Rifting above a mantle plume: structure and development of the Iceland Plateau

Research areas:

• Environnement, Paléo-Environnement et Bio-Indicateurs (2011 - 2016)

Year:

2005

Authors:

• Olivier Bourgeois
• O Dauteuil
• E Hallot

Journal:

GEODINAMICA ACTA

Volume:

18

Number:

1

Pages:

59-80

Month:

JAN-FEB

ISSN:

0985-3111

BibTex:

@article{WOS:000229911700005, author = "Olivier Bourgeois and O Dauteuil and E Hallot", abstract = "The interaction of the Mid-Atlantic Ridge with the North Atlantic Mantle Plume has produced a magmatic. plateau centred about Iceland. The crust of this plateau is 30 km thick on average. This abnormal thickness implies that, unlike other slow-spreading ridges, addition of magmatic material to the crust is not balanced by crustal stretching. The thermal effect of the plume also reduces the strength of the lithosphere. Both mechanisms affect the rifting process in Iceland. A structural review, including new field observations, demonstrates that the structure of the Iceland plateau differs from that of other slow-spreading oceanic ridges. Lithospheric spreading is currently accommodated in a 200 kin wide deformation strip, by the development of a system of half-grabens controlled by growth faults. Similar extinct structures, with various polarities, are preserved in the lava pile of the Iceland plateau. These structures are identified as lithospheric rollover anticlines that developed in hanging walls of listric faults. We introduce a new tectonic model of accretion, whereby the development of the magmatic plateau involved activation, growth and decay of a system of growth fault/rollover systems underlain by shallow magma chambers. Deactivation of a given extensional system, after a lifetime of a few My, was at the expense of the activation of a new, laterally offset, one. Correspondingly, such systems formed successively at different places within a 200 kin wide diffuse plate boundary. Unlike previous ones, this new model explains the lack of an axial valley in Iceland, the dip pattern of the lava pile, the complex geographical distribution of ages of extinct volcanic systems and the outcrops of extinct magma chambers. (c) 2005 Lavoisier SAS. All rights reserved.", doi = "10.3166/ga.18.59-80", extra = "PICL", issn = "0985-3111", journal = "GEODINAMICA ACTA", month = "JAN-FEB", number = "1", pages = "59-80", title = "{R}ifting above a mantle plume: structure and development of the {I}celand {P}lateau", volume = "18", year = "2005", }

Abstract:

The interaction of the Mid-Atlantic Ridge with the North Atlantic Mantle
Plume has produced a magmatic. plateau centred about Iceland. The crust
of this plateau is 30 km thick on average. This abnormal thickness
implies that, unlike other slow-spreading ridges, addition of magmatic
material to the crust is not balanced by crustal stretching. The thermal
effect of the plume also reduces the strength of the lithosphere. Both
mechanisms affect the rifting process in Iceland. A structural review,
including new field observations, demonstrates that the structure of the
Iceland plateau differs from that of other slow-spreading oceanic
ridges. Lithospheric spreading is currently accommodated in a 200 kin
wide deformation strip, by the development of a system of half-grabens
controlled by growth faults. Similar extinct structures, with various
polarities, are preserved in the lava pile of the Iceland plateau. These
structures are identified as lithospheric rollover anticlines that
developed in hanging walls of listric faults. We introduce a new
tectonic model of accretion, whereby the development of the magmatic
plateau involved activation, growth and decay of a system of growth
fault/rollover systems underlain by shallow magma chambers. Deactivation
of a given extensional system, after a lifetime of a few My, was at the
expense of the activation of a new, laterally offset, one.
Correspondingly, such systems formed successively at different places
within a 200 kin wide diffuse plate boundary. Unlike previous ones, this
new model explains the lack of an axial valley in Iceland, the dip
pattern of the lava pile, the complex geographical distribution of ages
of extinct volcanic systems and the outcrops of extinct magma chambers.
(c) 2005 Lavoisier SAS. All rights reserved.