2022
|
Chalot-Prat, F., Magott, R., Berthod, C. Ocean expansion: The role of detachment faults (Article de journal) Dans: no. 00, p. 1–8, 2022. @article{Chalot-Prat_etal2022,
title = {Ocean expansion: The role of detachment faults},
author = {F. Chalot-Prat and R. Magott and C. Berthod},
doi = {10.1111/ter.12624},
year = {2022},
date = {2022-01-01},
number = {00},
pages = {1--8},
abstract = {Detachment faulting at slow spreading ocean ridge axes is recognized as a major surface creation mechanism, yet the structural relationships of these faults with feeder-dykes of on-axis volcanoes remained unresolved. This summary study shows that surface creation leading to ocean widening is exclusively controlled by detachment faults, shallow tracers of tectonic stresses induced by the westward drift of plates. Volcanoes are fed by feeder-dykes following on-axis rotational detachment faults. Once formed volcanoes are dragged along the detachment whose footwall is made of mantle material sometimes hosting gabbro sills. Due to the faster drift of the uppermost lithospheric layer, the feeder-dykes are then intersected by active deeper low-angle detachments, become inactive and are replaced by new ones on-axis. Rooted vertically on either side of the plate boundary, the detachment flexing is all the earlier and more progressive as the faults are far from the axis, positioning gabbro as sills at shallow level within a deformed mantle interspersed with cataclasite horizons. Correlations between shallow and deep lithospheric processes are then clarified},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Detachment faulting at slow spreading ocean ridge axes is recognized as a major surface creation mechanism, yet the structural relationships of these faults with feeder-dykes of on-axis volcanoes remained unresolved. This summary study shows that surface creation leading to ocean widening is exclusively controlled by detachment faults, shallow tracers of tectonic stresses induced by the westward drift of plates. Volcanoes are fed by feeder-dykes following on-axis rotational detachment faults. Once formed volcanoes are dragged along the detachment whose footwall is made of mantle material sometimes hosting gabbro sills. Due to the faster drift of the uppermost lithospheric layer, the feeder-dykes are then intersected by active deeper low-angle detachments, become inactive and are replaced by new ones on-axis. Rooted vertically on either side of the plate boundary, the detachment flexing is all the earlier and more progressive as the faults are far from the axis, positioning gabbro as sills at shallow level within a deformed mantle interspersed with cataclasite horizons. Correlations between shallow and deep lithospheric processes are then clarified |
2021
|
Magott, R., Berthod, C., Chalot-Prat, F. Structural and paleostress analysis within a fossil slow-spreading ridge : Tectonic processes involved during ocean expansion (Article de journal) Dans: Journal of Structural Geology, vol. 150, p. 104402, 2021. @article{Magott_etal2021,
title = {Structural and paleostress analysis within a fossil slow-spreading ridge : Tectonic processes involved during ocean expansion},
author = {R. Magott and C. Berthod and F. Chalot-Prat},
doi = {10.1016/j.jsg.2021.104402},
year = {2021},
date = {2021-01-01},
journal = {Journal of Structural Geology},
volume = {150},
pages = {104402},
abstract = {This study aims to decipher the spatio-temporal chronology of tectonic processes leading to ocean widening at a slow-spreading oceanic ridge axis, involving mantle and gabbro exhumation and volcanism. Structural and petrographic studies of deformed lithologies were performed on peridotites, gabbros and basalts from the Chenaillet ophiolite (Alps, France). Inversion of fault-slip data reveals N030◦ and N060◦ $sigma$3 paleostress trends. The dominant N030◦ extension, is consistent with the NNW-SSE direction of volcano feeder-dykes and ENE dipping low-angle normal faults crosscutting the mantle. The N060◦ extension accords with the mantle dome structure formation to the east. Low-angle faults intersect roots of volcanoes that thus belong to their hanging walls. Hydrothermalism is contemporaneous with or postdates low-angle faulting. A feeder-dyke major virgation northwards, synchronous with eruptions, suggests a dextral transform fault consistent with a N120◦ $sigma$2. Oceanic expansion mechanisms are clarified. At the surface, magma eruption occurs along on-axis active high-angle normal faults, their footwalls enabling mantle exhumation. At depth, off-axis high-angle faults become lowangle faults as they spread at shallow level. With westward drift of the lithosphere, the uppermost levels of the ridge shift westward faster, such that volcanoes move to an off-axis position while their roots are cut by lowangle faults.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This study aims to decipher the spatio-temporal chronology of tectonic processes leading to ocean widening at a slow-spreading oceanic ridge axis, involving mantle and gabbro exhumation and volcanism. Structural and petrographic studies of deformed lithologies were performed on peridotites, gabbros and basalts from the Chenaillet ophiolite (Alps, France). Inversion of fault-slip data reveals N030◦ and N060◦ $sigma$3 paleostress trends. The dominant N030◦ extension, is consistent with the NNW-SSE direction of volcano feeder-dykes and ENE dipping low-angle normal faults crosscutting the mantle. The N060◦ extension accords with the mantle dome structure formation to the east. Low-angle faults intersect roots of volcanoes that thus belong to their hanging walls. Hydrothermalism is contemporaneous with or postdates low-angle faulting. A feeder-dyke major virgation northwards, synchronous with eruptions, suggests a dextral transform fault consistent with a N120◦ $sigma$2. Oceanic expansion mechanisms are clarified. At the surface, magma eruption occurs along on-axis active high-angle normal faults, their footwalls enabling mantle exhumation. At depth, off-axis high-angle faults become lowangle faults as they spread at shallow level. With westward drift of the lithosphere, the uppermost levels of the ridge shift westward faster, such that volcanoes move to an off-axis position while their roots are cut by lowangle faults. |
2018
|
Chalot-Prat, F., D’Eyrames, E. An alternative model of plate tectonics (Article de journal) Dans: Proceedings of the OUGS, vol. 4, p. 101, 2018. @article{Chalot-Prat+DEyrames2018,
title = {An alternative model of plate tectonics},
author = {F. Chalot-Prat and E. D’Eyrames},
year = {2018},
date = {2018-01-01},
journal = {Proceedings of the OUGS},
volume = {4},
pages = {101},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
2017
|
Chalot-Prat, F., Doglioni, C., Falloon, T. Westward migration of oceanic ridges and related asymmetric upper mantle differentiation (Article de journal) Dans: Lithos, vol. 268-271, p. 163–173, 2017. @article{Chalot-Prat_etal2017,
title = {Westward migration of oceanic ridges and related asymmetric upper mantle differentiation},
author = {F. Chalot-Prat and C. Doglioni and T. Falloon},
doi = {/10.1016/j.lithos.2016.10.036},
year = {2017},
date = {2017-01-01},
journal = {Lithos},
volume = {268-271},
pages = {163--173},
abstract = {Combining geophysical, petrological and structural data on oceanic mantle lithosphere, underlying asthenosphere and oceanic basalts, an alternative oceanic plate spreading model is proposed in the framework of the westward migration of oceanic spreading ridges relative to the underlying asthenosphere. This model suggests that evolution of both the composition and internal structure of oceanic plates and underlying upper mantle strongly depends at all scales on plate kinematics. We show that the asymmetric features of lithospheric plates and underlying upper asthenosphere on both sides of oceanic spreading ridges, as shown by geophysical data (seismic velocities, density, thickness, and plate geometry), reflect somewhat different mantle compositions, themselves related to various mantle differentiation processes (incipient to high partial melting degree, percolation/reaction and refertilization) at different depths (down to 300 km) below and laterally to the ridge axis. The fundamental difference between western and eastern plates is linked to the westward ridge migration inducing continuing mantle refertilization of the western plate by percolation-reaction with ascending melts, whereas the eastern plate preserves a barely refertilized harzburgitic residue. Plate thickness on both sides of the ridge is controlled both by cooling of the asthenospheric residue and by the instability of pargasiticamphibole producing a sharp depression in the mantle solidus as it changes fromvapour-undersaturated to vapour-saturated conditions, its intersection with the geotherm at 90 km, and incipient melt production right underneath the lithosphere-asthenosphere boundary (LAB). Thus the intersection of the geotherm with the vapour-saturated lherzolite solidus explains the existence of a low-velocity zone (LVZ). As oceanic lithosphere is moving westward relative to asthenospheric mantle, this partially molten upper asthenosphere facilitates the decoupling between lower asthenosphere and lithosphere. The reby the westward drift of the lithosphere is necessarily slowed down, top to down, inducing a progressive decoupling within the mantle lithosphere itself. This intra-mantle decoupling could be at the origin of asymmetric detachment faults allowing mantle exhumation along slow spreading ridges. Taking into account the asymmetric features of the LVZ, migration of incipient melt fractions and upwelling paths from the lower asthenosphere through the upper asthenosphere are oblique, upward and eastward. MORB are sourced froman eastward and oblique, near-adiabatic mantle upwelling fromt he lower asthenosphere. This unidirectional mantle transfer is induced by isostatic suction of the migrating spreading ridge.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Combining geophysical, petrological and structural data on oceanic mantle lithosphere, underlying asthenosphere and oceanic basalts, an alternative oceanic plate spreading model is proposed in the framework of the westward migration of oceanic spreading ridges relative to the underlying asthenosphere. This model suggests that evolution of both the composition and internal structure of oceanic plates and underlying upper mantle strongly depends at all scales on plate kinematics. We show that the asymmetric features of lithospheric plates and underlying upper asthenosphere on both sides of oceanic spreading ridges, as shown by geophysical data (seismic velocities, density, thickness, and plate geometry), reflect somewhat different mantle compositions, themselves related to various mantle differentiation processes (incipient to high partial melting degree, percolation/reaction and refertilization) at different depths (down to 300 km) below and laterally to the ridge axis. The fundamental difference between western and eastern plates is linked to the westward ridge migration inducing continuing mantle refertilization of the western plate by percolation-reaction with ascending melts, whereas the eastern plate preserves a barely refertilized harzburgitic residue. Plate thickness on both sides of the ridge is controlled both by cooling of the asthenospheric residue and by the instability of pargasiticamphibole producing a sharp depression in the mantle solidus as it changes fromvapour-undersaturated to vapour-saturated conditions, its intersection with the geotherm at 90 km, and incipient melt production right underneath the lithosphere-asthenosphere boundary (LAB). Thus the intersection of the geotherm with the vapour-saturated lherzolite solidus explains the existence of a low-velocity zone (LVZ). As oceanic lithosphere is moving westward relative to asthenospheric mantle, this partially molten upper asthenosphere facilitates the decoupling between lower asthenosphere and lithosphere. The reby the westward drift of the lithosphere is necessarily slowed down, top to down, inducing a progressive decoupling within the mantle lithosphere itself. This intra-mantle decoupling could be at the origin of asymmetric detachment faults allowing mantle exhumation along slow spreading ridges. Taking into account the asymmetric features of the LVZ, migration of incipient melt fractions and upwelling paths from the lower asthenosphere through the upper asthenosphere are oblique, upward and eastward. MORB are sourced froman eastward and oblique, near-adiabatic mantle upwelling fromt he lower asthenosphere. This unidirectional mantle transfer is induced by isostatic suction of the migrating spreading ridge. |
2013
|
Chalot-Prat, F., Faloon, T. J., Green, D. H., Hibberson, W. O Melting of plagioclase + spinel lherzolite at low pressures (0.5 GPa): An experimental approach to the evolution of basaltic melt during mantle refertilisation at shallow depths (Article de journal) Dans: Lithos, vol. 172-173, p. 61–80, 2013. @article{Chalot-Prat_etal2013,
title = {Melting of plagioclase + spinel lherzolite at low pressures (0.5 GPa): An experimental approach to the evolution of basaltic melt during mantle refertilisation at shallow depths},
author = {F. Chalot-Prat and T. J. Faloon and D. H. Green and W. O Hibberson},
doi = {10.1016/j.lithos.2013.03.012},
year = {2013},
date = {2013-01-01},
journal = {Lithos},
volume = {172-173},
pages = {61--80},
abstract = {The presence of plagioclase + spinel lherzolites among ocean floor samples and in some ophiolite complexes invites speculation on their origin and relationships to processes of magmatism and lithosphere refertilisation beneath mid-ocean ridges. In an experimental approach to their petrogenesis, we have determinedthe compositions of liquids and co-existing minerals in the six phase assemblage [liquid + olivine + orthopyroxene + clinopyroxene + plagioclase + spinel] at 0.5 GPa and 1100 textdegreeC to 1200 textdegreeC. In our experimental approach we maintained the olivine Mg# [Mg / (Mg + Fe)] close to 90 (i.e., 88.8--95.5) but varied plagioclase from anorthite to albite. The major variations in liquid compositions are related to plagioclase composition. Liquids have much lower MgO and FeO and higher SiO2 and Al2O3 than liquids in the 6-phase plagioclase + spinel lherzolite at 0.75 GPa and 1 GPa. Liquids are quartz-normative (silica-oversaturated) for plagioclase that are more calcic than An40 but nepheline-normative (critically silica undersaturated) for plagioclase that are more sodic than An25. Liquid compositions are quite unlike naturalMORB glasses with similarMg# (i.e., compatible with parental magmas fromlherzolitic mantlewith Mg# ≈ 90). Our study provides no supportfor models of MORB petrogenesis which suggest extraction of near-solidus melts from plagioclase lherzolite at low pressure. Similarly, referring to numerical models of melting volumes beneath mid-ocean ridges (Langmuir et al., 1992;McKenzie and Bickle, 1988) in which melt increments are calculated for different sites and these increments pooled to form MORB, our data argue that melts equilibrated with plagioclase textpm spinel lherzolite at b1 GPa cannot be significant components of such textquoteleftpooled melttextquoteright focussed from within the melting volume. The compositions of minerals from plagioclase textpm spinel lherzolite at Lanzo (northern Italy; Piccardo et al., 2007) are compared with our experimental assemblages at 0.5, 0.75 and 1 GPa, leading to the conclusion that the Lanzo plagioclase textpm spinel lherzolites equilibrated at pressures between 0.75 and 1 GPa, at temperaturestextasciitilde100--200 textdegreeC below the solidus. Field, petrological and geochemical studies argue that the Lanzo plagioclase textpm spinel lherzolites are textquoteleftrefertilisedtextquoteright by the reaction of residual harzburgite or lherzolite with percolating intergranular basaltic magma (Piccardo et al., 2007). The experimental study suggests that the process ofrefertilisation took place at depths of 25--30 km. Our experimental data also define the co-variance of Na2O in coexisting plagioclase (An25 to An94) and clinopyroxene at 0.5 and 0.75 GPa. From these data, the Na2O content of clinopyroxene can be used as a predictor for the co-existing plagioclase composition in the very common occurrences of partially serpentinised peridotite in which plagioclase is completely saussuritised.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The presence of plagioclase + spinel lherzolites among ocean floor samples and in some ophiolite complexes invites speculation on their origin and relationships to processes of magmatism and lithosphere refertilisation beneath mid-ocean ridges. In an experimental approach to their petrogenesis, we have determinedthe compositions of liquids and co-existing minerals in the six phase assemblage [liquid + olivine + orthopyroxene + clinopyroxene + plagioclase + spinel] at 0.5 GPa and 1100 textdegreeC to 1200 textdegreeC. In our experimental approach we maintained the olivine Mg# [Mg / (Mg + Fe)] close to 90 (i.e., 88.8--95.5) but varied plagioclase from anorthite to albite. The major variations in liquid compositions are related to plagioclase composition. Liquids have much lower MgO and FeO and higher SiO2 and Al2O3 than liquids in the 6-phase plagioclase + spinel lherzolite at 0.75 GPa and 1 GPa. Liquids are quartz-normative (silica-oversaturated) for plagioclase that are more calcic than An40 but nepheline-normative (critically silica undersaturated) for plagioclase that are more sodic than An25. Liquid compositions are quite unlike naturalMORB glasses with similarMg# (i.e., compatible with parental magmas fromlherzolitic mantlewith Mg# ≈ 90). Our study provides no supportfor models of MORB petrogenesis which suggest extraction of near-solidus melts from plagioclase lherzolite at low pressure. Similarly, referring to numerical models of melting volumes beneath mid-ocean ridges (Langmuir et al., 1992;McKenzie and Bickle, 1988) in which melt increments are calculated for different sites and these increments pooled to form MORB, our data argue that melts equilibrated with plagioclase textpm spinel lherzolite at b1 GPa cannot be significant components of such textquoteleftpooled melttextquoteright focussed from within the melting volume. The compositions of minerals from plagioclase textpm spinel lherzolite at Lanzo (northern Italy; Piccardo et al., 2007) are compared with our experimental assemblages at 0.5, 0.75 and 1 GPa, leading to the conclusion that the Lanzo plagioclase textpm spinel lherzolites equilibrated at pressures between 0.75 and 1 GPa, at temperaturestextasciitilde100--200 textdegreeC below the solidus. Field, petrological and geochemical studies argue that the Lanzo plagioclase textpm spinel lherzolites are textquoteleftrefertilisedtextquoteright by the reaction of residual harzburgite or lherzolite with percolating intergranular basaltic magma (Piccardo et al., 2007). The experimental study suggests that the process ofrefertilisation took place at depths of 25--30 km. Our experimental data also define the co-variance of Na2O in coexisting plagioclase (An25 to An94) and clinopyroxene at 0.5 and 0.75 GPa. From these data, the Na2O content of clinopyroxene can be used as a predictor for the co-existing plagioclase composition in the very common occurrences of partially serpentinised peridotite in which plagioclase is completely saussuritised. |
2012
|
Ouarhache, D., Charri`ere, A., Chalot-Prat, F., Wartiti, M. El Chronologie et modalités du rifting triasico-liasique `a la marge sud-ouest de la Téthys alpine (Moyen Atlas et Haute Moulouya, Maroc) ; corrélations avec le rifting atlantique : simultanéité et diachronisme (Article de journal) Dans: Bulletin de la Société Géologique de France, vol. 183, no. 3, p. 233–249, 2012. @article{Ouarhache_etal2012,
title = {Chronologie et modalit\'{e}s du rifting triasico-liasique `a la marge sud-ouest de la T\'{e}thys alpine (Moyen Atlas et Haute Moulouya, Maroc) ; corr\'{e}lations avec le rifting atlantique : simultan\'{e}it\'{e} et diachronisme},
author = {D. Ouarhache and A. Charri`ere and F. Chalot-Prat and M. El Wartiti},
doi = {10.2113/gssgfbull.183.3.233},
year = {2012},
date = {2012-01-01},
journal = {Bulletin de la Soci\'{e}t\'{e} G\'{e}ologique de France},
volume = {183},
number = {3},
pages = {233--249},
abstract = {Apparu `a ltextquoterightest du rift continental atlantique, un rift continental t\'{e}thysien stextquoterightest d\'{e}velopp\'{e} sur le domaine atlasique du Maroc au cours du Trias et du d\'{e}but du Jurassique. Dans le transect \'{e}tudi\'{e} du Moyen Atlas et de la Haute Moulouya(MAHM), ce d\'{e}but du rifting t\'{e}thysien, le « rifting initial », comporta 3 \'{e}tapes majeures. Au Trias sup\'{e}rieur, apparut une premi`ere g\'{e}n\'{e}ration de bassins syn-rift (sr1) continentaux et d\'{e}tritiques, associ\'{e}s au rejeu extensif de certaines sutures hercyniennes ; cette phase se poursuivit avec une transgression laguno-marine g\'{e}n\'{e}ralis\'{e}e dans un stade post-rift (pr1) au Carnien sup\'{e}rieur-Norien.Au voisinage de la limite Trias-Lias, se produisit une effusion de trapps basaltiques a\'{e}riens `a subaquatiques ; la r\'{e}gion subit ensuite une phase dtextquoteright\'{e}rosion.Au d\'{e}but du Lias, se diff\'{e}rencia une deuxi`eme g\'{e}n\'{e}ration de bassins syn-rift (sr2) continentaux ou laguno-marins, extensifs ou transtensifs, associ\'{e}s `a un volcanisme explosif localis\'{e} sur quatre zones faill\'{e}es (faille dtextquoterightAdarouch, accident du Tizi ntextquoterightTrett`ene, accident Sud Moyen atlasique, faille de Ksabi-Ahouli) ; cette phase se cl^otura avec ltextquoterightarriv\'{e}e de la mer dans un stade post-rift (pr2) d\'{e}butant au Sin\'{e}murien sup\'{e}rieur-Carixien inf\'{e}rieur. La zone du MAHM eut une histoire diff\'{e}rente des r\'{e}gions occidentales du domaine atlasique, qutextquoterightil stextquoterightagisse dtextquoterightunautre segment du rift atlasique (Haut Atlas de Marrakech) ou dtextquoterightune bordure du rift atlantique (Haut Atlas occidental). Pendant le rifting ante-trapp, alors que ces bassins occidentaux ont \'{e}t\'{e} structur\'{e}s par plusieurs s\'{e}quences tectono-s\'{e}dimentaires successives \'{e}tag\'{e}es du Permien sup\'{e}rieur au Trias sup\'{e}rieur, les bassins du MAHM ntextquoterightenregistr`erent qutextquoterightune seule m\'{e}gas\'{e}quence s\'{e}dimentaire triasique. Ainsi, les rifts continentaux atlantique et Ouest atlasique furent initi\'{e}s,simultan\'{e}ment (?), d`es le Permien sup\'{e}rieur, tandis que le rift continental de ltextquoterightAtlas central et oriental ntextquoterightapparut vraisemblablement qutextquoterightau Trias sup\'{e}rieur. La d\'{e}chirure du rift atlasique migra ainsi vers ltextquoterightest de la fin du Primaire aud\'{e}but du Secondaire. Durant la p\'{e}riode post-trapp, alors que les bassins occidentaux \'{e}taient le si`ege dtextquoterightun calme tectonique relatif, une fracturation majeure affecta le MAHM, g\'{e}n\'{e}rant de nouveaux bassins s\'{e}dimentaires associ\'{e}s `a un second \'{e}pisode volcanique, de nature explosive cette fois. Cette poursuite du rifting, apr`es les derni`eres effusions basaltiques et avant ltextquoterightarriv\'{e}ede la mer jurassique, pr\'{e}figura les d\'{e}coupages tectoniques qui continu`erent de se manifester dans les parties centrale et orientale du rift atlasique jusqutextquoterightau Jurassique moyen.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Apparu `a ltextquoterightest du rift continental atlantique, un rift continental téthysien stextquoterightest développé sur le domaine atlasique du Maroc au cours du Trias et du début du Jurassique. Dans le transect étudié du Moyen Atlas et de la Haute Moulouya(MAHM), ce début du rifting téthysien, le « rifting initial », comporta 3 étapes majeures. Au Trias supérieur, apparut une premi`ere génération de bassins syn-rift (sr1) continentaux et détritiques, associés au rejeu extensif de certaines sutures hercyniennes ; cette phase se poursuivit avec une transgression laguno-marine généralisée dans un stade post-rift (pr1) au Carnien supérieur-Norien.Au voisinage de la limite Trias-Lias, se produisit une effusion de trapps basaltiques aériens `a subaquatiques ; la région subit ensuite une phase dtextquoterightérosion.Au début du Lias, se différencia une deuxi`eme génération de bassins syn-rift (sr2) continentaux ou laguno-marins, extensifs ou transtensifs, associés `a un volcanisme explosif localisé sur quatre zones faillées (faille dtextquoterightAdarouch, accident du Tizi ntextquoterightTrett`ene, accident Sud Moyen atlasique, faille de Ksabi-Ahouli) ; cette phase se cl^otura avec ltextquoterightarrivée de la mer dans un stade post-rift (pr2) débutant au Sinémurien supérieur-Carixien inférieur. La zone du MAHM eut une histoire différente des régions occidentales du domaine atlasique, qutextquoterightil stextquoterightagisse dtextquoterightunautre segment du rift atlasique (Haut Atlas de Marrakech) ou dtextquoterightune bordure du rift atlantique (Haut Atlas occidental). Pendant le rifting ante-trapp, alors que ces bassins occidentaux ont été structurés par plusieurs séquences tectono-sédimentaires successives étagées du Permien supérieur au Trias supérieur, les bassins du MAHM ntextquoterightenregistr`erent qutextquoterightune seule mégaséquence sédimentaire triasique. Ainsi, les rifts continentaux atlantique et Ouest atlasique furent initiés,simultanément (?), d`es le Permien supérieur, tandis que le rift continental de ltextquoterightAtlas central et oriental ntextquoterightapparut vraisemblablement qutextquoterightau Trias supérieur. La déchirure du rift atlasique migra ainsi vers ltextquoterightest de la fin du Primaire audébut du Secondaire. Durant la période post-trapp, alors que les bassins occidentaux étaient le si`ege dtextquoterightun calme tectonique relatif, une fracturation majeure affecta le MAHM, générant de nouveaux bassins sédimentaires associés `a un second épisode volcanique, de nature explosive cette fois. Cette poursuite du rifting, apr`es les derni`eres effusions basaltiques et avant ltextquoterightarrivéede la mer jurassique, préfigura les découpages tectoniques qui continu`erent de se manifester dans les parties centrale et orientale du rift atlasique jusqutextquoterightau Jurassique moyen. |
2010
|
McCann, T., Chalot-Prat, F., Saintot, A. The Early Mesozoic evolution of the Western Greater Caucasus (Russia): Triassic Jurassic sedimentary and magmatic history (Article de journal) Dans: Geological Society of London Special Publication, vol. 340, p. 181–238, 2010. @article{McCann_etal2010,
title = {The Early Mesozoic evolution of the Western Greater Caucasus (Russia): Triassic Jurassic sedimentary and magmatic history},
author = {T. McCann and F. Chalot-Prat and A. Saintot},
doi = {10.1144/SP340.10},
year = {2010},
date = {2010-01-01},
journal = {Geological Society of London Special Publication},
volume = {340},
pages = {181--238},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Chalot-Prat, F., Falloon, T. J., Green, D. H., Hibberson, W. O. An Experimental Study of Liquid Compositions in Equilibrium with Plagioclase + Spinel Lherzolite at Low Pressures (0textperiodcentered75 GPa) (Article de journal) Dans: Journal of Petrology, vol. 51, no. 11, p. 2349–2376, 2010. @article{Chalot-Prat_etal2010,
title = {An Experimental Study of Liquid Compositions in Equilibrium with Plagioclase + Spinel Lherzolite at Low Pressures (0textperiodcentered75 GPa)},
author = {F. Chalot-Prat and T. J. Falloon and D. H. Green and W. O. Hibberson},
doi = {10.1093/petrology/egq060},
year = {2010},
date = {2010-01-01},
journal = {Journal of Petrology},
volume = {51},
number = {11},
pages = {2349--2376},
abstract = {Models of formation of basaltic crust at mid-ocean ridges by adiabatic upwelling of fertile mantle lherzolite require knowledge of phase relations and phase compositions during melting at appropriate pressures. Spinel+plagioclase lherzolites are found among peridotite samples from the ocean floor and ophiolitic exposures. At low pressure (51textperiodcentered2 GPa) the five-phase assemblage (olivine+orthopyroxene+clinopyroxene+plagioclase+spinel) is present at the anhydrous lherzolite solidus. New experimental data on mineral and melt compositions, at 0textperiodcentered75 GPa and 1140-12608C in the (Cr+Na+Fe+Ca+Mg+Al+Si) system, demonstrate smooth covariant relationships between oxides for melt compositions and in partition relationships both between mineral pairs and between minerals and melts. Molecular normative projections demonstrate that liquids on the five-phaseþliquid cotectic occupy a narrow compositional range. Of the mineral solid solutions that control the liquid composition, the [Ca/(Ca+Na)] or anorthite/albite content of the plagioclase is dominant and liquids vary from silica undersaturated and nepheline-normative at the sodic (oligoclase) end to orthopyroxene and quartz-normative at the calcic (anorthite) end of the cotectic. Spinel (Cr+Al) solid solution has limited variation on the five-phaseþliquid cotectic. It is very Cr-rich at the sodic end and has limited compositional variation from 50 to 20 in Cr/(Cr+Al) at the anorthitic end.With fixed plagioclase composition on the cotectic, melt compositions show small compositional shifts with Fe+Mg (at Mg# between 85 and 95) and with Cr/(Cr+Al). The compositional vectors are consistent with effects observed in the end-member simple systems (FCMAS) and (CrCMAS). In comparing liquids at the anorthite end of the five-phaseþliquid cotectic with those on the Cr-free CMAS four-phaseþliquid cotectic at 0textperiodcentered75 GPa, it is evident that the presence of Al-rich Cr-Al spinel shifts liquid compositions to more silica-rich and silica-oversaturated composition.These experimentally defined melt compositions in equilibrium with plagioclaseþspinel lherzolite are unlike quenched glasses from mid-ocean ridge settings.The data do not support models of mantle upwelling at low potential temperature (1280textdegreeC) that produces low melt fractions at low pressures, leaving residual plagioclase +spinel lherzolite. The detailed mineral compositional data at the solidus provide a template for comparison with natural plagioclase +spinel lherzolites refertilized by porous reactive flow.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Models of formation of basaltic crust at mid-ocean ridges by adiabatic upwelling of fertile mantle lherzolite require knowledge of phase relations and phase compositions during melting at appropriate pressures. Spinel+plagioclase lherzolites are found among peridotite samples from the ocean floor and ophiolitic exposures. At low pressure (51textperiodcentered2 GPa) the five-phase assemblage (olivine+orthopyroxene+clinopyroxene+plagioclase+spinel) is present at the anhydrous lherzolite solidus. New experimental data on mineral and melt compositions, at 0textperiodcentered75 GPa and 1140-12608C in the (Cr+Na+Fe+Ca+Mg+Al+Si) system, demonstrate smooth covariant relationships between oxides for melt compositions and in partition relationships both between mineral pairs and between minerals and melts. Molecular normative projections demonstrate that liquids on the five-phaseþliquid cotectic occupy a narrow compositional range. Of the mineral solid solutions that control the liquid composition, the [Ca/(Ca+Na)] or anorthite/albite content of the plagioclase is dominant and liquids vary from silica undersaturated and nepheline-normative at the sodic (oligoclase) end to orthopyroxene and quartz-normative at the calcic (anorthite) end of the cotectic. Spinel (Cr+Al) solid solution has limited variation on the five-phaseþliquid cotectic. It is very Cr-rich at the sodic end and has limited compositional variation from 50 to 20 in Cr/(Cr+Al) at the anorthitic end.With fixed plagioclase composition on the cotectic, melt compositions show small compositional shifts with Fe+Mg (at Mg# between 85 and 95) and with Cr/(Cr+Al). The compositional vectors are consistent with effects observed in the end-member simple systems (FCMAS) and (CrCMAS). In comparing liquids at the anorthite end of the five-phaseþliquid cotectic with those on the Cr-free CMAS four-phaseþliquid cotectic at 0textperiodcentered75 GPa, it is evident that the presence of Al-rich Cr-Al spinel shifts liquid compositions to more silica-rich and silica-oversaturated composition.These experimentally defined melt compositions in equilibrium with plagioclaseþspinel lherzolite are unlike quenched glasses from mid-ocean ridge settings.The data do not support models of mantle upwelling at low potential temperature (1280textdegreeC) that produces low melt fractions at low pressures, leaving residual plagioclase +spinel lherzolite. The detailed mineral compositional data at the solidus provide a template for comparison with natural plagioclase +spinel lherzolites refertilized by porous reactive flow. |
2007
|
Chalot-Prat, F., Tikhomirov, P., Saintot, A. Late Devonian and Triassic basalts from the southern continental margin of the East European Platform, tracers of a single heterogeneous lithospheric mantle source (Article de journal) Dans: Journal of Earth System Science, vol. 116, no. 6, p. 469–492, 2007. @article{Chalot-Prat_etal2007,
title = {Late Devonian and Triassic basalts from the southern continental margin of the East European Platform, tracers of a single heterogeneous lithospheric mantle source},
author = {F. Chalot-Prat and P. Tikhomirov and A. Saintot},
doi = {10.1007/s12040-007-0045-z},
year = {2007},
date = {2007-01-01},
journal = {Journal of Earth System Science},
volume = {116},
number = {6},
pages = {469--492},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
2006
|
Etxebarria, M., Chalot-Prat, F., Apraiz, A., Eguiluz, L. Birth of a volcanic passive margin in Cambrian time: Rift paleogeography of the Ossa-Morena Zone, SW Spain (Article de journal) Dans: Precambrian Research, vol. 147, p. 366–386, 2006. @article{Etxebarria_etal2006,
title = {Birth of a volcanic passive margin in Cambrian time: Rift paleogeography of the Ossa-Morena Zone, SW Spain},
author = {M. Etxebarria and F. Chalot-Prat and A. Apraiz and L. Eguiluz},
doi = {10.1016/j.precamres.2006.01.022},
year = {2006},
date = {2006-01-01},
journal = {Precambrian Research},
volume = {147},
pages = {366--386},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Saintot, A., Brunet, M. F., Yakovlev, F., Sébrier, M., Stephenson, R., Ershov, A., Chalot-Prat, F., McCann, T. The Mesozoic-Cenozoic tectonic evolution of the Greater Caucasus (Article de journal) Dans: Geological Society, London, Memoirs, vol. 32, p. 277–289, 2006. @article{Saintot_etal2006,
title = {The Mesozoic-Cenozoic tectonic evolution of the Greater Caucasus},
author = {A. Saintot and M. F. Brunet and F. Yakovlev and M. S\'{e}brier and R. Stephenson and A. Ershov and F. Chalot-Prat and T. McCann},
doi = {10.1144/GSL.MEM.2006.032.01.16},
year = {2006},
date = {2006-01-01},
journal = {Geological Society, London, Memoirs},
volume = {32},
pages = {277--289},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
2005
|
Chalot-Prat, F. An undeformed ophiolite in the Alps in Plates, plumes, and paradigms (Chapitre d'ouvrage) Dans: Foulger, G. R.; Natland, J. H.; Presnall, D. C.; Anderson, D. L. (Ed.): vol. 388, Chapitre An undeformed ophiolite in the Alps, p. 751-780, 2005, ISSN: 0072-1077. @inbook{nokey,
title = {An undeformed ophiolite in the Alps in Plates, plumes, and paradigms},
author = {F. Chalot-Prat},
editor = {G.R. Foulger and J.H. Natland and D.C. Presnall and D.L. Anderson},
issn = {0072-1077},
year = {2005},
date = {2005-08-01},
urldate = {2005-08-01},
journal = {Geological society of America Paper},
volume = {388},
pages = {751-780},
chapter = {An undeformed ophiolite in the Alps},
abstract = {Detailed mapping and geochemistry of an undeformed Jurassic ophiolite (Chenaillet-Montgen\`{e}vre, Franco-Italian Alps) were performed to document the volcanic architecture at an axial ridge and its relationships with the chemical evolution of basalts and ocean spreading. The architecture of the volcanic cover resembles an abyssal hill with hummocky ridges and hundreds of hummocks, as described at the Atlantic axial volcanic ridge. Mantle rocks and gabbros, below and on both sides of the volcanic hill, are capped with cataclasite horizons representing detachment faults responsible for their exhumation on the seafloor. Basaltic cover and gabbro sills are thin. They overlie a dome-forming mantle basement, the undulated top of which is responsible for the relief variations. Volcanoes formed on slopes, and the higher the edifice, the younger it is relative to the others. Two types of volcanic architecture, stairs and combs, exist. Stairs are associated with tongue-like volcanoes cascading down the steps. Combs consist of strings of conical volcanoes or hummocks, sitting at the intersections of major fissures parallel to the spreading axis, with oblique subsidiary fractures. Stairs emplaced by rifting of a basement in uplift and already denuded by detachment faulting. Combs formed on a basement in uplift and in the process of denudation along detachment faults serving as magma conduits at depth and as a conveyor belt for volcanoes on the sea floor to a limited extent (\<500 m). In both cases, the magma chamber remained beneath the highest part of the relief. In the stairs and combs, rhythmic or continuous compositional variations occurred with time. They attest to cyclic eruptions of primary and differentiated melts, or to extraction of melts as they formed successively. The magma conduits were rooted in ephemeral, small, and frequently recharged reservoirs, or even in the mantle source. Lithospheric tectonics controlled not only magma ascent but also mantle melting},
keywords = {},
pubstate = {published},
tppubtype = {inbook}
}
Detailed mapping and geochemistry of an undeformed Jurassic ophiolite (Chenaillet-Montgenèvre, Franco-Italian Alps) were performed to document the volcanic architecture at an axial ridge and its relationships with the chemical evolution of basalts and ocean spreading. The architecture of the volcanic cover resembles an abyssal hill with hummocky ridges and hundreds of hummocks, as described at the Atlantic axial volcanic ridge. Mantle rocks and gabbros, below and on both sides of the volcanic hill, are capped with cataclasite horizons representing detachment faults responsible for their exhumation on the seafloor. Basaltic cover and gabbro sills are thin. They overlie a dome-forming mantle basement, the undulated top of which is responsible for the relief variations. Volcanoes formed on slopes, and the higher the edifice, the younger it is relative to the others. Two types of volcanic architecture, stairs and combs, exist. Stairs are associated with tongue-like volcanoes cascading down the steps. Combs consist of strings of conical volcanoes or hummocks, sitting at the intersections of major fissures parallel to the spreading axis, with oblique subsidiary fractures. Stairs emplaced by rifting of a basement in uplift and already denuded by detachment faulting. Combs formed on a basement in uplift and in the process of denudation along detachment faults serving as magma conduits at depth and as a conveyor belt for volcanoes on the sea floor to a limited extent (<500 m). In both cases, the magma chamber remained beneath the highest part of the relief. In the stairs and combs, rhythmic or continuous compositional variations occurred with time. They attest to cyclic eruptions of primary and differentiated melts, or to extraction of melts as they formed successively. The magma conduits were rooted in ephemeral, small, and frequently recharged reservoirs, or even in the mantle source. Lithospheric tectonics controlled not only magma ascent but also mantle melting |
2004
|
Alexandre, P., Chalot-Prat, F., Saintot, A., Wijbrans, J., Stephenson, R., Wilson, M., Kithcka, A., Stovba, S. 40Ar/39Ar dating of magmatic activity in the Donbass foldbelt and the Scythian platform (Eastern European Craton) (Article de journal) Dans: Tectonophysics, vol. 23, p. 15, 2004. @article{Alexandre_etal2004,
title = {40Ar/39Ar dating of magmatic activity in the Donbass foldbelt and the Scythian platform (Eastern European Craton)},
author = {P. Alexandre and F. Chalot-Prat and A. Saintot and J. Wijbrans and R. Stephenson and M. Wilson and A. Kithcka and S. Stovba},
year = {2004},
date = {2004-01-01},
journal = {Tectonophysics},
volume = {23},
pages = {15},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Gasquet, D., Chevremont, P., Baudin, T., Chalot-Prat, F., Guerrot, C., Cocherie, A., Roger, J., Hassenforder, B., Cheilletz, A. Polycyclic magmatism in the Tagragra dtextquoterightAkka and Kerdous-Tafeltast inliers (Western Anti-Atlas, Morocco) (Article de journal) Dans: Journal of African Earth Sciences, vol. 39, p. 267–275, 2004. @article{Gasquet_etal2004,
title = {Polycyclic magmatism in the Tagragra dtextquoterightAkka and Kerdous-Tafeltast inliers (Western Anti-Atlas, Morocco)},
author = {D. Gasquet and P. Chevremont and T. Baudin and F. Chalot-Prat and C. Guerrot and A. Cocherie and J. Roger and B. Hassenforder and A. Cheilletz},
doi = {10.1016/j.jafrearsci.2004.07.062},
year = {2004},
date = {2004-01-01},
journal = {Journal of African Earth Sciences},
volume = {39},
pages = {267--275},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Tikhomirov, P. L., Chalot-Prat, F., Nazarevitch, B. P. Triassic volcanism in the eastern Fore-Caucasus: evolution and geodynamic interpretation (Article de journal) Dans: Tectonophysics, vol. 381, no. 1-4, p. 119–142, 2004. @article{Tikhomirov_etal2004,
title = {Triassic volcanism in the eastern Fore-Caucasus: evolution and geodynamic interpretation},
author = {P. L. Tikhomirov and F. Chalot-Prat and B. P. Nazarevitch},
doi = {10.1016/j.tecto.2003.10.014},
year = {2004},
date = {2004-01-01},
journal = {Tectonophysics},
volume = {381},
number = {1-4},
pages = {119--142},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
2003
|
Chalot-Prat, F., Ganne, J., Lombard, A. No significant element transfer from the oceanic plate to the mantle wedge during subduction and exhumation of the Tethys lithosphere (Western Alps) (Article de journal) Dans: Lithos, vol. 69, no. 3-4, p. 63–103, 2003. @article{Chalot-Prat_etal2003,
title = {No significant element transfer from the oceanic plate to the mantle wedge during subduction and exhumation of the Tethys lithosphere (Western Alps)},
author = {F. Chalot-Prat and J. Ganne and A. Lombard},
doi = {10.1016/S0024-4937(03)00047-1},
year = {2003},
date = {2003-01-01},
journal = {Lithos},
volume = {69},
number = {3-4},
pages = {63--103},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Cann, T. Mc, Saintot, A., Chalot-Prat, F., Kitchka, A., Fokin, P., A.,, Alekseev, Evolution of the southern margin of the Donbas (Ukraine) from Devonian to early carboniferous times (Article de journal) Dans: Special Publication ?Ĭ Geological Society of London, vol. 208, p. 117–135, 2003. @article{McCann_etal2003,
title = {Evolution of the southern margin of the Donbas (Ukraine) from Devonian to early carboniferous times},
author = {T. Mc Cann and A. Saintot and F. Chalot-Prat and A. Kitchka and P. Fokin and A. and Alekseev},
doi = {10.1144/GSL.SP.2003.208.01.06},
year = {2003},
date = {2003-01-01},
journal = {Special Publication ?\u{I} Geological Society of London},
volume = {208},
pages = {117--135},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
2000
|
Chalot-Prat, F., Girbacea, R. Partial delamination of continental mantle lithosphere, uplift-related crust-mantle decoupling, volcanism and basin formation : a new model for the Pliocene-Quaternary evolution of the southern East-Carpathians, Romania (Article de journal) Dans: Tectonophysics, vol. 327, p. 83–107, 2000. @article{Chalot-Prat+Girbacea2000,
title = {Partial delamination of continental mantle lithosphere, uplift-related crust-mantle decoupling, volcanism and basin formation : a new model for the Pliocene-Quaternary evolution of the southern East-Carpathians, Romania},
author = {F. Chalot-Prat and R. Girbacea},
doi = {10.1016/S0040-1951(00)00155-4},
year = {2000},
date = {2000-01-01},
journal = {Tectonophysics},
volume = {327},
pages = {83--107},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Ouarhache, D., Charriere, A., Chalot-Prat, F., Wartiti, M. El Sédimentation détritique continentale synchrone dtextquoterightun volcanisme explosif dans le Trias terminal ?Ĭ Infralias du domaine Atlastique (Haute Moulouya, Maroc) (Article de journal) Dans: Journal of African Earth Sciences, vol. 31, no. 3-4, p. 555–570, 2000. @article{Ouarhache_etal2000,
title = {S\'{e}dimentation d\'{e}tritique continentale synchrone dtextquoterightun volcanisme explosif dans le Trias terminal ?\u{I} Infralias du domaine Atlastique (Haute Moulouya, Maroc)},
author = {D. Ouarhache and A. Charriere and F. Chalot-Prat and M. El Wartiti},
year = {2000},
date = {2000-01-01},
journal = {Journal of African Earth Sciences},
volume = {31},
number = {3-4},
pages = {555--570},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
1999
|
Chalot-Prat, F., Arnold, M. Immiscibility between calcio-carbonatitic and silicate melts, and related wall-rock reactions in the upper mantle : a natural case study from Romanian mantle xenoliths (Article de journal) Dans: Lithos, vol. 46, no. 4, p. 627–659, 1999. @article{Chalot-Prat+Arnold1999,
title = {Immiscibility between calcio-carbonatitic and silicate melts, and related wall-rock reactions in the upper mantle : a natural case study from Romanian mantle xenoliths},
author = {F. Chalot-Prat and M. Arnold},
doi = {10.1016/S0024-4937(98)00067-X},
year = {1999},
date = {1999-01-01},
journal = {Lithos},
volume = {46},
number = {4},
pages = {627--659},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
1997
|
Chalot-Prat, F., Boullier, A. M. Metasomatism in the subcontinental mantle beneath the Eastern Carpathians (Romania): new evidence from trace element geochemistry (Article de journal) Dans: Contributions to Mineralogy and Petrology, vol. 129, p. 284–307, 1997. @article{Chalot-Prat+Boullier1997,
title = {Metasomatism in the subcontinental mantle beneath the Eastern Carpathians (Romania): new evidence from trace element geochemistry},
author = {F. Chalot-Prat and A. M. Boullier},
year = {1997},
date = {1997-01-01},
journal = {Contributions to Mineralogy and Petrology},
volume = {129},
pages = {284--307},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
1995
|
Chalot-Prat, F. Genesis of rhyolitic ignimbrites and lavas from distinct sources at a deep crustal level : field, petrographic, chemical and isotopic (Sr, Nd) constraints in the Tazekka volcanic complex (Eastern Morocco) (Article de journal) Dans: Lithos, vol. 36, p. 29–49, 1995. @article{Chalot-Prat1995,
title = {Genesis of rhyolitic ignimbrites and lavas from distinct sources at a deep crustal level : field, petrographic, chemical and isotopic (Sr, Nd) constraints in the Tazekka volcanic complex (Eastern Morocco)},
author = {F. Chalot-Prat},
year = {1995},
date = {1995-01-01},
journal = {Lithos},
volume = {36},
pages = {29--49},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Youbi, N., Cabanis, B., Chalot-Prat, F., Cailleux, Y. Histoire volcano-tectonique du massif permien de Khenifra (Sud-Est du Maroc Central) (Article de journal) Dans: Geodinamica Acta, vol. 8, no. 3, p. 158–172, 1995. @article{Youbi_etal1995,
title = {Histoire volcano-tectonique du massif permien de Khenifra (Sud-Est du Maroc Central)},
author = {N. Youbi and B. Cabanis and F. Chalot-Prat and Y. Cailleux},
year = {1995},
date = {1995-01-01},
journal = {Geodinamica Acta},
volume = {8},
number = {3},
pages = {158--172},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
