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| Titel |
Mapping modern CO2 fluxes and mantle carbon content all along the mid-ocean ridge system |
| VerfasserIn |
Deborah Chavrit, Eric Humler, Olivier Grasset, Yann Morizet, Didier Laporte |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099493
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| Publikation (Nr.) |
 EGU/EGU2014-15278.pdf |
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| Zusammenfassung |
| Quality criteria have been used to select ~ 400 vesicularity measurements on zero-age
mid-ocean ridge glasses from ~ 600 data available in the literature published over the past ~
30 years. At face value, observations show that for a given depth of sampling, enriched
basalts from slow spreading ridge segments are more vesicular than those from depleted and
intermediate or fast spreading ridges. A shallower depth of eruption enhances these effects
because lower hydrostatic pressure favours bubble expansion. In order to get an insight into
these complex and intermingled processes, we used empirical and semi-quantitative
approaches based on a limited number of inputs (segment depth, spreading rate and
K2O/TiO2 ratios). Both models give equivalent results and predict vesicularities within ±
50%. From these calculations, we compute the equivalent CO2 concentration at the depth of
eruption all along the oceanic ridge system. The total calculated CO2 fluxes are low ranging
from 6.5±1.8 to 8.7±2.8 x1011 mol/yr between the models and the CO2 mantle
content displays large variabilities from 66-19+27 to 78-40+82 ppm, with values
higher near hot spots. In order to test these results, the mantle 3He fluxes have been
evaluated using the calculated CO2 fluxes and a CO2/3He ratio of 2.2 x 109. These
fluxes range from 295±82 to 395±127 mol/yr and are close to the values reported
by Jean-Baptiste (1992) (267-534 mol/yr) and the most recent estimate (Bianchi
et al., 2010, ~527±102 mol/yr) using box-model of the three main ocean basins
constrained by measurements of 3He and radiocarbon data. As these independent
methods give similar helium fluxes at regional and global scales, it provides strong
support to a low and heterogeneous mantle carbon concentration and distribution. |
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