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Halogen-dominant mineralization at Mt. Calvario dome (Mt. Etna) as a response of volatile flushing into the magma plumbing system |
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| Authors: | Simona Mazziotti Tagliani Eugenio Nicotra Marco Viccaro Antonio Gianfagna |
| Institution: | 1. Dipartimento di Scienze della Terra, Sapienza Università di Roma, P.le A. Moro 5, 00185, Roma, Italy 2. Dipartimento di Scienze Biologiche, Geologiche ed Ambientali – Sezione di Scienze della Terra, Università di Catania, Corso Italia 57, 95129, Catania, Italy 3. Dipartimento di Scienze della Terra, Università della Calabria, Via P. Bucci 15/a, Arcavacata di Rende, 87036, Cosenza, Italy |
| Abstract: | The exceptional occurrence of fluorine-rich mineral phases in the benmoreitic lava dome of Mt. Calvario (south-western flank of Mt. Etna) has given the opportunity to understand the genetic process allowing their crystallization. Both primary and secondary mineral associations were found, namely: plagioclase, clinopyroxene, olivine, fluorapatite and iron oxides as primary assemblage, whereas fluoro-edenite and fluorophlogopite, ferroan-enstatite, hematite, pseudobrookite and tridymite as secondary mineralization. In addition to some major and trace elements (e.g., Fe, Ti, Na, K, P, Ba, Rb, Sm, Zr), particularly fluorine and chlorine concentrations of the whole rock are significantly higher than other Etnean prehistoric benmoreites, and cannot be accounted for common differentiation processes in the feeding system. The selective enrichment in some elements has been here attributed to volatile flushing occurring in the plumbing system, with fluid/melt ratio of ~0.65:1. The resulting high amount of fluorine, coupled with its high solubility even at low pressure for benmoreitic melts, finally led to nucleation and growth of F-rich mineral phases during syn- and post-eruptive conditions. |
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