Mantle Amphiboles and Mantle Plumes

Abstract

Metasomatic minerals such as clinopyroxene, amphibole, phlogopite or apatite found in many mantle xenoliths provide evidence for fluid migration through mantle rocks and reaction with mantle minerals. The chemical composition of these minerals give us insight into the nature and composition of the percolating fluids, the processes of fluid-melt interactions as well as the fractionation of incompatible elements in mantle minerals. This is particularly true above mantle plumes where fluids are thought to be released during ascent of hot material and interact with the lithospheric mantle. The chemical study of mantle xenoliths in such a context should give us valuable information about plume lithosphere interactions with implications for magma generation within mantle plumes. We report on the chemical composition of mantle minerals from two different localities: alnphibolebearing mantle xenoliths are found in two recent volcanic fields in Yemen, in relation to the uprising of the Afar mantle plume. These xenoliths and the processes they recorded are compared with mantle peridotites sampled in Tertiary and Quaternary volcanoes of the French Massif Central where the presence of a mantle plume is still highly questioned. Laboratoire de G6ologie, Universit6 Blaise Pascal, UMR 6524, 5 rue Kessler, 63038 Clermont-Ferrand, France