1,664 research outputs found
Sulfur isotopic signature of subduction-unrelated and subduction-related ophiolitic rocks
No full textSulfur (S) is one of the key volatiles in Earth’s chemical cycles as it affects biological, climate, ore-deposits, and redox processes. It is known that
S stored in the crust is recycled into the mantle at subduction zones. However, some aspects of the S cycle in the deep Earth such as S speciation, flux, isotope composition and fractionation processes still remain unclear. The study of ophiolites could provide information about contents and isotopic
features of S in subduction-unrelated and subduction-related geodynamic settings. In this work we compiled a global dataset of both subduction-unrelated and subduction-related ophiolitic basalts, and we measured their whole rock S contents and the relative S isotopic ratio (34S/32S) using an elemental analyzer coupled with a mass spectrometer (EA-IRMS). The
considered samples are Mid-Ocean Ridge Basalts (MORBs) from Corsica, Romania, Albania, and North Macedonia; ii) Island Arc Tholeiites (IAT)
from Albania and Greece; iii) Calc-Alkaline Basalts (CAB) from Greece, Romania, North Macedonia, and Iran already constrained from a petrological and geochemical point of view by different studies (Moberly et al., 2006; Saccani et al., 2011; Brombin et al., 2022). In the studied basalts, the S contents range from 200 and 300 ppm. Despite the different areas of provenance, for most of the samples the S isotopic signatures are similar in rocks having similar geochemical affinity. The average S isotopic ratios are –0.7‰, +5.8, and +7.4‰, for MORBs, IATs, and CABs, respectively. It is evident that only MORBs preserved the typical S signature of the Earth
mantle (i.e., from –2‰ to 0‰). The subduction related magmatic rocks (i.e., IATs and CABs) show positive S isotopic values, probably due to the contamination of i) enriched-34S subducting sediments in the magma sources or ii) fluids released by serpentinized rocks of the slab, which
typically have comparatively more positive S signature.
In summary, this work allowed the definition of: i) the S isotope compositions in both subduction-unrelated and subduction-related magmatic rocks; ii) the possible causes which modify the original S signature (e.g., contamination by subducting sediments). Research like this are therefore essential to unravel the global S cycle.
REFERENCES
Dilek Y., Furnes H., 2014. Ophiolites and Their origins. Elements, 10: 93-100.
Moberly, R., Ishii, T., Garcia, M.O., Ross, K., Artita, K., 2006. Enriched, transitional, and normal mid-ocean-ridge basalt glass, ODP Leg 203. In Schultz, A., Orcutt, J.A., and Davies, T.A. (Eds.), Proc. ODP, Sci. Results, 203, 1–36
Saccani E., Beccaluva L., Photiades A., Zeda O., 2011. Petrogenesis and tectono-magmatic significance of basalts and mantle peridotites from the Albanian–Greek ophiolites and subophiolitic mélanges. New constraints for the Triassic–Jurassic evolution of the Neo-Tethys in the Dinaride sector. Lithos, 124: 227-242.
Brombin V., Barbero E., Saccani E., Precisvalle N., Lepitkova S., Milevski I., Ristovski I., Milcov I., Dimov G., Bianchini G., 2022. Subduction signature of the Vardar ophiolite of North Macedonia: new constraints from geochemical
and stable isotope data. Ofioliti, 47: 85-102
Petrological and geochronological study of magmatic products and mantle xenoliths from Cenozoic Southalpine Magmatic Province (North-East Italy)
No full textThe Cenozoic Southalpine Magmatic Province, known as Veneto Volcanic Province (VVP; NE Italy) is one of the widest magmatic areas within the Adria plate. It is formed by five main magmatic districts that are from north-west to south-east: Val d’Adige, Lessini Mts., Marosticano, Berici Hills, and Euganean Hills. Only in this last district volcanic and subvolcanic rocks range from subordinate basalts to prevalently acidic types, mostly quartz-trachytes and rhyolites, while for the rest of the VVP districts the outcropping volcanics are wholly undifferentiated lavas, ranging in composition from mela-nephelinites to quartz-normative tholeiites. Commonly alkaline basalts host mantle peridotites. Despite the extensive petrological studies on this province, the geochronological data of the related magmatic activities for each district are poorly defined or even totally missing. The combination of previous biostratigraphic data with new 40Ar/39Ar radioisotopic ages of VVP magmatic products allowed to reconstruct the temporal evolution of the magmatic activity, which was discontinuous and covers a time-span of about 30 Ma (from late Paleocene to early Miocene). In addition, i) new isotropic and anisotropic tomographies for the Alpine region and ii) recent numerical modelling revealing the rarity of the magmatism induced by slab breakoff allow to develop a new model for mechanism triggering the VVP magmatism. This involves the upwelling of toroidal/poloidal flow induced by the progressive retreat and steepness of the subducting European slab after the Adria-Europe continent collision. A likely explanation for the southeastward migration of the magmatism can be accounted for the overidding Adria plate moving faster than the European slab retreatment. The geochemistry of the VVP mafic samples shows a typical OIB signature, as well as positive Ba, Sr, and P anomalies, probably inherited by a carbonatite metasomatized mantle source. This last consideration seems to be confirmed by the geochemical features of the new occurrences of Marosticano mantle xenoliths that reveal an unexpected on-craton type mantle with fingerprint of carbonatitic/CO2-rich silicatic melt metasomatism. According to the previous studies Val d’Adige and Lessini Mts. mantle xenoliths exhibit characteristics of off-craton lithospheric mantle variably affected by Na-alkaline silicatic metasomatism. However, on- and off-craton VVP mantle portions show similar Archean/Proterozoic Re-Os ages, suggesting that the Marosticano mantle domain could be interpreted as the vestige of an Archean/Proterozoic cratonic keel, whose signature was not erased by the carbonatitic/CO2-rich silicatic metasomatism, whereas Lessini Mts. and Val d’Adige xenoliths are remnants of circum-cratonic domains compositionally rejuvenated by infiltration of asthenospheric-derived melts, which upwelling could be induced by the retreatment of the European slab after the Adria/Europe collision.La Provincia Magmatica Cenozoica Sudalpina, nota in letteratura come Provincia Vulcanica Veneta (VVP; NE Italia), è una delle aree magmatiche più vaste della placca Adria. Procedendo all’interno della VVP, da nord-ovest verso sud-est, si riconoscono cinque distretti magmatici: Val d’Adige, Monti Lessini, Marosticano, Colli Berici e Colli Euganei. Solamente in quest’ultimo distretto le rocce vulcaniche e subvulcaniche variano da subordinatamente basaltiche, a prevalentemente acide, soprattutto quarzo-trachiti e rioliti, mentre nei restanti distretti della VVP le vulcaniti affioranti sono esclusivamente lave indifferenziate, varianti in composizione da mela-nepheliniti a tholeiiti quarzo-normative. Solitamente i basalti alcalini ospitano peridotiti mantelliche. Nonostante gli approfonditi studi petrologici su questa provincia, i dati geocronologici delle attività magmatiche di ogni distretto sono scarsamente definiti o persino totalmente mancanti. La combinazione delle già note età biostratigrafiche con i nuovi dati radioisotopici 40Ar/39Ar, ottenuti dai prodotti magmatici della VVP, ha permesso la ricostruzione dell’evoluzione temporale dell’attività magmatica, la quale è stata discontinua durante un arco di tempo di circa 30 Ma (dal tardo Paleocene fino al primo Miocene). Inoltre, i) nuove tomografie isotropiche e anisotropiche della regione alpina e ii) recenti modelli numerici, rivelanti la rarità del magmatismo indotto dallo slab breakoff, hanno permesso la costruzione di un nuovo modello per il processo innescante il magmatismo della VVP. Quest’ultimo coinvolge la risalita di un flusso toroidale/poloidale indotto dal progressivo ritiro e verticalizzazione dello slab europeo subducente in seguito alla collisione continentale Adria-Europa. La migrazione sud-orientale del magmatismo potrebbe essere dovuta al movimento della placca Adria più rapido del ritiro dello slab europeo. La geochimica dei campioni mafici della VVP mostra una tipica firma OIB, oltre ad anomalie positive in Ba, Sr e P, probabilmente ereditate da una sorgente mantellica carbonatitica. Quest’ultima considerazione parrebbe confermata dalla caratteristiche geochimiche di una nuova suite di xenoliti mantellici provenienti dal distretto del Marosticano, che rivelano un’innaspettata origine da un mantello di tipo on-craton avente un’impronta da metasomatismo di fusi carbonatitici/silicatici ricchi in CO2. Secondo gli studi precedenti, gli xenoliti mantellici della Val d’Adige e dei Monti Lessini esibiscono caratteristiche di mantello litosferico off-craton variabilmente influenzato da metasomatismo silicatico Na-alcalino. Nonostante ciò, le porzioni di mantello on- e off-craton della VVP mostrano simili età Re/Os Archeane/Proterozoiche, suggerendo che il domino mantellico del Marosticano potrebbe essere interpretato come resti di una porzione di cratone Archeano/Proterozoico, la cui firma non è stata elisa dal metasomatismo carbonatitico/silicatico ricco in CO2, mentre gli xenoliti dei Monti Lessini e della Val d’Adige rappresenterebbero resti di domini circum-cratonici composizionalmente ringiovaniti dall’infiltrazione di fusi astenosferici, la cui risalita potrebbe essere stata indotta dal ritiro dello slab europeo dopo la collisione Adria/Europa
Multi stable isotope ratio analysis for the traceability of northern Italian apples
No full textIsotope ratio mass spectrometry is a well-known technique used to trace the origin of agri-food products from different countries. Here this method was tested to trace the exact orchard of provenance of Italian apples harvested at sites close to each other. We measured the δ(13)C, δ(15)N, and δ(34)S values of apple subfractions (peel, petiole, pulp, seed) from two orchards in Ferrara and one orchard in Trento. Sulfur represents the best marker for tracing the regions of provenance of samples because it is linked to the presence of sulfate (Ferrara1: +9.0 ‰; Ferrara 2: +7.3 ‰) and sulfide (Trento: −1.3 ‰) minerals in soils. However, the δ(13)C of apple subfractions combined with the δ(34)S of seed in a linear discrimination analysis better discriminated the three orchards. The isotopic fingerprint of apples is thus significantly affected by the relative terroir, and it can be used as “isotopic identity card” to certify “protected designations of origin”
Influence of Al, C, N and H on the iron redox state in the Earth’s lower mantle: A geochemical quantum model
No full textIron is the most abundant element by weight in our planet, the dominant component of the core and the only major transition metal in the mantle. Its speciation in the present-day lower mantle remains one of the most controversial aspects to deal with in modelling the deep interiors of the Earth. Here, we present an unconventional approach that relies upon quantum mechanics and the bonding Bader theory to predict the iron oxidation state at lower mantle conditions (24/1900–90/2700 GPa/K) in bridgmanite, the major mineral phase. This approach provides insights into the lower mantle geochemistry on a global scale and a unified viewpoint. The chemical species that on account of their electronic/steric features and mobility expectably induce redox effects on iron in bridgmanite are Al, N, C and H. Hydrogen causes reduction, whereas the other species promote oxidation. The combination of the probability of occurrence of the Al-N-C-H driven reactions with the availability of the involved species points to iron never achieving full oxidation; instead, it reaches a maximum average oxidation number of ∼ 2.4. This is equivalent to a Fe3+/Fetot ratio that varies with depth from 15.9 to 12.1 % (if Al-N-C-H are accounted for), and from 19.3 to 29.0 % (if only Al is considered). Iron in the lower mantle is therefore more reduced than previously expected, in terms of ferric fraction, because of the important reducing action of H. If we assume that Fe3+ is always associated with iron disproportionation (3Fe2+→2Fe3++Fe0), then the Al-N-C–H atom exchange reactions yield an estimate of metallic iron fraction in the lower mantle as large as ∼ 0.4 wt%. This figure increases up to ∼ 0.8 wt% when neglecting N-C–H effects on ferric iron formation and is fully comparable to the latest experimental result (0.7 wt%) using aluminium only
sj-txt-1-hpq-10.1177_13591053231168040 – Supplemental material for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study
No full textsj-txt-1-hpq-10.1177_13591053231168040 for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study by Gaia Perego, Federica Cugnata, Chiara Brombin, Francesca Milano, Martina Mazzetti, Paola Taranto, Emanuele Preti, Rossella Di Pierro, Chiara De Panfilis, Fabio Madeddu and Valentina E Di Mattei in Journal of Health Psychology</p
sj-docx-5-hpq-10.1177_13591053231168040 – Supplemental material for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study
No full textSupplemental material, sj-docx-5-hpq-10.1177_13591053231168040 for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study by Gaia Perego, Federica Cugnata, Chiara Brombin, Francesca Milano, Martina Mazzetti, Paola Taranto, Emanuele Preti, Rossella Di Pierro, Chiara De Panfilis, Fabio Madeddu and Valentina E Di Mattei in Journal of Health Psychology</p
sj-pdf-3-hpq-10.1177_13591053231168040 – Supplemental material for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study
No full textsj-pdf-3-hpq-10.1177_13591053231168040 for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study by Gaia Perego, Federica Cugnata, Chiara Brombin, Francesca Milano, Martina Mazzetti, Paola Taranto, Emanuele Preti, Rossella Di Pierro, Chiara De Panfilis, Fabio Madeddu and Valentina E Di Mattei in Journal of Health Psychology</p
sj-RData-4-hpq-10.1177_13591053231168040 – Supplemental material for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study
No full textsj-RData-4-hpq-10.1177_13591053231168040 for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study by Gaia Perego, Federica Cugnata, Chiara Brombin, Francesca Milano, Martina Mazzetti, Paola Taranto, Emanuele Preti, Rossella Di Pierro, Chiara De Panfilis, Fabio Madeddu and Valentina E Di Mattei in Journal of Health Psychology</p
sj-pdf-2-hpq-10.1177_13591053231168040 – Supplemental material for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study
No full textsj-pdf-2-hpq-10.1177_13591053231168040 for Analysis of healthcare workers’ mental health during the COVID-19 pandemic: Evidence from a Three-Wave Longitudinal Study by Gaia Perego, Federica Cugnata, Chiara Brombin, Francesca Milano, Martina Mazzetti, Paola Taranto, Emanuele Preti, Rossella Di Pierro, Chiara De Panfilis, Fabio Madeddu and Valentina E Di Mattei in Journal of Health Psychology</p
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