Geochemical constraints on basalt petrogenesis in the Strait of Sicily Rift Zone (Italy): Insights into the importance of short lengthscale mantle heterogeneity

Silvio Giuseppe Rotolo, David A. Neave, Silvio G. Rotolo, Don F. Parker, John Charles White

Risultato della ricerca: Article

Abstract

Igneous activity from the late Miocene to historic time (most recently 1891 CE) in the Strait of Sicily has createdtwo volcanic islands (Pantelleria and Linosa) and several seamounts. These volcanoes are dominated by transitional(ol + hy-normative) to alkaline (ne-normative) basaltic lavas and scoriae; volcanic felsic rocks (peralkalinetrachyte-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 majorand trace element geochemistry both between and within the two islands that are due to short-length scalemantle 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 consistentwith the results of our geochemical modelling (59–60 km), which also suggest mantle potential temperaturesbetween 1415 and 1435 °C, similar to those documented in other continental passive rifts. Traceelement and isotopic data reveal that the asthenosphere beneath the Strait of Sicily is heterogenous at both interisland(100s of km) and intra-island (10s of km) scales. Although there is some compositional overlap betweenthe two major 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 ofrecycled MORB material, whereas the younger magmas (Monte Bandiera, 530 ka) formed as a result of ~2%partial melting of a similar mantle source. Pantelleria magmas formed from a higher degree (~6%) of partialmelting of a DMM source with a relatively greater amount of recycled MORB material and possibly othercomponents. Geochemical modelling also suggests the older magmas on Linosa differentiated at a much shallowerlevel (~8 km) than the younger magmas (~25 km, at or below the base of the crust) prior to eruption.Magmas stored in higher-level reservoirs were effectively homogenized and preserve a narrower compositionalrange than magmas sourced from depth. Data for the seamounts are scarce and compromised by significantseawater alteration; thus, these volcanic centers cannot be modelled but based on comparative geochemistrywith the islands are likely the result of even smaller (< 2%) degrees of partial melting beneath thicker(> 60 km) lithosphere. Despite the geophysical similarities between the two islands in terms of lithosphericthickness and crustal thinning, melt productivity has been greater at Pantelleria, producing a much larger islandand sustaining felsic magmatism, which we hypothesize may ultimately be entirely due to the local occurrence ofmuch more fusible mantle.
Lingua originaleEnglish
pagine (da-a)119650-
Numero di pagine18
RivistaChemical Geology
Volume545
Stato di pubblicazionePublished - 2020

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology

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