Magma chamber evolution prior to the Campanian Ignimbrite and Neapolitan Yellow Tuff eruptions (Campi Flegrei, Italy)

Abstract

The Campi Flegrei (Campanian Region, Italy) experienced two cataclysmic caldera-forming eruptions which produced the Campanian Ignimbrite (39 ka, CI) and the Neapolitan Yellow Tuff (15 ka, NYT). We studied the minor eruptions before both these large events to understand magma chamber evolution leading towards such catastrophic eruptions. Major, trace element, and Sr and Nd isotope compositions of pre-Campanian Ignimbrite and preNeapolitan Yellow Tuff products define distinct geochemical groups, which are here interpreted as distinct magma batches. These batches do not show any transitional trend towards the CI and NYT eruptions. The CI and NYT systems are decoupled geochemically and isotopically. At least one of the pre-CI and one of the pre-NYT erupted magma batches qualifies as mixing endmembers for the large CI and NYT eruptions, and thus, must have been stored in reservoirs for some time to remain available for the CI and NYT eruptions. The least evolved, isotopically distinct magma compositions that are typical of the last phases of the NYT and CI eruptions did not occur before caldera-forming events. Based on the new data, we propose the following scenario: Multiple magma chambers with distinct compositions existed below the Campi Flegrei before the CI and NYT eruptions and remained generally separated for some time unless new magma was recharged. In each case, one of the residing magma reservoirs was recharged by a new large-volume magma input of intermediate composition from a deeper differentiating magma reservoir. This may have triggered the coalescence of the previously separated reservoirs into one large chamber which fed the cataclysmic caldera-forming eruption. Large magma chambers in the Campi Flegrei may therefore be ephemeral features, interrupted by periods of evolution in individual, separated magma reservoirs.

New seismo-stratigraphic and marine magnetic data of the Gulf of Pozzuoli (Naples Bay, Tyrrhenian Sea, Italy): inferences for the tectonic and magmatic events of the Phlegrean Fields volcanic complex (Campania)

“…The Neapolitan Yellow Tuff is the most studied eruptive deposit between the Phlegrean products (Rosi and Sbrana 1987;Orsi et al 1996;Di Vito et al 1999;Pabst et al 2008). Its eruption, having a variable character from phreato-plinian to phreato-magmatic (Scarpati et al 1993;Orsi et al 1996), emitted a large amount of magmas having a composition from alkalitrachytic to latitic (Pabst et al 2008).…”

“…The corresponding volcanic deposits are separated by well stratified paleosols, emplaced within the caldera and along its outer margins (Deino et al 2004;Pabst et al 2008).…”

“…10) correlates with the volcanic units of the Pentapalummo Bank, a wide relict volcanic edifice located on the outer shelf of Pozzuoli Bay. These volcanites should be genetically related with the pre-caldera volcanic activity (Rosi et al 1996(Rosi et al , 1999 and deposited before the emplacement of the Neapolitan Yellow Tuff (12 ka; Pabst et al 2008). A pyroclastic unit (represented in pink; Fig.…”

The chronostratigraphy of the Haua Fteah cave (Cyrenaica, northeast Libya) — Optical dating of early human occupation during Marine Isotope Stages 4, 5 and 6

“…the CI from the largest of a number of precursor events (TLa, TLc and TLf: Orsi et al, 1996;Pabst et al, 2008;Tomlinson et al, 2012a) (Fig. 8).…”

“…The broad compositional similarity of HF_T513 with HF_T441/442 suggests that they are from the same Campi Flegrei source area, but, as can be seen in the major and trace element bi-plots, the two eruptions are compositionally distinct. Several 'Pre-CI' tephra layers have been described from outcrops within the Campi Flegrei (e.g., TLa, TLc and TLf: Orsi et al, 1996;Pabst et al, 2008;Tomlinson et al, 2012a), at sites across the Campanian Plain (e.g., SA3-a: Di Vito et al, 2008) and within the high resolution tephrostratigraphic record of Lago Grande di Monticchio (e.g., TM-20-2a and >8 other layers: Wulf et al, 2004). Based upon major, minor and trace elements compositions, the closest match for HF_T513 is to glass composition data on the TM-20-2a tephra layer from Lago Grande di Monticchio (Wulf et al, 2007;Fig.…”