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Le cœur alcalin du complexe du Messum, Namibie : Description pétrologique, interprétation de l'évolution minéralogique et relations roches sous- et sur-saturées en silice.

Abstract : The anorogenic annular Messum complex, associated with the basaltic province of Etendeka (Namibia), show the coexistence of silica under- and over-saturated rocks. A petrological detailed study is necessary to understand the mineralogical evolution of these two groups of rocks. In the first one, all the observations allowed us to propose a path of crystallization involving peritectic lines and explaining the late development of nepheline at the expense of the primary phases (olivine, plagioclase, aluminous clinopyroxene) and the intermediate meaning of pargasite. Not yet indicated significant minerals are described: spinels in the basic rocks, wohlérite and hiortdahlite in the most evolved syénites, as well as pyrochlores considered as potential indicators of the presence of cabonatitic material. Quartz-syenites appears as a composite set with several comings differently evolved. Paragenesis are more or less peralcalines, with fayalite, acmitic hedenbergite, and late development of riebeckite. The chevkinite, rare titano-silicate, is described in relatively plentiful quantity as a magmatic mineral. No mineralogical link exists between these two groups of rocks and its make difficult to pass from one to another by crustal contamination.
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https://tel.archives-ouvertes.fr/tel-00336485
Contributor : Simon Blancher <>
Submitted on : Tuesday, November 4, 2008 - 11:31:43 AM
Last modification on : Friday, December 11, 2020 - 11:58:03 AM
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  • HAL Id : tel-00336485, version 1

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Simon Blancher. Le cœur alcalin du complexe du Messum, Namibie : Description pétrologique, interprétation de l'évolution minéralogique et relations roches sous- et sur-saturées en silice.. Géologie appliquée. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨tel-00336485⟩

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