Petrology of some amphibole-bearing volcanics of the pre-Ellittico period (102-80 ka), Mt. Etna

We present here petrological and geochemical data on volcanics cropping out in southern and northeastern walls of the Valle del Bove (Mt. Etna), belonging to the Rocche, Serra Giannicola Grande and Canalone della Montagnola Units. These units constitute the remnants of several volcanoes that were active in the time span 102-80 ka, i.e. before the growth of the Ellittico-Mongibello strato-volcano. Their products, range in composition from hawaiites to benmoreites. Amphibole (kaersutite) is present as phenocryst in all the studied rocks, and commonly shows breakdown coronas of rhonite ± clinopyroxene and plagioclase formed during magma ascent. Nevertheless, in mafic rocks, amphibole occurs as an early liquidus phase enclosed in a Ca-rich plagioclase (up to An 87 ). We propose that early cotectic crystallization of amphibole and Ca- plagioclase may reflect H 2 O-rich melts. Variations in major and trace elements among lavas erupted from coeval centres, suggest that fractional crystallization was the principal evolutionary process but at the same time magmas feeding the various volcanoes belonging to the Rocche Unit were more heterogeneous with respect to the younger Units studied here.

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