The trachybasaltic volcanics of the Adrano area, Mount Etna, Sicily

Abstract

Summary: The Adrano area covers approximately 150 km² of the tower SW flanks of Mount Etna, Sicily. A wide selection of the rocks that occur on the volcano are represented in the area. Lavas of alkalic affinity form by far the greater proportion of the volcanics in the area, and comprise a trachybasaltic suite of lavas ranging from hawaiite through mugearite to benmoreite. There appears to be no overall progressive variation in the chemistry of these trachybasaltic lavas with time; rather that the parental magma has remained fairly constant in composition. Periodically, however, this parental magma has been able to differentiate into more evolved products. The chemical variation shown by the trachybasaltic lavas can be largely explained by crystal fractionation of augite, olivine, plagioclase and titanomagnetite at moderate to low pressures. Crystal fractionation, however, cannot explain the variation in the alkalis which is thought to be affected by volatile transfer.