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Copper oxides have recently emerged as promising precursor catalyst materials demonstrating enhanced reactivity and selectivity towards C2 and C3 products like ethylene, ethanol, and n-propanol generated from the direct electro-reduction reaction of CO2 (denoted as CO2RR). Advanced operando X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and Raman spectroscopy were employed to probe the potential-dependent changes of the chemical states of Cu species in the Cu oxide foams (referred to as CuxO) before and during the CO2RR. This complementary and holistic approach of ‘bulk’- and surface-sensitive techniques demonstrates that the electro-reduction of CuxO foams into metallic Cu is completed before hydrocarbon (e.g., ethylene, ethane) and alcohol (e.g., ethanol, n-propanol) formation sets in. There are, however, substantial differences in the potential dependence of the oxide reduction when comparing the ‘bulk’ with the respective ‘surface’ processes. Only in the very initial stage of the CO2RR, the reduction of the Cu oxide precursor species is temporarily superimposed on the production of CO and H2. Complementary identical location (IL) SEM analysis of the CuxO foams prior to and after the CO2RR reveals a significant alteration in the surface morphology caused by the appearance of smaller Cu nanoparticles formed by the reduction process of CuxO species.

There is debate to what degree mid-ocean ridge basalts (MORB) can be used to infer the composition of the sub-ridge mantle and whether the upper mantle contains components that are difficult to recognize by observations on MORB alone. Here we report trace element and isotope data on a fossil mantle section exposed in the ophiolitic Lanzo South massif, Italy. Our findings show the existence of clinopyroxenes in geochemically depleted melt-infiltrated harzburgites with an extreme radiogenic Hf-isotopic composition but MORB-like Nd isotopic compositions. The simplest way of explaining the depleted trace elements in combination with the decoupled isotopic compositions is that the harzburgites were infiltrated by a melt with isotopic compositions inherited from an anciently (>1 Ga) depleted source. The existence of melts from ultra-depleted sectors of the asthenosphere allows constraining of the configuration of the heterogeneities in the sub-ridge mantle. The parallel arrays in Hf–Nd isotope composition space of different Mid-Ocean ridge segments imply the ubiquitous presence of anciently depleted residual mantle as the matrix in which more enriched components occur in pockets.

A mineralogical, major, LA-ICP-MS trace element mineral chemistry and bulk-rock geochemical study of juvenile samples of the Mercato, Avellino, Pompeii and Pollena eruptions, collected in stratigraphically and volcano- logically well-characterized sections of the Somma-Vesuvius stratovolcano (Roman Magmatic Province), along with reference data on the 1944 CE and the Pomici di Base eruptions, highlights the compositional variability of bulk-rock and glass from leucite phonotephrite to garnet-bearing phonolite. The latter products have extreme fractionation of trace elements (e.g., La/Ybn = 126, Zr/Y = 89, Zr/Hf =78, Nb/Ta = 40; Th/U = 2.3), very low Sc, V, Y, HREE and very high As, Tl, Cs, Pb, Th and U. The Pomici di Base products, older than the eruptions described above, range from leucite-bearing shoshonites to trachytes, are devoid of garnet and belong to an independent liquid-line-of-descent, having also different fractionation between trace elements (e.g., La/Ybn = 15; Zr/Y = 12.4, Zr/Hf = 50, Nb/Ta = 15.6; Th/U = 3 in the Pomici di Base trachytes). A marked chemical variability of the observed phases is found. The geochemistry of garnet, amphibole, clinopyroxene and other phases shows wide variations of concentrations and elemental ratios (e.g., La/Ybn up to 520 in the sadanagaite coexisting with garnet). The magmatic evolution is dominated by low-pressure, oxidized, nearly closed-system fractional crystallization of clinopyroxene, plagioclase, leucite, ±magnetite, ±biotite, ±olivine and apatite in the transition tephrite-phonotephrite, and of potassic sanidine (±hyalophane), Fe-clinopyroxene, melanite garnet ±Fe-amphibole in the transition tephriphonolite-phonolite. Mineralogic and geochemical evidence and model- ling points out the existence of independent, zoned magma batches throughout the activity of the stratovolcano, which possibly started to crystallize at similar depths. The Somma-Vesuvius magmas thus evolved in shallow independent reservoirs with respect to those of the neighbouring volcanic complexes (Campi Flegrei, Ischia) as shown, for instance, by the contrasting compositional trends of clinopyroxene and amphibole, and have very limited evidence of crustal contamination (and/or carbonate assimilation).

An experimental geothermal monitoring, performed on the ground source heat pump (GSHP) system running in a nearly zero energy building (NZEB), has been realized in the protected hydrothermal area of Ponte Arche (Italian Alps), at the request of the competent geological authority. The scope is to assess if a thermal interference could appear between the exploitation of the shallow underground by borehole heat exchangers (BHEs) and nearby thermal baths. Currently, in this area an absolute prohibition for shallow geothermal applications is in force, the area is categorized “potentially subject to geothermal manifestations”. However, in light of new geological and hydrogeological knowledge, supported by long-term monitoring, the protection criterion and constraint geometry could be reviewed. Preliminary to the experimental geothermal monitoring, a detailed ground investigation campaign was performed, including: a geological setting overview based on existing cartography, one continuous core drilling, three downhole geophysical surveys, one thermal response test (TRT). The monitored parameters comprehend the underground temperature at different depths, the outdoor air temperature, and the ground-side heat flow of the GSHP. The collected data are presented and discussed, including considerations about the underground sustainability of the BHE field, and about the real heating and cooling operation of the GSHP ground-side.

A detailed petrochemical investigation of the peridotites from the Mt. Pollino area (Basilicata, Southern Italy) allowed to provide the first comprehensive reconstruction of the evolution and geodynamic setting of ophiolitic mantle from the Southern Apennines. These mantle peridotites firstly acquired strongly-refractory modal and chemical compositions consistent with large degrees of partial melting (≥ 23%). This process was presumably assisted by concomitant injection of melt increments rising from deeper levels of the mantle column, as suggested by relatively large Al and Fe contents of Ol, Opx and Sp. The porous flow ascent of melt increments produced by deeper near-fractional melting continued after the end of the partial melting, as recorded by precipitation of disseminated clinopyroxene out of thermal and chemical equilibrium with the other rock-forming minerals. The Pollino mantle sequence locally experienced reheating associated to a new episode of porous flow migration of melts with REE composition approaching that of N-MORB. The petrological evolution recorded by the peridotites of Mt. Pollino, their high equilibrium T (up to 1100 °C) and the absence of pyroxenites show remarkable analogies with modern abyssal peridotites, pointing to an intra-oceanic setting of the Jurassic Ligurian Tethys for this mantle sequence. According to the present knowledge about the Southern Apennines, the abyssal-like peridotites with the associated terrigenous sediments and continental crustal rocks were incorporated in the Ligurian Accretionary Complex and reached HP/LT conditions during a subduction event starting in Upper Oligocene, to be later exhumed in the Tortonian. The results of this study strongly support the existence of significant differences in terms of geodynamic evolution between Southern and Northern Apennines. © 2017 Elsevier B.V.

International audience; A detailed microstructural, geochemical and geochronological study was performed on zircon grains from plagioclase-rich dioritic dykes discordantly intruded within meta-diorites/gabbros forming the External Gabbro unit of the Finero Mafic Complex (Italian Alps). This unit is exposed as part of a near complete crustal section spanning from mantle rocks to upper crustal metasediments (Val Cannobina, Ivrea–Verbano Zone, Italy). The leucocratic dykes consist mainly of plagioclase (An18–24Ab79–82Or0.3–0.7) with subordinate amounts of biotite and spinel defining melanocratic layers. Zircon and corundum are common accessory phases. Both the dykes and the surrounding meta-diorites/gabbros show evidence of ductile deformation under amphibolite-facies conditions.Zircon grains/fragments (up to 2 mm in length) occur as porphyroclasts surrounded by fine-grained plagioclase within the leucocratic domains and may occur within the melanocratic layers completely or partially surrounded by biotite and spinels. Fractures are common within zircon, define networks and have associated displacements occasionally and/or they can be filled by secondary minerals.Cathodoluminescence (CL) images reveal that zircon grains from the leucocratic layers show relicts of primary magmatic (i.e. oscillatory and or sector) zoning generally related with the crystal shapes or crystallographic orientation, whereas those from the melanocratic domains do not. In both cases, zircon shows secondary CL features, i.e. mosaic-like textures, due to deformation. EBSD maps confirmed a profuse mosaic texture, resulting in an internal misorientation of ca. 10°, generally associated with fractures. Locally, zircon shows clear evidence of crystal-plastic deformation at the edges, with a gradual misorientations of up to 12°, suggesting an origin prior fragmentation.Trace elements and U–Pb analyses were carried out by LA-ICP-MS directly on petrographic thin sections. Such in situ investigations revealed a strong correlation between internal zircon structures, chemistry, U–Pb isotope ratios and mylonitic fabric.U–Pb data return highly discordant and variable ages. The 206Pb/238U ages may range from ca. 297 to 198 Ma within the same zircon grain from the leucocratic layers, whereas 206Pb/238U younger than 250 Ma were systematically obtained from zircon within the melanocratic layers. The 206Pb/238U data younger than ca. 240 Ma from zircon grains within the leucocratic layers were obtained from narrow axial stripes observed in CL images and oriented parallel or at low-angle with respect to the foliation planes. These stripes are characterized by an overall HREE, Y, U and Th enrichment possibly reflecting deformation of the grain in presence of interstitial fluid phases. Combining U–Pb data, microstructure and zircon CL features, we suggest a multistage evolution of the dykes whereby the melanocratic layers are the result of a Late Permian metasomatic event promoting modification of the pre-existing mineral assemblage of the (Late Carboniferous–Early Permian?) dykes and deformation and partial resetting of zircon porphyroclasts. This has important implications in the geology of the Ivrea–Verbano Zone because, having the dyke intruded the External Gabbro unit before Triassic (probably during Carboniferous–Permian), the latter cannot be considered a Triassic intrusion. At least part of the External Gabbro unit is Carboniferous–Permian as the other mafic bodies of the Ivrea–Verbano Zone.

International audience; Deep melt intrusion and melt-peridotite interaction may introduce small-scale heterogeneity in the MORB mantle. These processes generate pyroxenite-bearing veined mantle that represent potential mantle sources of oceanic basalts. Natural proxies of such veined mantle are very rare and our understanding of mechanisms governing the chemical modification of mantle peridotite by MORB-type pyroxenite emplacement is very limited. We report the results of detailed spatially-controlled chemical profiles in pyroxenite-peridotite associations from the Northern Apennine ophiolitic mantle sequences (External Liguride Units, Italy), and investigate the extent and mechanism driving the local modification of peridotite by the interaction with pyroxenite-derived melt. Pyroxenites occur as cm-thick layers parallel to mantle tectonite foliation and show diffuse orthopyroxene-rich reaction rims along the pyroxenite-peridotite contact. Relative to distal unmodified peridotites, wall-rock peridotites show i) modal orthopyroxene enrichment at the expense of olivine, ii) higher Al, Ca, Si contents and slightly lower XMg, iii) Al-richer spinel and lower-XMg pyroxenes. Clinopyroxenes from wall-rock peridotites exhibit variable LREE-MREE fractionation, always resulting in SmN/NdN ratios lower than distal peridotites. From the contact with pyroxenite layers, peridotite clinopyroxenes record a REE compositional gradient up to about 15 cm marked by an overall REE increase away from the pyroxenite. Beyond 15 cm, and up to 23 cm, the MREE and HREE content decreases while the LREEs remain at nearly constant abundances. This REE gradient is well reproduced by a two-step numerical simulation of reactive melt percolation assuming variable amounts of olivine assimilation and pyroxene crystallization. Percolative reactive flow at decreasing melt mass and rather high instantaneous melt/peridotite ratio (initial porosity of 30%), combined with high extents of fractional crystallization (i.e. relatively low Ma/Mc ratio), accounts for the overall REE enrichment in the first 15 cm. Change of melt-rock reaction regime, mostly determined by the drastic decrease of porosity (Φi = 0.01) due to increasing crystallization rates, results in more efficient chemical buffering of the host peridotite on the HREE composition of the differentiated liquids through ion-exchange chromatographic-type processes, determining the observed increase of the LREE/HREE ratio. Emplacement of thin (cm-sized) pyroxenite veins by deep melt infiltration is able to metasomatize a much larger volume of the host peridotite. Hybrid mantle domains made by pyroxenite, metasomatized peridotite and unmodified peridotite potentially represent mantle sources of E-MORB. Results of this work stress the key role of melt-peridotite reactions in modifying the upwelling mantle prior to oceanic basalts production.

The gabbroic bodies from the Jurassic Ligurian ophiolites are structurally and compositionally similar to the gabbroic sequences from the oceanic core complexes of the Mid Atlantic Ridge. Initial cooling of the Ligurian gabbros is associated with local development of hornblende-bearing felsic dykes and hornblende vein networks. The hornblende veining is correlated with the widespread development of hornblende as coronas/pseudomorphs after the clinopyroxene in the host gabbros. In addition, the studied gabbroic body includes a mantle sliver locally containing hornblende gabbros and hornblendite veins. The hornblendes from the felsic dykes and the hornblende-rich rocks within the mantle sliver show a similar geochemical signature, characterized by low Mg#, CaO and Al2O3, negligible Cl, and high TiO2, K2O, REE, Y, Zr and Nb concentrations. The whole-rock Sm–Nd isotopic compositions of the felsic dykes and the hornblende-rich rocks define a Sm–Nd isochron corresponding to an age of 154 ± 20 Ma and an initial eNd of 9.2 ± 0.5. The δ18O of the hornblendes and coexisting zircons from these rocks (about +4.5‰ and +5.8‰, respectively) do not indicate the presence of a seawater component in these melts. The formation of the felsic dykes and of the hornblende-rich rocks within the mantle sliver involved SiO2-rich silicate melts with negligible seawater component, which presumably were derived from high degree fractional crystallization of MOR-type basalts. The vein and the coronitic/pseudomorphic hornblendes show high Mg# and CaO, significant Cl (0.02–0.17 wt%) and low TiO2 and K2O concentrations. The coronitic/pseudomorphic hornblendes have trace element compositions similar to those of the clinopyroxenes from the gabbros and δ18O values (+1.0‰ to 0.7‰) close to seawater, suggesting an origin by reaction between migrating seawater-derived fluids and the host gabbros. The vein hornblendes commonly show slight LREE enrichment, relatively high concentrations of Nb (up to 2.5 ppm) and δ18O ranging from +3.7‰ to +0.8‰. The crystallization of these hornblendes most likely involved both seawater and magmatic components.

Examples of the latest stages of crystallization in evolved tholeiitic rocks can be found in the low-Ti, low-P Ferrar Magmatic Province in Antarctica (e.g., Them Promontory and Archambault Ridge) and Tasmania (e.g., the Red Hill intrusion and Mount Wellington sill). Evolved rocks of this magmatic province include: a) rocks of basaltic andesite composition containing plagioclase, augite, pigeonite, and interstitial Fe-Ti oxides; b) rocks of andesitic composition with plagioclase as a liquidus phase, a single Fe-rich subcalcic clinopyroxene and Fe-Ti oxides; and c) rocks of dacitic composition displaying granophyric texture, containing sodic plagioclase, alkali feldspar, ferrohedenbergite, fayalite, Fe-Ti oxides, quartz and accessory phases. The latest crystallization stages are thus characterized by the striking chemical convergence of subcalcic Fe-augite and Fe-pigeonite followed by more evolved rocks that preserve quartz-alkali feldspar cotectic (granophyric) relationships, lack subcalcic clinopyroxene and contain coexisting olivine and calcium-rich clinopyroxene. These features are consistent with crystallization at (or below) the quartz-fayalite-magnetite oxygen buffer at temperatures close to 800 degrees C. The trace element geochemistry of coexisting pyroxenes, feldspar and Fe-Ti oxides are entirely consistent with magmatic evolution caused by fractional crystallization of the observed phases. Similarities and differences with other silicic volcanic rocks elsewhere are also described. There is no evidence for liquid immiscibility. (C) 2013 Elsevier B.V. All rights reserved.

Anhydrous spinel peridotite xenoliths in Quaternary nepheline-basanite and melilite- or sodalite-bearing lavas of the Wau-en-Namus volcano in S Libya range from lherzolites to harzburgites recording melt extraction in a shallow setting (

Detailed Sm–Nd mineral ID-TIMS, EMPA and LA-ICP-MS analysis of meta-pegmatite minerals from the Koralpe–Stubalpe area, Austria, involving single crystal separation, step-wise dissolution and acid leaching techniques, yielded (i) information about the partitioning of REE between accessory and major mineral phases in meta-pegmatites, and (ii) age constraints on the long-lasting “Permian–Triassic event” in the Austroalpine basement units of the Eastern Alps. Internal Sm–Nd mineral isochrons performed on porphyroclast domains from the three localities Rostockbach, Kuppergrund and Wildbachgraben, including garnet, xenotime, apatite, monazite and feldspar indicate multiple emplacement of pegmatoid melts between 273 ± 2 and 258 ± 3 Ma. Other localities yielded younger ages, indicating that magmatic garnet crystallisation persisted from 251 ± 7 to c. 230 Ma. Ages calculated between high-REE accessories (monazite, apatite, xenotime) and the low-REE major phases feldspar and garnet are largely consistent. Zircon, however, plots clearly off the internal regression line. H 2 SO 4 leaching experiments on meta-pegmatite garnet rich in micron-sized xenotime and apatite inclusions, locally affected by dynamic recrystallisation, yielded information about the behaviour of the Sm–Nd system during strong tectono-metamorphic overprinting. The data suggest multiple injections of pegmatite melts, at distinctly different times, during protracted crustal thinning and heating in the Permian–Triassic. Ky-paramorphs after andalusite, and micro-inclusions of kyanite, staurolite and sillimanite in magmatic garnet indicate crystallisation of the garnet at moderately high, but variable pressure conditions. During subsequent eclogite-facies overprinting (peak PT c. 700 °C/2.2 GPa) and intense deformation in Cretaceous time, the magmatic chemical and isotopic signatures of porphyroclasts were largely preserved, except for localized within-grain micro-shear zones and outermost rim domains, whereas part of the feldspar-rich matrix recrystallised during pervasive mylonitisation along the eclogite- to amphibolite-facies-grade exhumation path.