A detailed geochemical and rock magnetic study of dredged basalt from the Sheba Ridge,Gulf of Aden |
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| Authors: | W O'Reilly K Brown P Styles T W Bloxam |
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| Institution: | (1) School of Physics, The University, NE1 7RU Newcastle upon Tyne, UK;(2) Department of Earth Sciences, University of Liverpool, L69 3BX Liverpool, UK;(3) Department of Earth Sciences, University College, SA2 8PP Swansea, UK |
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| Abstract: | We report the results of petrological, geochemical and rock magnetic studies of basalt dredged from the eastern end of the west Sheba Ridge during cruise 11/1979 of R. R. S. Shackleton to the Western Gulf of Aden. The ridge is part of the Red Sea-Gulf of Aden spreading axis and the basalts are olivine tholeiites. The abundances of some elements are characteristic of normal MORB (mid-ocean ridge basalt) but other elemental abundances suggest affinites with transitional-type MORB.The observed magnetic properties are interpreted in terms of the composition, concentration and microstructure of the magnetic mineral fraction by recourse to the available data on synthetic analogues. The analysis has been carried out in greater detail than has been attempted in previous  magneto-petrological studies. It appears that submarine weathering of the magnetic minerals (maghemitization) brings about not only the expected change in composition but also a fall in concentration of the magnetic fraction. This could result from the removal-of-iron oxidation mechanism operating in the submarine environment. It is also found that the fall in remanence with increasing degree of maghemitization is not explicable in terms of the change in composition and concentration of the magnetic minerals. A further influence—probably microstructural change—significantly reduces the remanence intensity. |
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