The crustal structure of the north-eastern Gulf of Aden continental margin: insights from wide-angle seismic data | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

Twitter

Aller au compte twitter

  The crustal structure of the north-eastern Gulf of Aden continental margin: insights from wide-angle seismic data

Type de publication:

Journal Article

Source:

Geophysical Journal International, Volume 184, Ticket 2, p.575-594 (2011)

ISBN:

0956-540X

Numéro d'accès:

ISI:000286225300004

URL:

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-246X.2010.04881.x/full?globalMessage=0

Mots-clés:

UMR 7154 ; Géosciences marines ; Controlled source seismology; Continental margins: divergent; Crustal structure; Indian Ocean

Résumé:

<p>P&gt;The wide-angle seismic (WAS) and gravity data of the Encens survey allow us to determine the deep crustal structure of the north-eastern Gulf of Aden non-volcanic passive margin. The Gulf of Aden is a young oceanic basin that began to open at least 17.6 Ma ago. Its current geometry shows first- and second-order segmentation: our study focusses on the Ashawq-Salalah second-order segment, between Alula-Fartak and Socotra-Hadbeen fracture zones. Modelling of the WAS and gravity data (three profiles across and three along the margin) gives insights into the first- and second-order structures. (1) Continental thinning is abrupt (15-20 km thinning across 50-100 km distance). It is accommodated by several tilted blocks. (2) The ocean-continent transition (OCT) is narrow (15 km wide). The velocity modelling provides indications on its geometry: oceanic-type upper-crust (4.5 km s-1) and continental-type lower crust (&gt; 6.5 km s-1). (3) The thickness of the oceanic crust decreases from West (10 km) to the East (5.5 km). This pattern is probably linked to a variation of magma supply along the nascent slow-spreading ridge axis. (4) A 5 km thick intermediate velocity body (7.6 to 7.8 km s-1) exists at the crust-mantle interface below the thinned margin, the OCT and the oceanic crust. We interpret it as an underplated mafic body, or partly intruded mafic material emplaced during a 'post-rift' event, according to the presence of a young volcano evidenced by heat-flow measurement (Encens-Flux survey) and multichannel seismic reflection (Encens survey). We propose that the non-volcanic passive margin is affected by post-rift volcanism suggesting that post-rift melting anomalies may influence the late evolution of non-volcanic passive margins.</p>

Notes:

Watremez, L. Leroy, S. Rouzo, S. d'Acremont, E. Unternehr, P. Ebinger, C. Lucazeau, F. Al-Lazki, A.