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

Abstract

We report the first experimentally-determined metal isotope equilibrium fractionation factors for a metal sulphide at ambient temperatures and pressures.

Experimental determination of iron isotope fractionations among Feaq2+–FeSaq–Mackinawite at low temperatures: Implications for the rock record

“…The isotopic fractionation remained constant when temperature was increased from 20°C to 35°C for fractionation factors between Fe 2þ aq , and mackinawite and between dominantly FeHS + and mackinawite. Synthesis experiments similar to those of Butler et al (2005) and Guilbaud et al (2010) at pH 4 show consistent results: over time, the aqueous Fe-mackinawite fractionation decreases but even after 38 days of aging the fractionation factor is far from the equilibrium value inferred using the three-isotope method. In contrast, at near-neutral pH the fractionation factor for the synthesis experiment reached the equilibrium value in 38 days.…”

Multiple sulfur isotope fractionation and mass transfer processes during pyrite precipitation and recrystallization: An experimental study at 300 and 350 °C

“…Thus, hydrothermal experiments at 77 300 and 350°C, 500 bars were carried out to assess the fractionation of multiple S isotopes 78 between dominant S-bearing aqueous species in the H 2 S-SO 4 -NaCl-FeCl 2 -HCl-H 2 O system 79 coexisting with pyrite. In the present experimental study, we apply the three isotope approach 80 initially developed by Matsuhisa et al [1978] for oxygen isotope fractionation ( 16 O, 17 Pyrite is ubiquitous in both marine and terrestrial hydrothermal systems and its 88 precipitation mechanisms have been studied and debated extensively [Berner, 1970;Butler et al, 89 2004; Guilbaud et al, 2011a;Guilbaud et al, 2010;Guilbaud et al, 2011b;Luther, 1991;90 Murowchick and Barnes, 1987;Rickard and Luther, 1997;Schoonen and Barnes, 1991; 91 Syverson et al, 2013;Yücel et al, 2011]. However, the potential role of pyrite in catalyzing or 92 inhibiting isotope exchange amongst aqueous S-species during precipitation and recrystallization 93 X-ray diffraction (XRD).…”

Fe Isotopic Compositions of Modern Seafloor Hydrothermal Systems and Their Influence Factors

“…Pyrite formation in nature requires two processes: (1) Fe 2+ first forms mackinawite in Fe-rich solutions (Fe 2+ aq + H 2 S aq /HS aq − → FeS); (2) mackinawite then dissolves and forms pyrite (FeS + S 2− /H 2 S → FeS 2 ). Earlier research included simulated Fe isotope fractionation experiments involving mackinawite deposition at room temperature and under acidic conditions [95,96]. At the beginning of the experiments, the 56 Fe value of the mackinawite was lighter than that of the solution by approximately 0.9‰.…”