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| Titel |
Is Earth coming out of the recent ice house age in the long-term? – constraints from probable mantle CO2-degassing reconstructions |
| VerfasserIn |
Jens Hartmann, Gaojun Li, A. Joshua West |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145831
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| Publikation (Nr.) |
 EGU/EGU2017-9804.pdf |
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| Zusammenfassung |
| Enhanced partial melting of mantle material probably started when the subduction motor
started around 3.2 Ga ago as evidenced by the formation history of the continental crust.
Carbon is degassing due partial melting as it is an incompatible element. Therefore, mantle
carbon degassing rates would change with time proportionally to the reservoir mantle
concentration evolution and the ocean crust production rate, causing a distinct CO2-degassing
rate change with time.
The evolution of the mantle degassing rate has some implications for the reconstruction of
the carbon cycle and therefore climate and Earth surface processes rates, as CO2-degassing
rates are used to constrain or to balance the atmosphere-ocean-crust carbon cycle
system.
It will be shown that compilations of CO2-degassing from relevant geological sources are
probably exceeding the established CO2-sink terrestrial weathering, which is often used to
constrain long-term mantle degassing rates to close the carbon cycle on geological time
scales.
In addition, the scenarios for the degassing dynamics from the mantle sources suggest that
the mantle is depleting its carbon content since 3 Ga. This has further implications for the
long-term CO2-sink weathering. Results will be compared with geochemical proxies for
weathering and weathering intensity dynamics, and will be set in context with snow ball
Earth events and long-term emplacement dynamics of mafic areas as Large Igneous
Provinces.
Decreasing mantle degassing rates since about 2 Ga suggest a constraint for the evolution
of the carbon cycle and recycling potential of the amount of subducted carbon. If the given
scenarios hold further investigation, the contribution of mantle degassing to climate forcing
(directly and via recycling) will decrease further. |
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