Fe isotope fractionation between chalcopyrite and dissolved Fe during hydrothermal recrystallization: An experimental study at 350 °C and 500 bars

Syverson, Drew D.; Luhmann, A. J.; Tan, Chunyang; Borrok, David M.; Ding, Kan; Seyfried, William E.

doi:10.1016/j.gca.2016.12.002

Cited by 37 publications

(29 citation statements)

References 102 publications

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“…This process can lead to gradually increasing d 56 Fe values from the exterior to the interior within the chimney wall. However, oxidation of H 2 S by oxygen in aqueous solution would produce more 34 S-depleted sulfate, and the residual H 2 S would be 34 S-enriched [63], implying sulfides with higher d 34 S values in the exterior chimney. Therefore, redox reactions can explain the decreasing d 56 Fe gradient in pyrite/sphalerite moving outward but are inconsistent with the d 34 S observations.…”

Section: Fe Isotope Compositionmentioning

confidence: 99%

“…Recent experimental and theoretical studies have determined sulfide-fluid isotope fractionation during sulfide precipitation and recrystallization, which is temperature-dependent in a certain range [27,[33][34][35][64][65][66][67][68][69] ) reaches equilibrium, which is temperaturedependent [27,33]. Either pathway could explain the observations from the EPR 9°-10°N hydrothermal field [29] and indicates greater fractionation between pyrite and aqueous Fe 2+ at lower temperatures.…”

Section: Fe Isotope Compositionmentioning

confidence: 99%

“…In the present case, pyrite recrystallization was assumed to be a pyrite-fluid exchange process [35]. The S isotope might achieve final pyrite-H 2 S equilibrium, in which we utilize the revised S isotope equilibrium fractionation value (1000 ln 34 a pyriteÀH 2 S = À1.9‰ at 350°C) [35] and estimate the relationship between 1000 ln 34 a pyriteÀH 2 S and temperature to be 1000 ln 34 a pyriteÀH 2 S = À0.7378 Â 10 6 /T 2 (T in K). The exchange process can be described as…”

Section: +mentioning

confidence: 99%

“…As the primary elements in these hydrothermal systems, Fe and S in sulfides have been studied extensively [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. The Fe and S isotopes in the sulfides are controlled both by fluids and by sulfide formation processes, thus, Fe and S isotopes in concurrent sulfides and vent fluids could be the best means of constraining the sulfide precipitation and recrystallization processes.…”

Section: Introductionmentioning

confidence: 99%

“…The Fe and S isotopes in the sulfides are controlled both by fluids and by sulfide formation processes, thus, Fe and S isotopes in concurrent sulfides and vent fluids could be the best means of constraining the sulfide precipitation and recrystallization processes. Previous studies reported the S isotope compositions of sulfides and coexisting vent fluids, where the sulfides, in particular pyrite, were more depleted in d 34 S than H 2 S in the vent fluids [22,29,31,36,37]. Pyrite has been reported to be far from S isotope equilibrium with H 2 S during pyrite formation [38], but a revised equilibrium fractionation factor suggested that pyrite was close to S isotope equilibrium with vent H 2 S [35].…”

Section: Introductionmentioning

confidence: 99%

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Coupled Fe–S isotope composition of sulfide chimneys dominated by temperature heterogeneity in seafloor hydrothermal systems

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Section: Fe Isotope Compositionmentioning

confidence: 99%

Section: Fe Isotope Compositionmentioning

confidence: 99%

Section: +mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coupled Fe–S isotope composition of sulfide chimneys dominated by temperature heterogeneity in seafloor hydrothermal systems

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The Role of Redox Processes in Determining the Iron Isotope Compositions of Minerals, Melts, and Fluids

Sossi¹,

Debret²

2021

Geophysical Monograph Series

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Stable isotope fractionation is a response to the minimisation of free energy associated with differences in vibrational frequencies during substitution of isotopic masses between two phases. Site properties are dictated by the bonding environment of iron, and influence its 'force constant', a descriptor for bond strength. Because iron readily transitions between its ferrous (Fe 2+ ) and ferric (Fe 3+ ) state over the oxygen fugacities (fO 2 ) of terrestrial magmas, redox processes are presumed to control iron isotope fractionation. In fact, both co-ordination and redox state are key to interpreting iron isotope variations in high-temperature, high-pressure geological systems. Determinations of iron force constants by experimental, theoretical and spectroscopic means in minerals, melts and fluids are reviewed, emphasising the effect of composition in influencing isotopic fractionation. Within this framework, the application of numerical models of partial melting to iron isotope variations in oceanic basalts and subduction-zone (or arc) magmas has shed light on their genesis. The influence of melt composition, mineral mode and fluid exsolution in producing iron isotope fractionation in evolving magmas is explored. Iron isotopic signatures in magmatic rocks are linked to that of their sources, and are influenced by the iron isotopic evolution of subducting slabs and transfer of fluids to the mantle wedge. 2.0. Principles and nomenclature Ratios of two isotopes, n and d of an element, E, are generally expressed relative to their ratio in a standard in delta notation, which is given by:(1) 𝛿 𝑛/𝑑 𝐸 = ( ( 𝑛 𝐸/ 𝑑 𝐸) 𝑠𝑎𝑚𝑝𝑙𝑒

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Texture and iron‐oxygen isotope composition of magnetite in the Sanaga iron ore prospect, Nyong Series, southwestern Cameroon: Implications for the origin of the magnetite mineralization

et al. 2023

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The Sanaga iron ore prospect within the Palaeoproterozoic Nyong Series in Cameroon is a magnetite‐dominated iron ore deposit hosted within granodioritic gneisses with an estimated resource of 82.9 Mt @ 32.1% Fe. The main ore mineral being magnetite, provides an opportunity to study the magnetite texture and iron‐oxygen isotope composition of the mineralization, which has heretofore not been reported. These offer insights into the nature and condition of formation of the mineralization thereby paving the way for better understanding the genesis and evolution of the mineralization as well as classifying it. The mineralization is characterized by Type I and Type II magnetite varieties based on their textural features. Type I magnetite is the dominant magnetite and is characterized by ilmenite oxy‐exsolution features with triple junction contacts, while Type II magnetite lacks these features. The presence of ilmenite oxy‐exsolution features in the Type I magnetite indicates a primary magmatic formation of the magnetite followed by re‐equilibration of primary Ti‐rich magnetite in the presence of a high‐temperature fluid. Oxygen isotope (δ18O) values for the magnetite range from +2.89% to 9.30‰ indicating precipitation from evolved ore‐forming fluids through reaction with country rocks. The iron isotope (δ56Fe) of the magnetite shows little variation, with positive values ranging from +0.49–0.66‰. These values plot within the magmatic and magmatic‐hydrothermal magnetite fields when compared to the published global range of δ56Fe values for different deposit types. A similar result is obtained by plotting the coupled Fe–O isotope pair, further buttressing the magmatic‐hydrothermal origin of the mineralization. Based on these data, the Sanaga iron mineralization is best explained as a magmatic‐hydrothermal deposit.

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Fe isotope fractionation between chalcopyrite and dissolved Fe during hydrothermal recrystallization: An experimental study at 350 °C and 500 bars

Cited by 37 publications

References 102 publications

Coupled Fe–S isotope composition of sulfide chimneys dominated by temperature heterogeneity in seafloor hydrothermal systems

Coupled Fe–S isotope composition of sulfide chimneys dominated by temperature heterogeneity in seafloor hydrothermal systems

The Role of Redox Processes in Determining the Iron Isotope Compositions of Minerals, Melts, and Fluids

Texture and iron‐oxygen isotope composition of magnetite in the Sanaga iron ore prospect, Nyong Series, southwestern Cameroon: Implications for the origin of the magnetite mineralization

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