Sulfur dissolution capacity of highly hydrated and fluid-saturated dacitic magmas at the lower crust and implications for porphyry deposit formation

Xu, Ting; Liu, Xingcheng; Xiong, Xiaolin; Wang, J.

doi:10.1016/j.gca.2022.07.004

Cited by 13 publications

(7 citation statements)

References 79 publications

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“…Based on the experimental constraint, S concentrations in hydrous hybrid melt at the interface is 2000 ppm S at 9 wt% H2O. Thermodynamic calculations (Table S5, Methods) give the oxidized (NNO+2.5) fluid sulfur concentrations of 10 5 ppm S similar to the reported in experiments on sulphate-sulfide transition 12 and highly hydrated and fluid-saturated system 16 .…”

Section: Hybrid S-rich Fluid As a Trigger Of Explosive Eruptionssupporting

confidence: 60%

“…In contrast, ref. 16 hypothesized the presence of (Fe,Ca)SO4 nH2O or (Na,K)2SO4 nH2O at similar physicalchemical conditions and similar hydrous system. In the experimental system studied here, the sulfur transport in the melt is decoupled from water and is likely related to the sulfur radical species, which have very poor solubility and chemical bonding in the aluminosilicate melt 12 , explaining the extremely rapid diffusion of these species in the hybrid melt.…”

Section: Sulfur Diffusion and Speciation In Hybrid Systemmentioning

confidence: 99%

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Open system fluid-assisted sulfide dissolution reaction triggers explosive volcanic eruptions and can control production of metallogenic provinces

BORISOVA

2024

Preprint

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Explosive eruptions are frequently triggered by mixing of contrast-type magmas such as mantle-derived basaltic magmas with hydrous silica-rich magmas. Up to date, the mechanisms and rates of reaction of sulfide dissolution in hydrous silica-rich melt are unknown. I experimentally model dissolution of pyrrhotite mineral in water-saturated hydrous rhyolite melt at conditions corresponding to sulphate-sulfide transition field. The reaction results in production of FeO(melt) and SO42- and H2, H2S and di- and trisulfur radical ions, S2- or S3- in fluid/melt. The calculated diffusion coefficient for the oxidized sulfur dissolved in the hydrous rhyolitic melt implies extremely fast sulfur diffusion in the hydrous hybrid melt. Hybridization and magma mixing are controlled by the fastest ever recorded chemical diffusion of sulfur in the form of S2- or S3-, which is converted to [SO4]2- in the quenched glass and is associated with the production of hybrid fluid saturated magma. The dissolution reaction of the lower crust-to-mantle-crust transition zone-derived sulfides can trigger explosive volcanic eruptions not only in volcanic arcs but also in hot spot geodynamic settings. The fluid-assisted sulfide dissolution reaction can also control production of chalcophile (Au, Ag, Cu, Mo and Pt) metallogenic provinces.

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Section: Hybrid S-rich Fluid As a Trigger Of Explosive Eruptionssupporting

confidence: 60%

Section: Sulfur Diffusion and Speciation In Hybrid Systemmentioning

confidence: 99%

Open system fluid-assisted sulfide dissolution reaction triggers explosive volcanic eruptions and can control production of metallogenic provinces

BORISOVA

2024

Preprint

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“…In run Cu-52, the FMQ buffer failed due to the absence of fayalite in the buffer assemblage after experiment. For runs Cu-8, MORB-L2, and Cu-50, fO 2 was calculated based on melt water activity following methods in Xu et al 23 and Burnham 24 . An estimated relative fO 2 sequence for the unbuffered runs, based on Cu solubility, is provided: Cu-8 > Cu-45 > Cu-6 > Cu-52 > Cu-47 > MORB-L2 > Cu-50 (detailed in the text).…”

Section: Resultsmentioning

confidence: 99%

“…Accurate fO 2 values were determinable for runs Cu-8, MORB-L2, and Cu-50, where fO 2 buffer control was successfully established. Methods outlined by Xu et al 23 and Burnham 24 estimated fO 2 in these runs, yielding a range from ΔFMQ − 1.8 to ΔFMQ + 3.1. Subsequently, the fO 2 conditions in unbuffered runs were estimated based on their respective melt Cu contents, as observed variations in Cu content primarily arise from differences in temperature and fO 2 .…”

Section: Resultsmentioning

confidence: 99%

Oxidation state of Cu in silicate melts at upper mantle conditions

Liu,

Zhang,

Zhu

et al. 2024

Sci Rep

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Beyond its economic value, copper (Cu) serves as a valuable tracer of deep magmatic processes due to its close relationship with magmatic sulfide evolution and sensitivity to oxygen fugacity (fO2). However, determining Cu’s oxidation state (+ 1 or + 2) in silicate melts, crucial for interpreting its behavior and reconstructing fO2 in the Earth’s interior, has long been a challenge. This study utilizes X-ray Absorption Near Edge Structure spectroscopy to investigate the Cu oxidation state in hydrous mafic silicate melts equilibrated under diverse fO2 (− 1.8 to 3.1 log units relative to the Fayalite–Magnetite–Quartz buffer), temperature (1150–1300 °C), and pressure (1.0–2.5 GPa) conditions. Our results reveal that Cu predominantly exists as Cu+ across all fO2 conditions, with a minor Cu2+ component. This dominance of Cu+ persists even in relatively oxidized melts, highlighting its limited sensitivity to fO2 under upper mantle conditions. This significantly constrains the utility of Cu as an oxybarometer in hydrous silicate melts in the deep Earth. However, our findings suggest that Cu isotopes primarily reflect the interplay of sulfide segregation/accumulation during magmatic differentiation, shedding light on these fundamental processes in Earth’s interior.

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“…These magmas typically record oxygen fugacity ( f O 2 ) values equal or greater than the Ni–NiO f O 2 buffer (Sun et al., 2015). The importance of high oxidation state to copper metallogenic fertility is the 10‐ to 20‐fold increase in a silicate melt sulfur‐carrying capacity as it rises into the predominance range of sulfate (Jugo et al., 2005; Park et al., 2021; Richards, 2015; Xu et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

Porphyry Copper Deposit Formation: Identifying Garnet and Amphibole Fractionation With REE Pattern Curvature Modeling

Tatnell

Anenburg

Loucks

2023

Geophysical Research Letters

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Empirical evidence for high oxidation state of porphyry-copper-deposit (PCD) generative arc magmas has been noted and discussed for decades (Burnham & Ohmoto, 1980;Hutchinson & Dilles, 2019;Park et al., 2021). These magmas typically record oxygen fugacity (fO 2 ) values equal or greater than the Ni-NiO fO 2 buffer (Sun et al., 2015). The importance of high oxidation state to copper metallogenic fertility is the 10-to 20-fold increase in a silicate melt sulfur-carrying capacity as it rises into the predominance range of sulfate (

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Sulfur dissolution capacity of highly hydrated and fluid-saturated dacitic magmas at the lower crust and implications for porphyry deposit formation

Cited by 13 publications

References 79 publications

Open system fluid-assisted sulfide dissolution reaction triggers explosive volcanic eruptions and can control production of metallogenic provinces

Open system fluid-assisted sulfide dissolution reaction triggers explosive volcanic eruptions and can control production of metallogenic provinces

Oxidation state of Cu in silicate melts at upper mantle conditions

Porphyry Copper Deposit Formation: Identifying Garnet and Amphibole Fractionation With REE Pattern Curvature Modeling

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