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Geophysics. Helium feels the heat in Earth's mantle

Albarède, Francis

Science (New York, N.Y.), 16 December 2005, Vol.310(5755), pp.1777-8 [Periódico revisado por pares]

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  • Título:
    Geophysics. Helium feels the heat in Earth's mantle
  • Autor: Albarède, Francis
  • Assuntos: Upper Mantle ; Rare Gases ; Solubility ; Hot Spots ; Geochemistry ; Heat Flow ; Mid-Ocean Ridges ; Potassium Isotopes ; Helium Isotopes ; Tectonophysics ; Mantle Convection ; Basalts ; Argon Isotopes ; Lower Mantle ; Helium ; Earth Structure ; Magma ; Earth Mantle ; Tectonics and Crustal Structure ; Geology and Geophysics
  • É parte de: Science (New York, N.Y.), 16 December 2005, Vol.310(5755), pp.1777-8
  • Descrição: For nearly two decades, geoscientists held that the terrestrial mantle behaves as two superposed layers separated by a discontinuity at a depth of 660 km. In this picture, convection of mantle material occurs separately in each layer. This view was challenged in the 1990s by evidence from seismic tomography that some subducting plates penetrate almost all the way down to the core-mantle boundary. Many of the arguments supporting layered-mantle convection still survive, however, and their impact--notably on chemical geodynamics and on the understanding of terrestrial evolution through geological ages--is still considerable. Most notably, researchers point to the noble gas helium. Reconciling whole-mantle convection with what we know about the abundances of helium isotopes in hotspot and mid-ocean ridge basalts demands a solubility level of this gas in minerals that is rarely considered as acceptable. Second, the terrestrial inventory of the isotope super(40)Ar created by radioactive decay of super(40)K leaves too much of this gas unaccounted for. This is commonly interpreted to mean that deep mantle material never came close to the surface to lose its gas content.
  • Idioma: Inglês

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