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Titel |
Role of ductile strain localization in the lithospheric mantle on continental rifting |
VerfasserIn |
Frédéric Gueydan, Jacques Précigout |
Konferenz |
EGU General Assembly 2014
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 16 (2014) |
Datensatznummer |
250093436
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Publikation (Nr.) |
EGU/EGU2014-8148.pdf |
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Zusammenfassung |
The strength of the lithospheric mantle controls the mode of lithosphere deformation: the
presence or absence of a high strength brittle mantle respectively leads to localized or
distributed rifting. However, first order geophysical data question the existence of such a
brittle mantle. Here we use 2-D finite-element large strain modelling to quantify the impact of
a ductile localizing mantle – instead of brittle – in triggering continental rifting. As a novelty,
the mantle rheology considers the effect of grain boundary sliding during strain-induced
grain size reduction, which may promote a significant strength drop and subsequent
strain localization at low mantle temperature (< 700-800°C). Our results reveal
that such ductile localizing mantle implies varying modes of continental rifting
that mainly depend on both the amount of weakening in the ductile mantle and the
strength of the lower ductile crust. A medium to strong lower crust implies coupling
between the upper crust and ductile localizing mantle, yielding to narrow continental
rifting. In contrast, a weak lower crust implies decoupling between the upper crust
and ductile localizing mantle, giving rise to a switch from distributed faulting at
incipient strain to localized faulting at large strain. Ductile strain localization in the
lithospheric mantle is therefore sufficient to trigger continental rifting, although a critical
amount of weakening is required. Such ductile localizing mantle provides a relevant
geological and mechanical alternative to the brittle mantle. It moreover provides a wider
variety of modes of upper crustal faulting that are commonly observed in nature. |
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