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Formation of cordierite-bearing lavas during anatexis in the lower crust beneath Lipari Island (Aeolian arc, Italy)

Martino C. Di·F. Forni·M.L. Frezzotti·R. Palmeri·J.D. Webster·R. A. Ayuso·F. Lucchi·C.A. Tranne
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Abstract

Cordierite-bearing lavas (CBL;~105 ka) erupted from the Mt. S. Angelo volcano at Lipari (Aeolian arc, Italy) are high-K andesites, displaying a range in the geochemical and isotopic compositions that reflect heterogeneity in the source and/or processes. CBL consist of megacrysts of Ca-plagioclase and clinopyroxene, euhedral crystals of cordierite and garnet, microphenocrysts of orthopyroxene and plagioclase, set in a heterogeneous rhyodacitic-rhyolitic groundmass containing abundant metamorphic and gabbroic xenoliths. New petrographic, chemical and isotopic data indicate formation of CBL by mixing of basaltic-andesitic magmas and high-K peraluminous rhyolitic magmas of anatectic origin and characterize partial melting processes in the lower continental crust of Lipari. Crustal anatectic melts generated through two main dehydration-melting peritectic reactions of metasedimentary rocks: (1) Biotite + Aluminosilicate + Quartz + Albite = Garnet + Cordierite + K-feldspar + Melt; (2) Biotite + Garnet + Quartz = Orthopyroxene + Cordierite + K-feldspar + Melt. Their position into the petrogenetic grid suggests that heating and consequent melting of metasedimentary rocks occurred at temperatures of 725 < T < 900°C and pressures of 0.4–0.45 GPa. Anatexis in the lower crust of Lipari was induced by protracted emplacement of basic magmas in the lower crust (~130 Ky). Crustal melting of the lower crust at 105 ka affected the volcano evolution, impeding frequent mafic-magma eruptions, and promoting magma stagnation and fractional crystallization processes.

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Martino C. Di, F. Forni, M.L. Frezzotti, R. Palmeri, J.D. Webster, R. A. Ayuso, F. Lucchi, C.A. Tranne. 2011-04-27. Formation of cordierite-bearing lavas during anatexis in the lower crust beneath Lipari Island (Aeolian arc, Italy). https://doi.org/10.1007/s00410-011-0637-0

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