Pyrite multiple-sulfur isotope evidence for rapid expansion and contraction of the early Paleoproterozoic seawater sulfate reservoir

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

“…It seems that either the deepocean redox state was too oxidised, relative to the strength of hydrothermal input, to form giant sedimentary iron deposits during this time interval, or that marine sulfate levels were high enough that the sulfide produced during bacterial sulfate reduction exceeded the hydrothermal Fe(II) supply -in this case iron sulfides would precipitate instead of iron oxides (see Kump and Seyfried, 2005 for further discussion). Several independent lines of evidence point toward high (mM) sulfate levels during the Lomagundi Event (Schröder et al, 2008;Planavsky et al, 2012b;Scott et al, 2014), consistent with the idea that growth of the marine sulfate reservoir consumed the hydrothermal Fe(II) flux, which ultimately exerted a first-order control on the distribution and abundance of IF.…”

“…Following the end of the Lomagundi carbon isotope excursion, multiple redox indicators point to the collapse of seawater sulfate and atmospheric/oceanic oxygenation (e.g., Planavsky et al, 2012b;Scott et al, 2008Scott et al, , 2014Bekker and Holland, 2012;Partin et al, 2013a, b). In the case of oxygen, estimates range from values as high as 40% PAL to account for persistent anoxia in the oceans (Canfield, 2005) to values as low as 0.1% PAL based on Cr isotopes in various Proterozoic strata (Planavsky et al, 2014b) (Fig.…”

A model for the oceanic mass balance of rhenium and implications for the extent of Proterozoic ocean anoxia

“…The high rates of primary productivity may have been driven by enhanced phosphorus fluxes to the oceans caused by the initial oxidative weathering of sulfide minerals in exposed Archean continental crust (Konhauser et al, 2011;Bekker and Holland, 2012). This organic matter burial event was likely accompanied by significant release of O 2 to the atmosphere (Karhu and Holland, 1996), consistent with geochemical and geological evidence for a shift to higher seawater concentrations of Mo, U, Cr, V, and SO 4 2-in response to this hypothesized increase in atmosphere-ocean oxygenation (Schrö der et al, 2008;Scott et al, 2008Scott et al, , 2014Bekker and Holland, 2012;Planavsky et al, 2012;Reuschel et al, 2012;Sahoo et al, 2012;Partin et al, 2013;Reinhard et al, 2013a). As for other redox-sensitive metals, the increase in oxidative terrestrial weathering accompanying the GOE would have permanently established a continuous riverine flux of dissolved Re to the oceans that, along with contraction of seafloor anoxia, enabled buildup of a larger dissolved Re reservoir in oxygenated seawater.…”

“…The Great Oxidation Event (GOE) is marked by a permanent increase of atmospheric O 2 content to >0.001% present atmospheric level (PAL), starting between 2.45 and 2.32 Ga (Pavlov and Kasting, 2002;Bekker et al, 2004;Gumsley et al, 2017). This transition was accompanied by the appearance of new mineral species containing redox-sensitive elements in their highest oxidation states, reduction in BIF deposition, disappearance of S-MIF, and an increase in seawater Mo, U, and sulfate concentrations Schrö der et al, 2008;Scott et al, 2008Scott et al, , 2014Sverjensky and Lee, 2010;Hazen et al, 2011;Planavsky et al, 2012;Reuschel et al, 2012;Partin et al, 2013;Reinhard et al, 2013a). The latter part of the GOE was marked by a protracted episode of elevated organic carbon burial (Lomagundi Event) between ca.…”

“…The latter part of the GOE was marked by a protracted episode of elevated organic carbon burial (Lomagundi Event) between ca. 2.22 and 2.06 Ga, which suggests a long-lasting, but transient increase in atmosphere-ocean O 2 contents to levels that may not have occurred again until the Neoproterozoic Oxidation Event (NOE) (Karhu and Holland, 1996;Scott et al, 2008Scott et al, , 2014Kump et al, 2011;Planavsky et al, 2011Planavsky et al, , 2012Planavsky et al, , 2014Bekker and Holland, 2012;Partin et al, 2013).…”