Iron isotope fractionation between aqueous ferrous iron and goethite

Fe isotope exchange between Fe(II)aq and nanoparticulate mackinawite (FeSm) during nanoparticle growth

“…Equilibrium enrichment of heavier Fe isotopes in FeS m is consistent with calculated fractionations for pyrite, which is predicted to incorporate heavy isotopes. Beard et al (2010) observed that in general, comparisons between predicted and observed equilibrium fractionations are more consistent for fluid-fluid or mineral-mineral fractionations, rather than for fluid-mineral fractionations. In our case, calculated values for FeS m β-factors are needed to assess the consistency between theory and experiments.…”

“…Experimental data on aqueous Fe species, Fe-oxides and Fe-carbonates have been documented and demonstrate that the largest Fe isotope fractionations are produced during redox reactions in both biologically mediated (Brantley et al, 2001Anbar, 2004;Johnson et al, 2004;Beard et al, 1999Beard et al, ,2003Icopini et al, 2004;Croal et al, 2004) and abiotic systems (Anbar et al, 2000;Skulan et al, 2002Brantley et al, 2004Welch et al, 2003;Matthews et al, 2004;Teutsch et al, 2005;Jang et al, 2008, Handler et al, 2009McAnena, 2009, Beard et al, 2010. Smaller, but significant fractionations have been seen in abiotic non-redox reactions (Wiesli et al, 2004;Wiedehold et al, 2006;Dideriksen et al, 2008;Mikutta et al, 2009), including the ligand-exchange process involved in mackinawite (FeS m ) formation (Butler et al, 2005).…”

Experimental determination of the equilibrium Fe isotope fractionation between and FeSm (mackinawite) at 25 and 2°C

“…Matsuhisa, 1979;Matthews et al, 1983a,b). More recently, three studies applied this method to the Fe isotope systematics: between oxide and silicate phases at high temperature (Shahar et al, 2008), between chloro-complexes in aqueous solutions (Hill and Schauble, 2008), and between Fe(II) aq and goethite (Beard et al, 2010).…”

Iron isotopes reveal distinct dissolved iron sources and pathways in the intermediate versus deep Southern Ocean

“…It can be inferred from these diverse signatures that iron isotopes will bring new constraints on DFe sources to the ocean. In addition, several processes involved in the iron cycling within the water column (e.g., biological uptake, remineralization, scavenging, adsorption, desorption, dissolution, precipitation, organic complexation, and redox processes) may fractionate iron isotopes (14,(18)(19)(20)(21)(22). Hence, such isotopic fractionations may also bring additional constraints on the iron cycle within the water column.…”