The Amsterdam-St. Paul Plateau: A complex hot spot/DUPAL-flavored MORB interaction

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Janin, Myriam, Hémond, Christophe, C, Maia, Marcia, Nonnotte, Philippe, Ponzevera, Emmanuel, Johnson, K.T.M.
• Other Authors: 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), Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Nîmes (UNIMES), Unité Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), School of ocean and earth science and technology, University of Hawai‘i Mānoa (UHM), Program EXTRAPLAC and Program SEDIT
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: DUPAL anomaly; Indian Ocean; Sr-Nd-Pb-Hf isotopes; ridge-hot spot interaction; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; Amsterdam Island
• Online Access: https://insu.hal.science/insu-00737400; https://insu.hal.science/insu-00737400/document; https://insu.hal.science/insu-00737400/file/G3-Janin.pdf; https://doi.org/10.1029/2012GC004165

International audience The Amsterdam-St Paul (ASP) oceanic plateau results from the interaction between the ASP hot spot and the Southeast Indian ridge. A volcanic chain, named the Chain of the Dead Poets (CDP), lies to its northward tip and is related to the hot spot intraplate activity. The ASP plateau and CDP study reveals that ASP plume composition is inherited from oceanic crust and pelagic sediments recycled in the mantle through a 1.5 Ga subduction process. The ASP plateau lavas have a composition (major and trace elements and Sr-Nd-Pb-Hf isotopes) reflecting the interaction between ASP plume and the Indian MORB mantle, including some clear DUPAL input. The Indian upper mantle below ASP plateau is heterogeneous and made of a depleted mantle with lower continental crust (LCC) fragments probably delaminated during the Gondwana break-up. The lower continental crust is one of the possible reservoirs for the DUPAL anomaly origin that our data support. The range of magnitude of each end-member required in ASP plateau samples is (1) 45% to 75% of ASP plume and (2) 25% to 55% of Indian DM within 0% to a maximum of 6% of LCC layers included within. The three end-members involved (plume, upper mantle and lower continental crust) and their mixing in different proportions enhances the geochemical variability in the plateau lavas. Consequently, the apparent composition homogeneity of Amsterdam Island, an aerial summit of the plateau, may result from the presence of intermediate magmatic chambers into the plateau structure.