Coexisting clinopyroxene,garnet and amphibole from an “eclogite”, Kakanui,New Zealand |
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| Authors: | A J R White B W Chappell P Jake? |
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| Institution: | (1) Department of Geology, Australian National University, Canberra, Australia;(2) Czech. Acad. Science, Geological Institute, Praha 6, Czechoslovakia;(3) Present address: Department of Geology, La Trobe University, Victoria, Australia |
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| Abstract: | Analyses of major and rare earth elements are presented for co-existing garnet, clinopyroxene, and amphibole from a Kakanui  eclogite .New and previously published analyses of garnets suggest a gradual increase of Fe and decrease of Mg from xenocrysts through garnet pyroxene eclogitic rocks to amphibole-rich eclogitic rocks. Clinopyroxenes show a parallel increase in Fe/Mg ratio and an increase in Jadeite component and decrease in Tschermak's component. These data indicate crystallization of garnet and clinopyroxene from an alkali-rich undersaturated magma and are consistent with the concept of eclogite fractionation, but rare earth data allow severe constraints to be placed on this process. The eclogites are considered to be deep-seated crystallization products of nephelinite, but eclogite fractionation is small and cannot account for the association of alkali basalt, basanite and nephelinite. |
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