Original paper

Magma mixing and magma mingling episodes throughout the volcanic history of Nisyros volcano, SE extremity of the Aegean Volcanic Arc, as registered by the plagioclase record

Zouzias, Dimitrios; St. Seymour, Karen


Mineral chemistry, microtextures and plagioclase phenocrysts zonation by Nomarski interferometry reveal that magma mixing and mingling has been operative throughout the volcanic history of Nisyros volcano. Magma mixing in the lower andesite lavas is not mesoscopically conspicuous and is the result of ?basalt-andesite?, ?basaltic andesite ? evolved andesite? end-members mixing. This type of mixing can only be observed on microscopic scale as ?exotic? mineralogy such as olivines with Fo# which are out of equilibrium with co-existing glass and by the mineral chemistry and microtextures of inherited plagioclase phenocrysts. Towards the upper parts of the volcanic stratigraphy pre- and post-caldera dacites offer evidence of magma mingling between hot basaltic and cold viscous felsic magmas which is discernible to a variable degree on outcrop scale by the presence of rounded mafic inclusions. Dacite hybrids display spectacular evidence of exotic mineralogy and heterogeneous plagioclase populations inherited from a mafic and a felsic end-member parent. Andesitic hybrids are rather homogeneous, however, dacite/rhyodacite hybrids are to a large degree inhomogeneous as a result of magma mingling.


chemical and mechanical mixingmicrotexturenisyros plagioclase mineral chemistrynomarski interferometry