Thermal regime of the Southeast Indian Ridge between 88°E and 140°E: Remarks on the subsidence of the ridge flanks

• Published in: Journal of Geophysical Research
• Main Authors: Géli, L., R. Cochran, J., C. Lee, T., Francheteau, J., Labails, C., Fouchet, C., Christie, D.
• Other Authors: Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Lamont-Doherty Earth Observatory (LDEO), Columbia University New York, College of Ocean and Atmospheric Sciences, Oregon State University (OSU), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), West Coast and Polar Regions Undersea Research Center, University of Alaska Fairbanks (UAF)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: Southeast Indian Ridge; seafloor subsidence; mantle temperature; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDE.MCG]Environmental Sciences/Global Changes; Antarctic; Australian-Antarctic Discordance; Indian; Antarc*
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-00188805; https://hal-insu.archives-ouvertes.fr/insu-00188805/document; https://hal-insu.archives-ouvertes.fr/insu-00188805/file/JGR-Geli-Franch-07.pdf; https://doi.org/10.1029/2006JB004578

International audience The flanks of the Southeast Indian Ridge are characterized by anomalously low subsidence rates for the 0–25 Ma period: less than 300 m Ma−1/2 between 101°E and 120°E and less than 260 m Ma−1/2 within the Australian-Antarctic Discordance (AAD), between 120°E and 128°E. The expected along-axis variation in mantle temperature (∼50°C) is too small to explain this observation, even when the temperature dependence of the mantle physical properties is accounted for. We successively analyze the effect on subsidence of different factors, such as variations in crustal thickness; the dynamic contribution of an old, detached slab supposedly present within the mantle below the AAD; and depletion in ϕ m, a parameter here defined as the “ubiquitously distributed melt fraction” within the asthenosphere. These effects may all contribute to the observed, anomalously low subsidence rate of the ridge flanks, with the most significant contribution being probably related to the depletion in ϕ m. However, these effects have a deep-seated origin that cannot explain the abruptness of the transition across the fracture zones that delineate the boundaries of the AAD, near 120°E and near 128°E, respectively.