Search

Geochemistry and Sr-Nd isotopes were determined in Triassic calcalkaline metalava and metapyroclastic rocks from Attica and Argolida, central Greece, to ascertain their origin, evolution, and emplacement timing. Sample protoliths were lavas, tuffs, and, subordinately, tuffites of basaltic to rhyolitic composition. Despite up to low-grade hydrothermal metamorphism, samples retain primary structures and geochemical characteristics; in particular, relatively high (La/Lu) chondrite-normalized ratios, pronounced negative Eu anomalies, and Large Ion Lithophile Element (LILE) enrichment. Unlike the narrow Nd isotopic range (0.512342-0.512625), the Sr isotopic range is relatively wide (0.705903-0.711739). As Sr and Nd isotopic ratios do not provide concordant geochronological age for rock emplacement, they were corrected at 170 Ma due to geologic and petrographic considerations. Geochemistry and Sr and Nd isotopic ratios provide evidence of subduction metasomatism and crustal contamination affecting the parental magmas of samples. Their Nd model ages resemble those of Enriched Mid-Ocean Ridge Basalts (E–MORB) under the northern Aegean and Triassic-rift mafic rocks from northern Greece. As a whole, the geological and petrological data suggest that samples were formed both onshore and offshore in the transition zone between the Pelagonian microcontinent, moving away from Gondwana’s Apulian promontory, and the newly-formed intracontinental basin of the Neotethyan Pindos Ocean. A short-lived immature subduction of young oceanic crust under Pelagonia gave samples their strong geochemical and geological characteristics of volcanic-arc. © 2020, Springer-Verlag GmbH Austria, part of Springer Nature.

The living euryhaline species Cyprideis torosa (Jones) undergoes morphometric variations in size, noding and sieve-pore shape linked to the environmental salinity. In particular it is known that salinity values around 8-9 psu represent the osmoregulation threshold and also the turning point between smaller and greater valve dimensions and prevailingly noded against un-noded valves. The variation of the percentage of round-, elongate- and irregular-shaped sieve-pores on the valves has shown an empiric logarithmic correlation with the water salinity from 0 to 100 psu. Due to this ecologically cued polymorphism, C. torosa represents 28 an invaluable palaeosalinometer for the Quaternary brackish basins. In this paper we attempt to verify whether the ecophenotypical behaviour of the post-evaporitic Messinian species Cyprideis agrigentina Decima was comparable with that of C. torosa. To reach this goal, three morphometric characters have been analysed: 1) size variability; 2) noding and ornamentation; 3) variability of the percentage of the sieve-pore shapes. The palaeoenvironmental interpretation was made using synecological and geochemical approaches [stable isotopes, trace elements, Sr-isotopes and natural radioactivity (NRD)]. For this study, the 250 m-thick Messinian Lago-Mare succession of Eraclea Minoa (Agrigento, Sicily) was chosen for the presence of monotypic assemblages made only by C. agrigentina for around 70 m of thickness. The results of the morphometric analyses showed that: 1) size variations are not related to the salinity changes recognized both from synecological and geochemical analyses; 2) no noded specimens have been recovered along the section; 3) the salinities calculated on the basis of the percentage of the sieve-pore shape are not correlated with the salinities inferred from the synecological and geochemical analyses. Thus in this paper we conclude that C. agrigentina cannot be considered a palaeosalinometer for the Messinian Salinity Crisis. There is a correlation of the 13 C and NRD data with the percentages of sieve-pore shapes, linking them to the oxygen availability at the bottom of the basin.

A giant carbonate vein (>= 50 m thick; fissure ridge travertines) and nearby travertine plateaus in the Semproniano area (Mt. Amiata geothermal field, southern Tuscany, Italy) are investigated through a multidisciplinary approach, including field and laboratory geochemical analyses (U/Th geochronology, C, Nd, O and Sr isotope systematics, REE abundances, and fluid inclusion microthermometry). The main aim of this work is to understand: (1) modes and rates for the growth of the giant vein and nearby travertine deposits within a Quaternary volcano-tectonic domain; (2) implications in terms of the CO2 leakage; and (3) possible relationships with Quaternary paleoclimate and hydrological oscillations. Results show that the giant vein was the inner portion of a large fissure ridge travertine and grew asymmetrically and ataxially through repeated shallow fluid injections between >650 and 85 ka, with growth rates in the 10(-2)-10(-3) mm/a order. The giant vein developed mainly during warm humid (interglacial) periods, partially overlapping with the growth of nearby travertine plateaus. Estimated values of CO2 leakage connected with the vein precipitation are between about 5 x 10(6) and 3 x 10(7) mol a(-1) km(-2), approximately representing one millionth of the present global CO2 leakage from volcanic areas. Temperature estimates obtained from O-isotopes and fluid inclusion microthermometry indicate epithermal conditions (90-50 degrees C) for the circulating fluid during the giant vein growth, with only slight evidence of cooling with time. Geochemical and isotope data document that the travertine deposits formed mainly during Pleistocene warm humid periods, within a tectonically-controlled convective fluid circuit fed by meteoric infiltration and maintained by the regional geothermal anomaly hosted by the carbonate reservoir of the Mt. Amiata field. (C) 2016 Elsevier B.V. All rights reserved.

A giant carbonate vein (≥ 50 m thick; fissure ridge travertines) and nearby travertine plateaus in the Semproniano area (Mt. Amiata geothermal field, southern Tuscany, Italy) are investigated through a multidisciplinary approach, including field and laboratory geochemical analyses (U/Th geochronology, C, Nd, O and Sr isotope systematics, REE abundances, and fluid inclusion microthermometry). The main aim of this work is to understand: (1) modes and rates for the growth of the giant vein and nearby travertine deposits within a Quaternary volcano-tectonic domain; (2) implications in terms of the CO 2 leakage; and (3) possible relationships with Quaternary paleoclimate and hydrological oscillations. Results show that the giant vein was the inner portion of a large fissure ridge travertine and grew asymmetrically and ataxially through repeated shallow fluid injections between > 650 and 85 ka, with growth rates in the 10 − 2 –10 − 3 mm/a order. The giant vein developed mainly during warm humid (interglacial) periods, partially overlapping with the growth of nearby travertine plateaus. Estimated values of CO 2 leakage connected with the vein precipitation are between about 5 × 10 6 and 3 × 10 7 mol a − 1 km − 2 , approximately representing one millionth of the present global CO 2 leakage from volcanic areas. Temperature estimates obtained from O-isotopes and fluid inclusion microthermometry indicate epithermal conditions (90–50 °C) for the circulating fluid during the giant vein growth, with only slight evidence of cooling with time. Geochemical and isotope data document that the travertine deposits formed mainly during Pleistocene warm humid periods, within a tectonically-controlled convective fluid circuit fed by meteoric infiltration and maintained by the regional geothermal anomaly hosted by the carbonate reservoir of the Mt. Amiata field. © 2016 Elsevier B.V.

Since the study of VESPER (1975) and ROSENFELD & VESPER (1977), it is known that the living anomalohaline species Cyprideis torosa (Jones) undergoes morphometrical variations in size, noding and sieve pore shape linked to the environmental salinity. Several studies (among others: CARBONEL, 1982; ALADIN, 1993; VAN HARTEN, 1996; KEYSER, 2005; BOOMER & FRENZEL, 2011; FRENZEL et al., 2011, 2012) showed that salinity values around 8-9 psu represent the osmoregulation threshold and also the turning point between smaller and greater valve dimensions and prevailingly noded against un-noded valves. The variation of the percentage of round-, elongate- and irregularshaped sieve pores on the valves has shown an empiric logarithmic correlation with the water salinity from 0 to 100 psu (ROSENFELD & VESPER, 1977). Due to this ecologically cued polymorphism, Cyprideis torosa represents an invaluable palaeosalinometer for Quaternary brackish basins. Some authors (ROSENFELD, 1977; BONADUCE & SGARRELLA, 1999) applied the counting of different sieve pore shapes also to the fossil species Cyprideis agrigentina Decima, distributed in the Mediterranean during the post-evaporitic Messinian lago-mare phase. In this paper we attempt to verify whether the ecophenotypical behaviour of C. agrigentina was comparable with that of C. torosa.

The source and cycling of Fe in groundwaters from the phreatic aquifer which characterizes a site impacted by metallurgical activity in a coastal area of northern Italy (Adriatic Sea) have been investigated by Fe-isotope analyses, H-O-Sr stable-isotope systematics and major and trace element chemistry. Waters are characterized by circum-neutral to alkaline pH and dissolved O-2 zoning, and range from a low-salinity Ca-Mg-HCO3 type to a brackish Na-Cl type resulting from seawater intrusion. The O-H isotopic data indicate that the Ca-Mg-HCO3 waters originate from meteoric precipitation that infiltrated at elevated altitudes, and that a variable seawater fraction, in some cases exceeding 90%, characterizes the Na-Cl type waters. The Fe content ranges from 0.48 to 9.99 mg/L and from 2.50 to 43.8 mg/L in low-salinity and brackish waters, respectively. The delta Fe-56 value varies over the wide range from +0.87 parts per thousand to -5.29 parts per thousand in low-salinity waters and between +2.15 parts per thousand and -2.34 parts per thousand in brackish waters. The isotopically lighter compositions are interpreted as reflecting isotopic fractionation during repeated cycling of Fe precipitation. Positive delta Fe-56 values might indicate either a higher solubility of oxyhydroxides, which during diagenesis preferentially incorporated the isotopically heavier fraction of Fe, or the leaching of the foundry landfill disposal which characterizes the site.

hosted in a folded and low to medium grade sedimentary and volcanic rocks, unconformably overlaid by Permo-Triassic to Cretaceous red beds and limestones. Intrusion of the hydrothermally altered multiphase ca. similar to 330-319 Ma Aouli granite batholith has contact metamorphosed the host rocks to a metamorphic assemblage of cordierite, andalusite, chlorite, muscovite, and biotite +/- sillimanite +/- garnet. The mineralized structures that consist mostly of quartz, fluorite, and barite occur principally as ENE-WSW, WNW-ESE, and E-W-trending trans-tensional steeply dipping veins, veinlets and en echelon tension gash fillings. Irrespective of colour, location, paragenesis and textural position within the mineralized vein structure, the fluorite is characterized by high total REY contents ranging from 250 to 662 ppm, distinctive positive Eu and Y anomalies, and middle rare-earth element enrichment. Fluid inclusion data indicate that the ore-forming fluids correspond to evolved NaCl-CaCl2 + other cations sedimentary (94-174 degrees C), saline (14-24 wt% NaCl equiv.) brines. The strontium isotopic compositions of fluorite (Sr-87/Sr-86 = 0.710155-0.712293) and barite (0.710215-0.701401), along with the Liassic dolomitized limestones (0.707867-0.708140) are more radiogenic than the Cambro-Ordovician and Triassic-Early Jurassic seawater values, with the Aouli Late Variscan granite (0.70814 +/- 12) and the Triassic arkoses (0.709839-0.712313) displaying the highest Sr-87/Sr-86 ratios. Barite separates show uniform delta S-34 ratios of +11% to +13.4% consistent with Permian-Triassic seawater sulphate. The calculated REY fluid compositions along with fluid inclusion, strontium and sulphur isotope data point to the role of hot sedimentary brines with fluid-rock interaction at high fluid/rock ratios. The fluid system is likely related to the Pangea rifting and subsequent Central Atlantic opening during Permian-Triassic time. The fluorite-barite mineralization is likely due to mixing at the basement-cover interface of an ascending deep-seated fluid that equilibrated with Variscan crystalline basement rocks and cooler more dilute formation water. (C) 2015 Published by Elsevier Ltd.

The final conclusions of a multidisciplinary study of Earth and Soil Sciences, carried out in the frame of Prin 2007 are presented. The study has dealt with a variety of natural materials, encompassing soils, waters, atmospheric depositions, the vegetation and the bottom sediments of a coastal lagoon, in the territory north of Ravenna, characterized by important agricultural and industrial activities. In particular, by chemical and isotopic methodologies and pedological survey, it has been studied the ecosystem of the San Vitale Pinewood and the Lagoon of Pialassa Baiona, both constituting the southernmost part of the Po river delta Park. The results obtained have shown that the Pinewood is affected by major salinization processes induced by local subsidence and concerning underground water and soils. This jeopardizes the vegetation's health, in particular, the pine trees that are the main characteristic species. Moreover, the proximity of the industrial zone of Ravenna to the Pinewood represents another threat to the environment, as it is a major pollution source by release of particulate matter with stacks. Therefore, potentially toxic elements may fallout onto the soils, waters and vegetation of the Pinewood, arising general concern on the preservation of the forest. The important traffic rolling on the road net contouring the Pinewood-Lagoon ecosystem is a further source of pollution, as indicated by the incoming diffusion of PGE on the topsoils bordering the roads. Lastly, the study of the bottom deposits of the Lagoon at the water-sediment interface has unveiled the diffuse presence of Hg with significant concentrations, derived from industrial wastewaters unloaded in the basin some decades ago. Luckily, Hg occurs in the element form and, thus, its mobility is very reduced, keeping so far the risk factor in the Lagoon low. As a whole, the Pinewood-Lagoon ecosystem is ailing due to incoming salinization processes and, subordinately, moderate pollution proceeding from the industrial zone and the traffic. Therefore, it is recommended to implement a monitoring survey of the study area on the ground of the parameters used in this research. In fact, they have been able to provide the local Administrations with punctual responses to the problem of degradation of the Pinewood-Lagoon ecosystem.

87Sr/ 86Sr measurements were carried out on planktonic foraminiferal shell samples collected in the Early Pliocene succession of DSDP Site 132 (Tyrrhenian Sea, Western Mediterranean). The measured ratios range between 0.708980 and 0.709023, showing moderate fluctuations and a maximum variation of 0.000043 that falls within the uncertainty range of the Sr isotope measurements (± 0.000022) and suggests relatively constant ratios throughout this succession. The Mediterranean seawater 87Sr/ 86Sr ratios measured in a sample collected 55 cm above the Miocene / Pliocene Boundary and dated to 5.31 ± 0.01 Ma, are consistent with those measured in coeval oceanic successions, confirming the open marine depositional environment revealed by foraminiferal assemblages. The measured ratios are consistent with those collected in the Lower Pliocene deep sea sequence at Hole 654A (about 70 km NW from DSDP Site 132) and these are also comparable with other data from coeval oceanic and on land successions, taking into account the uncertainty of the Sr isotope measurements. The occurrence of relatively constant ratios throughout this succession, as previously shown in other coeval deep sea sequences of the Mediterranean and if verified in other successions, may hamper precise age determinations of the Early Pliocene marine carbonate in this basin.

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. UTh geochronological data suggest two discrete depositional episodes: one at 50 ka (southern rim) and the other at 25 ka (southeastern rim). Oxygen isotopic compositions, 87Sr/86Sr and 234U/238U 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 CO2 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.

Albitization, locally accompanied by chloritization and epidotization, was characterized by strong leaching of Mg, Fe, K, and geochemically similar trace elements, and by a significant increase of Na. Ca, and P were moderately leached in the most metasomatized rocks. Other major (Si, Ti, Ca) and trace elements (U, Th, Y, and Zr), along with light (LREE) and middle (MREE) rare-earth elements, behaved essentially immobile at the deposit scale. Albitization was induced by non-magmatic fluids rich in radiogenic Sr, and occurred shortly after the granitoid emplacement. This conclusion is supported by Nd isotopes, because unaltered granitoids and albitites fit the same reference isochron at 274 Ma. The fluids acquired radiogenic Sr by circulation through the Lower Paleozoic metasedimentary basement. Specifically, it is estimated that Sr supplied by the non-carbonatic basement represents about 22 wt% of total Sr in albitite.

Two distinct occurrences of wollastonite- and melilite-bearing rocks from Ricetto and Colle Fabbri, which are located in the central Italy Apennine Range, are referred to as “paralavas” generated by melting and recrystallization of marly sediments “likely due to coal Þ res” by Melluso et al. (2003). We submit data demonstrating that these conclusions are incorrect. Ricetto is clearly pyrometamorphic, as described by Capitanio et al. (2001, 2004). Colle Fabbri is clearly an igneous outcrop as described in Stoppa (1988). It is quite different in scale, Þ eld relationships, and chemistry, and thus Ricetto is irrelevant to its petrogenesis. The sediment mixing model of Melluso et al. (2003) does not relate to the Colle Fabbri Þ eld data. Furthermore, the Ricetto Miocene ß ysch country-rock and the Colle Fabbri enclosing Pliocene clays were not analyzed by Melluso et al. (2003). A limestone-shale mixing calculation using Sr and Nd isotopic data in Melluso et al. (2003, Tables 3–4) and a 143Nd/144Nd ratio of 0.51213 for Apennine shales (op.cit. p. 1297) fails to account for the Colle Fabbri samples, which remain well clear of the hypothetical mixing line. Rocks of mantle origin, including micaceous kimberlites and Western Australia lamproites, plot in the variation Þ eld of Colle Fabbri and regionally associated igneous rocks. Colle Fabbri is but one of a series of similar igneous melilite-bearing and carbonatite occurrences that constitute the Intramontane Ultra-alkaline Province of central Italy (IUP), although Colle Fabbri does have unique features, as do other of these occurrences (Stoppa et al. 2003).

The fluorite-bearing hydrothermal mineralization in Sardinia mainly occurs within Paleozoic volcanic and metasedimentary rocks. Only 3 occurrences are located in volcanic and siliciclastic Cenozoic rocks. Most Sardinian fluorites exhibit relatively high rare earth and Y (REY) contents, strong positive Y anomalies, slightly negative Ce and generally positive Eu anomalies. These features indicate that the REY were mobilized mainly from non-carbonate rocks. Neither Sr nor Nd isotopes can be used to date radiometrically the Sardinian fluorites. However, the measured Sr-isotope ratios of the fluorites hosted by Paleozoic rocks fit mixing lines in the 1000/Sr versus 87Sr/86Sr plot once recalculated at 280 Ma, suggesting that the age inferred for the correction probably represents that of the formation of the fluorite mineralization. Mixing likely occurred between diluted surficial waters and brines circulating mainly through the Lower Paleozoic metasedimentary basement. The Cenozoic fluorites exhibit chemical and isotopic features similar to those of the Paleozoic fluorites, except the Nuraghe Onigu fluorite displaying a possible contribution of Sr from Cenozoic magmatic rocks. The initial eNd values of the Paleozoic fluorites fit the age proposed for the formation of the deposits. Moreover, the values suggest that radiogenic Nd was provided to the fluids from the Ordovician siliciclastic basement, except for 3 deposits where the potential source rocks of Nd were mainly Ordovician acidic magmatic rocks. The initial eNd values of the Cenozoic fluorites suggest a provenance of Nd essentially from the leaching of Variscan granitoids.