![]() thermal erosion in Bou Ibalghatene, favoured and guided by a dense network of melt conduits. The two xenolith suites illustrate distinct mechanisms of lithospheric thinning: extensional thinning in Tafraoute, where hydrous incongruent melting triggered by decompression probably played a key role in favouring strain localisation, vs. As a consequence the lithospheric mantle beneath Bou Ibalghaten was strongly modified by melt-rock interactions in the Cenozoic whereas the Tafraoute mantle preserves the record of extensional lithospheric thinning, most likely related to Mesozoic rifting. However, while the Bou Ibalghatene mantle was densely traversed by high melt fractions, mostly focused in melt conduits, the Tafraoute suite records heterogeneous infiltration of smaller melt fractions that migrated diffusively, by intergranular porous flow. Both xenolith suites record infiltration of sub-lithospheric melts that are akin to the Middle Atlas volcanism but were differentiated to variable degrees as a result of interactions with lithospheric mantle. ![]() While Bou Ibalghatene belongs to the main Middle Atlas volcanic field, in the 'tabular' Middle Atlas, Tafraoute is situated about 45 km away, on the North Middle Atlas Fault that separates the 'folded' Middle Atlas, to the South-East, from the 'tabular' Middle Atlas, to the North-West. Samples from the two main xenolith localities, the Bou Ibalghatene and Tafraoute maars, have been investigated for their mineralogy, microstructures, crystallographic preferred orientation, and whole-rock and mineral compositions. It is therefore a key area to study the mechanisms of lithospheric thinning and constrain the component of mantle buoyancy that is required to explain the Moroccan topography. ![]() The Middle Atlas is a region where xenolith-bearing volcanism roughly coincides with the maximum of lithospheric thinning beneath continental Morocco. Short wavelength lateral variability of lithospheric mantle beneath the Middle Atlas ( Morocco) as recorded by mantle xenolithsĮl Messbahi, Hicham Bodinier, Jean-Louis Vauchez, Alain Dautria, Jean-Marie Ouali, Houssa Garrido, Carlos J. X-Ray fluorescence is used to determine elemental composition of rock while X-Ray diffraction and the Raman spectroscopy are used to determine major crystalline phases (calcite and dolomite) and minor ones (quartz).The samples display typical EPR spectra of Mn2+ in calcite and reveal the presence of Fe3+ ions. El Amraoui, M.Ī series of marbles sampled from the region of Middle Atlas ( Morocco), are characterized by different complementary spectroscopic techniques. ![]() Study of marbles from Middle Atlas ( Morocco): elemental, mineralogical and structural analysis The Atlas Mountains of Morocco stand as an example of mantle-generated uplift and large-scale lithospheric loss in a mildly contractional orogen. Flow around the retreating Alboran slab focused upwelling mantle under the Middle Atlas, where we image the most recent delamination. The presence of hot mantle, sourced from regional upwellings in northern Africa or the Canary Islands, enabled the mobilization of this lithosphere. The Atlas lithosphere was made unstable by a combination of tectonic shortening and eclogite loading during Mesozoic rifting and Cenozoic magmatism. We propose discontinuous delamination of an intrinsically unstable Atlas lithosphere, enabled by the presence of anomalously hot mantle, as a mechanism for producing the imaged structures. We determine the geometry of lithospheric cavities and mantle upwelling beneath the Middle Atlas and central High Atlas, and image delaminated lithosphere at ~400 km beneath the Middle Atlas. A surface wave model provides constraint on the shallower layers. We use seismic tomography to image the upper mantle of Morocco by inverting teleseimic p-wave delay times, complemented with local delays, recorded on a dense array of stations in the Iberian peninsula and Morocco. Lithospheric delamination under the Atlas Mountains and thermal erosion caused by upwelling mantle have each been suggested as thinning mechanisms. The elevation of the intra-continental Atlas Mountains of Morocco and surrounding regions requires a mantle component of buoyancy, and there is consensus that this buoyancy results from an abnormally thin lithosphere. Piecewise Delamination Drives Uplift in the Atlas Mountains Region of Moroccoīezada, M.
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