Structure and development of a microcontinent: Elan Bank in the southern Indian Ocean

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Borissova, Irina, Coffin, Millard F., Charvis, Philippe, Operto, Stéphane
• Other Authors: Geoscience Australia, Commonwealth Scientific and Industrial Research Organisation Canberra (CSIRO), Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin Austin, Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Sud )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2003
• Subjects: [SDU]Sciences of the Universe [physics]; Elan Bank; Indian; Kerguelen; Southern Ocean; Antarc*; Antarctica
• Online Access: https://hal.science/hal-00406983; https://hal.science/hal-00406983/document; https://hal.science/hal-00406983/file/Borissova_et_al-2003-Geochemistry,_Geophysics,_Geosystems.pdf; https://doi.org/10.1029/2003GC000535

Geochemistry, Geophysics, Geosystems, v. 4, n. 9, p. 1071, 2003. http://dx.doi.org/10.1029/2003GC000535 International audience Microcontinents appear to commonly form on young continental margins close to hot spots, butdifficulties in understanding their geology and evolution have inhibited assessment of their globaldistribution and significance. Thick volcanic accumulations in areas affected by hot spot magmatismonly complicate the issue. Elan Bank, a large western salient of the Kerguelen Plateau, is amicrocontinent that originally lay between India and Antarctica in Gondwana. Recent regional platetectonic reconstructions suggest that during Gondwana breakup, Elan Bank and India initially separatedfrom Antarctica, and Elan Bank became isolated in the Southern Ocean via a ridge jump to the northbetween Elan Bank and India. In Albian time (108 Ma), voluminous magmatism attributed to theKerguelen hot spot overprinted and radically altered the original microcontinent and its surroundings.Recent ODP investigations, deep seismic reflection data, and a wide-angle seismic line on Elan Bankallow us to gain the first insight into the feature’s integrated crustal structure and geological evolutionand the adjacent continent-ocean transition zone. Our analysis shows that Elan Bank’s crust is at least16 km thick. The upper igneous crust consists of a 2–3 km thick layer with seismic velocities rangingfrom 4.4 to 5.9 km/s that can be interpreted as the result of accumulation of lava flows originating fromthe Kerguelen hot spot. Seismic velocities at the base of the crust are as low as 6.6 km/s, which isconsistent with a fragment of thinned continental crust 14 km thick. A high velocity body, located atdepths of 5 to 10 km, could be interpreted as plutonic rocks emplaced during the major regionalmagmatic episode. On the basis of deep seismic reflection data, we interpret extensional structuresbeneath the volcanic flows. In Albian time, when the area was affected by the Kerguelen hot spot,volcaniclastic material and lava ...