Campanian Volcanic Research Articles

Insights into the explosive eruption history of the Campanian volcanoes prior to the Campanian Ignimbrite eruption

The Campanian Volcanic Zone (CVZ) comprises multiple active volcanoes and includes the highly productive Campi Flegrei and Ischia caldera systems. These caldera volcanoes have produced probably the largest eruptions in Europe in the past 200 ka, such as the Monte Epomeo Green Tuff (MEGT; Ischia) at ca. 56 ka and the Campanian Ignimbrite (CI; Campi Flegrei) at ca. 40 ka, which form widespread isochrons across the Mediterranean region. These closely-spaced volcanic centres erupt phonolitic to trachytic glass compositions that are similar, and thus it can be challenging to correlate tephra deposits to specific volcanic sources. Here we present a detailed tephrostratigraphy for pre-CI eruption activity using the units preserved within a sequence at the coastal Acquamorta outcrop, on the western side of the CI caldera rim. Both the MEGT and CI units are present in the section, and they bracket twelve eruption units that were logged and sampled. New major and trace element glass chemistry data have been acquired for these Acquamorta tephra deposits. Three eruption deposits from Ischia and nine from Campi Flegrei are identified, which helps constrain the tempo of volcanic activity of these centres between the large caldera-forming eruptions. The three Ischia tephra deposits between the MEGT and the CI are indistinguishable based on both major and trace element glass chemistry and cannot be correlated to a specific or known eruption in this interval, such as the Schiappone tephra. The compositional variations between the Campi Flegrei eruptions reveal temporal shifts in the composition of the tephra deposits that reflect changes in the magmatic system prior to the CI eruption. These deposits indicate that there were at least nine eruptions at Campi Flegrei within 16 ka of the enormous CI eruption, and suggest that there was no significant period of repose before the caldera generating eruption.

Land-sea correlations in the Eastern Mediterranean region over the past c. 800 kyr based on macro- and cryptotephras from ODP Site 964 (Ionian Basin)

Direct correlations between terrestrial and marine climate-proxy records are essential in order to determine potential lead/lag relationships in the response of the terrestrial and marine realms to climate forcing. In the Eastern Mediterranean region, such land-sea correlations have not yet been established beyond c. 200 ka. To explore the potential of tephra layers for Late and Middle Pleistocene land-sea correlations in the Eastern Mediterranean region, we have revisited yet unconfirmed tephra layers previously reported from Ocean Drilling Program (ODP) Site 964 (Ionian Basin) for the past c. 800 kyr in order to identify their origin and examine potential terrestrial counterparts. Using major- and trace-element glass analyses, we confirmed the presence of seven visible tephra layers with ages from 623 to 38 ka. These tephra layers represent known tephra isochrons from Italian volcanic centers (Y-5, Y-7, X-6, and V-0) and three yet unknown eruptions from Etna (623 ka), the Campanian Volcanic Zone (CVZ; 238 ka), and Pantelleria (238 ka). Because the majority of the previously reported tephra layers from ODP Site 964 were identified as clastic layers of non-volcanic origin, cryptotephra analyses were carried out for cores spanning Marine Isotope Stages (MIS) 13 to 9 (500–320 ka). This effort yielded 19 cryptotephra layers originating from Santorini volcano, the CVZ, possibly Roccamonfina volcano, and an undefined source in either the Aeolian Islands or the South Aegean Volcanic Arc. Two tephra layers are correlated with potential equivalents from terrestrial archives on the Italian and Balkan Peninsulas, including tephra isochrons SC5/A7/OH-DP-1966 (c. 493 ka; Mercure basin, Acerno basin, and Lake Ohrid) and TP09–65.95 (c. 359 ka; Tenaghi Philippon) that represent an unknown eruption of Roccamonfina and the Cape Therma 1 eruption of Santorini, respectively. Direct linking of the marine record from ODP Site 964 with the terrestrial records from Tenaghi Philippon, Lake Ohrid, and the Acerno basin via tephra tie points allowed us to circumvent shortcomings of the individual age models, and to obtain a comprehensive picture of climate variability in the greater Eastern Mediterranean region for the MIS 13–9 interval.

Tectonics, Dynamics, and Plio‐Pleistocene Magmatism in the Central Tyrrhenian Sea: Insights From the Submarine Transitional Basalts of the Ventotene Volcanic Ridge (Pontine Islands, Italy)

AbstractIn the Tyrrhenian back‐arc basin, the Ventotene Volcanic Ridge (VR) represents a NW‐SE‐oriented morphological high, located 25 km north of Ventotene Island in the Eastern Pontine Islands. It is considered part of an alignment of volcanic edifices developed in the central‐eastern Tyrrhenian Sea, from the western Pontine Islands (WPI) to the Campanian Volcanic Region. The samples dredged along the VR are basalts to trachybasalts belonging to the transitional (TR) rock‐series, with a 40Ar‐39Ar age of 2.760 ± 0.039 Ma. Petrological and geochronological data link the VR basalts to the TR peralkaline rhyolites cropping out at the WPI (∼1.6‐1.1 Ma); here, during a time span of ∼4.5‐1.0 Ma highly differentiated products of high‐potassium calc‐alkaline (HKCA, ∼4.5‐2.9 Ma) and K‐alkaline (KA, ∼1 Ma) series were also erupted. Notably, the parental melts of the three rock‐series were recognized in the continental slope close to the WPI (TR, HKCA) and eastward, namely in eastern Pontine Islands (KA), at the VR (TR), and in the Campanian Plain (HKCA). All the parental melts show typical orogenic geochemical signatures being originated from a similar heterogeneous suprasubduction mantle source, without the involvement of anorogenic sources. Tectonically, the faults bordering the VR, associated to the Pliocene E‐W directed rifting stage of the Tyrrhenian back‐arc basin were characterized by a more intense activity during the time span ∼5.0‐2.0 Ma (the emplacement time of HKCA and TR series), while KA products are related to a later stage of extension deformation (<∼2.0 Ma) when the extensional direction changed to NW‐SE and the VR fault activity decreased.

Quantification of excess 231Pa in late Quaternary igneous baddeleyite

AbstractInitial excess protactinium (231Pa) is a frequently suspected source of discordance in baddeleyite (ZrO2) geochronology, which limits accurate U/Pb dating, but such excesses have never been directly demonstrated. In this study, Pa incorporation in late Holocene baddeleyite from Somma-Vesuvius (Campanian Volcanic Province, central Italy) and Laacher See (East Eifel Volcanic Field, western Germany) was quantified by U-Th-Pa measurements using a large-geometry ion microprobe. Baddeleyite crystals isolated from subvolcanic syenites have average U concentrations of ~200 ppm and are largely stoichiometric with minor abundances of Nb, Hf, Ti, and Fe up to a few weight percent. Measured (231Pa)/(235U) activity ratios are significantly above the secular equilibrium value of unity and range from 3.4(8) to 14.9(2.6) in Vesuvius baddeleyite and from 3.6(9) to 8.9(1.4) in Laacher See baddeleyite (values within parentheses represent uncertainties in the last significant figures reported as 1σ throughout the text). Crystallization ages of 5.12(56) ka (Vesuvius; MSWD = 0.96, n = 12) and 15.6(2.0) ka (Laacher See; MSWD = 0.91, n = 10) were obtained from (230Th)/(238U) disequilibria for the same crystals, which are close to the respective eruption ages. Applying a corresponding age correction indicates average initial (231Pa)/(235U)0 of 8.8(1.0) (Vesuvius) and 7.9(5) (Laacher See). For reasonable melt activities, model baddeleyite-melt distribution coefficients of DPa/DU = 5.8(2) and 4.1(2) are obtained for Vesuvius and Laacher See, respectively. Speciation-dependent (Pa4+ vs. Pa5+) partitioning coefficients (D values) from crystal lattice strain models for tetra- and pentavalent proxy ions significantly exceed DPa/DU inferred from direct analysis of 231Pa for Pa5+. This is consistent with predominantly reduced Pa4+ in the melt, for which D values similar to U4+ are expected. Contrary to common assumptions, baddeleyite-crystallizing melts from Vesuvius and Laacher See appear to be dominated by Pa4+ rather than Pa5+. An initial disequilibrium correction for baddeleyite geochronology using DPa/DU = 5 ± 1 is recommended for oxidized phonolitic melt compositions.

Central Mediterranean explosive volcanism and tephrochronology during the last 630 ka based on the sediment record from Lake Ohrid

Lake Ohrid, located in the Central Mediterranean region downwind of the Italian volcanoes, has great potential for developing a detailed record of the explosive activity of these volcanoes. Electron microprobe and Laser Ablation Inductively Coupled Plasma Mass Spectrometry geochemical analyses of juvenile glass fragments of previously not analysed tephra layers of the DEEP site sediment record of Lake Ohrid expand the existing tephrostratigraphy for the interval Marine Isotope Stages 1–16. The geochemical signatures of all tephra layers suggest an origin exclusively from the Italian volcanism.Eight of these tephra layers have potential equivalents in marine and terrestrial archives of the Central Mediterranean region (OH-DP-1966/SC5/A7; OH-DP-1955/CES1/A2; OH-DP-1055/S1; OH-DP-1006/S2; OH-DP-0997/S3, OH-DP-0710/S8/C-51; OH-DP-0766/ODP5/P-13; OH-DP-0505/ODP4). Nine tephra layers, which have not been described so far, help to reconstruct the late volcanic activity of Mount Vulture (OH-DP-2439) and the Paleovulsini (OH-DP-1998), the pre- and post Rio Rava activity of the Roccamonfina volcano (OH-DP-1911/-1812/-1733/-1640/-1527), the early activity of the Aeolian Arc (OH-DP-1513/-1520), and the Bracciano activity of the Monti Sabatini volcanic district (OH-DP-1175). The multi-proxy dataset and chronology of the DEEP site sediments allowed definition of the climatostratigraphic position for all tephra layers and constrain the ages of so far unknown and/or undated tephra layers. The presented data provide a crucial increase of knowledge of the Middle Pleistocene tephrostratigraphy in the Central Mediterranean back to 630 ka and allows new insights of the volcanic activity of Roccamonfina, the Roman Province, the Campanian Volcanic Zone (CVZ), the Aeolian Arc, Pantelleria, and Mount Vulture.

Eastern Mediterranean volcanism during marine isotope stages 9 to 7e (335–235 ka): Insights based on cryptotephra layers at Tenaghi Philippon, Greece

Tephra layers preserved in distal sedimentary archives represent chronicles of explosive volcanism that can complement the often more fragmentary information from near-source volcanic deposits to establish complete volcanic histories. With regard to these aspects, the Middle Pleistocene of the Eastern Mediterranean region stands out as it has a complex and diverse, but as yet largely unexplored record of volcanic eruptions. Here we present the first distal tephra record for the Eastern Mediterranean region spanning from 335 to 235 ka (corresponding to Marine Isotope Stages [MIS] 9 to 7e); our record has been derived from peat cores from the iconic terrestrial climate archive of Tenaghi Philippon (NE Greece). We have identified twenty-seven cryptotephra layers that represent eruptions from diverse Mediterranean sources. Six cryptotephra layers can be linked to Campanian volcanoes, and another six layers are tentatively correlated to Aeolian Arc volcanism. Of the ten cryptotephra layers that we have identified as deriving from the Aegean Arc, eight originate from Santorini volcano and two are tentatively attributed to either Kos or Milos. Five cryptotephra layers have yet unknown origins.Most of the identified cryptotephras represent previously undocumented eruptions. We provide age estimates for all cryptotephras and, by extension, for the underlying eruptions based on orbitally tuned pollen data from the same cores. The only cryptotephra layer in the 335–235 ka record from Tenaghi Philippon that represents a previously known eruption has a palynostratigraphically derived age of c. 289 ka and can be tentatively linked to the Seiano Ignimbrite from the Campanian Volcanic Zone; this represents the first time that this eruption can be traced beyond its proximal area. The documentation and geochemical characterization of tephra layers from different Mediterranean sources in the Tenaghi Philippon peat cores for MIS 9–7e is an important step towards the integration of regional Mediterranean tephrostratigraphic information for the Middle Pleistocene.

Evidence for sub-lacustrine volcanic activity in Lake Bolsena (central Italy) revealed by high resolution seismic data sets

The Bolsena caldera that formed between 0.6 and 0.2Ma has a well preserved structural rim, which makes it an ideal site to study the tectonic and volcanic evolution of calderas. However, the main area is covered by a 150m deep lake which makes it rather difficult to investigate the subsurface structure directly. To overcome this problem new high resolution hydro-acoustic surveys using a multichannel reflection seismic system and a sediment echo-sounder system were conducted in September 2012. As space was limited we used a rowing boat towed by a rubber boat to handle a 36m long and 24 channel streamer to receive seismic reflections produced using a Mini GI-Gun (0.25 l).The subsurface structure of Lake Bolsena was imaged up to a sediment depth of ~190m, which is estimated to have filled over a period of 333kyrs. However, massive pyroclastic flow deposits found in the deeper parts of the basin indicate an initial infill of volcanic deposits from two adjacent younger calderas, the Latera (W) and Montefiascone (SE) calderas. Our data suggest that the caldera has a long history of active volcanism, because the lacustrine sediments show post-sedimentary influences of geothermal fluids. We mapped several mound structures at various stratigraphic depths. Two volcanic structures outcrop at the modern lake surface implying recent activity. One of these structures is hardly covered by sediments and has a crater-like feature in its summit. The other structure shows a pockmark-like depression on top. Another observable feature is a partially sediment filled crater located in the western part of the lake which further implies the existence of a magma chamber located beneath the Bolsena caldera. Since the late Pleistocene and Holocene, the sedimentation was mainly hemipelagic evidenced by a sediment drape of up to 10m thick sediment drape on the uppermost sediments. Beneath the drape we found evidence for a distal tephra layer likely related to an explosive eruption from the Campanian Volcanic Province occurring as the Neapolitan Yellow Tuff. Our new geophysical data set is a valuable record with a potential to constrain the sedimentary and volcanic evolution of the Vulsini Volcanic District in areas that have not been assessed previously due to logistical challenges of conducting surveys in water-filled settings.

Multidisciplinary tephrochronological correlation of marker events in the eastern Tyrrhenian Sea between 48 and 105 ka

The basal portion (2.92–5.08m from core top) of the CET1 core located in a bathyal area of the eastern Tyrrhenian Sea is the subject of a multidisciplinary investigation, encompassing tephrostratigraphy, quantitative analyses of planktonic foraminifera and calcareous nannofossil assemblages, and δ18O measurements, supported by a 40Ar/39Ar age determination. Calcareous nannofossil assemblages allowed the attribution of the analyzed sediments to the biozone MMN21a, and the succession spans from more than 48 to ca. 105ka, although there are at least two stratigraphic gaps and minor resedimentation episodes. A paleoclimatic reconstruction obtained via δ18O and planktonic foraminifera data identifies several of the major climatic events that occurred in the investigated time span.A total of 13 visible tephra layers and cryptotephras are recognized and correlated with their volcanic sources (Campanian Volcanic Zone and Pantelleria volcano) and, when possible, with well-known and dated events or with widespread marker tephras.Using a combination of biostratigraphic, oxygen isotope, and tephrostratigraphic correlations, we develop a chronostratigraphy for the main climatic events and tephra layers in the core and pinpoint tephra markers for the climatic events comprised between GS 22 and GI 24 in the eastern Tyrrhenian Sea.

Pb Isotopes Data from the Campanian Volcanic Province: A Model to Generate These Distinctive Pb Isotopic Variations

A broad set of samples from the CVP has been analyzing Pb isotopes. Campanian Volcanic Province (CVP) has been produced by various ranges of mixing between three components: 1) MORB, 2) Hercynian basement and 3) upper crust. Anyhow, the upper crust that has modified the Pb isotopic composition also shows trends towards an Achaean upper crust. This is consistent for all Mediterranean area. This is not in contrast with the past plate tectonic reconstruction. Also the surface sediments (GLOSS) may have been a mixing between the Achaean upper crust and a Hercynian component with an implication worldwide due to the rock cycle processes.

The Montalbano Jonico marine succession: An archive for distal tephra layers at the Early–Middle Pleistocene boundary in southern Italy

The lithological content and mineralogical assemblage of main tephra layers (V1, V2, V3, V4, V5, V7) embedded in the Montalbano Jonico succession have been fully characterized. Major-element analyses were carried out on the juvenile glass fractions and main crystal phases, and trace-element contents were determined on glasses extracted from the thickest layer of the sequence (V5). Single crystal 40Ar/39Ar laser fusions were performed on sanidine from the V4 layer, yielding a weighted mean age of 773.9 ± 1.3 ka. The Vulture volcano is likely the source of two tephra layers, V3 and V4, embedded to the middle part of the Interval B of the sequence, which represent the oldest products of this center ever found. Moreover, the V4 layer was emplaced near the Matuyama–Bruhnes Chron boundary, and thus serves as an important chronostratigraphic marker. Complete chemical characterization of V5 allows us to suggest the Campanian Volcanic Zone as its eruptive source; corroborating the idea that activity there began at ∼720 ka and spanned most of the Middle Pleistocene. Finally, we insert our new framework from the Montalbano Jonico sequence into a reappraised tephra sequence from the Middle Pleistocene to present in southern Italy, which results in a more robust series of tephrostratotypes and improves the reliability of inter-archive correlations.

Occurrence and origin of soils with andic properties in Calabria (southern Italy)

Andic-like soils, along with Andosols, have previously been reported in non-volcanic ecosystems of the coastal and mountainous areas of the Calabria region (southern Italy), but little is known about their properties, soil formation processes and volcanic source areas. Chemical, mineralogical, microscopic, sub-microscopic and magnetic analyses were carried out on 8 soils which were selected from the major Calabrian geological sectors in order to assess relationships between parent material and bedrock. Soil chemical properties revealed an occurrence of andic or vitric properties in the studied soils as a whole, and the optical microscopy enabled to identify volcanic glass, micro-pumices and soil isotropic matrix, clearly indicating volcanic inputs. Three groups of soils, identified on the basis of the degree of andic properties, showed rather homogeneous also in terms of chemical properties, clay mineralogy and land use, as well as with regard to micromorphology and magnetic susceptibility. Part of the intra-group similarities was a consequence of similar distances between sites and volcanic source area, as suggested by the correlations found between ferrihydrite content, andic (i.e. % of ammonium oxalate extractable Al+0.5 Fe and phosphate retention) and magnetic properties vs. distances from several Sicilian districts. The elemental composition obtained by SEM/EDS analyses of soil glass fragments supported these findings and related the origin of most of the studied soils to the high potassium calc-alkaline magmatism of the southernmost Eolian Islands (mainly Lipari and Vulcano), except for soils from the marine terraces of northern Calabria (PRA) and the Aspromonte Massif (DEL), which were both linked, albeit uncertainly, to Campanian volcanism. Soil magnetic properties were significantly (0.79**) correlated to the andic properties, so confirming the high performance of magnetic susceptibility as low cost proxy for the identification of volcanic constituents.

Petrogenesis of trachyte and rhyolite magmas on Ponza Island (Italy) and its relationship to the Campanian magmatism

Magmatism on Ponza island (Italy) has been reviewed, considering both new and literature data, and compared with the Campanian Volcanic District (CVD) rocks. Different origins have been inferred for the two main rock types (trachyte and rhyolite). The trachytes were formed by fractional crystallization (FC) processes coupled with minor upper crustal contamination from magmas similar to the least evolved magma erupted into CVD. The rhyolites formed by partial melting of a lower crust component. The two lithotypes evolved through intra-suite FC, and they are correlated with the volcanic rocks of the CVD by major element, trace element and isotope data, extending the Campanian compositional spectrum. To explain the FC and the melting processes, a tectonic model is developed in which most of the FC for the CVD occurred in the lower-intermediate crust where magma rises from the upper mantle and is stored in a process of magma accumulation and fractionation. These processes have produced enough heat to melt the crust and cause several rhyolite episodes in Ponza Island. A subduction-related setting must be inferred to explain the origin of the Ponza trachytes and rhyolites and the rest of the CVD volcanism.

The possible role of extensional faults in localizing magmatic activity: a crustal model for the Campanian Volcanic Zone (eastern Tyrrhenian Sea, Italy)

Abstract: Three crustal geological sections of the Campanian Volcanic Zone (Italy) were reconstructed by integrating basin architecture and deep well stratigraphies. In addition, mapping of the fault system and of large-volume ignimbrites was carried out. A linked fault system has been identified, which was responsible for asymmetric subsidence contemporaneous with the eruption of ignimbrites. Late Quaternary extension is characterized by a WNW–ESE stretching axis, NNE–SSW normal faults and reactivation of inherited structures. Structural, stratigraphic and palaeogeographical analyses reveal evidence for up to 750 m of subsidence, which has occurred at a mean rate of up to 4.9 mm a −1 over the past 154 ka. These rates suggest that extensional tectonics was responsible for the regional subsidence. A 6 km deep seismic reflector was associated with a magmatic reservoir underlying Campi Flegrei. By matching the structural and stratigraphic architecture with published geophysical and geochemical data a crustal tectonomagmatic model was constructed that displays high-angle faults that root into a low-angle detachment, which in turn roots into a deep sill-like magma reservoir. This model suggests the possible role of extensional faults in localizing magmatic activity, as faults controlled magma rise from deep to shallow reservoirs and to the surface during ignimbrite eruptions. Supplementary material: Seismic reflection profiles and interpretations are available at http://www.geolsoc.org.uk/SUP18451 .

Low VS crustal zones in the Campanian Plain (Southern Italy)

Shear wave velocities of the lithospheric structure to 73 km depth have been defined along three profiles crossing the Campanian Plain (Southern Italy) from the simultaneous non linear inversion of the local and regional dispersion data. The former consist of group velocity dispersion data obtained from some seismic events which occurred at the borders of the Campanian Plain and recorded at Napoli, and the latter of group and phase dispersion data obtained in previous studies. The main features of the representative VS models are a carbonate basement deepening to ∼5 km in the central part of the Plain and a low velocity zone at a depth of ∼15 km, rising to 7 km in the southern part, close to Somma-Vesuvio. The low velocity layer can be correlated with that found at ∼10 km of depth below Campi Flegrei and the Neapolitan area, and at 5 km below the Somma-Vesuvio caldera area. Such regional velocity reduction can be associated to the presence of a zone with less than 5% partial melting that can be interpreted as magmatic reservoir of the Campanian volcanism.

Seismic reflection data processing in active volcanic areas: an application to Campi Flegrei and Somma Vesuvius offshore (Southern Italy)

The Campanian volcanism develops near the sea. Therefore, the geophysical study of the marine environment is a key to a better understanding of the tectonic evolution and the origin of volcanism in the area. An abundance of high quality seismic data in the marine sector, where little direct information is available, is critical to the study of Campanian volcanism. This paper concerns the reprocessing of a seismic reflection dataset acquired in Naples Bay and processed during 1973. Even though the overall data quality was high for that time, of course their acquisition technological limits have been overcome by the new processing. Our reprocessing aimed at: 1) reduction of random noise in the data; 2) removal of unwanted coherent events; 3) reduction of spatial aliasing by means of trace interpolation on Commod Shot Point (CSP) gathering; 4) improvement of resolution of the seismic wavelet with spiking deconvolution algorithms and finally 5) reposition of reflectors in their correct locations in the space-TWT domain by means of dip moveout and post-stack time migration. A comparison between the new and old data shows that the new sections are characterized by a much higher S/N ratio. Diffraction hyperbole has been collapsed. Reverberations, ghosts and multiples have been removed or greatly attenuated, especially between the reflectors of interest, allowing us to follow them with more detail and with greater continuity. Furthermore, data resolution has been boosted by the reprocessing, allowing the interpreter to evaluate reflector position and continuity in greater detail. The reinterpretation phase of such lines, that is already in an advanced stage, will therefore allow us to gain new insights into the structural setting of the bay, with the aim of exploring the connection between tectonics and volcanism.

Mineral control of arsenic content in thermal waters from volcano-hosted hydrothermal systems: Insights from island of Ischia and Phlegrean Fields (Campanian Volcanic Province, Italy)

This paper documents arsenic concentrations in 157 groundwater samples from the island of Ischia and the Phlegrean Fields, two of the most active volcano-hosted hydrothermal systems from the Campanian Volcanic Province (Southern Italy), in an attempt to identify the environmental conditions and mineral-solution reactions governing arsenic aqueous cycling. On Ischia and in the Phlegrean Fields, groundwaters range in composition from NaCl brines, which we interpret as the surface discharge of deep reservoir fluids, to shallow-depth circulating fluids, the latter ranging from acid-sulphate steam-heated to hypothermal, cold, bicarbonate groundwaters. Arsenic concentrations range from 1.6 to 6900 μg·l − 1 and from 2.6 to 3800 μg·l − 1 in the Phlegrean Fields and on Ischia, respectively. They increase with increasing water temperature and chlorine contents, and in the sequence bicarbonate groundwaters < steam-heated groundwaters < NaCl brines. According to thermochemical modeling, we propose that high As concentrations in NaCl brines form after prolonged water–rock interactions at reservoir T, fO 2 and fH 2S conditions, and under the buffering action of an arsenopyrite + pyrite + pyrrhotite rock assemblage. On their ascent toward the surface, NaCl brines become diluted by As-depleted meteoric-derived bicarbonate groundwaters, giving rise to hybrid water types with intermediate to low As contents. Steam-heated groundwaters give their intermediate to high As concentrations to extensive rock leaching promoted by interaction with As-bearing hydrothermal steam.

Campanian volcanism within the Asher-1 borehole

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Evidence of crustal contamination, sediment, and fluid components in the campanian volcanic rocks

The Campanian Volcanic Subprovince is part of the classic western potassic volcanic province of the Italian Peninsula. The Campanian volcanic products show the effects of shallow assimilation and fractional crystallisation, and the contribution of regional crustal sources (e.g., Hercynian basement–Calabrian crust). The Roccamonfina, Campi Flegrei, and Ventotene volcanic rocks are characterised by wide isotopic and geochemical variations. Such variations appear to reflect both AFC processes and chemical heterogeneity in the upper mantle that may be linked to subduction processes. Mixing curves (Th/Ce–, Ba/K– and Eu/Eu*– 143Nd/ 144Nd) linking sediments and mantle end-members account for the variations in the Campanian Subprovince volcanic rocks with a sediment contribution of 2-10%. The upper mantle sources for the low- and high-K rocks at Roccamonfina have been constrained on the basis of a multi-element normalised diagram. The two sources require different amounts of sediment in the mantle wedge (LK∼2% versus HK∼10%) and a fluid component probably from altered ocean crust to explain the fluid mobile elements. Low-K Roccamonfina rocks are geochemically similar to those from Campi Flegrei, Ventotene, and Somma-Vesuvius, suggesting a similar proportion of sediment in their upper mantle source regions.

Pre-eruptive geochemistry of the ignimbrite-forming magmas of the Campanian Volcanic Zone, Southern Italy, determined from silicate melt inclusions

¶The Campanian Ignimbrite rock samples include two compositionally distinct populations of clinopyroxene phenocrysts, and the entrapped MI (melt inclusions) are also different in composition. The cores of the more MgO-enriched phenocrysts carry basaltic trachyandesite MI that contain >6 wt.% MgO, whereas other phenocrysts contain MI with <4 wt.% MgO. The MgO-enriched MI also contain comparatively greater abundances of F, CaO, TiO2, P2O5, SO2, and Sr and show marginally higher ratios of (CaO/Al2O3) than the low-MgO MI. Most of the high-MgO MI also contain comparatively more H2O. The MgO-enriched MI are restricted to diopsidic clinopyroxenes and show minimal compositional variability, demonstrating that they were derived from a common magmatic source or sources. We interpret these MI to represent primary, mafic magma. In contrast, the more evolved, low-MgO melt inclusions, which are restricted to salitic clinopyroxenes, span the compositional range of trachyandesite to trachyte. The low-MgO fractions of Campanian Ignimbrite magma evolved via fractional crystallization with or without mingling or mixing with more primitive, high-MgO magma. Interestingly, the MI from the Giugliano sample also cluster into low-MgO and high-MgO fractions, and the evolutionary trends for major, minor, and trace elements mirror those exhibited by the Campanian Ignimbrite MI, suggesting that both magmas were derived from similar or the same source(s) and that the processes of magma evolution were equivalent for both magmas. The MI also indicate that the Campanian Ignimbrite and Giugliano magmas did not form by evolution of Taurano magma, because the geochemical trends expressing melt evolution of the former and latter magmas are too dissimilar. Most Taurano MI show higher (CaO/Al2O3) and contain less SiO2, (Na2O+K2O), Cl, Li, Rb, Cs, Sr, Nb, Th, and U than the high-MgO and low-MgO Campanian Ignimbrite and Giugliano MI, indicating that the Taurano MI represent magmas which were much more primitive.

Structural setting of the Bay of Naples (Italy) seismic reflection data: implications for Campanian volcanism

This paper focuses on the recent tectonic evolution of the Bay of Naples with the aim of exploring the connection between local tectonics and volcanism. We reprocessed the seismic reflection dataset acquired in the area in the late 1973. The new processing was highly successful in obtaining a decisive strong reduction of random noise, removal of coherent noise and reduction of spatial aliasing. Classical interpretative schemes and complex attributes of seismic traces were used to reconstruct fault kinematics and reflector patterns. The results show that the faults affecting the Bay of Naples exhibit prevailing NE structural strikes, with the exception of the Pozzuoli Caldera where NW patterns are also common. Many faults are subvertical and show seismic evidence of volcanic activity along them. A main alignment of conjugate NE–SW faults, named here as “Magnaghi–Sebeto line”, intersects several submarine volcanic banks and separates the bay into two sectors, characterized by important geological, geophysical and petrochemical differences. The structural configuration of the bay may reflect the occurrence of either oblique extension or a transfer zone of the NW–SE fault system, along which, in the Campanian–Lucanian Apennine chain, great vertical displacements occur.