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MORB

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Encyclopedia of Astrobiology

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Synonyms

Mid-ocean ridge basalt

Definition

MORB (acronym of mid-ocean ridge basalt) is the rock (basaltic in composition) formed by eruption of magma at the oceanic spreading centers to form the oceanic crust. It is commonly porphyritic with plagioclase or more rarely olivine phenocrysts. Eruption under water produces pillow lava interspersed with rare sheet flows. The basalt is relatively magnesian (5–11% MgO) and characterized by high Al2O3 content (12–18%) and low concentrations of K2O. In N-MORB (normal MORB), the incompatible elements are depleted relative to more compatible elements reflecting derivation from depleted (previously melted) upper mantle. MORB forms as the upper mantle passively upwells and partially melts beneath spreading ocean plates.

See also

Asthenosphere

Basalt

Magma

Mid-Ocean Ridges

Oceanic Crust

Pillow Lava

Plate Tectonics

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Author information

Authors and Affiliations

  1. Maison des Géosciences, LGCA, Université J. Fourier, 1381, rue de la Piscine, St-Martin d’Hères, 38400, France

    Prof. Nicholas Arndt

Authors
  1. Prof. Nicholas Arndt
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Correspondence to Nicholas Arndt .

Editor information

Editors and Affiliations

  1. Astrophysicist, Laboratoire d’Astrophysique de Bordeaux, BP 89, 33270, Floirac, France

    Muriel Gargaud

  2. Departamento de Planetología y Habitabilidad Centro de Astrobiología (CSIC-INTA), Universidad Autónoma de Madrid Campus Cantoblanco, Torrejón de Ardoz, 28049, Madrid, Spain

    Ricardo Amils

  3. Department of Astrophysics, Centro de Astrobiología (INTA-CSIC) Ctra de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain

    José Cernicharo Quintanilla

  4. Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC, 20015, USA

    Henderson James (Jim) Cleaves II

  5. Department of Astronomy, University of Massachusetts Lederle Graduate Research, 710 North Pleasant Street, Amherst, MA, 01003-9305, USA

    William M. Irvine

  6. GEOTOP & Départment des Sciences de la Terre et de l’Atmosphère, Université du Québec à Montréal, CP 8888, succ. Centre-Ville, Montréal, QC, H3C 3P8, Canada

    Daniele L. Pinti

  7. Astrobiology, CNES/DSP/EU, 2 place Maurice-Quentin, 75039, Paris, France

    Michel Viso

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© 2011 Springer-Verlag Berlin Heidelberg

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Arndt, N. (2011). MORB. In: Gargaud, M., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-11274-4_1027

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