Coupled molybdenum, iron and uranium stable isotopes as oceanic paleoredox proxies during the Paleoproterozoic Shunga Event

Asael, Dan; Tissot, F. L. H.; Reinhard, Christopher T.; Rouxel, Olivier; Dauphas, N.; Lyons, Timothy W.; Ponzevera, Emmanuel; Liorzou, Céline; Chéron, Sandrine

doi:10.1016/j.chemgeo.2013.08.003

Cited by 132 publications

(100 citation statements)

References 166 publications

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“…These processes provide a means to use U concentration in the sedimentary record as a proxy for changes in the oxygen content of the atmosphere-ocean system. In terms of the sedimentary record, U abundances have been investigated in both the IF and black shale records (Partin et al (2013a,b), respectively, while U isotopes have been used in some studies to better illuminate the oxygenation of the oceans (Asael et al, 2013;Kendall et al, 2013Kendall et al, , 2015a A C C E P T E D M A N U S C R I P T…”

Section: Uraniummentioning

confidence: 99%

“…In addition to trace metal contents, sedimentary Fe speciation analysis (Poulton and Canfield, 2005) serves as an indicator of local paleoredox conditions on the ocean floor (i.e., oxic; anoxic, ferruginous; or euxinic) (e.g., Poulton et al, 2004;Canfield et al, 2007;Lyons et al, 2009;Reinhard et al, 2009;Poulton et al, 2010;Planavsky et al, 2011;Asael et al, 2013). The trace element concentrations of anoxic and euxinic…”

Section: Shalesmentioning

confidence: 99%

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Trace elements at the intersection of marine biological and geochemical evolution

Robbins

Lalonde

Planavsky

et al. 2016

Earth-Science Reviews

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158

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Life requires a wide variety of bioessential trace elements to act as structural components and reactive centers in metalloenzymes. These requirements differ between organisms and have evolved over geological time, likely guided in some part by environmental conditions. Until recently, most of what was understood regarding trace element concentrations in the Precambrian oceans was inferred by extrapolation, geochemical modeling, and/or genomic studies. However, in the past decade, the increasing availability of trace element and isotopic data for sedimentary rocks of all ages have yielded new, and potentially more direct, insights into secular changes in seawater composition -and ultimately the evolution of the marine biosphere. Compiled records of many bioessential trace elements (including Ni, Mo, P, Zn, Co, Cr, Se, and I) provide new insight into how trace element abundance in Earth's ancient oceans may have been linked to biological evolution. Several of these trace elements display redox-sensitive behavior, while others are redox-sensitive but not bioessential (e.g., Cr, U). Their temporal trends in sedimentary archives provide useful constraints on changes in atmosphere-ocean redox conditions that are linked to biological evolution, for example, the activity of oxygen-producing, photosynthetic cyanobacteria. In this review, we summarize available Precambrian trace element proxy data, and discuss how temporal trends in the seawater concentrations of specific trace elements may be linked to the evolution of both simple and complex life. We also examine several biologically relevant and/or redox-sensitive trace elements that have yet to be fully examined in the A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT3 sedimentary rock record (e.g., Cu, Cd, W) and suggest several directions for future studies.

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Section: Uraniummentioning

confidence: 99%

Section: Shalesmentioning

confidence: 99%

Trace elements at the intersection of marine biological and geochemical evolution

Robbins

Lalonde

Planavsky

et al. 2016

Earth-Science Reviews

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158

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“…Pyrrhotite is typically grouped with the Fe py pool with the assumption that it formed either as a primary phase or from pyrite, and in either case marks euxinic depositional conditions (e.g. Asael et al, 2013;März et al, 2008;Reuschel et al, 2012).…”

Section: Sequential Extraction Poolsmentioning

confidence: 99%

The effects of metamorphism on iron mineralogy and the iron speciation redox proxy

Slotznick

Eiler

Fischer

2018

Geochimica et Cosmochimica Acta

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As the most abundant transition metal in the Earth's crust, iron is a key player in the planetary redox budget. Observations of iron minerals in the sedimentary record have been used to describe surface atmospheric and aqueous redox environments over the evolution of our planet; the most common method applied is iron speciation, a geochemical sequential extraction method in which proportions of different iron minerals are compared to calibrations from modern sediments to determine water-column redox state. Less is known about how this proxy records information through post-depositional processes, including diagenesis and metamorphism. To get insight into this, we examined how the iron mineral groups/pools (silicates, oxides, sulfides, etc.) and paleoredox proxy interpretations can be affected by known metamorphic processes. Well known metamorphic reactions occurring in sub-chlorite to kyanite rocks are able to move iron between different iron pools along a range of proxy vectors, potentially affecting paleoredox results. To quantify the effect strength of these reactions, we examined mineralogical and geochemical data from two classic localities where SilurianDevonian shales, sandstones, and carbonates deposited in a marine sedimentary basin with oxygenated seawater (based on global and local biological constraints) have been regionally metamorphosed from lower-greenschist facies to granulite facies: Waits River and Gile Mountain Formations, Vermont, USA and the Waterville and Sangerville-Vassalboro Formations, Maine, USA. Plotting iron speciation ratios determined for samples from these 2 localities revealed apparent paleoredox conditions of the depositional water column spanning the entire range from oxic to ferruginous (anoxic) to euxinic (anoxic and sulfidic). Pyrrhotite formation in samples highlighted problems within the proxy as iron pool assignment required assumptions about metamorphic reactions and pyrrhotite's identification depended on the extraction techniques utilized. The presence of diagenetic iron carbonates in many samples severely affected the proxy even at low grade, engendering an interpretation of ferruginous conditions in all lithologies, but particularly in carbonate-bearing rocks. Increasing metamorphic grades transformed iron in carbonates into iron in silicate minerals, which when combined with a slight increase in the amount of pyrrhotite, drove the proxy toward more oxic and more euxinic conditions. Broad-classes of metamorphic reactions (e.g. decarbonation, silicate formation) occurred at distinct temperatures-pressures in carbonates versus siliciclastics, and could be either abrupt between metamorphic facies or more gradual in nature. Notably, these analyses highlighted the importance of trace iron in phases like calcite, which otherwise might not be included in iron-focused research i.e. ore-system petrogenesis, metamorphic evolution, or normative calculations of mineral abundance. The observations show that iron is mobile and reactive during diagenesis and metamorphism, a...

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“…Biological extinctions and radiations correlate with changes in the amount of O 2 in the atmosphere and ocean (e.g., Berner et al, 2007;Canfield et al, 2007;Lenton et al, 2014 Pufahl et al, 2012;Lyons et al, 2009;Asael et al, 2013). Unfortunately, iron formations are only common in the Paleoarchean and Paleoproterozoic, while phosphorites formed almost exclusively in the Phanerozoic (Pufahl et al, 2012).…”

mentioning

confidence: 99%

Uranium isotope fractionation during coprecipitation with aragonite and calcite

Chen

Romaniello

Herrmann

et al. 2016

Geochimica et Cosmochimica Acta

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Natural variations in 238 U/ 235 U of marine carbonates might provide a useful way of constraining redox conditions of ancient environments. In order to evaluate the reliability of this proxy, we conducted aragonite and calcite coprecipitation experiments at pH ~7.5 and ~ 8.5 to study possible U isotope fractionation during incorporation into these minerals.Small but significant U isotope fractionation was observed in aragonite experiments at pH ~ 8.5, with heavier U in the solid phase. 238 U/ 235 U of dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00007+0.00002/-0.00003, 1.00005 ± 0.00001, and 1.00003 ± 0.00001. In contrast, no resolvable U isotope fractionation was observed in an aragonite experiment at pH ~7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among different aqueous U species is the most likely explanation for these findings. Certain charged U species are preferentially incorporated into calcium carbonate relative to the uncharged U species Ca 2 UO 2 (CO 3 ) 3 (aq), which we hypothesize has a lighter equilibrium U isotope composition than most of the charged species. According to this hypothesis, the magnitude of U isotope fractionation should scale with the fraction of dissolved U that is present as Ca 2 UO 2 (CO 3 ) 3 (aq). This expectation is confirmed by equilibrium speciation modeling of our experiments. Theoretical calculation of the U isotope fractionation factors between different U species could further test this hypothesis and our proposed fractionation mechanism.ii These findings suggest that U isotope variations in ancient carbonates could be controlled by changes in the aqueous speciation of seawater U, particularly changes in seawater pH, P CO2 , [Ca], or [Mg] concentrations. In general, these effects are likely to be small (<0.13 ‰), but are nevertheless potentially significant because of the small natural range of variation of 238 U/ 235 U.

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Coupled molybdenum, iron and uranium stable isotopes as oceanic paleoredox proxies during the Paleoproterozoic Shunga Event

Cited by 132 publications

References 166 publications

Trace elements at the intersection of marine biological and geochemical evolution

Trace elements at the intersection of marine biological and geochemical evolution

The effects of metamorphism on iron mineralogy and the iron speciation redox proxy

Uranium isotope fractionation during coprecipitation with aragonite and calcite

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