Evaluating the roles of melt-rock interaction and partial degassing on the CO2/Ba ratios of MORB: Implications for the CO2 budget in the Earth’s depleted upper mantle

Shimizu, K.; Saal, A. E.; Hauri, E. H.; Perfit, Michael R.; Hékinian, Roger

doi:10.1016/j.gca.2019.06.013

Cited by 20 publications

(17 citation statements)

References 105 publications

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“…The undersaturated glass CO 2 /Ba and CO 2 /Nb ratios were reported by Shimizu et al (2016); Michael and Graham (2015). port to the argument of (Shimizu et al, 2019); that the Garrett melt inclusions represent a rare case of the inclusions preserving largely undegassed melts.…”

Section: Global Upper Mantle Co 2 Heterogeneitymentioning

confidence: 73%

“…The strength of the correlation between CO 2 /Nb and Ba/Nb shown in Figure 10f arises from the low CO 2 /Nb ratios associated with the samples with low Ba/Nb. The low Ba/Nb samples are from eruptions in fracture zones, including the melt inclusion datasets from the Garrett and Siqueiros fracture zones (Shimizu et al, 2019). Hirschmann (2018) suggests that the correlation may arise from Nb being fractionated from Ba and CO 2 during mantle melting.…”

Section: Global Upper Mantle Co 2 Heterogeneitymentioning

confidence: 99%

“…Ratios of CO 2 and trace-element concentrations One process affecting carbon that it may be possible to successfully control for is melting. Ratios of CO 2 to Ba or Nb concentrations have been used to achieve this (Saal et al, 2002;Le Voyer et al, 2017;Hauri et al, 2018;Michael and Graham, 2015;Shimizu et al, 2016;Tucker et al, 2019;Shimizu et al, 2019;Miller et al, 2019), since CO 2 , Ba, and Nb partition similarly during mantle melting (Saal et al, 2002;Rosenthal et al, 2015). Given this similarity in partitioning behaviour, it should be expected that pre-degassing magmatic values of CO 2 /Ba and CO 2 /Nb will not be fractionated from their mantle sources; the exception to this being that even small differences between the partition coefficients can cause large variations in the CO 2 /Ba and CO 2 /Nb of instantaneous fractional melts extracted from a previously depleted source (Rosenthal et al, 2015).…”

Section: Estimating Mantle Carbonmentioning

confidence: 99%

“…Datasets that do not exhibit correlations likely have a more complex multi-stage degassing history, making them less reliable records of mantle CO 2 /Ba ratios. Shimizu et al (2019) recently demonstrated that not all melt inclusion datasets require a partialdegassing and mixing process to explain their CO 2trace element systematics. For inclusions from the Siqueiros and Garrett transform faults, Shimizu et al (2019) showed that the covariance of CO 2 with a broad suite of trace elements is compatible with the trapped melts having a single mantlederived CO 2 /Ba ratio for variable Ba concentration.…”

Section: Estimating Mantle Carbonmentioning

confidence: 99%

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Melt inclusion constraints on mantle carbon heterogeneity within an individual mantle plume and at the global scale

Matthews¹,

Shorttle²,

Maclennan³

et al. 2019

Preprint

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The Earth’s mantle holds more carbon than its oceans, atmosphere and continents combined, yet the distribution of carbon within the mantle remains uncertain. Global variations in the carbon content of the depleted mantle have been inferred from carbon-trace element systematics of ultra-depleted mid-ocean ridge glasses and melt inclusions, though the origin of mantle carbon variability remains uncertain. A variety of observations suggest that the mantle plumes underlying ocean islands have high bulk carbon contents, but the characterisation of individual mantle plume components has not been possible.We supplement the existing melt inclusion data from Iceland with four new datasets, significantly en- hancing the spatial and geochemical coverage. Within the combined dataset there is significant variation in melt inclusion CO2/Ba ratio, which is tightly correlated with trace element enrichment. The trends in CO2/Ba–Ba space displayed by our new data coincide with the same trends in data compiled from global ocean islands and mid-ocean ridges, forming a global array. The overall structure of the global CO2/Ba array is not a property of the source, instead controlled by CO2 degassing before melt inclusion entrapment, and CO2 loss by decrepitation following inclusion entrapment.The position of melt inclusion datasets within the global array allows us to filter out inclusions likely tohave undergone decrepitation. Providing earlier CO2 degassing and magma mixing have not destroyed themantle signal, the remaining inclusions may preserve mantle CO2/Ba values. Using the observed covariationof the filtered CO2/Ba ratio with radiogenic isotope tracers of mantle source, we find CO2 concentrationsin the Icelandic depleted mantle of 102+53 -27 ppmw, typical of mantle underlying the mid-ocean ridge system,and high CO concentrations of 2.2+3.8 -1.5 wt% associated with the high 3He/4He component of the Iceland plume. However, source and process are difficult to deconvolve for the eruptions most sensitive to enriched, or recycled, mantle components; the presently available data is consistent with recycled material being either enriched or depleted in carbon.Extending our approach globally, we find no systematic variation in CO2/Ba or CO2/Nb with enrichment (in the absence of a primordial mantle contribution). The lack of global co-variation suggests mechanisms recycling CO2 from the surface into the convecting mantle are decoupled from those recycling most trace elements. However, the variation of CO2/Nb with Ba/Nb suggests Ba may behave similarly to CO2 during recycling.

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Section: Global Upper Mantle Co 2 Heterogeneitymentioning

confidence: 73%

Section: Global Upper Mantle Co 2 Heterogeneitymentioning

confidence: 99%

Section: Estimating Mantle Carbonmentioning

confidence: 99%

Section: Estimating Mantle Carbonmentioning

confidence: 99%

See 2 more Smart Citations

Melt inclusion constraints on mantle carbon heterogeneity within an individual mantle plume and at the global scale

Matthews¹,

Shorttle²,

Maclennan³

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Melting is one process affecting carbon that it may be possible to successfully control for. Ratios of C to Ba, or Nb, concentrations have been used to achieve this (Saal et al, 2002;Le Voyer et al, 2017;Hauri et al, 2018;Michael and Graham, 2015;Shimizu et al, 2016;Tucker et al, 2019;Shimizu et al, 2019;Miller et al, 2019), since C, Ba, and Nb partition similarly during mantle melting (Saal et al, 2002;Rosenthal et al, 2015).…”

Section: Ratios Of Carbon and Trace-element Concentrationsmentioning

confidence: 99%

The global melt inclusion C/Ba array: mantle variability, melting process, or degassing?

Matthews¹,

Shorttle²,

Maclennan³

et al. 2022

Preprint

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Persistent gas emission originating from a deep basaltic magma reservoir of an active volcano: the case of Aso volcano, Japan

Kawaguchi

Hasenaka

Koga

et al. 2021

Contrib Mineral Petrol

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Volcanic gas emission is considered to reflect the degassing of magma beneath volcanoes. The combined observations of gas measurement and petrological study are expected to constrain the volatile concentrations and storage depths of the preeruptive and primitive magma. Aso volcano (Japan) is a constantly-monitored, persistently-degassing volcano, and an ideal site to acquire gas and petrologic data. We analyzed the melt inclusions and phenocryst minerals of Holocene basaltic eruption products, and reported their major and volatile element concentrations. The samples showed abundant evidence of magma mixing, such as reverse mineral zoning, and highly variable mineral and glass compositions. SiO2 measured in melt inclusions varied from 46.0 to 65.8 wt. %. High-volatile concentration, S up to 3750

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Evaluating the roles of melt-rock interaction and partial degassing on the CO2/Ba ratios of MORB: Implications for the CO2 budget in the Earth’s depleted upper mantle

Cited by 20 publications

References 105 publications

Melt inclusion constraints on mantle carbon heterogeneity within an individual mantle plume and at the global scale

Melt inclusion constraints on mantle carbon heterogeneity within an individual mantle plume and at the global scale

The global melt inclusion C/Ba array: mantle variability, melting process, or degassing?

Persistent gas emission originating from a deep basaltic magma reservoir of an active volcano: the case of Aso volcano, Japan

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