Provenance of volcaniclastic beach sand in a magmatic arc-setting: an example from Lipari Island (Aeolian archipelago

Lipari, an active volcanic island in the Aeolian magmatic arc, is an excellent area todetermine the effects of multiple source lithology, climate, weathering, transport and depositionalenvironment on epiclastic sand composition. Volcaniclastic sand samples from 12 modern beacheswere petrographically characterized using the Gazzi–Dickinson method, and the proportions of sourcerocks in combination with topography in associated coastal drainage basins were quantified usingGIS. Several types of bedrock in the 12 drainage basins that are the likely prominent sources for sandat each sampled beach were recognized, and divided into two categories of provenance lithotypes:lavas and pyroclastic rocks ranging in composition from basaltic andesitic, to andesitic, to rhyolitic.Volcanic lithic fragments from Lipari beach sand consist of colourless and black glassy volcanicfragments with lathwork, felsitic, vitric and microlitic textures. Moreover, high amounts of detritalless durable minerals, such as pyroxene, olivine and Fe oxides, illustrate how the analysed sandspreserve the source rock(s) provenance signals. Applying the concept of Sand Generation Index wesee that these lithotypes have different propensities to create detritus, in terms of both grain-size andcomposition. Clastic contribution from pyroclastic rock outcrops such as pumice is not found in thesize ranges studied, suggesting that these pumiceous source rocks probably only produce gravel orvery fine sand and silt. This finding has implications for the stratigraphic record because pumice clasts,ranging from medium to fine grain-size, could be underrepresented in older volcaniclastic depositsand overrepresented in other size fractions.