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Volcanic passive margins: another way to break up continents.

Geoffroy L, Burov EB, Werner P - Sci Rep (2015)

Bottom Line: Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere.Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain.Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

View Article: PubMed Central - PubMed

Affiliation: Université de Bretagne Occidentale, Brest, 29238 Brest.

ABSTRACT
Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

No MeSH data available.


Related in: MedlinePlus

Necking (a) and mantle exhumation (b) stages at non-volcanic passive margins1314.A tectonized continental block (H-Block) is isolated during the necking stage, bounded by conjugate master faults dipping “oceanward”. It is further dissected at both conjugate margins during a subsequent stage when bulk deformation becomes simple shear and lithospheric mantle is exhumed and serpentinized. All deformation is coeval with subsidence and sedimentation. From refs 13 and 14, modified (author: L.G., using CorelDraw11).
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f1: Necking (a) and mantle exhumation (b) stages at non-volcanic passive margins1314.A tectonized continental block (H-Block) is isolated during the necking stage, bounded by conjugate master faults dipping “oceanward”. It is further dissected at both conjugate margins during a subsequent stage when bulk deformation becomes simple shear and lithospheric mantle is exhumed and serpentinized. All deformation is coeval with subsidence and sedimentation. From refs 13 and 14, modified (author: L.G., using CorelDraw11).

Mentions: SPMs show no record of significant mantle melting in their upper crustal section immediately before and throughout lithosphere extension10. In such settings, sub-crustal mantle can be exhumed and serpentinized in association with extreme crustal stretching and thinning (Fig. 1)5678910111213. Lithosphere necking is accommodated by an early system of upward-concave conjugate detachment faults dipping “oceanward”513 (Fig. 1a). A major trans-lithospheric detachment developing seaward would finally exhume the upper lithospheric mantle through a rolling-hinge deformation of the footwall512 (Fig. 1b). Asthenospheric mantle melting and generation of MORB-type magmas would finally occur through impingement of the main detachment fault1314. An alternative model invoking the exhumation of a mechanically weak lower crust has also been proposed for SPMs15.


Volcanic passive margins: another way to break up continents.

Geoffroy L, Burov EB, Werner P - Sci Rep (2015)

Necking (a) and mantle exhumation (b) stages at non-volcanic passive margins1314.A tectonized continental block (H-Block) is isolated during the necking stage, bounded by conjugate master faults dipping “oceanward”. It is further dissected at both conjugate margins during a subsequent stage when bulk deformation becomes simple shear and lithospheric mantle is exhumed and serpentinized. All deformation is coeval with subsidence and sedimentation. From refs 13 and 14, modified (author: L.G., using CorelDraw11).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595843&req=5

f1: Necking (a) and mantle exhumation (b) stages at non-volcanic passive margins1314.A tectonized continental block (H-Block) is isolated during the necking stage, bounded by conjugate master faults dipping “oceanward”. It is further dissected at both conjugate margins during a subsequent stage when bulk deformation becomes simple shear and lithospheric mantle is exhumed and serpentinized. All deformation is coeval with subsidence and sedimentation. From refs 13 and 14, modified (author: L.G., using CorelDraw11).
Mentions: SPMs show no record of significant mantle melting in their upper crustal section immediately before and throughout lithosphere extension10. In such settings, sub-crustal mantle can be exhumed and serpentinized in association with extreme crustal stretching and thinning (Fig. 1)5678910111213. Lithosphere necking is accommodated by an early system of upward-concave conjugate detachment faults dipping “oceanward”513 (Fig. 1a). A major trans-lithospheric detachment developing seaward would finally exhume the upper lithospheric mantle through a rolling-hinge deformation of the footwall512 (Fig. 1b). Asthenospheric mantle melting and generation of MORB-type magmas would finally occur through impingement of the main detachment fault1314. An alternative model invoking the exhumation of a mechanically weak lower crust has also been proposed for SPMs15.

Bottom Line: Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere.Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain.Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

View Article: PubMed Central - PubMed

Affiliation: Université de Bretagne Occidentale, Brest, 29238 Brest.

ABSTRACT
Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

No MeSH data available.


Related in: MedlinePlus