Petrology articles within Nature Geoscience

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  • Letter |

    Magma in Earth’s crust is in a crystal-rich mushy state, yet must be fluidized before eruptions. Numerical simulations show that rapid injection of new magma into a reservoir creates a mixing bowl of fluid and crystals that are able to erupt.

    • G. W. Bergantz
    • , J. M. Schleicher
    •  & A. Burgisser

  • Article |

    How plate tectonic subduction is initiated is unclear. Analysis of sediments and rock cores taken from the Izu–Bonin–Mariana subduction zone trench suggests subduction started spontaneously in this region around 50 million years ago.

    • Richard J. Arculus
    • , Osamu Ishizuka
    •  & Zhaohui Zhang

  • Letter |

    NASA’s Curiosity rover detected light-toned rocks along its traverse on Mars. Geochemical data suggest that the rocks represent a diversity of silica-rich magmatic rock types that may be analogous to Earth’s early continental crust.

    • V. Sautter
    • , M. J. Toplis
    •  & J. J. Wray

  • News & Views |

    Metals often accumulate in the crust beneath volcanoes. Laboratory experiments and observations reveal important roles for magmatic vapours and brines in transporting and concentrating the metals into deposits worth targeting for extraction.

    • Olivier Nadeau

  • Letter |

    The geochemical variability of lavas erupted at mid-ocean ridges is lowest where plate spreading rates are high, implying that large-scale plate motions mix the mantle—yet lavas erupted at slow-spreading ridges are also quite homogeneous. Numerical simulations suggest that small-scale convection in the mantle mixes and homogenizes the lavas erupted at slow-spreading ridges.

    • Henri Samuel
    •  & Scott D. King

  • Letter |

    Giant volcanic eruptions occur when large volumes of magma accumulate in crustal reservoirs and do not cool and crystallize to form a solid pluton of rock within the crust. Geochronological dating of a pluton from Elba, Italy, shows that the magma solidified in the crust within just 10–40 thousand years of being injected into the crust, implying that the time window for an eruption was short.

    • Mélanie Barboni
    •  & Blair Schoene

  • News & Views |

    Carbon loss from subducting slabs is thought to be insufficient to balance carbon dioxide emissions at arc volcanoes. Analyses of ancient subducted rocks in Greece suggest that fluid dissolution of slab carbonate can help solve this carbon-cycle conundrum.

    • Craig E. Manning

  • Letter |

    The balance between carbonate subduction into the deep Earth and CO2 release through degassing at volcanoes is critical for the carbon cycle. Geochemical analyses of an exhumed subduction zone complex in Greece show that fluid-mediated reactions could liberate significant amounts of carbon from the subducting slab for later release at arc volcanoes.

    • Jay J. Ague
    •  & Stefan Nicolescu

  • Article |

    Upwelling mantle plumes are thought to be sheared by the motions of the overlying tectonic plates. Seismic imaging of a hotspot beneath the Galápagos Islands, however, identifies a plume that is not deflected in the direction of plate motion and whose characteristics are instead controlled by multistage melting processes.

    • Darwin R. Villagómez
    • , Douglas R. Toomey
    •  & Sean C. Solomon

  • Letter |

    Supervolcano eruptions dwarf all historical eruptions, but their trigger mechanisms are unclear. Experimental measurements of magma density at high pressures and temperatures show that the buoyancy of magma alone can impose sufficient pressure at the roof of a supervolcano magma chamber to induce an eruption.

    • Wim J. Malfait
    • , Rita Seifert
    •  & Carmen Sanchez-Valle

  • News & Views |

    The Archaean Earth was much hotter than today. Numerical modelling shows that the base of thickened crust that formed at the time would have been so dense that it dripped back into the mantle.

    • Claude Herzberg

  • Letter |

    The volume of Archaean crust preserved at Earth’s surface today is low. Thermodynamic calculations and geodynamic modelling show that the thick, primary crust that would have formed on a much hotter Archaean Earth was denser than the underlying mantle, and would have therefore been recycled back into the mantle as drips.

    • Tim E. Johnson
    • , Michael Brown
    •  & Jill A. VanTongeren

  • Letter |

    Felsic rocks have not been identified on Mars, a planet that lacks plate tectonics to drive the magmatic processes that lead to evolved silica-rich melts. Spectral observations by the Mars Reconnaissance Orbiter indicate that felsic lithologies occur at multiple localities on Mars and suggest prolonged magmatic activity on ancient Mars.

    • James J. Wray
    • , Sarah T. Hansen
    •  & Mark S. Ghiorso

  • Letter |

    The formation of the silicate mineral anorthosite is thought to require magmatic processes that are not expected on Mars because of its predominately mafic terrains. Localized spectral detections by the Mars Reconnaissance Orbiter are consistent with anorthosite, suggestive of ancient intrusive igneous processes similar to those active on Earth.

    • J. Carter
    •  & F. Poulet

  • Letter |

    Carbon is carried into the Earth at subduction zones. Geochemical analysis of subducted sediments now exhumed in Alpine Corsica, France, reveal the formation of graphite during shallow subduction, implying that carbonate transformation to graphite aids transport into the deeper Earth.

    • Matthieu E. Galvez
    • , Olivier Beyssac
    •  & Jacques Malavieille

  • News & Views |

    Sinking slabs of oceanic lithosphere often stagnate in Earth's mantle. Experiments show that common slab minerals transform to their high-pressure, high-density counterparts at very slow rates, thus keeping the slabs buoyant and impeding subduction.

    • Craig R. Bina

  • Letter |

    Lavas erupted from individual volcanic centres often have one of two distinct compositions. High pressure and temperature experiments on lava samples collected from St Vincent Volcano in the Caribbean, combined with thermal modelling, show that this compositional bimodality is generated by volcanic systems with low heat and water content.

    • Elena Melekhova
    • , Catherine Annen
    •  & Jon Blundy

  • News & Views |

    Gold is often deposited in Earth's crust by fluids that percolate through rock fractures. Earthquakes cause rock fractures to expand rapidly and could cause the fluids to evaporate, triggering almost instantaneous gold deposition.

    • Dave Craw

  • News & Views |

    The presence of water in lunar volcanic rocks has been attributed to delivery after the Moon formed. Water detected in rocks from the ancient lunar highlands suggests that the Moon already contained water early in its history, and poses more challenges for the giant impact theory of Moon formation.

    • Erik H. Hauri

  • Letter |

    Ridges of thick, raised crust on the Indian Ocean floor were thought to be mostly volcanic seamounts formed above the Réunion mantle plume. Dating of zircon minerals in Mauritian lavas, however, indicates that fragments of an ancient microcontinent may be preserved beneath the seamounts, contributing to the thickened crust.

    • Trond H. Torsvik
    • , Hans Amundsen
    •  & Bjørn Jamtveit

  • Review Article |

    Magma erupted at subduction-zone volcanoes contains mantle rocks and a mixture of fluids and sediments derived from the subducted slab. A synthesis of work over past years provides an integrated physico-chemical framework for subduction zones with mixing at the slab–mantle interface and transport towards the surface volcanoes by buoyant diapirs.

    • Horst R. Marschall
    •  & John C. Schumacher

  • Letter |

    The mantles of the terrestrial planets contain elemental abundances that suggest accretion continued at a late stage, after core formation. Geochemical data of meteorites from differentiated asteroids are consistent with such a late accretion event, suggesting that the phenomenon occurred throughout the Solar System and was related to planet formation.

    • James M. D. Day
    • , Richard J. Walker
    •  & Douglas Rumble III

  • Letter |

    The mantle and continental crust contain excessive amounts of radiogenic lead, implying that a complementary reservoir of unradiogenic lead should exist somewhere on Earth. Isotopic analyses of mantle rocks exposed on the Atlantic Ocean floor reveal that sulphide inclusions can have extremely unradiogenic lead compositions, suggesting that the reservoir could exist within the mantle itself.

    • Kevin W. Burton
    • , Bénédicte Cenki-Tok
    •  & Ian J. Parkinson

  • Letter |

    Volcanic eruptions can inject hazardous ash clouds into the atmosphere. Numerical simulations and experiments on volcanic rock samples show that clasts initially formed deep in the volcanic conduit break-up during collisions in the conduit, thus generating fine-grained clouds of ash.

    • Josef Dufek
    • , Michael Manga
    •  & Ameeta Patel

  • Letter |

    Subduction modifies the cycling of Earth’s volatile elements. Geochemical analyses of fragments of mantle rocks collected above the Batan Island subduction zone, Philippines, suggest that wet sediment melts are released from the subducted slab, followed later by release of aqueous fluids, yet a significant amount of water is retained in the wedge.

    • Simon Turner
    • , John Caulfield
    •  & Gaelle Prouteau

  • News & Views |

    A series of extreme cooling episodes, starting 750 million years ago, could have repeatedly turned the planet into an ice-covered snowball. Carbon cycle modelling suggests that the timing of the glaciations can be explained by chemical weathering rates.

    • A. Joshua West

  • Letter |

    Carbonaceous minerals in 3.8-billion-year-old rocks from West Greenland have been used as evidence for early life on Earth. Geochemical analyses of similar carbon minerals in 3.75- to 4.2-billion-year-old rocks from Canada show that they can be derived from subsequent alteration more than a billion years after the initial formation.

    • D. Papineau
    • , B. T. De Gregorio
    •  & M. L. Fogel

  • Article |

    Individual rock units are predicted by tectonic models to undergo numerous, complex cycles of subduction. Analysis of high-pressure rocks exposed in the Sesia zone, Italian Western Alps, suggest that slices of the crust underwent two distinct episodes of subduction to mantle depths in fewer than 20 million years.

    • Daniela Rubatto
    • , Daniele Regis
    •  & Sarlae R. B. McAlpine

  • Letter |

    The Adula nappe, Central Alps, was thought to be a mélange of rock fragments, some of which were subducted and then exhumed from the mantle. Lu–Hf dating of two populations of garnets in one rock sample instead indicates that the nappe twice experienced subduction and exhumation as one coherent unit.

    • Daniel Herwartz
    • , Thorsten J. Nagel
    •  & Nikolaus Froitzheim

  • Letter |

    Magma transports metals to the Earth’s surface to form ore deposits, but only sulphide-undersaturated magmas were thought to be capable of generating large amounts of ore. Laboratory experiments indicate that large volumes of gold ore can also be generated by sulphide-saturated magma, if the redox conditions of the magma are suitable.

    • Roman E. Botcharnikov
    • , Robert L. Linnen
    •  & Jasper Berndt

  • News & Views |

    Andesite magmas were once thought to be simple melts derived from a subducting oceanic slab or the mantle. Analysis of lavas at Mount Hood shows that instead andesites are a complex mixture of magmas formed in the continental crust just before eruption.

    • John Eichelberger

  • Letter |

    At subduction zones, andesite lavas erupt in greater abundance than the individual magmas that mix to produce them. Textural and geochemical analyses of andesites from Mount Hood, Oregon, reveal that injection and mixing of iron- and magnesium-rich magma in the magma chamber can initiate the volcanic eruption.

    • Adam J. R. Kent
    • , Cristina Darr
    •  & Kari M. Cooper

  • News & Views |

    The amount of pore space in most unweathered granite is too small to support a plant-based ecosystem. But porosity grows as intact rock interacts with surface waters beneath the soil.

    • Susan L. Brantley

  • News & Views |

    The earliest evolution of our planet is difficult to reconstruct. Ancient rocks in Western Australia show an isotopic signature that links their formation with 4.3-billion-year-old crust.

    • Stephen J. Mojzsis

  • Letter |

    There is evidence for the existence of differentiated crust early in Earth’s history, but little is known about the timing and nature of the crust and its formation. New samarium–neodymium data from the Dresser Formation in Western Australia point to differentiation of the early crust from the mantle more than 4.3 billion years ago.

    • Svetlana G. Tessalina
    • , Bernard Bourdon
    •  & Pascal Philippot

  • News & Views |

    Where the Pacific and Australian tectonic plates collide under the South Island of New Zealand large quantities of aqueous fluid are produced. But how does this happen? Geophysical and petrological data indicate that it may not be as we thought.

    • Philip E. Wannamaker

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