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

By Hazel Margaret Prichard and J. R. Cann

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

Topics: QE Geology
Year: 1982
DOI identifier: 10.1007/BF00376960
OAI identifier: oai:http://orca.cf.ac.uk:11994
Provided by: ORCA
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