Amphibole control on copper systematics in arcs: Insights from the analysis of global datasets

Barber, Nicholas; Edmonds, Marie; Jenner, Frances E.; Audétat, Andreas; Williams, Helen M.

doi:10.1016/j.gca.2021.05.034

Cited by 35 publications

(11 citation statements)

References 82 publications

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“…Although, magmas with larger concentrations of magmatic H 2 O are able to dissolve a larger amount of sulfur before reaching sulfide saturation and thus inhibiting sulfide formation (e.g., Fortin et al, 2015), amphibole fractionation would cause a decrease of the total Fe of the melt, like in the case of magnetite fractionation, converting soluble sulfate (S 6+ ) into less soluble sulfide (S 2− ) and thus promoting sulfide saturation (Carroll & Rutherford, 1988). In fact, a recent study has shown that extensive amphibole fractionation in andesitic rocks at temperatures below 1050°C, which is also the case here with the type-ii gabbroic enclaves of the NLF corresponding to a temperature range of 920-1044°C (Klaver et al, 2017), would substantially decrease the melt FeO tot content and thus also the sulfur content at sulfide saturation (Barber et al, 2021). Considered altogether deep forming "amphibole sponges" appear to be an important sink for sulfur and chalcophile elements in the continental crust.…”

Section: Amphibole Crystallization As a Trigger For Sulfide Saturationsupporting

confidence: 68%

Deep to Shallow Sulfide Saturation at Nisyros Active Volcano

Georgatou

Chiaradia

Klaver

2022

Geochem Geophys Geosyst

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Section: Amphibole Crystallization As a Trigger For Sulfide Saturationsupporting

confidence: 68%

Deep to Shallow Sulfide Saturation at Nisyros Active Volcano

Georgatou

Chiaradia

Klaver

2022

Geochem Geophys Geosyst

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“…In addition to high V/Sc and Sr/Y, a striking feature of the chemistry of the Vanuatu Forearc magmas is their evolution during fractionation to extremely high Cu contents of ∼600 ppm compared to the other arc magmas (Figure 4c). For example, previous compilations using >13,000 analyses have shown that arc magmas rarely exceed Cu concentrations of >300 ppm during fractionation (Barber et al., 2021; Chiaradia, 2014). The behavior of Cu during magmatic processes is dominated by Cu‐loving sulfides (Jenner et al., 2010).…”

Section: Discussionmentioning

confidence: 99%

The Influence of Ridge Subduction on the Geochemistry of Vanuatu Arc Magmas

et al. 2022

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The effects of buoyant ridge subduction have been researched for decades. However, it remains unclear how this process influences magma chemistry. Here we use a compilation of geochemical data, well‐established geochemical proxies (i.e., Ba/Nb, Th/Nb) and mantle redox modeling (i.e., V/Sc, Cu) to propose that the subduction of a ridge underneath the central portion of the Vanuatu arc causes shallow‐angle subduction and the development of a slab tear. We suggest that the shallow slab pinches out the asthenospheric mantle and bulldozes ancient metasomatized lithospheric mantle from the forearc toward the main‐arc. Slab‐fluxed melting of this bulldozed material could account for the along‐arc 87Sr/86Sr‐143Nd/144Nd variations of the Vanuatu magmas. The influx of hot sub‐slab material into the Vanuatu arc mantle wedge through a slab tear produces magmatism within the forearc. Modeling of V/Sc and Cu systematics suggest that the mantle source of the forearc magmas has a higher fO2 and Cu content than the source of the main‐arc and rear‐arc samples. The main‐arc and rear‐arc mantles were metasomatized by both slab‐derived fluids and melts. Whereas release of high Cu‐SO2 slab‐derived fluids caused oxidation and Cu enrichment of the forearc mantle. These systematics indicate a decrease in the fO2 of slab fluxes with increasing depth‐to‐slab and distance‐from‐trench. Our findings highlight the role of ridge subduction in controlling the along‐arc and across‐arc variations in the chemistry of Vanuatu arc magmas. This updated geodynamic model, based on geochemistry, is consistent with recent geophysical constraints and 3D numerical modeling.

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“…The systematic loss of Cu in intermediate magmas of increasingly thicker arcs could be the result of continuous iron depletion in this setting 56 due to fractionation not only of magnetite 7 and garnet 56 , as previously suggested, but also of abundant amphibole (Figs. 5 and 9a) as recently suggested by 57 : fractionation of all these minerals drive the evolution of thick arc magmas into the calc-alkaline eld. A dominant proportion of amphibole in the fractionating assemblage of thick arc magmas (Fig.…”

Section: Discussionmentioning

confidence: 53%

Zinc Systematics Quantify Crustal Thickness Control on Fractionating Assemblages of Arc Magmas

Chiaradia

2021

Preprint

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Understanding the processes leading to the broad chemical variability of arc magmas is an essential, yet not fully elucidated, issue in Earth Sciences. Here, I show that Zn-MgO-SiO2 systematics of magmatic arc rocks correlate significantly with arc thickness. Because Zn-MgO-SiO2 systematics are mostly controlled by fractionation of different mineral phases this suggests a systematic change in the proportions of fractionating mineral assemblages depending on arc thickness. Using a mass balance model with a Monte Carlo approach, I show that Zn-MgO-SiO2 systematics can be quantitatively explained by a continuous transition from plagioclase-dominated fractionating assemblages in thin arcs to amphibole-garnet-magnetite-dominated assemblages in increasingly thicker arcs. Such a systematic change results from the increase of average depth of magma differentiation that is ultimately controlled by arc thickness. Results presented have implications on the causes of different geochemical trends in arcs, the role of arcs as H2O filters, and their association with major porphyry deposits.

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Amphibole control on copper systematics in arcs: Insights from the analysis of global datasets

Cited by 35 publications

References 82 publications

Deep to Shallow Sulfide Saturation at Nisyros Active Volcano

Deep to Shallow Sulfide Saturation at Nisyros Active Volcano

The Influence of Ridge Subduction on the Geochemistry of Vanuatu Arc Magmas

Zinc Systematics Quantify Crustal Thickness Control on Fractionating Assemblages of Arc Magmas

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