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A tephra layer was recovered within the Holocene fluvial succession of the Cerro Colorado Cultural and Natural Reserve in the Córdoba Province (Argentina). Radiocarbon dating on organic matter preserved within the paleosoil beneath the tephra layer indicate that the ash layer is younger than ca. 4700 cal yr BP. Radiocarbon ages, Sr and Nd isotope data on the bulk rock, and microanalytical data on glass shards allow us to identify the Andean Central Volcanic Zone as the possible source area of the analyzed tephra. Our data highlight that the tephra layer recovered in the Córdoba Province was produced by volcanoes of the southern fringe of the Andean Central Volcanic Zone and that it can be confidently correlated with the Cerro Blanco 4200 cal yr BP eruption. These findings are also coherent with the known dispersion axis of the products of this eruption and allow further constraining their dispersion. This latter is extremely important for any attempt in volcanic hazard assessment.

Explosive activity preceding the ~40 ka Campanian Ignimbrite (CI) eruption in the Neapolitan volcanic area, Southern Italy, has long been speculated based on the occurrences of widespread tephra layers, with a Campanian geochemical signature, such as the C-22, X-5, and X-6, preserved in Mediterranean Marine Isotope Stage (MIS) 5 sedimentary records. However, previous studies of pre-CI pyroclastic units occurring in close proximity of the Neapolitan volcanoes, including Campi Flegrei, Somma-Vesuvius, Ischia and Procida islands, did not allow a conclusive identification of the near-source equivalents of these tephra markers. Here we present a comprehensive characterization of four pyroclastic units from the Campanian Plain, comprising major and trace element glass compositions, Sr[sbnd]Nd isotopes and 40Ar/39Ar dating. Our data allowed the identification of the medial equivalents of the MIS 5 tephra markers, including the widespread C-22, X-5, and X-6 tephra, and their assignment to previously undocumented Campi Flegrei activity between 109 and 92 ka. In addition to substantially extending Campi Flegrei explosive activity deeper in time, and thus providing the basis for a revaluation of its history, our findings provide new precise radioisotopic dating to better constrain the chronology of the millennial scale climatic oscillations of the MIS 5c-d in the Mediterranean area and possibly on a larger scale.

The Fucino Basin, central Italy, with its long and continuous history of Quaternary sediment accumulation, is one of the richest Mediterranean Middle Pleistocene tephra records. Here, we present a new detailed investigation of tephra layers (tephras) of the 250–170 thousand years before present (ka) interval, corresponding to the entire Marine Isotope Stage (MIS) 7 and parts of the MIS 8 and MIS 6. The investigated tephras have been characterised in terms of major, minor and trace elements, Sr–Nd isotopic compositions and 40Ar/39Ar ages. For correlation purposes, glass compositions and several new 40Ar/39Ar ages of selected proximal pyroclastic units spanning the same temporal interval from Vulsini (Latera Volcanic Complex), Sabatini, and Vico volcanic systems, central Italy, were measured. The late MIS 8-early MIS 6 Fucino tephras were backtracked to their corresponding volcanic sources, which include the Vulsini, Vico, Sabatini, Roccamonfina, Ischia and Campi Flegrei volcanic systems. While some of these tephras have been correlated to specific eruption units, other layers are currently not documented or described in near-vent sections, thus highlighting previously unrecognised events generated by these volcanic systems. Furthermore, the new high precision 40Ar/39Ar ages provide improved temporal constraints for Fucino making it one of the most detailed and chronologically best constrained tephra records for central Mediterranean MIS 7 tephrochronology. The Fucino record thus provides new integrative information for reconstructing the explosive history of Italian volcanoes during the investigated time interval. Furthermore, the geochronological constraints provide the basis for future paleoclimatic investigations at local and regional scale.

Helium (He) with its isotopes (3He, 4He) is a key tracer enabling the Earth’s mantle and dynamics to be characterized. Enrichment in primordial helium (3He) has been detected in volcanic gases of numerous magmatic systems in different geodynamic settings. Despite past use to monitor volcano-tectonic unrest, temporal 3He/4He variability in volcanic emissions is still poorly constrained. Here, we investigate noble gas chemistry of Piton de la Fournaise hotspot volcano, where temporal fluctuations of 3He/4He in response to the eruptive activity have never been studied. We compare the 3He/4He signature of volcanic gases and fluid inclusions and we highlight analogous evolution of the 3He/4He signature in both during the last decades of eruptive activity (1990–2017), even during the same eruption. We show that the maximum enrichment in 3He is found in magmatic fluids that fed the most voluminous eruptions which culminated in caldera collapse events. We argue that this enrichment in 3He mostly reflects a greater contribution of magmatic fluids from a primitive component of the mantle plume. These results emphasize that He isotopes may provide warnings of increases in deep magmatic contributions that potentially herald paroxysmal eruptions, as documented here at Piton de la Fournaise (2007) and also at Kilauea (2018).

La isla de El Hierro es la isla más joven y occidental de las Islas Canarias. Su aparente escasa variabilidad petrológica y geoquímica generó una menor ¿atracción¿ geológica para los científicos, ralentizando su estudio. Antes de la erupción submarina a finales de 2011 en el área de La Restinga, la investigación geológica en El Hierro fue intermitente, siendo el trabajo de Carracedo et al. (2001) el estudio más completo que sobre la geología de la isla y su inclusión en el contexto del Archipiélago Canario. El interés mediático y científico que suscitó la erupción de 2011, p. ej., con la controversia sobre el origen de los fragmentos rocosos flotantes de ¿restingolitas¿, pusieron de manifiesto la necesidad de una mejor comprensión sobre la evolución petrológica y geoquímica de la isla. En este trabajo presentamos una visión general de las características petrológicas y geoquímicas del vulcanismo en El Hierro dentro del contexto más amplio del magmatismo en las Islas Canarias.

El litio (Li) tiene dos isótopos estables, 7Li (92,4%) y 6Li (7,6%). Su gran diferencia relativa en masa puede conducir a un fraccionamiento isotópico significativo a baja temperatura. Este hecho y su alta solubilidad en fluidos acuosos, hacen que los isótopos de Li sean potencialmente útiles como trazadores de procesos de enfriamiento magmático y alteraciones. Por otra parte, el fraccionamiento de isótopos de Li puede ocurrir a alta temperatura debido a diferencias en su difusividad y al reparto entre minerales y magma. Hasta la fecha, no se han realizado investigaciones de Li sobre productos volcánicos del archipiélago canario para estudiar los procesos magmáticos y la composición del manto de la Tierra. Este estudio es una prueba piloto de la utilización de los isótopos de Li para estudiar los procesos magmáticos del volcanismo holoceno en El Hierro. Esta investigación se financia con el proyecto LAJIAL (ref. PGC2018-101027-B-I00, MCIU / AEI / FEDER, UE) y se realiza en el marco de los Grupos Consolidados de Investigación GEOVOL (Gobierno de Canarias, ULPGC) y GEOPAM (Generalitat de Catalunya, 2017 SGR 1494). Abstract, Lithium (Li) has two stable isotopes, 7Li (92.4%) and 6Li (7.6%). Their large relative difference in mass can lead to significant isotopic fractionation, especially in low temperature environments. This feature together with its high solubility in aqueous fluids, makes Li isotopes potentially useful tracers of magmatic cooling histories and weathering. On the other hand, Li isotope fractionation can occur at high temperature due to differences in diffusivity as well as partitioning of Li between minerals and melt. To date, no Li investigations have been performed on volcanic products from the Canarian Archipelago in order to study magmatic processes and Earth’s mantle composition. This study acts as a driving factor towards the utilization of the Li-isotope systematics for future studies in the Canary Islands. In this contribution, we test the application of the Li-isotope to shed new light on the magmatic processes involved during the Holocene volcanism at El Hierro

The prehistoric (< 7 ka) Zaro eruption at Ischia island (Southern Italy) produced a lava complex overlaying a pyroclastic deposit. Although being of low energy, the Zaro eruption might have caused casualties among the neolithic population that inhabited that area of Ischia, and damages to their settlements. A similar eruption at Ischia with its present-day population would turn into a disaster. Therefore, understanding the magmatic processes that triggered the Zaro eruption would be important for volcanic hazard assessment and risk mitigation, so as to improve a knowledge that can be applied to other active volcanic areas worldwide. The main Zaro lava body is trachyte and hosts abundant mafic and felsic enclaves. Here all juvenile facies have been fully characterized from petrographic, geochemical and isotopic viewpoints. The whole dataset (major and trace element contents; Sr-Nd isotopic composition) leads to rule out a genetic link by fractional crystallization among the variable facies. Thus, we suggest that the Zaro mafic enclaves could represent a deep-origin mafic magma that mingled/mixed with the main trachytic one residing in the Ischia shallow magmatic system. The intrusion of such a mafic magma into a shallow reservoir filled by partly crystallized, evolved magma could have destabilized the magmatic system presumably acting as a rapid eruption trigger. The resulting processes of convection, mixing and rejuvenation have possibly played an important role in pre- and syn-eruptive phases also in several eruptions of different sizes in the Neapolitan area and elsewhere in the world.

The Holocene volcanism at El Hierro consists of basaltic monogenetic volcanic fields associated with o the three rift systems present in this island. In this work we report preliminary petrological and geochemical data of Holocene lava flows belonging to the WNW-striking rift. Sampling was focused in three zones: Orchilla, Verodal-Sabinosa, and Tanganasoga. Petrography of the studied lavas shows that they are homogeneous. All samples are porphyritic with macrocrysts of clinopyroxene and olivine immersed in a groundmass formed by microcrysts of plagioclase, Fe-Ti oxides and clinopyroxene. Clinopyroxenes are diopsides, olivines have forsterite contents ranging from 74 to 84 % and anorthite in plagioclase varies from 66 to 76% (labradorite). Whole-rock geochemical results evidence that all magmas are basic in composition, ranging from picrobasalts to phonotephrites. Major, trace elements and isotope support fractional crystallization as the main process of magma evolution. However, petrography and chemistry of clinopyroxene cores agree with a xenocrystic nature of some of them. We suggest that these clinopyroxene cores crystallized from a genetically related magma and subsequently were entrapped or cannibalized by the basic rising magmas. © 2019 Sociedad Geologica de Espana. All rights reserved.

The Holocene basaltic monogenetic volcanic fields in El Hierro, Canary Islands, are associated to three rift systems of this island. We report preliminary petrological and geochemical data of Holocene lava flows located in the WNW rift. Sampling focused in three active volcanic zones during Holocene: Orchilla, Verodal-Sabinosa, and Tanganasoga. Petrography of the studied lavas showed that they are homogeneous. All samples were porphyritic with macrocrysts of clinopyroxene and olivine immersed in a groundmass formed by microcrysts of plagioclase, Fe-Ti oxides and clinopyroxene. Clinopyroxenes were diopsides, olivines had forsterite contents ranging from 74 to 84 % and anorthite in plagioclase varied from 66 to 76% (labradorite). Whole-rock geochemical results evidenced that all magmas are basic in composition, ranging from picrobasalts to phonotephrites. Major, trace elements and isotope support fractional crystallization as the main process of magma evolution. However, petrography and chemistry of clinopyroxene cores agree with a xenocrystic nature of some of them. These could either represent recycled crystals through diverse magma replenishment events or accumulations of crystals from the magma. This work was partially funded by the Agencia Canaria de Investigación, Innovación y Sociedad de la Información (SolSubC200801000047).

El volcanismo holoceno en el Hierro está formado por campos volcánicos monogenéticos asociados a las tres estructuras de tipo rift que modelan la isla. En ese trabajo se presentan los resultados petrológicos y geoquímicos preliminares de las lavas Holocenas del rift ONO. El muestreo se concentró en tres zonas: Orchilla, Verodal-Sabinosa y Tanganasoga. La petrografía de las lavas estudiadas muestra que son bastante homogéneas. Todas las lavas son porfídicas con macrocristales de clinopiroxeno y olivino inmersos en una matriz formada por microcristales de plagioclasa, óxidos de Fe-Ti y clinopiroxeno. Los clinopiroxenos son diópsiodos, los olivinos presenten contenidos en forsterita que varían entre 74 y 84% forsteritas, y el contenido en anortita en las plagioclasas varía entre 66 y 76% (labradorita). Los resultados geoquímicos de roca total evidencian que todos los magmas son básicos con composiciones que varían entre picrobasaltos y fonotefritas. Los elementos mayoritarios, trazas e isótopos sugieren que la cristalización fraccionada es el principal proceso. Aun así, la petrografía y química de los núcleos de los clinopiroxenos sugieren que algunos de ellos son xenocristales. Se sugiere que estos núcleos cristalizaron a partir de un magma genéticamente relacionado y que posteriormente fueron atrapados o canibalizados por el magma básico en ascenso.

We report on the variation of the elemental (He, Ne, and Ar) and isotopic (He and Ar) compositions of olivine- and clinopyroxene-hosted fluid inclusions hosted in lavas, pyroclastics, and cumulate xenoliths from the last 60ka of the eruptive history of Stromboli volcano, Italy. Samples belong to (i) the present-day activity as represented by shoshonitic (SHO) basalts, i.e., pumices with low porphyritic (LP) content and high porphyritic (HP) scoriae; (ii) the subalkaline versus alkaline products erupted at Stromboli during its subaerial history among the extreme magmatic series, i.e., calc-alkaline (CA) and potassic (KS); and (iii) the only known ultramafic cumulates (San Bartolo wehrlite xenoliths, SBX) outcropping in the island, carried to the surface by recent (ca. 2ka) basaltic lava. To interpret the results better, we also investigated trace elements in the clinopyroxenes of wehrlite xenoliths and the Sr and Nd isotopes of all of the products in which the 3He/4He ratio was measured.Wehrlite xenoliths are igneous cumulates crystallized at mantle depth that mostly consist of clinopyroxene and olivine crystals with limited compositional variation. The texture, mineral chemistry, pattern of trace elements and Sr-Nd-isotope ratios (in clinopyroxene) suggest that these cumulates were produced by the early crystallization of a primitive basaltic magma with CA or HKCA-SHO affinity.The gas contents measured in the mafic crystals decrease from the wehrlite xenoliths through LP pumice, CA and KS lavas and, finally, to the HP scoria. This observation is consistent with crystallization and fluid entrapment from mantle depths to progressively shallower crustal levels. The low gas content extracted from the HP crystals did not allow measurement of their 3He/4He ratios.Most of the investigated crystals exhibit a 3He/4He ratio in the range of 4.0-4.9 Ra, with only the KS mafic minerals exhibiting lower 3He/4He values (≤3.5 Ra). The low values of He-isotope ratios relative to tho

Tephra layers from six deep-sea cores, recovered between the Ionian and the Aegean Seas, and covering a time span between ~ 102 and ~ 8.2 ka BP, were investigated with the aim of identifying their volcanic source. The stratigraphic position of each tephra layer defined by means of nannofossil biostratigraphy and occurrence of sapropel layers was integrated with a thorough geochemical characterization of glass shards based on major oxides and trace elements content, and Sr-Nd isotope ratios. Major oxides composition permitted their subdivision into three groups (K-trachyte, peralkaline rhyolite, andesite), confirmed by Principal Component Analysis on trace elements data. Primordial mantle-normalized trace elements distribution patterns allowed for precise identification of the geochemical affinity and geodynamical setting of each group. Although the Sr isotopic composition of some investigated tephras was deeply affected by seawater alteration as expected, the 143Nd/144Nd values discriminate well the three groups of tephras in combination with major oxides and trace elements data. Therefore, La/Yb and Th/Y vs. 143Nd/144Nd discrimination diagrams are proposed for identification of potential volcanic sources active in the 102–8.2 ka BP time span in the Eastern Mediterranean area for unknown tephras. The obtained results have permitted the attribution of six K-trachytic tephras to the Y-5 stratigraphic marker (Campanian Ignimbrite eruption of Campi Flegrei, Southern Italy, ~ 39 ka BP), and two pantelleritic (= peralkaline rhyolite) tephras to the Y-6 stratigraphic marker (Green Tuff eruption of Pantelleria Island, Sicily Channel, ~ 46 ka BP). The andesitic tephra, stratigraphically constrained between ~ 39 and ~ 83–102 ka BP, might correspond to the X-1 stratigraphic marker, found in several deep-sea cores of the Eastern Mediterranean Sea, although its attribution is still debated in the literature. On the basis of trace elements content, supported by Sr-Nd isotopic fea