Geochemistry articles within Nature

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  • News & Views |

    An assessment of crystallization processes occurring in magma chambers in the ocean floor finds an unexpected enrichment in trace elements, reviving an old theory of the cycling of magma in these chambers. See Article p.698

    • Albrecht W. Hofmann

  • News & Views |

    The finding that pools of gas hydrates — compounds that trap natural gas emissions — in ocean sediments are deeper than expected implies that the hydrates are destabilizing, and might release gigatonnes of methane. See Letter p.527

    • Juergen Mienert

  • Letter |

    Lunar magmatic rocks are shown to be enriched in the heavy isotopes of zinc and to have lower zinc concentrations than terrestrial or Martian igneous rocks; these variations represent the large-scale evaporation of zinc, most probably in the aftermath of the Moon-forming giant impact event.

    • Randal C. Paniello
    • , James M. D. Day
    •  & Frédéric Moynier

  • Letter |

    The solubility of argon in lower mantle minerals is shown to be much higher than for xenon, so that the depletion of xenon relative to argon in Earth’s atmosphere can be explained by mantle degassing.

    • Svyatoslav S. Shcheka
    •  & Hans Keppler

  • News & Views |

    A study reveals cyclic changes in the rate of burial of biogenic calcium carbonate at the Pacific ocean floor 43 million to 33 million years ago, as Earth exited a warm 'greenhouse' state to become an ice-capped planet. See Article p.609

    • Heather Stoll

  • News & Views |

    The cocktail of noble-gas isotopes in an Icelandic rock suggests that the upper mantle does not, and never did, receive gas from a deeper mantle reservoir. This challenges ideas of deep Earth's behaviour and formation. See Letter p.101

    • Chris J. Ballentine

  • News & Views |

    An analysis of geochemical data reveals a substantial change in the composition of Earth's magmas about 2.5 billion years ago, just as Earth's atmosphere and climate were also changing drastically. See Letter p.490

    • William M. White

  • News & Views |

    There have been conflicting claims about the composition of Earth's lower mantle. The latest Brillouin-spectroscopy data suggest that this section of the planet's interior may contain more silica than the upper mantle. See Letter p.90

    • Ian Jackson

  • News & Views |

    A study suggests that hydrocarbons released from sedimentary basins formed part of a climatic feedback mechanism that exacerbated global warming during the Eocene epoch.

    • Henrik Svensen

  • News & Views |

    Multi-scale modelling of the deformation of magnesium oxide reveals the need for a re-examination of the way in which laboratory data are used to estimate the strength of Earth's lower mantle. See Letter p.177

    • Andrew M. Walker

  • Letter |

    The Antarctic Peninsula is currently one of the fastest-warming locations on Earth, but its long-term variability has remained unclear. This study uses TEX86 sea surface temperature proxy evidence to show that a long-term cooling of about 3–4 °C occurred in waters near the tip of the Antarctic Peninsula over the past 12,000 years, consistent with orbitally controlled changes in insolation. Shorter-term variability in temperature at the Antarctic Peninsula appears to have been strongly influenced by the position of westerly winds. The present influence of the El Niño/Southern Oscillation system on the Antarctic Peninsula may have arisen only during the late Holocene.

    • A. E. Shevenell
    • , A. E. Ingalls
    •  & C. Kelly

  • Letter |

    Here it is shown that the ratio of zinc to total iron content constrains the valence state of iron in primary arc basalts and their mantle sources. Primitive arc magmas have identical Zn/FeT ratios (FeT = Fe2+ + Fe3+) as mid-ocean-ridge basalts, indicating a similar iron oxidation state of primary mantle melts in arcs and ridges and that the subduction of oxidized crustal material may not significantly alter the redox state of the mantle wedge. It is concluded that the observed higher oxidation states of arc lavas must therefore be, in part, a consequence of shallow-level differentiation processes.

    • Cin-Ty A. Lee
    • , Peter Luffi
    •  & William P. Leeman

  • Letter |

    Cratons, the ancient cores of continents, extend laterally for hundreds of kilometres, and are underlain to depths of 180–250 km by mantle roots that are chemically and physically distinct from surrounding mantle. But how can these roots stay so isolated from mantle convection? Here it is shown that olivine in peridotite xenoliths from the lithosphere–athenosphere boundary region of the Kaapvaal craton mantle root is water-poor, providing sufficient viscosity contrast with the underlying asthenosphere to explain the root's stability.

    • Anne H. Peslier
    • , Alan B. Woodland
    •  & Marina Lazarov

  • Article |

    These authors show that changes in seismic anisotropy with depth across the stable part of North America reveal the presence of two lithospheric layers. The top layer, which is chemically depleted, is ∼150 km thick under the ancient core of the continent and tapers out along its younger borders. The bottom of the lithosphere is relatively flat, in agreement with the presence of a thermal conductive root that subsequently formed around the depleted chemical layer.

    • Huaiyu Yuan
    •  & Barbara Romanowicz

  • News & Views |

    Geochemical evidence for the existence of the mother of all mantle-source reservoirs for volcanism has come to light. The new results have provocative implications for our understanding of Earth's interior.

    • David Graham

  • Letter |

    The physics of thermal diffusion — mass diffusion driven by a temperature gradient — is poorly understood. One obstacle has been that the Soret coefficient (ST, which describes the steady-state result of thermal diffusion) is sensitive to many factors. It is now shown that the difference in ST between isotopes of diffusing elements that are network modifiers is independent of composition and temperature. The findings suggest a theoretical approach for describing thermal diffusion in silicate melts and other complex solutions.

    • F. Huang
    • , P. Chakraborty
    •  & C. E. Lesher

  • Letter |

    For the first billion years or so of the Earth's history, there may have been whole-mantle convection, but after this period differentiation of the Earth's mantle has been controlled by solid-state convection. Many trace elements — known as 'incompatible elements' — preferentially partition into low-density melts and are concentrated into the crust, but half of these incompatible elements should be hidden in the Earth's interior. It is now suggested that a by-product of whole-mantle convection is deep and hot melting, resulting in the generation of dense liquids that sank into the lower mantle.

    • Cin-Ty A. Lee
    • , Peter Luffi
    •  & John Hernlund

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