Three-dimensional seismic structure of the Dragon Flag oceanic core complex at the ultraslow spreading Southwest Indian Ridge (49°39′E). - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Geochemistry, Geophysics, Geosystems Année : 2013

Three-dimensional seismic structure of the Dragon Flag oceanic core complex at the ultraslow spreading Southwest Indian Ridge (49°39′E).

Résumé

The Southwest Indian Ridge (SWIR) is an ultraslow spreading end-member of mid-ocean ridge system. We use air gun shooting data recorded by ocean bottom seismometers (OBS) and multibeam bathymetry to obtain a detailed three-dimensional (3-D) P wave tomographic model centered at 49390E near the active hydrothermal ‘‘Dragon Flag’’ vent. Results are presented in the form of a 3-D seismic traveltime inversion over the center and both ends of a ridge segment. We show that the crustal thickness, defined as the depth to the 7 km/s isovelocity contour, decreases systematically from the center (7.0–8.0 km) toward the segment ends (3.0–4.0 km). This variation is dominantly controlled by thickness changes in the lower crustal layer. We interpret this variation as due to focusing of the magmatic activity at the segment center. The across-axis velocity model documents a strong asymmetrical structure involving oceanic detachment faulting. A locally corrugated oceanic core complex (Dragon Flag OCC) on the southern ridge flank is characterized by high shallow crustal velocities and a strong vertical velocity gradient. We infer that this OCC may be predominantly made of gabbros. We suggest that detachment faulting is a prominent process of slow spreading oceanic crust accretion even in magmatically robust ridge sections. Hydrothermal activity at the Dragon Flag vents is located next to the detachment fault termination. We infer that the detachment fault system provides a pathway for hydrothermal convection.
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Dates et versions

hal-00914264 , version 1 (09-06-2017)

Identifiants

Citer

Minghui Zhao, Xuelin Qiu, Jiabiao Li, Daniel Sauter, Aiguo Ruan, et al.. Three-dimensional seismic structure of the Dragon Flag oceanic core complex at the ultraslow spreading Southwest Indian Ridge (49°39′E).. Geochemistry, Geophysics, Geosystems, 2013, 14, pp.4544-4563, doi:10.1002/ggge.20264. ⟨10.1002/ggge.20264⟩. ⟨hal-00914264⟩
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