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Petrology and mineralogy of dredged gabbro from Gettysburg Bank, eastern Atlantic

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Abstract

Gabbros have been dredged from Gettysburg Bank, 110 km west of Portugal on the Azores/Gibraltar fracture zone. Primary minerals in olivine, pyroxene and brown hornblende gabbros are partially replaced by metamorphic minerals. Igneous textures are inhomogeneously overprinted by a granular polyhedral deformation and a cataclastic deformation. Amphiboles show characteristics which indicate a transition from crystallisation in a magma chamber to formation of amphibole in solid gabbro under metasomatic conditions. Of the amphiboles analysed, chlorine was present in the green amphiboles but below 0.05% in the brown suggesting the penetration of sea water after the formation of the brown amphibole but during the formation of the green.

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Authors and Affiliations

  1. Department of Earth Sciences, The Open University, Walton Hall, MK76AA, Milton Keynes, England

    H. M. Prichard

  2. Department of Geology, University of Newcastle-upon-Tyne, Daysh Building, NE1 7RU, Newcastle-upon-Tyne, England

    J. R. Cann

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  1. H. M. Prichard
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  2. J. R. Cann
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Prichard, H.M., Cann, J.R. Petrology and mineralogy of dredged gabbro from Gettysburg Bank, eastern Atlantic. Contr. Mineral. and Petrol. 79, 46–55 (1982). https://doi.org/10.1007/BF00376960

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  • DOI: https://doi.org/10.1007/BF00376960

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