Maurizio Barbieri

Petrology and geochemistry of volcanic rocks from the island of Panarea: implications for mantle evolution beneath the Aeolian island arc (southern Tyrrhenian sea)

Abstract Major, trace element and radiogenic isotope (Sr, Nd, Pb) data are reported for a suite of rocks from the Panarea volcano, a large structure that is largely hidden below sea level and outcrops only as a group of small islands between Lipari–Vulcano and Stromboli in the eastern Aeolian arc. The exposed rocks mostly consist of high-potassium calc-alkaline (HKCA) andesites, dacites and some rhyolites; shoshonitic basalts have been collected from submarine centres; mafic calc-alkaline (CA) rocks occur as thin layers of late-erupted strombolian scoriae. Major and trace element data are scattered, but define generally linear trends on inter-element diagrams; Sr-isotope ratios do not display significant increase with evolution, although rough positive trends of 87Sr/86Sr versus SiO2 and Rb/Sr can be recognised within some units. The mafic rocks display varying enrichment in potassium, from CA to shoshonitic compositions, and are characterised by variable abundances of incompatible trace elements, which increase with potassium. There is an increase of 87Sr/86Sr ratios and a decrease of 143Nd/144Nd and 206Pb/204Pb ratios from CA to HKCA and shoshonitic mafic rocks. The scattered and incomplete nature of the outcrops make it difficult to constrain magmatic evolution at Panarea; geochemical and isotopic data suggest that AFC and mixing were important evolutionary processes. However, geochemical modelling does not support the possibility that the first-order compositional variations observed in the mafic rocks are the result of these processes, and suggests a genesis in a heterogeneous mantle source. Recent studies have highlighted strong differences in terms of incompatible trace element ratios and isotopic signatures, between the western-central and the eastern Aeolian arc. Rocks from the western islands (Alicudi, Filicudi, Salina, Vulcano) have typical magmatic arc geochemical signatures and relatively unradiogenic Sr-isotope compositions. By contrast, the eastern island of Stromboli has a more radiogenic Sr-isotope signature, and shows trace element abundances and ratios that are intermediate between arc and intraplate compositions. Panarea mafic rocks have geochemical and isotopic signatures that are intermediate between those observed in the two sectors of the arc. The late-erupted CA scoriae of Panarea have trace element and isotopic compositions similar to those of the mafic rocks from the western islands of Filicudi and Alicudi, whereas the HKCA and shoshonitic mafic rocks have isotopic and trace element signatures that are closer to those of Stromboli. This reflects the particular position of Panarea, which is sited midway between the western-central arc and Stromboli. According to some recent views, subduction of the Ionian sea plate is actively occurring beneath the eastern Aeolian arc, with rollback of the subduction zone toward the southeast. The Tindari–Letoianni–Malta Escarpment fault zone is considered to be the boundary between the active subducting plate in the east and the African plate and western Aeolian arc in the west. It is suggested that the rollback of the Ionian plate generated inflow of mantle material from below the western arc into the mantle wedge above the subducting Ionian slab. This situation generated a hybrid mantle beneath Panarea, which resulted in a mixture of western-type and resident eastern-arc mantle materials; the latter had a composition akin to the source of Stromboli magmas. Early HKCA and shoshonitic magmatism tapped such a hybrid source, whereas the younger CA activity has been derived from melting of unmodified western-type mantle material. The late eruption of CA rocks with a composition similar to western arc can be explained by assuming that a continuing inflow process had increased the amount of western-type mantle with time, thus favouring the late appearance of CA magmas. This hypothesis accounts for the overall decrease of potassium with time, which is the opposite of the trend observed in other Aeolian islands.

Cadmium-inducible expression of the ABC-type transporter AtABCC3 increases phytochelatin-mediated cadmium tolerance in Arabidopsis

Highlight AtABCC3 detoxifies cadmium by transporting phytochelatin–cadmium complexes into the vacuoles, and it can functionally complement abcc1 abcc2 mutants.

The new chronology of the Ceprano calvarium (Italy)

IntroductionThe fossil human calvarium known as Ceprano (Latium, Italy) iscommonly dated to 800e900 ka, on the basis of geological andstratigraphical inferences (Ascenzi et al., 1996, 2000). This chro-nology appeared somehow consistent with the “archaic”morphology of the calvarium and its peculiar combination offeatures, which gave rise to a controversial taxonomic identity(Ascenzietal.,1996,2000;Clarke,2000;Manzietal.,2001;Mallegniet al., 2003; Bruner and Manzi, 2005, 2007). A re-evaluation of thislate Early Pleistocene chronology has been advanced by Muttoniet al. (2009) on the basis of paleomagnetic data. This hypothesis istested here, based on the combined evaluation of the multidisci-plinary evidence collected during recent systematic excavations.The specimen was discovered on 13 March 1994 within a claylevel partly destroyed by bulldozers working for a new road ina locality known as Campogrande (Fig. 1), about 3 km SW ofCeprano and 100 km SE of Rome, in Central Italy (for review andreferences see Manzi, 2004). The sediment containing the cranialfragments yielded more than 50 fragments. However, the craniumremainedincompletebecauseneitherportionsof thefacenorteethwere retrieved.The geological history of the Campogrande area was initiallyreferred to two main stratigraphic complexes (Ascenzi et al., 1996,2000; Ascenzi and Segre, 1997a,b): 1) upper fluvio-colluvialdeposits, with variable occurrence of volcanoclastic products (lateEarly to Middle Pleistocene); 2) lower lacustrine deposits, withoutvolcanoclastic products (roughly predating 1.0 Ma). The layercontaining the human calvarium was considered to belong to thelower portion of the upper stratigraphic complex. Its chronologywas inferred as more ancient than the Acheulean site of FontanaRanuccio, near Anagni (458 5.7 ka; Segre and Ascenzi, 1984),possiblyolderthan700ka,adatecorrespondingtothebeginningofthe volcanic activity in the region (Fornaseri, 1985).Given the presence in the Ceprano basin of various LowerPaleolithic assemblages, the archaic features of the calvarium andits hypothetical chronological position were considered in associ-ation with Mode 1, or Oldowan, techno-complexes (Biddittu,1984;Ascenzietal.,1996,2000).Mode1Paleolithicintheareacomefromvarious localities, including Arce, Castro de’ Volsci, Fontana Liri(Biddittu, 1972, 1974), as well as from the Campogrande area itself(see SOM-1), whose assemblages are characterized by flint orlimestone pebble-tools (mostly choppers, chopping-tools andpercussion tools), by debitage with hammerstone flakes, and byrelatively frequent cores, with a low degree of exploitation, mostoften unifacial, and high frequencyof cortical striking platforms. Asfor Mode 2 or Acheulean assemblages, new recent data (excava-tions 2001e2006; see below) have made it possible to bettercharacterize the material from Campogrande. These materials arenot numerically rich, but they yield evidence of each production

An enriched mantle source for Italy’s melilitite-carbonatite association as inferred by its Nd-Sr isotope signature

Abstract New Sr-Nd isotope data were obtained from Late Pleistocene carbonatite-kamafugite associations from the Umbria-Latium Ultra-Alkaline District of Italy (ULUD) with the aim of constraining their origin and possible mantle source(s). This is relevant to the origin and evolution of ultrapotassic (K/Na ≫ 2) and associated rocks generally, notably the occurrences from Ugandan kamafugites,Western Australian lamproites and South African orangeites. The selected ULUD samples yielded 87Sr/86Sr and 143Nd/144Nd ranging from 0.7100 to 0.7112 and from 0.5119 to 0.5121 respectively, similar to cratonic potassic volcanic rocks with higher Rb/Sr and lower Sm/Nd ratios than Bulk Earth. Silicate and carbonate fractions separated from melilitite are in isotopic equilibrium, supporting the view that they are cogenetic. The ULUD carbonatites yielded the highest radiogenic Sr so far reported for carbonatites. In contrast, sedimentary limestones from ULUD basement formations are lower in radiogenic Sr, i.e. 87Sr/86Sr = 0.70745−0.70735. The variation trend of ULUD isotopic compositions is similar to that reported for Ugandan kamafugites and Western Australian lamproites and overlaps the values for South African orangeites in the ƐSr-ƐNd diagram. A poor correlation between Sr/Nd and 87Sr/86Sr ratios in ULUD rocks is inconsistent with a mantle source generated by subduction-driven processes, while the negligible Sr and LREE in sedimentary limestones from the ULUD region fail to account for a hypothetical limestone assimilation process. The Nd model ages of 1.5−1.9 Ga have been inferred for a possible metasomatic event, allowing further radiogenic evolution of the source, a process which may have occurred in isolation until eruption time. While the origin of this component remains speculative, the Sr-Nd isotope trend is consistent with a simple mixing process involving an OIB-type mantle and a component with low ƐNd and high ƐSr.

Mineralogical and geochemical study of granular xenoliths from the Alban Hills volcano, Central Italy: bearing on evolutionary processes in potassic magma chambers

Granular xenoliths (ejecta) from pyroclastic deposits emplaced during the latest stages of activity of the Alban Hills volcano range from ultramafic to salic. Ultramafic types consist of various proportions of olivine, spinel, clinopyroxene and phlogopite. They show low SiO2, alkalies and incompatible element abundances and very high MgO. However, Cr, Co and Sc are anomalously low, at a few ppm level. Olivine is highly magnesian (up to Fo%=96) and has rather high CaO (1% Ca) and very low Ni (around a few tens ppm) contents. These characteristics indicate a genesis of ultramafic ejecta by thermal metamorphism of a siliceous dolomitic limestone, probably with input of chemical components from potassic magma. The other xenoliths have textures and compositional characteristics which indicate that they represent either intrusive equivalents of lavas or cumulates crystallized from variably evolved ultrapotassic magmas. One sample of the former group has major element composition resembling ultrapotassic rocks with kamafugitic affinity. Some cumulitic rocks have exceedingly high abundances of Th (81–84 ppm) and light rare-earth elements (LREE) (La+Ce=421–498 ppm) and extreme REE fractionation (La/Yb=288–1393), not justified by their modal mineralogy which is dominated by sanidine, leucite and nepheline. Finegrained phases are dispersed through the fractures and within the interstices of the main minerals. Semiquantitative EDS analyses show that Th and LREE occur at concentration levels of several tens of percent in these phases, indicating that their presence is responsible for the high concentration of incompatible trace elements in the whole rocks. The interstitial position of these phases and their association with fluorite support a secondary origin by deposition from fluorine-rich fluids separated from a highly evolved potassic liquid. The Nd isotopic ratios of the cjecta range from 0.51182 to 0.51217. 87Sr/86Sr ratios range from 0.70900 to 0.71036. With the exception of one sample, these values are lower than those of the outcropping lavas, which cluster around 0.7105±3. This indicates either the occurrence of several isotopically distinct potassic magmas or a variable interaction between magmas and wall rocks. However, this latter hypothesis requires selective assimilation of host rocks in order to explain isotopic and geochemical characteristics of lavas and xenoliths. The new data indicate that the evolutionary processes in the potassic magmas of the Alban Hills were much more complex than envisaged by previous studies. Interaction of magmas with wall rocks may be an important process during magmatic evolution. Element migration by gaseous transfer, often invoked but rarely constrained by sound data, is shown to have occurred during the latest stages of magmatic evolution. Such a process was able to produce selective enrichment of Th, U, LREE and, to a minor degree, Ta and Hf in the wall rocks of potassic magma chamber. Finally, the occurrence of xenoliths with kamafugitic composition points to the existence of this type of ultrapotassic magma at the Alban Hills.

Sr isotopic systematics in volcanic rocks from the Island of Stromboli, Italy (Aeolian arc)

Abstract Sr isotope compositions are reported for 37 volcanic rocks from the Island of Stromboli and for 8 samples from the islands of Filicudi and Alicudi, Aeolian Arc, south Tyrrhenian Sea. The rocks cover the entire compositional range of the Aeolian volcanics which vary from calc-alkaline (CA) to high-K calc-alkaline (HKCA), shoshonitic (SHO) up to potassic series (KS). In the Island of Stromboli the Sr isotopic ratio ranges from 0.70519 to 0.70757 and increases regularly from the CA to HKCA and SHO, reaching the highest values in the KS volcanics. Significant variations are also observed within individual magmatic series, especially the KS. The Filicudi and Alicudi samples include typical CA basalts and basaltic andesites that display lower Sr isotopic ratios (0.70379–0.70538) than the Stromboli volcanics. The data indicate that fractional crystallization has been the leading process in the evolution of the HKCA and SHO series, although some samples show clear evidence of mixing with CA and KS magmas. The KS volcanics display a range of isotopic composition which is negatively correlated with Sr abundance, indicating processes of crustal assimilation. The overall Sr isotopic variations in the Stromboli rocks and the positive relationship with K enrichment are interpreted as indicating either the genesis of parent magmas of the different series in a heterogeneous mantle source or formation by processes of crystal fractionation associated with assimilation and mixing in a periodically refilled and tapped deep magma chamber.

Hydrogeochemistry and strontium isotopes of spring and mineral waters from Monte Vulture volcano, Italy

Abstract This paper describes the results of a study that was conducted to determine the relationship between hydrogeochemical composition and 87Sr/86Sr isotope ratios of the Mt. Vulture spring waters. Forty samples of spring waters were collected from local outcrops of Quaternary volcanites. Physico-chemical parameters were measured in the field and analyses completed for major and minor elements and 87Sr/86Sr isotopic ratios. A range of water types was distinguished varying from alkaline-earth bicarbonate waters, reflecting less intense water–rock interaction processes to alkali bicarbonate waters, probably representing interaction with volcanic rocks of Mt. Vulture and marine evaporites. The average 87Sr/86Sr isotope ratios suggest at least 3 different sources. However, some samples have average Sr isotope ratios (0.70704–0.70778) well above those of the volcanites. These ratios imply interaction with other rocks having higher 87Sr/86Sr ratios, probably Triassic evaporites, which is substantiated by their higher content of Na, SO4 and Cl. The Sr isotope ratios for some samples (e.g. Toka and Traficante) are intermediate between the value for the Vulture volcanites and that for the local Mesozoic rocks. The salt content of these samples also lies between the value for waters interacting solely with the volcanites and the value measured in the more saline samples. These waters are thus assumed to result from the mixing of waters circulating in volcanic rocks with waters presumably interacting with the sedimentary bedrock (marine evaporites).

Major, trace element and Sr isotopic composition of lavas from Vico volcano (Central Italy) and their evolution in an open system

Major, trace element and Sr isotopic compositions have been determined on 21 lava samples from Vico volcano, Roman Province, Central Italy. The rocks investigated range from leucite tephritic phonolites to leucite phonolites and trachytes. Trace element compositions are characterized by high enrichments of incompatible elements which display strong variations in rocks with a similar degree of evolution. Well-defined linear trends are observed between pairs of incompatible trace elements such as Th-Ta, Th-La, Th-Hf. A decrease of Large Ion Lithophile (LIL) elements abundance contemporaneously with the formation of a large central caldera is one of the most prominent characteristics of trace element distribution. Sr isotope ratios range from 0.71147 to 0.71037 in the pre-caldera lavas and decreases to values of 0.70974–0.70910 in the lavas erupted after the caldera collapse. Theoretical modelling of geochemical and Sr isotopic variations indicates that, while fractional crystallization was an important evolutionary process, AFC and mixing also played key roles during the evolution of Vico volcano. AFC appears to have dominated during the early stages of the volcanic history when evolved trachytes with the highest Sr isotope ratios were erupted. Mixing processes are particularly evident in volcanites emplaced during the late stages of Vico evolution. According to the model proposed, the evolution of potassic magmas emplaced in a shallow-level reservoir was dominated by crystal fractionation plus wall rock assimilation and mixing with ascending fresh mafic magma. This process generated a range of geochemical and isotopic compositions in the mafic magmas which evolved by both AFC and simple crystal liquid fractionation, producing evolved trachytes and phonolites with variable trace element and Sr isotopic compositions.

Human alteration of groundwater–surface water interactions (Sagittario River, Central Italy): implication for flow regime, contaminant fate and invertebrate response

Many rivers worldwide are undergoing severe man-induced alterations which are reflected also in changes of the degree of connectivity between surface waters and groundwater. Pollution, irrigation withdrawal, alteration of freshwater flows, road construction, surface water diversion, soil erosion in agriculture, deforestation and dam building have led to some irreversible species losses and severe changes in community composition of freshwater ecosystems. Taking into account the impact of damming and flow diversion on natural river discharge, the present study is aimed at (i) evaluating the effects of anthropogenic changes on groundwater/surface water interactions; (ii) analyzing the fate of nitrogenous pollutants at the floodplain scale; and (iii) describing the overall response of invertebrate assemblages to such changes. Hydrogeological, geochemical and isotopic data revealed short- and long-term changes in hydrology, allowing the assessment of the hydrogeological setting and the evaluation of potential contamination by nitrogen compounds. Water isotopes allowed distinguishing a shallow aquifer locally fed by zenithal recharge and river losses, and a deeper aquifer/aquitard system fed by surrounding carbonate aquifers. This system was found to retain ammonium and, through the shallow aquifer, release it in surface running waters via the hyporheic zone of the riverbed. All these factors influence river ecosystem health. As many environmental drivers entered in action offering a multiple-component artificial environment, a clear relationship between river flow alteration and benthic and hyporheic invertebrate diversity was not found, being species response driven by the combination of three main stressors: ammonium pollution, man-induced changes in river morphology and altered discharge regime.

Calcite in fractures in a volcanic environment (Vulcano Island, Italy): contribution of geochronological and isotopic studies to volcanotectonics

Abstract The southern and southeastern rim of the present caldera (La Fossa caldera) at Vulcano Island (Aeolian Islands, Italy) is crosscut by a network of fractures filled with calcite and minor chalcedony. Fluid inclusion studies indicate that both mineral phases were deposited from hydrothermal solutions. Several calcite samples were analyzed and their U, Sr, Nd, O and C isotopic composition was determined. U Th geochronological data suggest two discrete depositional episodes: one at 50 ka (southern rim) and the other at 25 ka (southeastern rim). Oxygen isotopic compositions, 87 Sr 86 Sr and 234 U 238 U ratios exclude that seawater was involved significantly in the hydrothermal system, in agreement with fluid inclusion studies which did not document the presence of NaCl. The Nd and Sr isotopic composition of calcite reflects the composition of the host rocks. The oxygen isotopic composition excludes a post-depositional interaction with meteoric water and suggests a depositional temperature consistent with that obtained from the fluid inclusion study (160–170 °C), assuming equilibrium conditions and a fluid isotopic composition close to present-day steam emissions. The positive correlation between U content and C isotopic composition indicates a rapid change in CO 2 pressure during calcite deposition. This observation is consistent with a rapid fluid ascent, likely connected to two phases of collapse of the La Fossa caldera. The ages of the calcites which fill the fractures at the La Fossa caldera indicate the activation time of the fracture systems which, in turn, are connected to the above mentioned phases of the caldera collapse.