White, J.C., Neave, D.A., Rotolo, S.G., Parker, D.F., 2020, Geochemical constraints on mantle sources and basalt petrogenesis in the Strait of Sicily Rift Zone (Italy): Insights into the importance of short lengthscale mantle heterogeneity. Chemical Geology, v. 545, 119650, 18 p. (doi: 10.1016/j.chemgeo.2020.119650)
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Igneous activity from the late Miocene to historic time (most recently 1891 ce) in the Strait of Sicily has created two islands (Pantelleria and Linosa) and several seamounts. These volcanoes are dominated by transitional (ol+hy-normative) to alkaline (ne-normative) basaltic lavas and scoriae; peralkaline felsic rocks (trachyte-rhyolite) crop out only on Pantelleria. Although most likely erupted through continental crust, basalts demonstrate no evidence of crustal contamination and are geochemically similar to oceanic island basalts (OIB). Despite their isotopic similarities, there are considerable compositional differences with respect to major and trace element geochemistry both between and within the two islands that are due to short-length scale mantle heterogeneity beneath the region as well as variability in partial melting and magma storage conditions. Published geophysical surveys suggest that lithospheric thickness beneath both islands is ~60 km; this is consistent with the results of our geochemical modelling (59-60 km), which also suggest mantle potential temperatures between 1415-1435°C, similar to other documented continental passive rifts. Although there is some compositional overlap between the three synthems at Linosa, in general the older magmas (Arena Bianca, 700 ka) formed as a result of ~5% partial melting of a depleted MORB mantle (DMM) source enriched with a relatively small amount of recycled MORB material, which differentiated in a shallow-level (~8 km) magma chamber prior to eruption whereas the younger magmas (Monte Bandiera, 530 ka) formed as a result of ~2% partial melting of a similar mantle source, which differentiated in a magma chamber at or below the base of the crust (~25 km). Pantelleria magmas formed from a higher degree (~6%) of partial melting of a DMM source enirched with a relatively greater amount of recycled MORB material with possibly other components. Data for the seamounts are scarce and compromised by significant seawater alteration; thus, these volcanic centers cannot be modelled but based on comparative geochemistry with the islands are likely the result of even smaller (<2%) degrees of partial melting beneath thicker (>60 km) lithosphere. Magmas stored in the higher-level chamber were more effectively homogenized and preserve a narrower compositional range. Despite the geophysical similarities between the two islands in terms of lithospheric thickness and crustal thinning, melt productivity has been greater at Pantelleria, producing a much larger island and sustaining felsic magmatism, which may ultimately be entirely due to the local occurrence of much more fusible mantle.