Experimentally derived F, Cl, and Br fluid/melt partitioning of intermediate to silicic melts in shallow magmatic systems

Cassidy, Michael; Iveson, Alexander A.; Humphreys, Madeleine C. S.; Mather, Tamsin A.; Helo, Christoph; Castro, Jonathan M.; Ruprecht, Philipp; Pyle, David M.

doi:10.2138/am-2022-8109

Cited by 8 publications

(6 citation statements)

References 88 publications

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“…In contrast, SO 2 /HF was very high over the lava field, suggesting that HF does not behave in a similar fashion to HCl under the conditions at Holuhraun and was not significantly degassing in the flows syn-eruption—this is consistent with other measurements made of gas around the eruption site that likely reflect a combination of the main plume and the lava field emissions (Gíslason et al 2015 ; Ilyinskaya et al 2017 ; Stefánsson et al 2017 ), and with the HCl/HF ratios. It is also consistent with recent work on F partitioning (Cassidy et al 2022 ). These results are in contrast to the filter pack measurements report in Sigmarsson et al( 2020 ) who found that SO 2 /HF was much lower (two orders of magnitude) in the residual gas from the lava field (after the eruption finished) than during the eruption.…”

Section: Discussionsupporting

confidence: 93%

“…Their model suggests that such systems should move from an initially S-rich melt and gas towards a relatively Cl–Br rich melt and gas, as is also suggested by our data, particularly from Fimmvörðuháls. Furthermore, recent studies suggest that Cl solubility in the melt is strongly dependent on temperature, with decreasing temperature in mafic systems leading to decreasing Cl solubility (Cassidy et al 2022 ; Thomas and Wood 2021 ), consistent with some HCl degassing from the flows. Cassidy et al ( 2022 ) further note that the partitioning of halogen species is strongly compositionally dependent, with their experimental measurements of D Br f/m ranging from 7.1 + / − 6.4 in basaltic andesite to 31.3 + / − 20.9 in dacite.…”

Section: Discussionmentioning

confidence: 86%

“…Furthermore, recent studies suggest that Cl solubility in the melt is strongly dependent on temperature, with decreasing temperature in mafic systems leading to decreasing Cl solubility (Cassidy et al 2022 ; Thomas and Wood 2021 ), consistent with some HCl degassing from the flows. Cassidy et al ( 2022 ) further note that the partitioning of halogen species is strongly compositionally dependent, with their experimental measurements of D Br f/m ranging from 7.1 + / − 6.4 in basaltic andesite to 31.3 + / − 20.9 in dacite. They also note that Br is more sensitive to temperature than Cl in these more silicic systems.…”

Section: Discussionmentioning

confidence: 86%

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Insights into volcanic hazards and plume chemistry from multi-parameter observations: the eruptions of Fimmvörðuháls and Eyjafjallajökull (2010) and Holuhraun (2014–2015)

Donovan,

Pfeffer,

Barnie

et al. 2023

Nat Hazards

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The eruptions of Eyjafjallajökull volcano in 2010 (including its initial effusive phase at Fimmvörðuháls and its later explosive phase from the central volcano) and Bárðarbunga volcano in 2014–2015 (at Holuhraun) were widely reported. Here, we report on complementary, interdisciplinary observations made of the eruptive gases and lavas that shed light on the processes and atmospheric impacts of the eruptions, and afford an intercomparison of contrasting eruptive styles and hazards. We find that (i) consistent with other authors, there are substantial differences in the gas composition between the eruptions; namely that the deeper stored Eyjafjallajökull magmas led to greater enrichment in Cl relative to S; (ii) lava field SO2 degassing was measured to be 5–20% of the total emissions during Holuhraun, and the lava emissions were enriched in Cl at both fissure eruptions—particularly Fimmvörðuháls; and (iii) BrO is produced in Icelandic plumes in spite of the low UV levels.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 86%

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Insights into volcanic hazards and plume chemistry from multi-parameter observations: the eruptions of Fimmvörðuháls and Eyjafjallajökull (2010) and Holuhraun (2014–2015)

Donovan,

Pfeffer,

Barnie

et al. 2023

Nat Hazards

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“…Instead, the compositional trend of our apatite inclusions closely matches those of the H2O-saturated crystallisation models (Fig. 7g), where Cl is partitioned from the melt into an exsolving vapour phase while F is retained in the felsic melt (Candela, 1986;Cassidy et al, 2022;Doherty et al, 2014;Stock et al, 2018;Webster et al, 2009). As the solubility of H2O in a magmatic system is mainly pressure-dependent, the trajectory of apatite volatile evolution should be different during isobaric and polybaric (decompressed) H2O-saturated crystallisation.…”

Section: 𝐷 /supporting

confidence: 66%

Reconstructing volatile exsolution in a porphyry ore-forming magma chamber: Perspectives from apatite inclusions

Huang,

Stock,

Guyett

et al. 2024

American Mineralogist

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Porphyry-type deposits in the shallow crust (3-5 km) are formed from metal-rich fluids exsolved from underlying magma chambers (5-15 km). However, a direct volatile record of the fluid exsolution in the magma chamber is commonly lacking.Here, we analyse the compositions of apatite inclusions (in biotite and plagioclase phenocrysts, and fully-/partly-included in zircon microphenocrysts) and the apatite in groundmass from the largest Cretaceous Luoboling porphyry Cu-Mo deposit in South China. In combination with thermodynamic models, we reconstructed the volatile This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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“…has been shown to be <0.1 (Webster and Holloway 1990), and more recent experiments show that D fluid−melt F(i) is generally <1 in felsic magma systems (Cassidy et al 2021).…”

Section: Modelling Melt Volatile Evolution Under Fluid-saturated and ...mentioning

confidence: 96%

Apatite evidence for a fluid-saturated, crystal-rich magma reservoir forming the Quellaveco porphyry copper deposit (Southern Peru)

Nathwani¹,

Large²,

Brugge³

et al. 2023

Contrib Mineral Petrol

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Large volume, intermediate-felsic magma reservoirs are the source of melt and mineralising fluids which generate porphyry copper deposits. Cooling and crystallisation of hydrous magmas drives the exsolution and expulsion of a magmatic volatile phase—a process which remains challenging to constrain in porphyry Cu systems where the record of magma volatile compositions is rarely preserved. Here, we use the halogen compositions of apatite inclusions shielded as inclusions within zircon to constrain volatile evolution in magma reservoirs which pre-date and are synchronous with porphyry Cu mineralisation at Quellaveco, Southern Peru. Geochemical and textural data confirm that the zircon-included apatites escaped re-equilibration with hydrothermal fluids, unlike apatites found in the groundmass of the same rocks. We, therefore, recommend that future studies attempting to reconcile magmatic volatile budgets using apatite in porphyry Cu systems should focus on apatite inclusions in zircon. By combining the apatite inclusion data with numerical modelling, we find evidence that the magma reservoir sourcing porphyry Cu mineralisation remained fluid-saturated for the entire period recorded by apatite crystallisation. By contrast, the pre-mineralisation batholith shows more variable, potentially fluid-undersaturated behaviour. Our modelling suggests that in order to attain the porphyry melt volatile compositions inferred from apatite, the magma reservoir must have exsolved a large proportion of its volatile budget, consistent with having been held at high crystallinity (40–60% crystals). This crystallisation interval coincides with peak chlorine and copper extraction from intermediate-felsic magmas, and would have permitted efficient fluid migration and accumulation at the roof of the system. We suggest that the storage of large-volume, long-lived, crystal-rich magma reservoirs in magmatic arcs may be a critical step in generating world-class porphyry copper deposits.

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Experimentally derived F, Cl, and Br fluid/melt partitioning of intermediate to silicic melts in shallow magmatic systems

Cited by 8 publications

References 88 publications

Insights into volcanic hazards and plume chemistry from multi-parameter observations: the eruptions of Fimmvörðuháls and Eyjafjallajökull (2010) and Holuhraun (2014–2015)

Insights into volcanic hazards and plume chemistry from multi-parameter observations: the eruptions of Fimmvörðuháls and Eyjafjallajökull (2010) and Holuhraun (2014–2015)

Reconstructing volatile exsolution in a porphyry ore-forming magma chamber: Perspectives from apatite inclusions

Apatite evidence for a fluid-saturated, crystal-rich magma reservoir forming the Quellaveco porphyry copper deposit (Southern Peru)

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