Short wavelength lateral variability of lithospheric mantle beneath the Middle Atlas (Morocco) as recorded by mantle xenoliths

Messbahi, Hicham El; Bodinier, Jean-Louis; Vauchez, Alain; Dautria, Jean-Marie; Ouali, Houssa; Garrido, Carlos J.

doi:10.1016/j.tecto.2014.11.020

Cited by 24 publications

(18 citation statements)

References 75 publications

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“…Geochemical analyses from the spinel lherzolite xenoliths in the CVP show a moderately fertile mantle with low degree of partial melting that underwent two metasomatizing events associated with subduction-related melt and alkaline melt (Villaseca et al, 2010). The analyses of peridotite xenoliths recovered from Pliocene-Quaternary alkaline basaltic melts in the Middle Atlas performed by Raffone et al (2009) and El Messbahi et al (2015) show an extreme lithological and chemical heterogeneity that is consistent with widespread and variable degree of metasomatism in their lithospheric mantle source.…”

Section: 1029/2019jb018445mentioning

confidence: 75%

Deep seated density anomalies across the Iberia-Africa plate boundary and its topographic response

Jiménez‐Munt

Torné

Fernández

et al. 2020

Preprint

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<p>The modes in which the lithosphere deforms during continental collision and the mechanisms involved are not well understood. While continental subduction and mantle delamination are often invoked in tectonophysical studies, these processes are difficult to be confirmed in more complex tectonic regions such as the Gibraltar Arc. We study the present-day density and compositional structure of the lithosphere along a transect running from S Iberia to N Africa crossing the western Gibraltar Arc. This region is located in the westernmost continental segment of the African-Eurasian plates, characterized by a diffuse transpressive plate boundary. An integrated and self-consistent geophysical-petrological methodology is used to model the lithosphere structure variations and the thermophysical properties of the upper mantle. The crustal structure is mainly constrained by seismic experiments and geological data, whereas the composition of the lithospheric mantle is constrained by xenolith data. The results show large lateral variations in the topography of the lithosphere-asthenosphere boundary (LAB). We distinguish different chemical lithospheric mantle domains that reproduce the main trends of the geophysical observables and the modelled P- and S-wave seismic velocities. A sublithospheric body colder than the surrounding mantle is needed beneath the Betics-Rif to adjust the measured potential fields. We link this body to the Iberian slab localized just to the east of the profile and having some effect on the geoid and Bouguer anomalies. Local isostasy allows explaining most of the topography, but an elastic thickness higher than 10 km is needed to explain local misfits between the Atlas and the Rif Mountains. This work has been supported by Spanish Ministry by the projects MITE (CGL2014-59516) and GeoCAM (PGC2018-095154-B-100).</p>

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Section: 1029/2019jb018445mentioning

confidence: 75%

Deep seated density anomalies across the Iberia-Africa plate boundary and its topographic response

Jiménez‐Munt

Torné

Fernández

et al. 2020

Preprint

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“… Variation of Ca content in amphibole as a function of total alkali content in amphiboles from this study (squares) and previous experimental studies (circles) plotted as a function of (a) bulk CaO and (b) bulk alkali content of volatile‐bearing peridotite (Condamine & Médard, ; Fumagalli et al, ; Fumagalli & Poli, 2005; Green et al, ; Mallik et al, ; Mengel & Green, ; Tumiati et al, ; Wallace & Green, ). The light yellow‐orange field in the background represents amphibole compositions from cratonic peridotite xenoliths (Beard et al, ; Frey & Green, ; Gamble & Kyle, ; Griffin, ; Griffin et al, ; Glaser et al, ; Ionov, ; Lucassen et al, ; Messbahi et al, ; Scott et al, ; Witt & Seck, ; Xu et al, ).…”

Section: Discussionmentioning

confidence: 99%

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

Saha

Dasgupta

Tsuno

2018

Geochem Geophys Geosyst

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We present phase equilibria experiments on a depleted peridotite (Mg# 92) fluxed with variable proportions of a slab‐derived rhyolitic melt (with 9.4 wt.% H2O, 5 wt.% CO2), envisaging an interaction that could occur during formation of continents by imbrication of slabs/accretion of subarc mantles. Experiments were performed with 5 wt.% (Bulk 2) and 10 wt.% (Bulk 1) melt at 950–1175°C and 2–4 GPa using a piston‐cylinder and a multi‐anvil apparatus, to test the hypothesis that volatile‐bearing mineral‐phases produced during craton formation can cause reduction in aggregate shear‐wave velocities (VS) at mid‐lithospheric depths beneath continents. In addition to the presence of olivine, orthopyroxene, clinopyroxene, and garnet/spinel, phlogopite (Bulk 1: 3–7.6 wt.%; Bulk 2: 2.6–5 wt.%) at 2–4 GPa, and amphibole (Bulk 1: 3–9 wt.%; Bulk 2: 2–6 wt.%) at 2–3 GPa (≤1050°C) are also present. Magnesite (Bulk 1: ∼1 wt.% and Bulk 2: ∼0.6 wt.%) is present at 2–4 GPa (<1000°C at 3 and < 1050°C at 4 GPa) and its thermal breakdown coincides with the visual appearance of trace‐melt. However, an extremely small fraction of melt is inferred at all experiments based on the knowledge of fluid‐saturated peridotite solidus and the difference between bulk H2O and total H2O stored in the hydrous phases. Calculated mineral end‐member volume‐proportions were used to calculate VS of the resulting assemblage at experimental conditions and along representative continental geotherms (surface heat flow of 40–50 mWm−2). We note that reactive crystallization of phlogopite ± amphibole by infiltration of 3–10% slab‐derived hydrous‐silicic melt can cause up to 6% reduction in VS and that the estimated reduction in VS increases with increasing melt:rock ratio. The presence of phlogopite limits amphibole‐stability, making phlogopite a more likely candidate for MLDs at >100 km depth.

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“…Neither sedimentary rock fragments prior to the Lias nor upper or middle crust fragments have ever been found among the clasts, suggesting that the water interacting with the magma was stored in the same Liasic layers as those surrounding the edifices, therefore at relatively shallow depths (several tens of metres, less than 150 m). In contrast, deep crustal granulite and lithospheric mantle peridotite fragments are often present: they correspond to xenoliths entrained by the juvenile basalts (El Messbahi et al, 2015 and references therein).…”

Section: Inventory Of the Hydrovolcanic Edifices In The Azrou-timahdimentioning

confidence: 99%

Eruption dynamics of pleistocene maars and tuff rings from the Azrou-Timahdite district (Middle Atlas, northern Morocco) and its relevance to environmental changes and ground water table characteristics

Messbahi

Dautria

Jourde

et al. 2020

Journal of African Earth Sciences

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Short wavelength lateral variability of lithospheric mantle beneath the Middle Atlas (Morocco) as recorded by mantle xenoliths

Cited by 24 publications

References 75 publications

Deep seated density anomalies across the Iberia-Africa plate boundary and its topographic response

Deep seated density anomalies across the Iberia-Africa plate boundary and its topographic response

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

Eruption dynamics of pleistocene maars and tuff rings from the Azrou-Timahdite district (Middle Atlas, northern Morocco) and its relevance to environmental changes and ground water table characteristics

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Short wavelength lateral variability of lithospheric mantle beneath the Middle Atlas (Morocco) as recorded by mantle xenoliths

Cited by 24 publications

References 75 publications

Deep seated density anomalies across the Iberia-Africa plate boundary and its topographic response

Deep seated density anomalies across the Iberia-Africa plate boundary and its topographic response

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO2‐H2O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

Eruption dynamics of pleistocene maars and tuff rings from the Azrou-Timahdite district (Middle Atlas, northern Morocco) and its relevance to environmental changes and ground water table characteristics

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High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity