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No slab-derived CO₂ in Mariana Trough back-arc basalts: Implications for carbon subduction and for temporary storage of CO₂ beneath slow spreading ridges

Macpherson, C.G.; Hilton, D.R.; Hammerschmidt, K.

No slab-derived CO₂ in Mariana Trough back-arc basalts: Implications for carbon subduction and for temporary storage of CO₂ beneath slow spreading ridges Thumbnail


Authors

D.R. Hilton

K. Hammerschmidt



Abstract

[1] The Southern Mariana Trough is particularly well suited to study mass balance in subduction zones because the flux of material recycled from the subducted slab has been shown to diminish to negligible levels in the southernmost part of the area. We present new He and Ar concentration and isotopic data for 16 back-arc basaltic glasses and combine these with previously published CO2 and H2O concentration and δ13C data to explore the recycling of carbon and light noble gases in the Mariana back arc. Degassing has affected all samples and is particularly extensive in more water-rich samples, i.e., those containing the largest recycled component. The degassing history features three stages: (1) deep degassing which commenced when the melt reached saturation of CO2 and noble gases in the mantle, (2) preeruptive degassing during storage in the crust-mantle transition zone which involved addition of extraneous CO2 to the vapor phase, and (3) eruption. CO2 released during stage 1 was, at least partially, incorporated into wall rock and subsequently remobilized during stage 2 degassing of later magma batches. Reconstructed parental values for 3He/4He, δ13C, CO2/3He, and CO2/40Ar* are indistinguishable from those of mid-ocean ridge basalt. This implies that there is negligible recycling of subducted carbon, helium, or argon into the source of Mariana Trough basalt.

Citation

Macpherson, C., Hilton, D., & Hammerschmidt, K. (2010). No slab-derived CO₂ in Mariana Trough back-arc basalts: Implications for carbon subduction and for temporary storage of CO₂ beneath slow spreading ridges. Geochemistry, Geophysics, Geosystems, 11(11), Article Q11007. https://doi.org/10.1029/2010gc003293

Journal Article Type Article
Publication Date Nov 12, 2010
Deposit Date Nov 12, 2010
Publicly Available Date Mar 29, 2024
Journal Geochemistry, Geophysics, Geosystems
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 11
Issue 11
Article Number Q11007
DOI https://doi.org/10.1029/2010gc003293
Keywords CO2, Noble gas, Mariana Trough, Basalt, Assimilation, Subduction.
Publisher URL http://www.agu.org/journals/gc/gc1011/2010GC003293/

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Copyright Statement
© 2010 American Geophysical Union.





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