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Trace element abundance and isotopic composition determinations of distal tephra levels is not currently a routine analysis, so the main objective of this work was to obtain full geochemical and isotopic data on well-known regional markers, aiming at enriching the comparison data-base for future tephrostratigraphic investigations. We chose to work on distal tephra embedded in the San Gregorio Magno (SGM) lacustrine sequence (Campania, Southern Italy) because its high sedimentation rates, should make it easier to avoid the problems linked to the mixing of volcanic fragments related to different explosive events occurred very close in time. Where necessary, due to the lack of data on comparison tephra from literature, marine distal equivalent were also fully characterized. The main tephra layers extracted from both sequences, already characterized as to major element composition (Munno and Petrosino, 2007; Morabito et al.,2014; Petrosino et al., 2016), were analyzed through LA-ICP-MS to evaluate the abundance of trace elements. The isotopic composition has been measured on a hand-picked glass amounts and when possible on minerals. The results of these analyses made it possible to refine some correlations previously hypothesized, as that of sample SGM16, which definitely results the distal counterpart of Monte Epomeo eruption of Ischia Island, aged ca. 55 ka, and well repeats the composition of the widespread tephra marker Y-7. The bimodal composition of layer SGM11 is confirmed by the trace element abundance, and only one of the two compositions (Na2O/K2O ca. 0.45) fully corresponds to that of marker X-5 (ca. 105 ka), here firstly fully characterized in a marine sequence from a Tyrrhenian sea core. The glass fragments displaying a different chemical composition (Na2O/K2O ca. 0.9) are probably the product of the reworking of the slightly older tephra SGM10, the distal counterpart of marker X-6 (ca. 109 ka). Few tephra layers are deeply altered, as evidenced by the high amount of clay minerals found by XRD analyses and for such a reason the results of 87Sr/86Sr and 143Nd/144Nd isotopic analysis on their glasses were not reliable. To bypass the problems linked to secondary alteration, where possible, we analyzed feldspar crystals, less prone than glass to chemical alteration, and obtained better results. In conclusion, the data produced in this work highlight that the full geochemical characterization of tephra levels, integrated by isotopic data, makes it possible to identify their source and, in most cases, to correlate them to a specific well known eruptive event. Morabito, S., Petrosino, P., Milia, A., Sprovieri, M., Tamburrino, S. (2014). A multidisciplinary approach for reconstructing the stratigraphic framework of the last 40ka in a bathyal area of the eastern Tyrrhenian Sea. Global and Planetary Change, 123, 121-138. Munno R., Petrosino P. (2007). The late Quaternary tephrostratigraphical record of the San Gregorio Magno basin (southern Italy). Journal of Quaternary Science, 22, 247-266. Petrosino, P., Morabito, S., Jicha, B. R., Milia, A., Sprovieri, M., Tamburrino, S. (2016). Multidisciplinary tephrochronological correlation of marker events in the eastern Tyrrhenian Sea between 48 and 105 ka. Journal of Volcanology and Geothermal Research, 315, 79-99.

We applied Ba diffusion chronometry to sanidine phenocrysts from the trachytic Agnano-Monte Spina eruption (A-MS ~4.7 ka) in order to constrains the time between reactivation and eruption of magma batches in the Campi Flegrei caldera (CFc, Napoli, southern Italy), one of the most hazardous volcanic areas on Earth. The A-MS products display variable 87Sr/86Sr and trace elements features that suggest magma mixing between two magma end-members. Resulting zonation patterns in phenocryst minerals are an ideal case to study timescales of magma mobilization at the CFc. Ba zonation profiles of 50 sanidine phenocrysts (Fig. 1) have been determined through combined energy-dispersive and wavelength-dispersive electron microprobe analyses (EDS-WDS-EMPA). We focused on compositional breaks near the rim of the crystals that represent the last mixing event prior to eruption. Profiles were measured by approaches: (1) quantitative BaO point-measurements at 10 μm spatial resolution, (2) gray-scale swath profiles from accumulated BSE images and (3) Ba X-ray scans. Since Ba dominates the backscattered electron intensities in sanidines, grayscale gradients extracted from the images using ImageJ® are a diffusive tracer proxy. Each profile from the different approaches was interpolated through a non-linear Boltzmann fit curve with Mathematica® software. We always choose the steepest gradients close to the crystal rims. However, any effects from cutting angles or crystal orientation always give longer apparent diffusion times. Our diffusion time estimates are thus minimum values. Gray-scale swath profiles and X-ray scans modelled for 930°C give short diffusion times of

The Zaro lava complex, located on the western sector of the Ischia volcanic island (Gulf of Naples, southern Italy), is the product of one of the few effusive eruptions occurred in the last period of activity (< 5 ka). The complex is made up of a white trachytic main lava flow (Zaro lava s.s.), hosting rounded-shaped enclaves of both mafic (shoshonite) and felsic (trachyte) composition. Major and trace elements and isotopic (87Sr/86Sr and 143Nd/144Nd) data have been acquired on whole rocks and separated minerals. Mafic enclaves (Mg# = 60-62, CaO = 7.71-8.31 wt%, Cr =117-143 ppm, Ni = 52-61 ppm, Zr =150-164 ppm, Sr = 503-526 ppm, LREE enriched compared to HREE) have low 87Sr/86Sr (0.70495- 0.70501) and high 143Nd/144Nd (0.51268-0.51269). Trachytic lavas and felsic enclaves (SiO2 = 60.61-61.71 wt%, K2O = 6.51-7.43 wt%, Na2O = 5.00-6.83 wt%, Rb = 243-428 ppm, Sr = 90-158 ppm, Zr = 385-773 ppm) exhibit higher 87Sr/86Sr (0.70608-0.70615) and lower 143Nd/144Nd (0.51255-0.51256). The strong isotopic difference between mafic enclaves and trachytes rules out a simple crystallization process for the variable facies of the Zaro lava complex. Moreover, in mafic enclaves petrochemical and possibly isotopic disequilibria between phenocrysts and their host rocks suggest occurrence of mingling processes or crystals entrapment from a distinct magmatic phase: indeed, many clinopyroxene and feldspar crystals are in chemical equilibrium with more evolved compositions (trachytic to trachyphonolitic). Trachytic lavas and felsic enclaves are chemically similar and do not display isotopic disequilibria between phenocrysts and host rocks. The last 5 ka of volcanic activity at Ischia were characterized by emplacement of products resulting from interaction between chemically and isotopically distinct batches of magma (Cava Nocelle, Vateliero and Molara; D’Antonio et al., 2013). Although these products show features comparable to those of the Zaro mafic enclaves, the last have significantly lower Sr and higher Nd isotopic ratios. Therefore, enrichment processes, such as assimilation of continental crust or mantle contamination in different conditions, should be invoked to justify the difference in isotopic features. Additionally, although the two evolved facies of the Zaro lavas have comparable chemical compositions and “uniform” isotopic signature, field analysis shows evidence of mingling between similar magmas with different viscosities. This process could have played a significant role in triggering the eruption. D’Antonio, M., Tonarini, S., Arienzo, I., Civetta, L., Dallai, L., Moretti, R., Orsi, G., Andria, M., Trecalli, A. (2013): 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). Contrib. Mineral. Petrol., 165,1173-1194.

The south Ardestan region in the Urumieh-Dokhtar arc covers an area of about 250 km2 that is characterized by plutonic rocks with a compositional spectrum ranging from gabbro, gabbro-norite, gabbroic diorite, diorite, tonalite to granodiorite. Gabbroic rocks are mainly tholeiitic in character, whereas the diorites, tonalites and granodiorites show increasingly stronger calc-alkaline affinity. Gradual compositional variation and limited variation in radiogenic isotopic ratios indicate that these different rock types are petrogenetically related and most probably are derived from a common primitive source. U-Pb LA-ICP-MS dating of zircon from four granitoids yielded ages that range from 25 to 24 Ma. For tonalitic rocks, internal Rb-Sr isochron ages (biotite, feldspars) indicate cooling ages that lie in the range 20.4 +/- 0.1 to 22.1 +/- 0.5 Ma, slightly younger than the zircons’ ages. Their uniform initial Sr-Nd isotopic values imply that the major source component has probably been an asthenospheric mantle domain. This is further supported by the mantle-derived geochemical affinity of the plutonic rocks. A geodynamic model is presented in which the asthenospheric upwelling and partial melting in the south Ardestan has been triggered by Late Oligocene-Miocene rollback of the Neotethyan subducting slab. These melts were subsequently slightly modified through assimilation, fractional crystallization (AFC) en-route to the surface (A less than 6%). The trace element rich and high radiogenic Sr signature of some gabbros, this is the likely perturbation and then mobilization of Sr in the rock system during alteration. 43% fractional crystallization dominated by plagioclase and orthopyroxene is found responsible for magmatic evolution from gabbro to gabbroic diorite. Whereas, 44% fractional crystallization of a plagioclase-dominated mineral assemblage that also include clinopyroxene, titanomagnetite and orthopyroxene is found responsible for the evolutionary path from the gabbroic diorite to diorite. 22% fractional crystallization of amphibole and plagioclase is calculated as responsible for the differentiation path from diorite to tonalite. Assuming 6% crustal contamination effect inferred from isotopic trace elemental modelling by Cadomian crust, the major elemental crustal contamination effect on AFC product is found to be trivial. That is for K2O it is 10% and for other major elements less than 5%. M-REE abundances of the tonalites likely imply that a parental melts of these rocks have experienced significant amphibole differentiation due to a greater depth of magma chamber formation. We do not claim that our petrogenetic model for the south Ardestan plutonic rocks is representative for the whole UDMA. However, the new isotopic age and bulk rock data along with the mantle-dominated geochemical characteristics of the studied plutonic rocks open a new window for geodynamic interpretation and support a model suggesting that subduction still affected the UDMA in Miocene time.

An investigation through Sr-He-O isotopes and major oxides was carried out on Mg-rich olivine and clinopyroxene phenocrysts from a selection of volcanic rocks of the Neapolitan Volcanoes (southern Italy), which include Somma- Vesuvius, Phlegraean Fields, and the islands of Ischia and Procida. The data produced in the present work extend the Sr-He-O dataset available for the Neapolitan volcanic districts (e.g., Graham et al., 1993; Martelli et al., 2004; Di Renzo et al., 2011; D’Antonio et al., 2013; Iovine et al., 2017), improving the knowledge especially on helium isotopic compositions of the Mt. Somma rocks, never analysed before. 3He/4He ratios (2.60-5.12 R/RA) of the investigated Mgrich phenocrysts are markedly lower than those measured at most volcanic arcs worldwide, and are among the lowest measured in subduction zones. This range of 3He/4He is coupled with quite large ranges of 87Sr/86Sr (0.704882 – 0.708480) and δ18O (4.85 – 6.70‰) measured in the same mafic minerals. The 3He/4He values, and the lowest measured Sr- and O-isotope ratios, do not suggest significant crustal or fluid contamination occurred during magmatic evolution, and they should reflect the composition of the metasomatized mantle beneath the Neapolitan region. Moreover, these values display a clear geographic trend, with radiogenic 4He-87Sr, and 18O generally increasing in on-lands districts. The results of these investigations are expected to allow us to better understand the original characteristics of the mantle source(s), and to define those of other components, likely originated in the continental crust, that were involved in the genesis of the primitive magmas feeding the Neapolitan volcanoes. D’Antonio, M., Tonarini, S., Arienzo, I., Civetta, L., Dallai, L., Moretti, R., Trecalli, A. (2013): 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). Contrib. Mineral. Petrol., 165, 1173-1194. Di Renzo, V., Arienzo, I., Civetta, L., D'Antonio, M., Tonarini, S., Di Vito, M.A., Orsi, G. (2011): The magmatic feeding system of the Campi Flegrei caldera: architecture and temporal evolution. Chem. Geol., 281, 227-241. Graham, D.W., Allard, P., Kilburn, C.R.J., Spera, F.J., Lupton, J.E. (1993): Helium isotopes in some historical lavas from Mount Vesuvius. J. Volcanol. Geotherm. Res., 58, 359-366. Iovine, R.S., Mazzeo, F.C., Arienzo, I., D’Antonio, M., Wörner, G., Civetta, L., Orsi, G. (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; 1302AD). J. Volcanol. Geotherm. Res., 331, 1-15. Martelli, M., Nuccio, P.M., Stuart, F.M., Burgess, R., Ellam, R.M., Italiano, F. (2004): Helium-strontium isotope constraints on mantle evolution beneath the Roman Comagmatic Province, Italy. Earth Planet. Sci. Letters, 224, 295-308.

A detailed petrochemical investigation of the peridotites from the Mt. Pollino area (Basilicata, Southern Italy) allowed to provide the first comprehensive reconstruction of the evolution and geodynamic setting of ophiolitic mantle from the Southern Apennines. These mantle peridotites firstly acquired strongly-refractory modal and chemical compositions consistent with large degrees of partial melting (≥ 23%). This process was presumably assisted by concomitant injection of melt increments rising from deeper levels of the mantle column, as suggested by relatively large Al and Fe contents of Ol, Opx and Sp. The porous flow ascent of melt increments produced by deeper near-fractional melting continued after the end of the partial melting, as recorded by precipitation of disseminated clinopyroxene out of thermal and chemical equilibrium with the other rock-forming minerals. The Pollino mantle sequence locally experienced reheating associated to a new episode of porous flow migration of melts with REE composition approaching that of N-MORB. The petrological evolution recorded by the peridotites of Mt. Pollino, their high equilibrium T (up to 1100 °C) and the absence of pyroxenites show remarkable analogies with modern abyssal peridotites, pointing to an intra-oceanic setting of the Jurassic Ligurian Tethys for this mantle sequence. According to the present knowledge about the Southern Apennines, the abyssal-like peridotites with the associated terrigenous sediments and continental crustal rocks were incorporated in the Ligurian Accretionary Complex and reached HP/LT conditions during a subduction event starting in Upper Oligocene, to be later exhumed in the Tortonian. The results of this study strongly support the existence of significant differences in terms of geodynamic evolution between Southern and Northern Apennines. © 2017 Elsevier B.V.

The olivine melilitites from the southern part of the 6.8 Ma-old Takarindiona volcanic field (Eastern Madagascar) are olivine ± chromite -phyric lavas, with zoned titanaugite, perovskite, melilite, nepheline, monticellite, Ba–Ti-mica and Fe–Ti oxides as microphenocrysts and groundmass phases. The rocks are very primitive, rich in incompatible trace elements (e.g., Ba = 1049 ± 153 ppm, Sr = 1050 ± 167 ppm, Nb = 98 ± 13 ppm; La/Ybn = 41 ± 5; La/Nb = 0.88 ± 0.05), and have restricted ranges of initial 87Sr/86Sr (0.70391–0.70410) and 143Nd/144Nd (0.51272–0.51282). The rocks follow a differentiation trend controlled by ab. 20% removal/addition of phenocryst olivine ± chromite. The olivine melilititic magmas are the product of small degrees of partial melting (1–3%) of a peridotitic source, enriched in highly incompatible trace elements by CO2-, F-, and H2O-rich melts, located within the garnet stability field (3–3.5 GPa and ~100 km depth) of sub-continental lithospheric mantle, where carbonates (dolomite) and possibly phlogopite were stable phases. Mantle xenoliths within the volcanics are mostly spinel harzburgites having mineral modes and chemical compositions suggesting variable degrees of “basalt” melt extraction. Based on textural and chemical evidence, and quantitative thermobarometric estimates, the xenoliths were incorporated at a pressure of ~1.1 GPa (~35–40 km depth), far shallower than the source of the melilititic magmas, and along a predictably cool geotherm beneath Archean continental lithosphere. Highly resorbed orthopyroxene xenocrysts mantled by augite indicate that the melilitites may have also entrained lower crustal materials or underplated subalkaline rocks. The mantle sources of the lavas and mantle xenoliths of the Takarindiona district indicate stratification of the lithospheric mantle, and help constraining the lithospheric features and the magmatic history of the Eastern Madagascar craton.

The Punta delle Pietre Nere (Gargano, Southern Italy) igneous body is constituted by gabbroic and syenitic rocks with lamprophyric affinity of different age (58 and 62 Ma, respectively). The chemical composition of the minerals clearly indicates that there is no genetic relationship between the two lithotypes, in agreement with their significant age difference. The chemical (trace elements) and Sr-Nd-Pb-isotopic composition of these rocks highlights an “anorogenic” geochemical affinity derived from mixed DMM-HIMU-EM mantle reservoirs, similarly to other Paleogene-Oligocene magmatic provinces in the Circum-Mediterranean Area. In past literature, these features were interpreted as evidences for enriched asthenospheric mantle plume upwelling from deep regions beneath the Western Europe. Here we suggest that the HIMU-like composition of Punta delle Pietre Nere rocks is related to a lithospheric mantle source bearing amphibole-rich veins, resulting from crystallization of melts within the amphibole stability field in presence of H2O, as shown by several experimental works. Our results suggests partial melting at 70–90 km depth, which corresponds to the spinel-garnet transition (2.5–3.5 GPa) close to the amphibole stability limit (~90–110 km and 2.5–3.5 GPa).

Barium diffusion chronometry applied to sanidine phenocrysts from the trachytic Agnano-Monte Spina eruption (∼4.7 ka) constrains the time between reactivation and eruption of magma batches in the Campi Flegrei caldera. Backscattered electron imaging and quantitative electron microprobe measurements on 50 sanidine phenocrysts from representative pumice samples document core-to-rim compositional zoning. We focus on compositional breaks near the crystal rims that record magma mixing processes just prior to eruption. Diffusion times were modeled at a magmatic temperature of 930 °C using profiles based on quantitative BaO point analyses, X-ray scans, and grayscale swath profiles, yielding times ≤60 years between mixing and eruption. Such short timescales are consistent with volcanological and geochronological data that indicate that at least six eruptions occurred in the Agnano-San Vito area during few centuries before the Agnano-Monte Spina eruption. Thus, the short diffusion timescales are similar to time intervals between eruptions. Therefore, the rejuvenation time of magma residing in a shallow reservoir after influx of a new magma batch that triggered the eruption, and thus pre-eruption warning times, may be as short as years to a few decades at Campi Flegrei caldera.

We have carried out a detailed petrological investigation on products of the poorly understood Nisida eruption, one of the most recent volcanic events (~ 4 ka BP) at Campi Flegrei caldera. We present major oxide contents and Sr–Nd isotopic data determined on bulk rock, groundmass and separated phenocrysts, along with major and volatile elements (H 2 O Cl, S and CO 2 ) content of clinopyroxene-hosted melt inclusions from pumice fragments representative of the eruption. We use these to elaborate the role of magmatic evolution processes and fluid transfer prior to, and during, the Nisida eruption. The results indicate that the eruption was triggered by the arrival of a volatile-rich, shoshonite–latite magma. This magma was similar in terms of Sr and Nd isotopes ( 87 Sr/ 86 Sr ~ 0.70730; 143 Nd/ 144 Nd ~ 0.51250) to the Astroni 6 magmatic component. We infer that emplacement of this magma triggered resurgence of the caldera floor, and fed a large part of the volcanic activity at Campi Flegrei caldera during the past 5 ka. The new data on the Nisida eruption and other recent eruptions at Campi Flegrei, together with published data, suggest that fractional crystallization, and potentially fluid transfer from deep to shallow depths may account for most of the chemical variability of the erupted melt. Additional processes, such as magma mingling/mixing, and/or entrapment of antecrysts into the magma prior to the Nisida eruption are required to explain the large isotopic variation displayed by the analyzed products. The Nisida eruption occurred in the eastern sector of the resurgent Campi Flegrei caldera. In this sector, presently affected by an extensional stress regime, previous studies suggest that a Nisida-like eruption would be likely if the level of activity in the caldera were to intensify. In an area with such structural conditions, the ascent of a volatile-rich magma such as that which erupted at Nisida should generate geophysical and geochemical signals detectable by an efficient monitoring network. The results of this investigation should inform the study of other active calderas worldwide that are experiencing persistent unrest, such as Rabaul, Aira, Iwo-Jima, Santorini, Long Valley and Yellowstone.