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Abundant carbon in the mantle beneath Hawai`i

Nature Geoscience

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https://doi.org/10.1038/ngeo3007

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Abstract

Estimates of carbon concentrations in Earths mantle vary over more than an order of magnitude, hindering our ability to understand mantle structure and mineralogy, partial melting, and the carbon cycle. CO2 concentrations in mantle-derived magmas supplying hotspot ocean island volcanoes yield our most direct constraints on mantle carbon, but are extensively modified by degassing during ascent. Here we show that undegassed magmatic and mantle carbon concentrations may be estimated in a Bayesian framework using diverse geologic information at an ocean island volcano. Our CO2 concentration estimates do not rely upon complex degassing models, geochemical tracer elements, assumed magma supply rates, or rare undegassed rock samples. Rather, we couple volcanic CO2 emission rates with probabilistic magma supply rates, which are obtained indirectly from magma storage and eruption rates. We estimate that the CO2content of mantle-derived magma supplying Hawai‘is active volcanoes is 0.97−0.19+0.25 wt%—roughly 40% higher than previously believed—and is supplied from a mantle source region with a carbon concentration of 263−62+81ppm. Our results suggest that mantle plumes and ocean island basalts are carbon-rich. Our data also shed light on helium isotope abundances, CO2/Nb ratios, and may imply higher CO2 emission rates from ocean island volcanoes.

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Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Abundant carbon in the mantle beneath Hawai`i
Series title:
Nature Geoscience
DOI:
10.1038/ngeo3007
Volume:
10
Year Published:
2017
Language:
English
Publisher:
Springer Nature
Contributing office(s):
Volcano Science Center
Description:
5 p.
First page:
704
Last page:
708
Country:
United States
State:
Hawaii