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Up to 10 per cent of the ocean floor consists of plateaux 1 —regions of unusually thick oceanic crust thought to be formed by the heads of mantle plumes. Given the ubiquitous presence of recycled oceanic crust in the mantle source of hotspot basalts, it follows that plateau material should also be an important mantle constituent. Here we show that the geochemistry of the Pleistocene basalts from Logudoro, Sardinia, is compatible with the remelting of ancient ocean plateau material that has been recycled into the mantle. The Sr, Nd and Hf isotope compositions of these basalts do not show the signature of pelagic sediments. The basalts’ low CaO/Al 2 O 3 and Ce/Pb ratios, their unradiogenic 206 Pb and 208 Pb, and their Sr, Ba, Eu and Pb excesses indicate that their mantle source contains ancient gabbros formed initially by plagioclase accumulation, typical of plateau material. Also, the high Th/U ratios of the mantle source resemble those of plume magmas. Geochemically, the Logudoro basalts resemble those from Pitcairn Island, which contain the controversial EM-1 component that has been interpreted as arising from a mantle source sprinkled with remains of pelagic sediments 2 , 3 . We argue, instead, that the EM-1 source from these two localities is essentially free of sedimentary material, the geochemical characteristics of these lavas being better explained by the presence of recycled oceanic plateaux. The storage of plume heads in the deep mantle through time offers a convenient explanation for the persistence of chemical and mineralogical layering in the mantle.

The Austroalpine Sesia-Lanzo inlier and upper Austroalpine Dent Blanche, Mt. Mary and Pillonet outliers occur on top of the western-Alpine orogenic wedge and, as a whole, override the structurally composite ophiolitic Piemonte zone. Instead, the Mt. Emilius, Glacier-Rafray, Etirol-Levaz and other lower Austroalpine eclogitic outliers are inserted within the Piemonte zone, between its upper (Combin) and lower (Zermatt-Saas) tectonic elements, or within the latter. Rb-Sr dating on phengitic micas show that the eclogitic imprint in the lower Austroalpine outliers, conventionally regarded as Late Cretaceous by comparison with the Sesia-Lanzo inlier, is of Eocene age (49-40 Ma), like the underlying Zermatt-Saas ophiolite (45-42 Ma) between the Aosta valley and Gran Paradiso massif. super(40)Ar- super(39)Ar plateau ages on the same mica concentrates of the ophiolitic Zermatt-Saas nappe (46-43 Ma) are consistent with Rb-Sr dating, whereas that on the Austroalpine Glacier-Rafray klippe (92 Ma) is influenced by argon excess. The lower Austroalpine outliers underwent the subduction metamorphism concurrently with the Zermatt-Saas nappe, 20-25 Ma later than the eclogitic Sesia-Lanzo inlier and blueschist Pillonet klippe. The temporal gap and present intra-ophiolitic position mean that the lower Austroalpine outliers were probably derived from an intraoceanic extensional allochthon (Mt. Emilius domain) stranded inside the Piemonte-Ligurian ocean far from the Dent Blanche-Sesia domain and Adriatic margin.

Leucosomes, mesosomes and melanosomes, including 12 leucosome-host rock pairs have been studied for Sr and Nd isotopic systematics in migmatitic metapelites of the Serre (southern Calabria) which experienced granulite facies conditions in Hercynian times. Most samples came from the deep to middle part of a metapelitic unit, which is 5-6 km thick. The leucosomes presently occurring in the migmatites are mainly K-poor peraluminous leucotonalites; the host rocks (metapelites, metagreywackes and opx-bearing rocks) are more or less depleted in \"granitic\" component and have molar Al2O3/(CaO + Na2O + K2O) (A/CNK) ratios up to 15; the highest values relate to garnet + sillimanite-rich metapelites. Sm/Nd ratios are generally lower in the leucosomes and Rb/Sr ratios are very low (<< 1) and lower than in related mesosomes and melanosomes. The isotopic Sr and Nd values vary in a wide range within the various kinds of host-rocks and within the leucosomes. A correlation of Nd- and Sr- isotopic compositions between coexisting leucosomes and host-rocks has not been found. The isotopic Sr and Nd values of the leucosomes are less variable than the host-rocks; melanosomes having A/CNK ratios > 3 concentrate at the lowest [straight epsilon]Nd290 Ma values, owing to retention of garnet and accessories and depletion of feldspars. The leucosomes define a hyperbolic trend where most samples concentrate in the middle part. These features are interpreted as reflecting melting of several rock types generating melts having a weighted mean composition from the contributing sources. The prevailing leucotonalites and their very low Rb/Sr ratios indicate that plagioclase played a more important role than mica in the melting processes which produced the studied leucosomes. Since assemblages lacking or very poor in biotite and K-feldspar are common in metapelitic restites, potassic melts, as one should expect from melting of micas, must have been extracted before the leucosomes under study formed. Aufschmelzung im Ungleichgewicht dokumentiert an granulitfaziellen Metasedimenten der nördlichen Serre (Kalabrien, Süditalien) Die Sr und Nd Isotopensystematik von Leuko-, Meso- und Melanosomen, einschließlich von 12 Leukosom- und Nebengesteinspaaren, wurde untersucht. Sie treten in migmatitischen Metapeliten der Serre (südliches Kalabrien) auf, deren granulitfazielle Metamorphose als hercynisch eingestuft wird. Die meisten Proben stammen aus dem unteren Teil der mittleren Metapeliteinheit, die eine Mächtigkeit von 5-6 km erreicht. Die in den Migmatitien auftretenden Leukosome sind hauptsächlich K-arme, peraluminöse Leukotonalite. Die Nebengesteine (Metapelite, Metagrauwacken, und Opx-führende Gesteine) sind mehr oder weniger an \"granitischer\" Komponente verarmt und haben molare A/CNK Verhältnisse bis 15, mit den höchsten Werten in Granat- Sillimanit- reichen Metapeliten. Die Sm/Nd- Verhältnisse sind generell niedriger in den Leukosomen. Rb/Sr ist sehr niedrig (<< 1) und niedriger als in den Meso- und Melanosomen. Die Sr- und Nd-Isotopenzusammensetzungen variieren stark innerhalb der verschiedenen Nebengesteine und ihrer assoziierten Leukosome. Eine Korrelation der Nd- und Sr- Isotopenzusammensetzungen zwischen koexistierenden Leukosomen und Nebengesteinen konnte nicht festgestellt werden. Die Sr- und Nd-Isotopie der Leukosome ist weniger variabel als die der Nebengesteine. Die Melanosome, sie haben A/CNK > 3, zeigen die niedrigsten [straight epsilon]Nd290 Ma Werte als Folge der Retention von Granat und Akzessorien und der Verarmung an Feldspat. Die Leukosome definieren einen hyperbolischen Trend, wobei die meisten Proben in der Mitte zu liegen kommen. Dies wird so interpretiert, dass mehrere Gesteinstypen, die eine gewichtete mittlere Zusammensetzung der an der Aufschmelzung beteiligten Ausgangsmaterialien darstellen, aufgeschmolzen wurden. Die vorherrschenden Leukotonalite und ihre sehr niedrigen Rb/Sr Verhältnisse zeigen, dass Plagioklas eine wichtigere Rolle bei den leukosombildenden Schmelzprozessen spielte als Glimmer. Da Mineralvergesellschaftungen, die arm an Biotit und Alkalifeldspat sind, häufig in metapelitischen Restiten auftreten, müssen K-reiche Schmelzen - sie sind zu erwarten wenn Glimmer aufgeschmolzen werden - vor der Bildung der Leukosome extrahiert worden sein.

We use the WISE all sky survey observations to look for counterparts of hard X-ray selected sources from the XMM-Newton-SDSS survey. We then measure the 12 μm luminosity of the AGN by decomposing their optical to infrared SEDs with a host and an AGN component and compare it to the X-ray luminosity and their expected intrinsic relation. This way we select 20 X-ray under-luminous heavily obscured candidates and examine their X-ray and optical properties in more detail. We find evidence for a Compton-thick nucleus for six sources, a number lower than what expected from X-ray background synthesis models, which shows the limitations of our method.

We present the X-ray point-source catalogs in two of the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) fields, W-CDF-S (4.6 deg\\(^2\\)) and ELAIS-S1 (3.2 deg\\(^2\\)), aiming to fill the gap between deep pencil-beam X-ray surveys and shallow X-ray surveys over large areas. The W-CDF-S and ELAIS-S1 regions were targeted with 2.3 Ms and 1.0 Ms of XMM-Newton observations, respectively; 1.8 Ms and 0.9 Ms exposures remain after flare filtering. The survey in W-CDF-S has a flux limit of 1.0 \\(\\times\\) 10\\(^{-14}\\) erg cm\\(^{-2}\\) s\\(^{-1}\\) over 90% of its area in the 0.5-10 keV band; 4053 sources are detected in total. The survey in ELAIS-S1 has a flux limit of 1.3 \\(\\times\\) 10\\(^{-14}\\) erg cm\\(^{-2}\\) s\\(^{-1}\\) over 90% of its area in the 0.5-10 keV band; 2630 sources are detected in total. Reliable optical-to-IR multiwavelength counterpart candidates are identified for \\(\\approx\\) 89% of the sources in W-CDF-S and \\(\\approx\\) 87% of the sources in ELAIS-S1. 3186 sources in W-CDF-S and 1985 sources in ELAIS-S1 are classified as AGNs. We also provide photometric redshifts for X-ray sources; \\(\\approx\\) 84% of the 3319/2001 sources in W-CDF-S/ELAIS-S1 with optical-to-NIR forced photometry available have either spectroscopic redshifts or high-quality photometric redshifts. The completion of the XMM-Newton observations in the W-CDF-S and ELAIS-S1 fields marks the end of the XMM-SERVS survey data gathering. The \\(\\approx\\) 12,000 point-like X-ray sources detected in the whole \\(\\approx\\) 13 deg\\(^2\\) XMM-SERVS survey will benefit future large-sample AGN studies.

In the context of the upcoming SRG/eROSITA survey, we present an N-body simulation-based mock catalogue for X-ray selected AGN samples. The model reproduces the observed hard X-ray AGN luminosity function (XLF) and the soft X-ray logN-logS from redshift 0 to 6. The XLF is reproduced to within \\(\\pm5\\%\\) and the logN-logS to within \\(\\pm20\\%\\). We develop a joint X-ray -- optical extinction and classification model. We adopt a set of empirical spectral energy distributions to predict observed magnitudes in the UV, optical and NIR. With the latest eROSITA all sky survey sensitivity model, we create a high-fidelity full-sky mock catalogue of X-ray AGN. It predicts their distributions in right ascension, declination, redshift and fluxes. Using empirical medium resolution optical spectral templates and an exposure time calculator, we find that \\(1.1\\times10^6\\) (\\(4\\times10^5\\)) fiber-hours are needed to follow-up spectroscopically from the ground the detected X-ray AGN with an optical magnitude \\(21

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