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| Titel |
Heat-Flow and Subsurface Temperature History in Eastern Senegal (West Africa) |
| VerfasserIn |
F. Lucazeau, F. Rolandone |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059494
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| Zusammenfassung |
| New temperature measurements from eight drill holes in the West African Craton reveal
significant perturbations up to 100 meters below the alteration zone. These perturbations are
mostly related to the recent global warming (1.5 °C since 1940) and to the circulations of
water at the base of a 20-30 m thick alteration zone. The past ground surface temperatures
inferred from boreholes are very consistent with the surface air temperatures recorded after
1940 in nearby meteorological stations, and do not show any significant change
before 1900. Site effects are observed in the upper part of temperatures logs and
are exclusively interpreted by the subsurface conditions, either the lower thermal
conductivity and / or the circulation of water at the base of the alteration zone. In order to
evaluate their importance at each borehole, we used a 1D finite differences model that
includes both the temperature changes at the Earth surface and the heat transport by
fluids: the eight temperature profiles can be well explained by models with the
same surface temperature variations and the same basal heat flow, but with different
characteristics of the heat transfers in the alteration zone. The basal heat flow estimated
from these models (31 ± 1 mWm-2) is consistent with that determined in the
lowest portion of the deepest boreholes and confirms the previous measurements
(33 ± 8 mWm-2) in the southern part of the West African Craton (Leo Rise). |
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