Volcanic passive margins: another way to break up continents

Type Article
Date 2015-10
Language English
Author(s) Geoffroy Laurent1, 2, Burov E. B.3, 4, Werner P.5
Affiliation(s) 1 : Univ Bretagne Occidentale, F-29238 Brest, France.
2 : CNRS, UMR 6538, Lab Domaines Ocean, F-29280 Plouzane, France.
3 : Univ Paris 06, Sorbonne Univ, F-75005 Paris, France.
4 : CNRS, UMR 7193, Inst Sci Terre Paris iSTeP, F-75005 Paris, France.
5 : TOTAL, Explorat Prod, F-92078 Paris, France.
Source Scientific Reports (2045-2322) (Nature Publishing Group), 2015-10 , Vol. 5 , P. 14828 (12p.)
DOI 10.1038/srep14828
WOS© Times Cited 45
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 synmagmatic 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.

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