Amsterdam Island,an isolated volcano in the southern Indian ocean |
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| Authors: | B M Gunn C E Abranson J Nougier N D Watkins A Hajash |
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| Institution: | (1) Department of Geology, Université de Montréal, Montreal, Quebec, Canada;(2) Laboratoire de Géologie 1, Faculté des Sciences, Université de Paris, France;(3) Graduate School of Oceanography, University of Rhode Island, Kingston, R. I., USA;(4) Department of Geophysics, Stanford University, Stanford, California, USA |
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| Abstract: | Twelve lavas have been sampled on Amsterdam Island, which is an extinct shield volcano located on a transform fault crossing the south-eastern branch of the Indian Ocean rise. Chemical analyses show that the lavas have mainly tholeiitic affinities, ranging from olivine tholeiites to plagioclase basalts with accumulation of bytownite. The high alumina lavas are similar to bytownite cumulates dredged from the Indian Ocean rise, and the low alumina lavas resemble tholeiites of Hawaii. The volcano appears to be in an early stage of evolution from oceanic ridge basalt to an alkaline volcano. |
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