Geochemical heterogeneities within the Crozet hotspot

• Published in: Earth and Planetary Science Letters
• Main Authors: Breton, Thomas, Nauret, François, Pichat, Sylvain, Moine, Bertrand N., Moreira, Manuel, Rose-Koga, Estelle, Auclair, Delphine, Bosq, Chantal, Wavrant, Laurène-Marie
• Other Authors: Laboratoire Magmas et Volcans (LMV), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: Sr-Nd-Pb-He isotopes; trace elements; FOZO; plume-ridge interaction; SWIR; [SPI]Engineering Sciences [physics]; Five Islands; Indian; Possession Islands; Crozet Islands
• Online Access: https://hal.science/hal-00981442; https://hal.science/hal-00981442/document; https://hal.science/hal-00981442/file/Breton2013.pdf; https://doi.org/10.1016/j.epsl.2013.06.020

International audience The Crozet Plateau is a 54 Ma-old volcanic plateau that supports five islands characterized by recent volcanic manifestations that are the surface expression of a deep-mantle plume. Due to their remote location and difficult access, the Crozet Islands are poorly sampled. Both the petrological descriptions and geochemical data are scarce. Thus, the sources of the Crozet plume are still under debate. Similarly, the interactions between the Southwest Indian Ridge (SWIR) and the Crozet plume remain questioned. Here, we present a new set of isotopes (Pb, Sr, Nd and He), major and trace elements data on basalts from three islands of the Crozet Archipelago: Penguins, East, and Possession Islands. Our main purpose is to characterize the sources of the Crozet plume and to test its influence at regional scale. Two groups of lavas can be distinguished based on the isotopic data: East and Possession lavas, and Penguins lavas. Principal component analyses on our high-precision Pb isotopes data and literature data show that two mantle sources can explain most of the geochemical variability measured in Crozet lavas. A third minor contribution is however needed to fully explain the data. The entire set of isotopic compositions (Pb, Sr, Nd and He) can be explained by a mixing between three mantle sources: (1) a FOZO (Focus Zone) component, with 206Pb/204Pb higher than 19.5 and high 207Pb/204Pb, 208Pb/204Pb 87Sr/86Sr, 143Nd/144Nd and R/RaR/Ra (R/Ra=(He3/He4)sample/(He3/He4)atmosphere) ratios, that is mainly sampled Penguins lavas, (2) a component called "East-Possession" that is mostly sampled by the East-Possession lava group and which presents Pb, Sr and Nd isotope signatures similar to those of the Reunion-Mauritius Islands, and (3) a third minor contribution of the local Depleted MORB Mantle (DMM). The new He isotopes data on the Crozet plume allow us to propose that Crozet plume material is present in the segment of the Southwest Indian Ridge located between the Indomed (ITF) and Gallieni (GTF) ...