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| Titel |
A review of the heat flow data of NE Morocco |
| VerfasserIn |
Paolo Chiozzi, Alae-Eddine Barkaoui, Abdelkrim Rimi, Massimo Verdoya, Yassine Zarhloule |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250134706
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| Publikation (Nr.) |
 EGU/EGU2016-15454.pdf |
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| Zusammenfassung |
| The Atlas chain is characterised by a SW-NE trending volcanic belt roughly extending from
the Atlantic to the Mediterranean Sea and showing activity that spans in age mainly from
Middle Miocene to Quaternary (14.6-0.3 Ma). The geochemical features of volcanism are
mostly intraplate and alkaline with the exception of the northeastern termination of the belt
where calc-alkaline series crop out. Lithospheric thermal and density models so far proposed,
constrained by heat flow, gravity anomalies, geoid, and topography data, show that the Atlas
chain is not supported isostatically by a thickened crust and a thin, hot and low-density
lithosphere explains the high topography. One of the possible explanations for lithospheric
mantle thinning, possibly in relation with the observed alkaline volcanism, is thermal
erosion produced by either small-scale convection or activation of a small mantle
plume, forming part of a hot and deep mantle reservoir system extending from the
Canary Islands. This paper focuses on the several geothermal data available in the
northeastern sector of the volcanic belt. The occurrence of an extensive, often artesian,
carbonatic reservoir hosting moderately hot groundwater might boost the temperature
gradient in the overlying impermeable cover, and consequently mask the deep thermal
regime. We therefore revised the available dataset and investigated the contribution of
advection. Temperature data available from water and oil wells were reprocessed and
analysed in combination with thermal conductivity measurements on a wide set of
lithotypes. Data were filtered according to rigid selection criteria, and, in the deeper
boreholes, the heat flow was inferred by taking into account the porosity variation with
depth and the temperature effect on the matrix and pore-filling fluid conductivity.
Moreover, the possible effect of advection was evaluated with simple analytical models
which envisage the carbonatic layers as confined aquifers heated by the background
terrestrial heat flow and loosing heat by conduction through the overlying cover. The
results slightly modify the heat-flow picture proposed in previous investigations and
point to negligible effects of advection. The heat flow ranges from 64 to 112 mW
m−2, showing a variation in relation to the different tectonic units, and increases
with the decrease of crustal thickness. Heat-flow data do not satisfactorily track the
volcanism of the northeastern sector. The largest values (86-112 mW m−2) are
found in the Oujda region, at the easternmost edge of the investigated area. The
mantle origin of this thermal anomaly can be neither ruled out nor proved using only
heat flow data, because ∼15 Ma or less is a too short time to enhance the surface
heat flow for pure conduction through a ∼ 100 km-thick lithosphere. We speculate
that the heat flow in the Oujda region might be related to subduction and rifting
processes that occurred during the opening of the western Mediterranean basins. |
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