Vulture Volcano Research Articles

CO2‐Rich Xenoliths at Mt. Vulture Volcano (Southern Italy): New Constraints on the Volcano Plumbing System

ABSTRACTThis study provides new mineral chemistry data together with micro‐thermometric measurements on fluid inclusions hosted in ultramafic xenoliths (lherzolite, wehrlite, and dunite) brought to the surface by the last Mt. Vulture volcano activity (140 ka; southern Italy), and fed by melilitite‐carbonatite magmas. Petrographic evidence and mineralogical compositions of Mt. Vulture xenoliths are consistent with an origin in the upper mantle. Fluid inclusions in rock‐forming minerals of lherzolite and wehrlite xenoliths are CO2‐dominated. The equilibrium temperature calculated by geothermometric estimates ranges from 1039 C (±36°C) to 1142°C (±15°C), and entrapment pressures of fluid inclusions with post‐trapping re‐equilibration correspond to the local crust–mantle boundary (32 km depth), and to a shallow reservoir located at 12–14 km depth. These results contribute to constrain the origin of these xenoliths and the depth of storage of magmas erupted from Mt. Vulture, where carbonatite‐like metasomatism and mantle‐derived CO2 degassing occur.

Multidisciplinary study of the Lower Palaeolithic site of Cimitero di Atella (Basilicata), Italy

The Lower Palaeolithic site of Cimitero di Atella is located in the Basilicata region (Southern Italy), about 10 km south of the extinct Monte Vulture volcano. The site was discovered in the early 1990s and was continuously excavated for nearly twenty years under the supervision of Professor E. Borzatti von Löwenstern (University of Florence). This open-air site contained a 5-m-thick fluvio-lacustrine sequence characterized by the occurrence of two main archaeological units with lithic industries and faunal remains. Based on the composition of the lithic assemblages, and in particular the presence of handaxes in the Lower unit, Borzatti von Löwenstern (et al., 1997) attributed the site to the Early Acheulean. Cimitero di Atella was interpreted as the result of various lake shore occupations linked to the exploitation of large mammals (Palaeoloxodon antiquus and Bison sp.) and the opportunistic use of raw materials to produce simple small and large lithic tools (Borzatti von Löwenstern et al., 1997).The purpose of this paper is to present the last five years of research at the site. Geochronological, palaeontological and palynological investigations have been conducted to shed light on the environmental and chronological context of the site and the associated human occupations levels. This essential step enables us to evaluate the nature and potential of archaeological data in order to place the results in a broader framework. The accurate study of the context and of the archaeological material of Cimitero di Atella enable us to rethink the crucial question of the emergence of the bifacial phenomenon in Europe.

First measurements of the Fe oxidation state of spinel inclusions in olivine single crystals from Vulture (Italy) with the in situ synchrotron micro-Mössbauer technique

Abstract. The redox state of the Earth's upper mantle (i.e., oxygen fugacity, fO2) is a key variable that influences numerous processes occurring at depth like the mobility of volatile species, partial melting, and metasomatism. It is linked to the oxidation state of peridotite rocks, which is normally determined through the available oxythermobarometers after measuring the chemical composition of equilibrated rock-forming minerals and the Fe3+ in redox-sensitive minerals like spinel or garnet. To date, accurate measurements of Fe3+ / ∑Fe in peridotites have been limited to those peridotites (e.g., harzburgites and lherzolites) for which an oxythermobarometer exists and where spinel (or garnet) crystals can be easily separated and measured by conventional 57Fe Mössbauer spectroscopy. Wehrlitic rocks have been generally formed by the interaction of a lherzolite with carbonatitic melts and, therefore, have recorded the passage of (metasomatic) fluids at mantle conditions. However, no oxythermobarometer exists to determine their equilibrium fO2. The aim of this study was to retrieve the fO2 of the mantle beneath Mt. Vulture volcano (Italy) through the study of a wehrlitic lapillus emitted during the last eruption (∼ 140 kyr ago) that contain olivines with multiple tiny spinel inclusions with sizes < 40 µm. To our knowledge, the Fe oxidation state of these inclusions has been never determined with the Mössbauer technique due to their small sizes. Here, we present measurements of the Fe3+ / ∑Fe using in situ synchrotron Mössbauer spectroscopy coupled with chemical and spectroscopic analysis of both host olivine and spinel inclusions. The results show Fe3+ / ∑Fe ratios of 0.03–0.05 for olivine and 0.40–0.45 for the included spinels, the latter of which appear higher than those reported in literature for mantle spinel harzburgites and lherzolites. Given the evidence of the mantle origin of the trapped spinels, we propose that the high fO2 (between 0.81 and 1.00 log above the fayalite–magnetite–quartz buffer; FMQ) likely results from the interaction between the pristine spinel lherzolite and a CO2-rich metasomatic agent prior to the spinel entrapment in olivines at mantle depths.

New volcanological and palethnological data from Avetrana site (Southern Italy)

This work describes the Mousterian lithic artifacts found in the Avetrana karst filling (Apulia), among the oldest of southern Italy. A volcanoclastic layer found at the base of Bed 8, in the highest part of the stratigraphic succession, is also described. The compositional characteristics of the glasses of this volcanoclastic layer indicate a possible area of origin in the Mount Vulture volcano, and allow us to suggest that it is an aeolian fallout that occurred during or immediately after a late eruption of the Mount Vulture, probably within the 132 ± 10 ka time span. The chronological result relating to the volcanoclastic sediments would place the underlying beds in the last Interglacial, MIS 5e, and the overlying Bed 8 at the onset of last Glacial period, MIS 5d. Moreover, it is in agreement with the paleoclimatic considerations based on the ecological and biogeographical features of mammal assemblages and it has a very important significance also for the biochronology of the Pleistocene. In fact, it allows us to confirm that some taxa found in the Avetrana succession, such as Crocidura gr. suaveolens, Arvicola italicus, the evolved form of Microtus (Terricola) gr. savii, and the modern form of Dama dama, occur for first time in Italy at the beginning of Late Pleistocene.

New Inferences on Magma Dynamics in Melilitite‐Carbonatite Volcanoes: The Case Study of Mt. Vulture (Southern Italy)

AbstractThis study provides the first micro‐thermometric data of fluid inclusions (FIs) in mafic loose (disaggregated) xenocrysts and ultramafic xenoliths in explosive products of the melilitite‐carbonatite Mt. Vulture volcano (southern Italy). Pure CO2 late stage FIs hosted in rock‐forming minerals of wehrlite xenoliths and clinopyroxene xenocrysts were trapped at the local crust‐mantle boundary (32 km). In contrast, trapping pressures within the loose olivine xenocrysts are from 3.2 to 4.5 kbar (8–13 km). Considering the ongoing degassing of mantle‐derived CO2 rich gases, together with seismic evidences of the presence of low amount of melts at depth, and the tectonic control of the past volcanic activity, our study opens new perspective about the hazardous nature of the “quiescent” melilitite‐carbonatite volcanoes.

Petrological footprints of the millstones of Megara Hyblaea (Sicily Island, Italy) highlight the human interactions with Mediterranean volcanoes

A petrographic and geochemical study of several volcanic millstones, representative of 119 artifacts found in the ancient Greek colony of Megara Hyblaea (Sicily Island) and recording the grinding device evolution from the Archaic to the Hellenistic period, unravelled the volcanoes involved as quarrying and production areas. This was possible also through the comparison with available petrographic and geochemical literature data of ancient volcanic millstones found in the whole Mediterranean. Saddle querns, hopper-rubber, rotary Morgantina- and Delian-type millstones of Megara Hyblaea consist of lithotypes belonging to five magmatic series: Tholeiitic, Na-Alkaline, Tholeiitic Transitional, Calcalkaline and High-K Alkaline. A provenance from the Eastern Sicily, i.e. mugearites from Etna and basalts and basaltic andesites from the Hyblaean Mountains were recognized for all the four investigated grinding devices. By contrast, a sea-trade is involved for several saddle querns made of calcalkaline basaltic andesites and andesites lavas (Aegean Islands) and two Morgantina-type millstones consisting of a calcalkaline rhyodacite ignimbrite from the quarrying site of Mulargia (Sardinia). A wide millstone trade, both local (Eastern Sicily) or maritime (Central-Eastern Mediterranean) was thus constrained through six centuries, from the foundation of the Greek colony up to the destruction of the settlement at the end of third century BCE. Finally, Vulture Volcano (southern Italian peninsula) is the most probable candidate for the only leucite- and haüyne-bearing phonolite of the High-K Alkaline Series.

The Na-rich and the K-rich Basic Melts of Vulture Volcano, Italy and Their Sources: Evidence from the Melt Inclusion Study in Clinopyroxene from the Haüyne Foidite

The Na-rich and the K-rich Basic Melts of Vulture Volcano, Italy and Their Sources: Evidence from the Melt Inclusion Study in Clinopyroxene from the Haüyne Foidite

Structural and Mineralogical Characterization of a Fossil Hydrothermal System Located at the Outermost Front of the Southern Apennines Fold-and-Thrust Belt

Aiming at investigating the hydrothermal circulation along the eastern flank of the Vulture volcano, along the outermost edge of the southern Apennine fold-and-thrust belt (ftb), we studied the fossil hydrothermal alteration that mineralized a transtensional fault that crosscuts volcanoclastic rocks in the Rapolla area. On the basis of structural, mineralogical, and fluid inclusion data, three main stages of activity of the hydrothermal system are documented. Stage 1 was produced by the circulation of fluids having low-pH conditions (pH ≈ 3-4) and relatively high-SO42- activity, as testified by the hydrothermal alteration mainly carried out by the alunite group minerals (particularly jarosite), which is typical of an advanced argillic alteration facies. Hydrothermal fluids were characterized by a high temperature of about 200°-210°C. These hot fluids altered and mineralized the matrices of pyroclastic rocks and sealed both burial-related and fault-related fracture networks. Later hydrothermal circulation (Stage 2) was recorded by opal A-rich veins present both within and outside the fault zone. The fluids responsible of opal A precipitation were characterized by lower temperature conditions, probably lower than 100°C. Current goethite mineralization takes place along the main slip surfaces of the study high-angle fault zone due to low temperature (<30°C) underground water circulation. This study highlights that a high-temperature hydrothermal system developed in the past within the transtensional fault zone of the Rapolla area when a high thermal anomaly was present. If we take into account that this area is still affected by a heat flux positive anomaly (90 mW/m2), we may infer that it has the potentiality to be considered an interesting site for future exploration devoted to the finding of medium-enthalpy geothermal resources at depth.

Constraints on the dispersal of Mt. Vulture pyroclastic products: implications to mid-Pleistocene climate conditions in the foredeep domain of southern Italy

Mt. Vulture volcano is located on the thrust front of the southern Apennines. Its mid-Pleistocene products are spread southeastward in the adjacent Bradano foredeep basin. The stratigraphic record of the volcano within the Quaternary sedimentary successions helps to better understand the paleo-environmental setting of the foredeep. Volcaniclastic deposits cropping out close to the edifice, tephra levels and associated paleosols recovered from the southernmost sector of the foredeep are of key importance in reconstructing the Pleistocene morpho-climatic conditions in which they formed, using a multiproxy approach. Geomorphological observations and stratigraphic sampling come from the Venosa lacustrine-alluvial basin and from the areas of Irsina and Pomarico villages, where pumice fall levels and related paleosols are present at the top of the lower-middle Pleistocene sedimentary succession. Geochemical and mineralogical analyses of paleosols and pyroclastic rocks have indicated that the Pomarico pumices, reworked and deposited in an alluvial environment, could be likely correlated to the Fara d'Olivo ignimbrites (39Ar/40Ar age < 687 ± 8 ka) present in the basal unit of the Mt. Vulture volcanic succession. The presence of a 7A halloysite phase in the paleosols from two different sites suggests that the Pleistocene weathering likely developed in a dry-humid climate with an alternation of rainy seasons and dry periods.

State of the art: Italian carbonatites and their potential for critical-metal deposits

This paper is an updated overview, including many new data, of what is known about Italian alkaline–carbonatite complexes, plus a new description of a carbothermal residua-related district, and its potential for mineral deposits. The Italian carbonatite occurrences can be divided into two belts. The first is a 350km long and 75km wide belt along the Apennines mountain range mainly with primary extrusive carbonatites generally from monogenic volcanoes and from the Vulture volcanic complex; the second belt is 60km long and 20km wide in the Northern Latium region in which carbothermal residua carbonatites and fluorite mineralisation deposited by high-temperature fluids rich in CO2, SO2 and fluorine are occurring in caldera volcanoes. Several of the raw materials, such as Light Rare Earth Elements, vanadium, niobium, zirconium, fluorite and phosphate are identified as critical as well as other commodities, occur in Italian carbonatites and alkaline rocks. At the Pianciano quarry (Bracciano) fluorite-rich ore (fluor-ore=fluorite in a mineralised gangue) is actually exploited as flux for cement, but Rare Earth Elements (+V) could be a notable by-product (300,000metric tonnes, equivalent to 4.2% of European resources). Pyrochlore, monazite, apatite, and britholite bearing subvolcanic rocks in ejecta from the Vulture volcano are of a near-economic grade, but their geological constraints are not known. A conceptual framework of combined geological and geochemical data improves the general understanding of this regional magmatic system, aimed at laying the foundations of a future geological model disclosing unrecognised potential exploration targets. However, this paper is not intended for direct use by the exploration industry; rather it is principally aimed at mineralogists and petrologists who could develop strategies for the identification of unexposed or unrecognised deposits.

Mineralogical and textural characterization of the Alimini beach sands: implication on their provenance and transport processes

This work shows the granulometric, mineralogical and micromorphoscopic data of the Alimini (Lecce, Apulia) beach, an important touristic site with a strong erosive rate. Our study demonstrates that the sediments forming the sands are rarely related to the carbonatic rocks outcropping in the area. Rather, they are mainly represented by heavy minerals and quartz of volcanic and metamorphic origin. The presence of peculiar mineral phases as the melanitic garnet points to a provenance from the Vulture volcano. However, the occurrence of quartz, microcline and piralspitic garnets points to a simultaneous feeding from the southern Appenninic units. Sediments are probably eroded and transported by the Ofanto river. The high roundness of the grains witnesses the long transport along the coast and, probably, also the continuous recycle from the dune to the beach and vice versa.

Depth influence on the distribution of chemical elements and saturation index of mineral phases in twins maar lakes: The case of the Monticchio lakes (southern Italy)

In this paper we provide a systematic geochemical study of the Monticchio maar lakes, on the Mt. Vulture volcano, southern Italy, to understand the processes affecting the distribution of chemical elements. A high-resolution conductivity–temperature–depth profile was obtained, and water samples were collected at various depths for analyses of major and trace elements. Although the two lakes are separated by less than 200m, they exhibit different behaviour. The Ca–Na–HCO3 composition of “Lago Grande” water suggests that low-temperature fluids are leached from the host volcanic rocks. Na–Ca–HCO3 in near-surface “Lago Piccolo” water is derived from the dissolution of local volcanic rocks, while the deepest water samples are bicarbonate alkaline-earth in composition and generally show an enrichment in solutes with respect to the epilimnion layer (except for SO42− content). The hypolimnion water is principally governed by both the input of saline groundwater from the lake bottom and authigenic processes within bottom sediments. In addition, the occurrence of anoxic conditions and microbial activity is responsible for the transformation of sulphates to hydrogen sulphide, and for the precipitation of Fe sulphide phases. Both processes cause a change in the chemical composition of saline groundwater as it moves upwards. Overall, the water chemistry of the Monticchio lakes is principally affected by: i) the input of CO2-rich volcanic gas; ii) evaporative processes that deplete near-surface water in some elements; and iii) the occurrence of chemical, physical and biological conditions causing the transformation of molecular complexes and consequently promoting mineral precipitation.

Mantle CO2 degassing at Mt. Vulture volcano (Italy): Relationship between CO2 outgassing of volcanoes and the time of their last eruption

Mantle volatiles are mainly lost from the Earth to the atmosphere through subaerial and submarine volcanism. Recent studies have shown that degassing of mantle volatiles also occurs from inactive volcanic areas and in tectonically active areas. A new challenge in Earth science is to quantify the mantle-derived flux of volatiles (e.g., CO2) which is important for understanding such diverse issues as the evolution of the atmosphere, the relationships between magma degassing and volcanic activity, gas pressure and seismogenic processes, and the hazards posed by volcanic lakes. Here we present a detailed study of mantle-derived CO2 budget from Mt. Vulture volcano in the Apennines, Italy, whose latest eruption occurred 141±11 kyr ago.The relationship between δ13CCO2 and total dissolved carbon at Mt. Vulture volcano indicates that the emitted CO2 is a mixture of a biogenic end-member with an average δ13CCO2 of about −17‰ and a mantle-derived CO2 end-member with δ13CCO2 values from −3‰ to +2‰. These values of mantle-derived δ13CCO2 are in the range of those for gas emitted from active volcanoes in the Mediterranean. We calculated the contribution of individual components (CO2 in groundwater, in lakes and from main pools) to the total CO2 budget in the area. We used new measurements of water flow, combined with literature data, to calculate the CO2 flux associated with groundwater, and measured the gas flux from the main pools on the volcanic edifice. Finally, we calculated the CO2 flow in the lakes based on the gradient concentration and eddy diffusivity. The total mantle-derived CO2 budget in the area is 4.85×108 molyr−1, which is more than double previous estimates. This is higher than those observed in younger volcanic systems elsewhere, thereby supporting the existence of actively degassing mantle melts below Mt. Vulture volcano.A structural map highlights the tectonic control on CO2 flow across the Mt. Vulture volcanic edifice. Indeed, the tectonic discontinuities that controlled the magma upwelling during the most recent volcanic activity are still the main active degassing structures.The new estimate of CO2 budget in the Mt. Vulture area, together with literature data on CO2 budget from historically active and inactive Italian volcanoes, suggests a power-law functional relationship between the age of the most recent volcanic eruption and both total discharged CO2 (R2=0.73) and volcano size-normalized CO2 flux (R2=0.66). This relation is also valid by using data from worldwide volcanoes highlighting that deep degassing can occur over very long time too. In turn, the highlighted relation provides also an important tool to better evaluate the state of activity of a volcano, whose last activity occurred far in time.Finally, our study highlights that in the southern Apennines, an active degassing of mantle-derived volatiles (i.e., He, CO2) occurs indiscriminately from west to east. This is in contrast to the central–northern Apennine, which is characterized by a crustal radiogenic volatile contribution, which increases eastward, coupled to a decrease in deep CO2 flux. This difference between the two regions is probably due to lithospheric tears which control the upwelling of mantle melts, their degassing and the transport of volatiles through the crust.

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.

Mantle-derived fluids discharged at the Bradanic foredeep/Apulian foreland boundary: The Maschito geothermal gas emissions (southern Italy)

The mephitis of Maschito, known since historical times as Lago Fetente (Smelly Lake) -although the lake is now dry-, is located 20 km from the Mt. Vulture volcanic edifice (Southern Italy). It is placed along the same regional tectonic discontinuity where some maars are located, close to the boundary between the foredeep and the Apulian foreland. About 300 m2 of surface is lacking in flora, while dead animals are frequently found all around it. The smelly exhalations are mainly composed of CO2 (∼98%), and, in lesser amounts, of H2S, N2, CH4 and other hydrocarbons. He, Ne and Ar occur in trace amounts. The CO2 isotopic composition is in the range of that of the main active Italian volcanic gases. The helium isotopic ratio (4.7 Ra) fits with the values measured in Mt. Vulture volcano and particularly with the olivine and pyroxene fluid inclusions of mantle xenoliths ejected during its last volcanic activity (140,000 years). The 40Ar/36Ar isotopic ratio of ∼320 supports some minor non-atmospheric contributions. The C/3He ratio (2.9 × 109) is in the typical range of magma released fluids, while δC(CH4)13 and δD(CH4) values fall in the field of thermogenic methane.The amount of CO2 released is about 3200 tons/year. The flux of mantle-derived helium (>7 × 1010 atoms m−2 s−1) is at least three orders of magnitude higher than that of a stable continental crust. This study strongly supports the possibility that Maschito manifestations are fed by a geothermal system, which is powered by a degassing melt, bearing in mind that the Maschito gas emissions fall along the same fault system of the Monticchio maars, which formed during Mt. Vulture volcano's last activity.

Geochemical insight into differences in the physical structures and dynamics of two adjacent maar lakes at Mt. Vulture volcano (southern Italy)

AbstractWe report on the first geochemical investigation of the Monticchio maar lakes (Mt. Vulture volcano, southern Italy) covering an annual cycle that aimed at understanding the characteristic features of the physical structures and dynamics of the two lakes. We provide the first detailed description of the lakes based on high‐resolution conductivity‐temperature‐depth (CTD) profiles, chemical and isotopic (H and O) compositions of the water, and the amounts of dissolved gases (e.g., He, Ar, CH4, and CO2). The combined data set reveals that the two lakes, which are separated by less than 200 m, exhibit different dynamics: one is a meromictic lake, where the waters are rich in biogenic and mantle‐derived gases, while the other is a monomictic lake, which exhibits complete turnover of the water in winter and the release of dissolved gases. Our data strongly suggest that the differences in the dynamics of the two lakes are due to different density profiles affected by dissolved solutes, mainly Fe, which is strongly enriched in the deep water of the meromictic lake. A conceptual model of water balance was constructed based on the correlation between the chemical composition of the water and the hydrogen isotopic signature. Gas‐rich groundwaters that feed both of the lakes and evaporation processes subsequently modify the water chemistry of the lakes. Our data highlight that no further potential hazardous accumulation of lethal gases is expected at the Monticchio lakes. Nevertheless, geochemical monitoring is needed to prevent the possibility of vigorous gas releases that have previously occurred in historical time.

Active degassing of mantle-derived fluid: A geochemical study along the Vulture line, southern Apennines (Italy)

We report the results of a geochemical study of gas emissions along a NE–SW transect in southern Italy in order to test the hypothesis that the region around Monte Vulture is affected by degassing of mantle-derived fluids through a lithospheric discontinuity. We also investigated lavas from the Monte Vulture volcano displaying 3He/4He (up to ~6.0 Ra) and Sr isotopes that are consistent with an origin in mantle that has had minimal pollution from subducted Adriatic slab. Similar 3He/4He in fluids from around Mt. Vulture indicate that the deep volcanic system is still degassing. Mantle-derived He occurs in fluids along the length of the Vulture line, reinforcing the hypothesis that it is a deep tectonic discontinuity along which mantle fluids and/or melts advect to the surface. The CO2/3He ratios are highly variable (2.7×108–2.15×1011) in response to processes such as gas dissolution into aquifers, addition of crustal gases and degassing fractionation.

Tectonic and eustatic controls on Pliocene accommodation space along the front of the southern Apennine thrust-belt (Basilicata, southern Italy)

The stratigraphical organization of the Pliocene thrust-top deposits cropping out at the front of the Southern Apennine thrust-belt has been debated for a long time taking a great importance in the context of the geodynamics of the Central Mediterranean area. During this time, spreading episodes in the Apennine backarc zone alternate with important phases of overthrusting in the thrust-belt. As a consequence, the Pliocene succession appears to be arranged in a series of stacked units, recording the poliphase tectonic history that leads to the building of the front of the southern Apennine thrust-belt. Although there is not yet an accordance on the nature and position of the main unconformities bounding the thrust-top units, all authors agree that the creation of new accommodation space is mainly ruled by contractional tectonics consequent to the eastward nappe propagation according to the Apennine vergence polarity. A detailed geological survey, carried out along a large portion of southern Apennine thrust-belt front, running south of the Vulture volcano, allowed the collecting of new data concerning the basinal-formation mechanisms acting during the sedimentation of Pliocene deposits. From this analysis, it is clear that even if contractional tectonics is the predominant factor controlling the creation or destruction of accommodation space, other mechanisms, as well as wedge uplift-related extensional tectonics and eustasy, could have also played a significant role in the basin accommodation. In order the considered sector of southern Apennines can provide an useful example about the complex phenomena occurring at mountain belt front where the accommodation space results from a concomitance of eustatic and tectonic factors mainly linked to the accretionary wedge activity.

Groundwaters of Mt. Vulture volcano, southern Italy: Chemistry and sulfur isotope composition of dissolved sulfate

We report the chemical composition of groundwaters—including the first data on the sulfur isotopic composition of dissolved sulfate—from the volcanic aquifers of Mt. Vulture, one of the most important hydrological basins of southern Italy. A total of 27 water samples taken at different altitudes among drilled wells and springs were collected. The majority of groundwaters have a bicarbonate alkaline and bicarbonate alkaline-earth composition. High-salinity waters are sulfatebicarbonate alkaline in composition. The water-rock interaction process is mainly affected from uprising of CO2-rich gases which cause an increase of the water acidity promoting basalt weathering with an enrichment in certain chemical species (i.e., Na+, Ca2+, SO4 2–) and a high total carbon content. The δ34S values of dissolved sulfate ranging from +4‰ to +8.6‰ can be explained by leaching of volcanites. Higher δ34S values (from 9.6‰ to 10.4‰) detected in a few water springs can be ascribed either to the interaction with the pyroclastic layer rich in feldspathoids, such as hauyna, that have sulfur isotopic compositions up to +10.6‰ or animal manure contamination inducing localized bacterial sulfate reduction with an increase in the δ34S of sulfate. Taking into account that Upper Triassic evaporite deposits have higher δ34S values (from +13.5‰ to +17.4‰,) than those measured in all water samples the dissolution of these deposits could be excluded.

Silicate-carbonate-salt liquid immiscibility and origin of the sodalite-haüyne rocks: study of melt inclusions in olivine foidite from Vulture volcano, S. Italy

Abstract Melt inclusions in clinopyroxenes of olivine foidite bombs from Serra di Constantinopoli pyroclastic flows of the Vulture volcano (Southern Italy) were studied in detail. The rocks contain abundant zoned phenocrysts and xenocrysts of clinopyroxene, scarce grains of olivine, leucite, haüyne, glass with microlites of plagioclase and K-feldspar. The composition of clinopyroxene in xenocrysts (Cpx I), cores (Cpx II), and in rims (Cpx III) of phenocrysts differs in the content of Mg, Fe, Ti, and Al. All clinopyroxenes contain two types of primary inclusion-pure silicate and of silicate-carbonate-salt composition. This fact suggests that the phenomena of silicate-carbonate immiscibility took place prior to crystallization of clinopyroxene. Homogenization of pure silicate inclusions proceeded at 1 225 – 1 190°C. The composition of conserved melts corresponded to that of olivine foidite in Cpx I, to tephrite-phonolite in Cpx II, and phonolite-nepheline trachyte in Cpx III. The amount of water in them was no more than 0.9 wt.%. Silicate-carbonate inclusions decrepitated on heating. Salt globules contained salts of alkali-sulphate, alkali-carbonate, and Ca-carbonate composition somewhat enriched in Ba and Sr. This composition is typical of carbonatite melts when decomposed into immiscible fractions. The formation of sodalite-haüyne rocks from Vulture is related to the presence of carbonate-salt melts in magma chamber. The melts conserved in clinopyroxenes were enriched in incompatible elements, especially in Cpx III. High ratios of La, Nb, and Ta in melts on crystallization of Cpx I and Cpx II suggest the influence of a carbonatite melt as carbonatites have extremely high La/Nb and Nb/Ta and this is confirmed by the appearance of carbonatite melts in magma chamber. Some anomalies in the concentrations and relatives values of Eu and especially Ga seems typical of Italian carbonatite related melts. The mantle source for initial melts was, most likely, rather uniform, undepleted and was characterized by a low degree of melting and probable presence of garnet in restite.