Preliminary Investigations of the Most Recent Lava Flows

from Mount Etna, Southern Italy

Natalie J. MacLean

Department of Geology

University of Regina

Abstract

Mount Etna is located in southern Italy, on the island of Sicily, and most recently erupted July 17 - August 10, 2001 and October 26, 2002 - January 28, 2003. These eruptions occurred on the volcano’s southern flank and the most recent eruption also had flows from the northeast rift. The petrographic character of Etnean basalts has changed slightly throughout its eruptive history. The tholeiitic to alkaline magmas of the volcano crystallize as basalts of hawaiite-andesite composition with phenocrysts of olivine, plagioclase, clinopyroxene and minor titano-magnetite.

The flow tops are blocky, and the blocks average approximately 40 cm in length. Limestone xenoliths from the basement are not plentiful, but when present, baked margins were not evident. Hand specimen and thin section samples show phenocrysts of plagioclase, clinopyroxene and olivine that range in diameter from 0.2 to 2.0 cm. Thin sections from flow samples show mineral alignment due to flow; whereas, samples from blocks do not. Carlsbad twinning and zoning is common in plagioclase, and clinopyroxene grains. Initial geochemical analyses indicate that samples from the recent eruptions of Mount Etna are alkaline, potassium-rich, and are of trachy-basalt composition. Chondrite normalizing values show that the basalts are LREE enriched in comparison to HREE. The same values indicate that samples from the northeast rift of the volcano are slightly more evolved than those from the south flank; as well, the south flows seem to have evolved slightly since the 2001 eruption. The geochemical signature of these lavas indicates that Mount Etna is the result of within plate tectonics. Mount Etna, however, is located in a tectonically complex area and there are numerous theories regarding its tectonic setting. The geochemical data, as well as helium isotope and electron microprobe analyses of plagioclase, clinopyroxene and olivine grains will be used to compare the chemistry of these most recent lava flows to past eruptions of Mount Etna, to infer the evolution of the magma chamber and to hopefully gain a better understanding of the tectonic setting.