Ni isotope fractionation during sorption to ferrihydrite: Implications for Ni in banded iron formations

The Isotope Geochemistry of Ni

“…As noted earlier, there is a near constant and 750 smaller fractionation when Ni is sorbed from aqueous solution to ferrihydrite (Wasylenki et al, 2015) and further experiments suggest that such Ni remains immobile during subsequent diagnesis (Robbins et al, 2015). Hence the isotopic composition of Ni in BIF, originally sorbed from Archaen seawater is anticipated to be isotopically heavy for a system in which methanogens dominated the marine Ni cycle.…”

“…Peacock and Sherman, 2007). However, experimental work by Wasylenki et al (2015) documents that sorption of Ni onto the ferrihydride favours the lighter isotopes, leaving an isotopically heavier residual Ni in solution (Fig. 9).…”

“…Earlier in geological history, sorption of Ni to iron oxide phases, preserved in BIF, may 680 have been a significant sink for oceanic Ni. The near constant Δ 60/58 Ni dissolved-sorbed = 0.35±0.10 determined by for Ni sorption onto ferrohydrite over a range of conditions (Wasylenki et al, 2015) gives encouragement for recovering information on past ocean compositions from BIF. It is worth noting that this fractionation, however, is in the wrong direction to account for the isotopic difference between seawater and modern Fe-Mn crusts (Fig.…”

Weathering and vegetation controls on nickel isotope fractionation in surface ultramafic environments (Albania)

“…However, unlike Cu and Zn, Ni enriches the solid phase, rather than the soil solution, in lighter isotopes (the soil solution is therefore isotopically heavier). Presumably, fractionation is controlled by the coordination chemistry of the dissolved phase rather than the solid phase, as demonstrated, for instance, by Cd sorption onto birnessite (Wasylenki et al, 2014) or by Mo or Se oxyanions onto Fe-oxyhydroxides (Goldberg et al, 2009;Zhu et al, 2014). Wasylenki et al (2015) recently demonstrated experimentally that Ni adsorption onto Fe-oxyhydroxides is accompanied by an enrichment of the light isotopes in the solid phase.…”

“…Ni enrichment in the weathered products mainly results from adsorption and Mg-Fe substitution processes (Butt and Cluzel, 2013). The sorption mechanism onto soil or mineral particles has been studied for several isotope systems (Si, Fe, Zn, Cu, Mo, Cd) and has been shown to lead to contrasting fractionation in terms of sign and magnitude (Balistrieri et al, 2008;Delstanche et al, 2009;Goldberg et al, 2009;Mikutta et al, 2009;Wasylenki et al, 2014). In the case of Ni, Wasylenki et al (2015) recently performed experimental adsorption and co-precipitation of dissolved Ni onto Fe-oxyhydroxides and they identified an equilibrium isotope effect leading to the preferential adsorption of light Ni isotopes onto the solid phase with a separation factor ( 60 Ni dissolved-sorbed ) of 0.35 ± 0.10h (1SD).…”