to iden- UCB 399, 2200 Colorado Avenue, Boulder, CO 80309-0399, USA. Tel.: +1 303 492 5014; tify various sulfur sources to sedimentary pyrite because before about fax: +1 303 492 2606. 2400 Ma the sulfur isotopic compositions of marine (and presumably E-mail address: [email protected] (S.J. Mojzsis). 1 fi Current address: Center for Applied Geoscience (ZAG), Eberhard-Karls-University lacustrine) sedimentary sul de and sulfate minerals record mass- 33 34 Tübingen, Sigwartstrasse 10, 72076 Tübingen, Germany. independent fractionation with the relationship δ S ≠ 0.515 ⋅ δ S 0009-2541/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.chemgeo.2013.07.022 132 E.D. Swanner et al. / Chemical Geology 362 (2013) 131–142 that is imparted by deep-UV photolysis of SO–SO2 from volcanic gases represents the Australian record of these purported global glaciations, processed in an anoxic atmosphere (Farquhar et al., 2000; Pavlov and then the sedimentary pyrites from the Boolgeeda Iron Formation should 33 Kasting, 2002; Bekker et al., 2004). Sulfate aerosols and SO2 (+Δ S), show a similar pattern of multiple sulfur isotope variations with a gen- 33 and S8 aerosols, H2SandHS(−Δ S), were an important source of eral progression from large to attenuated range of MIF culminating in MIF-S to the ocean, and accounted for 1–2% of the sedimentary sulfur the irreversible transition to MDF-S as documented in glacial succes- budget (Farquhar and Wing, 2003). This MIF-S is widely preserved in sions within the North American Huronian Supergroup and the South authigenic Archean marine pyrite, and can be used to differentiate mi- African Transvaal Supergroup cited above. Previous analyses reported crobial and abiotic pathways of sulfur cycling and to identify the sulfur for authigenic and detrital pyrites within diamictite horizons of the source at time of deposition (Mojzsis, 2007; Philippot et al., 2007, Boolgeeda Iron Formation from the Duck Creek Syncline at Boundary 2012; Ueno et al., 2008). Moreover, patterns in δ34S, δ33SandΔ33Svalues Ridge and at the Deepdale locality near Yeera Bluff apparently did not of detrital pyrite in Archean siliciclastic sediments reflect composition of show such a trend (Williford et al., 2011). Here, we re-examine the ar- the source (Hofmann et al., 2009). Multiple sulfur isotope data in ancient gument that the Meteorite Bore Member glacial diamictite is recorded sulfides substantially augments the information provided by pyrite tex- in the Boundary Ridge and the Deepdale locations by significantly tures, morphologies and elemental composition in determining the expanding the database of trace element compositions and multiple source of sulfur in pyrite and the environmental processes by which it sulfur isotope measurements of pyrite within these samples. The formed, and is now routinely employed in analysis of ancient sediments. syngenicity and also synchronicity of the diamictites from the Boolgeeda The disappearance of MIF-S from the pyrite record before about Iron Formation with Paleoproterozoic glacial sediments elsewhere that 2300 Ma occurred in the context of what is regarded as an epoch of span the GOE can therefore be tested by comparison of the multiple sul- Paleoproterozoic “Snowball Earth” events, a name coined for worldwide fur isotope composition of authigenic pyrites to existing records from the ice ages that extended to low latitudes (Kirschvink, 1992). It has been Huronian Supergroup in North America and the Transvaal Supergroup in suggested that the Paleoproterozoic ice ages were accompanied by fluc- South Africa. tuations in the atmospheric oxygen level; the rise of atmospheric oxy- The GOE might have been preceded by a geologically protracted gen led to decrease in atmospheric methane, a strong greenhouse gas time interval of progressive surface oxygenation marked by transient in the Archean, and thence to global glaciation (Kirschvink et al., oxygenation events, the so-called ‘whiffs’ (e.g., Anbar et al., 2007; 2000). Atmospheric oxygen levels fell during these glaciations, which Papineau et al., 2007; Kaufman et al., 2007). It is plausible that oxidative resulted in higher CO2 and methane levels, greenhouse feedback and continental weathering emerged before the disappearance of MIF-S subsequent deglaciation (Bekker and Kaufman, 2007). The Espanola from the rock record (Konhauser et al., 2011), since sulfate delivered Formation of the 2.45–2.22 Ga Huronian Supergroup records a large to the ocean from the continents when sulfides were oxidized for the range in δ34S values of MDF sulfur that was interpreted to reflect the first time is expected to carry MIF (Farquhar and Wing, 2003). The aver- onset of atmospheric oxidation in the Paleoproterozoic (Papineau age Δ33S value of the Archean continental crust is poorly known, but et al., 2007). In addition, the underlying McKim and Pecors formations available data for Archean sedimentary sulfides and sulfates show a also show attenuated range of MIF in sulfur isotopes of sedimentary sul- clear bias towards positive values (Mojzsis et al., 2003; Farquhar and fides (Wing et al.,
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