| Type |
Article |
| Date |
1998-07 |
| Language |
English |
| Author(s) |
Recq M1, Goslin J1, Charvis P2, Operto S2 |
| Affiliation(s) |
1 : Univ Bretagne Occidentale, CNRS Domaines Ocean, UMR 6538, F-29285 Brest, France.
2 : Observ Oceanol Villefrance Sur Mer, CNRS Geosci Azur, ORSTOM, UR14,UMR 6526, F-06235 Villefranche Sur Mer, France. |
| Source |
Geophysical Journal International (0956-540X) (Wiley-blackwell), 1998-07 , Vol. 134 , N. 1 , P. 145-156 |
| DOI |
10.1046/j.1365-246x.1998.00530.x |
| WOS© Times Cited |
25 |
| Keyword(s) |
aseismic ridge, Crozet Islands platform, crustal structure, gravity anomalies, hotspots, seismic refraction |
| Abstract |
The Crozet Bank, the easternmost region of the Crozet Plateau (austral Indian Ocean), is capped by two groups of islands which form the Crozet Archipelago (Terres Australes and Antarctiques Francaises). A N-S-trending 2 km deep basin, the Indivat Basin, extends between the two groups of islands and bisects the Crozet Bank into two separate domains. The interpretation of the KeOBS8 seismic refraction profile shot during the KeOBS/MD66 cruise (January-February 1991) over the eastern Crozet Plateau was carried out by ray tracing and the computation of synthetic seismograms. This interpretation leads to a rather complex seismic structure and outlines a pronounced eastward crustal thinning from 16.5 to 10 km at the expense of layer 2. The thinning of the crust is abrupt east of the Indivat Basin. Unlike below the Hawaiian Islands and the Marquesas Islands, no underplated mantle material underlies the crust of the Crozet Bank. Moreover, this deep seismic sounding has further revealed that a high-velocity feature outcropping the seabed 30 km east of Ile aux Cochons could be a major structural feature, deeply rooted within the lower crust. The occurrence of this feature (a submarine volcano?) is associated with a mantle dyke causing a steep shallowing of the lower crustal interfaces. Gravity modelling was performed along line KeOBS8, with a density structure deduced from the seismic section, to model free-air anomalies derived from altimetry data, This modelling confirms that the Indivat Basin, underlined by a gravity low running roughly N-S between the two groups of islands, is a major structural boundary. As the model generates medium-wavelength anomalies of adequate amplitude, it also confirms that the volcano, located west of the Indivat Basin, is a deeply rooted feature. The Crozet Bank clearly appears as a plume-affected structure, which may have originated from a deep thermal anomaly within the lithosphere. More recent volcanic episodes, related to a still active plume activity under the Crozet Bank, could have uplifted upper-mantle material and caused the emplacement of the newly discovered feature and of the western group of islands. |
| Full Text |
| File |
Pages |
Size |
Access |
| Publisher's official version |
12 |
1 MB |
Open access |
|
