The history of the Campi Flegrei Magma System through time: the key to understand present and future volcanic processes
Mineralogy, Petrology and Geochemistry
Final Report Abstract
Based on this comprehensive sample set that covers the entire eruption history of campi Flegrei we were able to achieve the following goals: Source and evolution of Arso lavas (Ischia): Geochemical and Sr- and O-isotopic on whole rock and separated mineral samples from volcanic products of the 1302 AD Arso eruption, Ischia highlight petrographic and isotopic disequilibria between phenocrysts and their host magma and suggest mixing between chemically and isotopically distinct batches of magma that are derived from different magma sources. Model calculations indicate that <7% of granodioritic basement rocks were assimilated into mantle-derived mafic magma. A small part of this research is based on a prior master's study of the PhD student Iovine. The origin of "enriched" magma sources at Campi Flegrei: The origin of large variations in isotope compositions of magmas erupted from the Neapolitan volcanoes and isotopic disequilibrium between minerals and their host magmas has always been contentious. Our 87Sr/86Sr, 18O/16O and 17O/16O data on separated minerals (feldspar, clinopyroxene and olivine phenocrysts) from volcanics of the Neapolitan volcanic area (Phlegrean Fields and Somma-Vesuvius) robustly indicate that magmas were generated from a mantle source that was contaminated by up to 10% of a 1:1 mixture of pelagic and carbonate sediments. Due to severe analytical problems early during O-isotope analyses we lost substantial time and - in some cases - limited sample material and therefore this new and relatively large data set is in fact smaller than it would have been otherwise. This first study of combined triple-O-isotopes and Sr-isotopes on separated minerals throughout the volcano's history provides robust evidence for an enriched mantle source and the mass balance of its components. Magma residence times from diffusion speedometry: The zoning patterns of Ba in sanidine crystals allow to reconstruct the origin and residence times of crystals from diffusion modelling. We analyzed zoned sanidines from pumices from the medium-sized Agnano Monte Spina eruption by combined electron microprobe. Distinct compositional breaks near the crystal rims represent the last mixing event prior to eruption. Estimates for diffusion times (at a T=930°C) are mostly < 60 years with only few crystals up to 160 years. Volcanological and geochronological data on the activity in the Agnano-San Vito area predating the Agnano-Monte Spina eruption suggests that such timescales are similar to the time intervals between eruptions. These diffusion times likely represent the time between magma mixing and eruption of magma that was residing in a shallow reservoir after periods of longer residence as testified by the complex core-rim interior zoning of sanidine phenocrysts and our previously obtained U-Th isotope dating on phenocryst minerals. Using the same approach, we found considerably longer reactivations times (<=500 years; up to 3.000 years ) for the large-volume Campanian Ignimbrite eruption. These results highlight the difference between large and small magma reservoirs with respect to residence and reactivations times and are essential to evaluate risks from, and warning times before, future eruptions in the area.
Publications
- (2015) The history of the Campi Flegrei (Napoli, Italy) magma system through time: the key to understand present and future volcanic processes. Rendicinti online Societa Geological Italiana 35 (2), Congressso Il Pianeta Dinamico: sviluppie e prospettive a 100 anni da Wegener, 2015. July 2015, EIMP- AIV-SoGeI-SGI (2015)
Iovine RS, Wörner G, Pabst S, Arienzo I, Civetta L, D’Antonio M, Orsi G
- (2015) Timescales of mixing from diffusion chronometry on alkali feldspar phenocrysts from the Agnano-Minte Spina eruption (4.7 ka), Campi Flegrei (southern Italy). Rendicinti online Societa Geological Italiana 35 (2), Congressso Il Pianeta Dinamico: sviluppie e prospettive a 100 anni da Wegener, 2015. July 2015, EIMP-AIV-SoGeI-SGI (2015)
Mazzeo FC, Lorenzo F, Iovine RS, Arienzo I, Cavallo A, D’Antonio M
- (2016) Residence times of alkali feldspar phenocrysts from magma feeding the Agnano-Monte Spina Eruption (4.7 ka), Campi Flegrei caldera (Napoli, southern Italy) based on Ba-zonation modelling. EGU conference Wien (2016)
Iovine RS, Wörner G, Carmine Mazzeo F, Arienzo I, Fedele L, Civetta L, D'Antonio M, Orsi G
- (2016) Sr-O-isotope systematics on the Campi Flegrei magma system. EGU conference Wien (2016)
Iovine RS, Wörner G, Carmine Mazzeo F, Arienzo I, Civetta L, D'Antonio M, Orsi G
- (2017) Magma residence times from diffusion chronometry on zoned alkali feldspar phenocrysts from the Campi Flegrei caldera (Napoli, southern Italy): the case of Agnano-Monte Spina (4.7 ka) and Campanian Ignimbrite eruptions (39 ka). DGGV-DMG conference Bremen 2017
Iovine RS, Wörner G, Carmine Mazzeo F, Arienzo I, Fedele L, D'Antonio M
- (2017) Source and magmatic evolution inferred from geochemical and Sr-O-isotope data on hybrid lavas of Arso, the last eruption at Ischia island (Italy; 1302 AD). J Volcanol Geoth Res 331: 1-15
Iovine RS, Mazzeo FC, Arienzo I, D’Antonio M, Wörner G, Civeta L, Pastore Z, Orsi G
(See online at https://doi.org/10.1016/j.jvolgeores.2016.08.008) - (2017) Timescales of magmatic processes prior to the Agnano-Monte Spina eruption (Campi Flegrei, caldera, Southern Italy) based on diffusion chronometry on sanidine phenocrysts. Bull Volcanol (2017) 79: 18
Iovine RS, Mazzeo FC, Fedele L, Arienzo I, Cavallo A, Wörner G, Orsi G, Civetta L, D’Antonio M
(See online at https://doi.org/10.1007/s00445-017-1101-4) - (2018) Coupled δ18O-δ17O and 87Sr/86Sr isotope compositions suggest a radiogenic and 18O-enriched magma source for Neapolitan volcanoes (Southern Italy). Lithos 316-317: 199-211
Iovine RS, Mazzeo FC, Wörner G, Pelullo C, Cirillo G, Arienzo I, Pack A, D’Antonio M
(See online at https://doi.org/10.1016/j.lithos.2018.07.009)
