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| Titel |
Is the Gop rift oceanic? A reevaluation of the Seychelles-India conjugate margins |
| VerfasserIn |
Huixin Guan, Philippe Werner, Laurent Geoffroy |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127737
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| Publikation (Nr.) |
 EGU/EGU2016-7643.pdf |
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| Zusammenfassung |
| Recent studies reevaluated the timing and evolution of the breakup process between the
Seychelles continental ridge and India, and the relationship between this evolution and mantle
melting associated with the Deccan Igneous Province1,2,3.
Those studies, mainly based on gravity and seismic refraction surveys, point that the
oceanic domain located between the Seychelles and the Laxmi Ridge (here designed as the
Carlsberg Basin) is the youngest oceanic domain between India and the Seychelles. To the
East of the Laxmi Ridge, the aborted Gop Rift is considered as an older highly
magmatic extensional continental system with magmatism, breakup and oceanic
spreading being coeval with or even predating the emplacement of the major pulse
of the Deccan trapps. This interpretation on the oceanic nature of the Gop Rift
conflicts with other extensive surveys based on magnetic and seismic reflection
data4 which suggest that the Gop Rift is an extended syn-magmatic continental
domain.
In our work based (a) on the existing data, (b) on new deep-seismic reflection surveys
(already published by Misra5) down to the Moho and underlying mantle and (c) on new
concepts on the geometry of volcanic passive margins, we propose a distinct interpretation of
the Seychelles-India system.
As proposed by former authors6,7, the Indian margin suffered some continental stretching
and thinning before the onset of the Deccan traps during the Mesozoic. Thus continental crust
thickness cannot be used easily as a proxy of syn-magmatic stretching-thinning processes or
even to infer the presence or not of oceanic-type crust based, solely, on crustal thickness.
However, some remarkable features appear on some of the deep penetration seismic lines we
studied.
We illustrate that the whole Seychelles/India system, before the opening of the
present-day “Carlsberg Basin” may simply be regarded as a pair of sub-symmetric conjugate
volcanic passive margins (VPMs) with inner and outer SDR wedges dipping towards the Gop
Rift axis. We propose that the conspicuous buoyant central part of the Gop Rift is likely
associated with a continental C-Block as described in a recent paper on conjugated VPMs8, at
least in the southern part of the Gop Rift. The crust below the Laxmi basin is probably
transitional continental i.e. strongly intruded. West of India and west of the Laxmi Ridge, the
transition to the Carlsberg Basin occurs along a clearly-expressed transform fault,
not through an extended and thinned continental margin. We reinterpret the whole
system based on those observations and propositions, giving some explanations on
controversial magnetic anomalies based on similar observations from the southern Atlantic
Ocean.
1: Collier et al., 2008. Age of the Seychelles–India break-up. Earth and Planetary Science
Letters.
2: Minshull et al., 2008. The relationship between riftingand magmatism in the
northeastern Arabian Sea. Nature Geoscience.
3 : Armitage et al., 2010. The importance of rift history for volcanic margin.
Nature.
4 : Krishna et al., 2006. Nature of the crust in the Laxmi Basin (14 degrees–20 degrees
N), western continental margin of India. Tectonics.
5 : Misra et al., 2015. Repeat ridge jumps and microcontinent separation: insights from
NE Arabian Sea. Marine and Petroleum Geology.
6 : Biswas, 1982. Rift basins in the western margin of India and their hydrocarbon
prospects. Bull. Am. Assoc. Pet. Geol.
7 : Chatterjee et al., 2013. The longest voyage: Tectonic, magmatic, and paleoclimatic
evolution of the Indian plate during its northward flight from Gondwana to Asia. Gondwana
Research.
8 : Geoffroy et al., 2015. Volcanic passive margins: anotherway to break up continents.
Scientific Reports. |
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