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 D’Antonio M.1*,2 , Tonarini S.3, Arienzo I.2, Civetta L.1,2, Dallai L.3, Moretti R.4,2, Orsi G.2, Andria M.1, Trecalli A.1

 

Mantle and crustal processes in the magmatism of the Campania region: inferences from mineralogy, geochemistry, and Sr-Nd-O isotopes of young hybrid volcanics of the Ischia island (South Italy)

 

1 Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II, Largo San Marcellino 10, 80138 Napoli, Italy
2 Istituto Nazionale di Geofisica e Vulcanologia, sezione di Napoli Osservatorio Vesuviano, Via Diocleziano 328, 80124 Napoli, Italy
3 Consiglio Nazionale delle Ricerche, Istituto di Geoscienze e Georisorse, Via Moruzzi 1, 56124 Pisa, Italy
4 Dipartimento di Ingegneria Civile, Seconda Università degli Studi di Napoli, Via Roma 29, 81031 Aversa (CE), Italy
* Corresponding author:
Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II, Largo San Marcellino 10, 80138 Napoli, Italy
Phone: +39 081 2538323
Fax: +39 081 2538338
E-mail address: masdanto@unina.it
 
IN CORSO DI STAMPA SU:

CONTRIBUTIONS TO MINERALOGY AND PETROLOGY

DOI: 10.1007/s00410-013-0853-x

  

Abstract
Fig DAntonioIschia, one active volcano of the Phlegraean Volcanic District, prone to very high risk, is dominated by a caldera formed 55 ka BP, followed by resurgence of the collapsed area. Over the past 3 ka, the activity extruded evolved potassic magmas; only a few low-energy explosive events were fed by less evolved magmas. A geochemical and Sr-Nd-O isotope investigation has been performed on minerals and glass from products of three of such eruptions, Molara, Vateliero and Cava Nocelle (<2.6 ka BP).Data document strong mineralogical, geochemical and isotopic heterogeneities likely resulting from mingling/mixing processes among mafic and felsic magmas that already fed the Ischia volcanism in the past. Detailed study on the most mafic magma has permitted to investigate its origin. The mantle sector below Ischia underwent subduction processes that modified its pristine chemical, isotopic and redox conditions by addition of ≤1 % of sediment fluids/melts. Similar processes occurred from South-East to North-West along the Apennine compressive margin, with addition of up to 2.5% of sediment-derived material. This is shown by volcanics with poorly variable, typical δ18O mantle values, and 87Sr/86Sr progressively increasing toward typical continental crust values. Multiple partial melting of this modified mantle generated distinct primary magmas that occasionally assimilated continental crust, acquiring more 18O than 87Sr. At Ischia, 7% of Hercynian granodiorite assimilation produced isotopically distinct, K-basaltic to latitic magmas. A SW-NE regional tectonic structure gave these magmas coming from large depth the opportunity to mingle/mix with felsic magmas stagnating in shallower reservoirs, eventually triggering explosive eruptions.
 

 

Keywords: Ischia; Mineral chemistry; Isotope geochemistry; Mingling/mixing; Mantle enrichment/crustal contamination; Oxidizing fluids