Multianalytical provenance analysis of Eastern Ross Sea LGM till sediments (Antarctica): Petrography, geochronology, and thermochronology detrital data

In order to reveal provenance of detrital sediments supplied by West Antarctic Ice Sheet (WAIS), 19 glaciomarine cores of Last Glacial Maximum age were analyzed from Eastern Ross Sea and Sulzberger Bay. Analytical techniques included petrographic analysis of gravel-sized clasts, geochronology (zircon U-Pb: Zrn-UPb) and thermochronology (apatite fission track: AFT) of sand-sized fractions. Petrographic analysis revealed a similarity with the lithologies presently exposed in western Marie Byrd Land (MBL), with major roles played by low-grade metamorphic rocks and granitoids. Furthermore Zrn-UPb and AFT data allowed to identify the ages of formation and cooling of sedimentary source area, consisting of Cambrian-Precambrian basement (i.e., Swanson Formation in western MBL) which underwent at least two episodes of magma intrusion, migmatization and cooling during Devonian-Carboniferous and Cretaceous-Paleocene times. Scarcity of volcanic clasts in the region of Ross Sea along the front of West Antarctica Ice Streams in association with the occurrence of AFT Oligocene-Pliocene dates suggests a localized tectonic exhumation of portions of MBL, as already documented for the opposite side of West Antarctic Rift System in the Transantarctic Mountains. Furthermore, a Zrn-UPb and AFT population of Late Triassic-Jurassic age indicates the presence of unexposed rocks that formed or metamorphosed at that time in the sedimentary source area, which could be identified in McAyeal Ice Stream and Bindschadler Ice Stream catchment areas

Geochemistry of sapphirine-apatite-calcite-bearing gabbroic dykes from the Finero Phlogopite Peridotite (Ivrea-Verbano Zone): evidence for multistage interaction with the ambient peridotite

The Finero Phlogopite-Peridotite (FPP) is a mantle unit outcropping in the northernmost tip of the Ivrea-Verbano Zone (IVZ, Southern Alps). It shows a virtually complete recrystallization due to pervasive to channelled melt migration. The pervasive metasomatism formed a main lithologic association constituted by phlogopite harzburgites associated to phlogopite pyroxenites (mainly olivine-websterites, websterites and orthopyroxenites). These lithologies are also rich in amphibole and do not show significant chemical gradients among them (Zanetti et al., 1999). The channelled migration stages formed dunite bodies, which sometimes contain stratiform chromitites and, more rarely, pyroxenite layers similar to those associated to phlogopite harzburgite. The FPP also shows a discrete number of other, subordinate rock-types, which are characterised by the presence of apatite usually associated to carbonates (i.e. calcite or dolomite) and exhibit marked modal and chemical gradients with respect to the host phlogopite harzburgite. Examples of these lithologies are apatite-dolomitebearing wehrlites and harzburgites (e.g. Zanetti et al. 1999; Morishita et al., 2008), apatite-calcite zircon-syenites and hornblendites. Ar-Ar amphibole analysis and U-Pb zircon and apatite data return Triassic ages for these rocks, which have been considered to document the time of melt/fluid injection. Notwithstanding the apparent mineralogical and chemical differences with the main lithologic sequences, apatite-carbonates-bearing rocks have been frequently interpreted as cogenetic to phlogopite harzburgites. To debate the petrogenesis of these rocks, a detailed field, petrological and geochemical investigation has been carried out on a swarm of apatite-calcite-bearing gabbroic veins that randomly cut the main lithologic association. Preliminary investigation evidenced as these veins show complex metasomatic haloes and a symmetric internal layering, characterised by crystallisation of magmatic sapphirine (Giovanardi et al., 2013). The mineral assemblage of the veins is dominated by titanian pargasite towards the host peridotite and by plagioclase at the vein centre. The veins also present phlogopite and spinel. Field and petrographic evidence, major and trace element data and the O isotopic composition of such gabbroic veins indicate that they formed at shallow mantle conditions by multistage fractional crystallisation of a migrating melt unrelated to those forming phlogopite harzburgites. Besides, local strong enrichments in LILE, LREE and 18O in vein minerals confirm that such melt was deeply modified by interaction with the host phlogopite peridotite. The genetic relationships with other intrusive events recorded by the FPP and the associated crustal sequence will be addressed with the aim of placing new constraints on the petrologic and geodynamic evolution of the IVZ

A 70-year long lessepsian colonization: the conquest of Malta by Amphistegina lobifera

The highly invasive Amphistegina lobifera (Larsen, 1976), a non-indigenous benthic foraminifera coming from the Red Sea through the Suez Canal, has colonized the Eastern Mediterranean during the last decades and in 2006 it was recorded for the first time from the Maltese Islands (Central Mediterranean). Here, we report new data from a sediment core collected in May 2018 near the northern coast of Malta. Results show that A. lobifera reached Malta between 1950 and 1955; then it progressively increased in abundance with time, probably favoured by the rising of Mediterranean SST during the last 40 years.peer-reviewe

The Cotoncello Shear Zone (Elba Island, Italy): The deep root of a fossil oceanic detachment fault in the Ligurian ophiolites

The ophiolite sequences in the western Elba Island are classically interpreted as a well-exposed ocean-floor section emplaced during the Apennines orogeny at the top of the tectonic nappe-stack. Stratigraphic, petrological and geochemical features indicate that these ophiolite sequences are remnants of slow-ultraslow spreading oceanic lithosphere analogous to the present-day Mid-Atlantic Ridge and Southwest Indian Ridge. Within the oceanward section of Tethyan lithosphere exposed in the Elba Island,we investigated for the first time a 10s of meters-thick structure, the Cotoncello Shear Zone (CSZ), that records high-temperature ductile deformation. We used a multidisciplinary approach to document the tectono-metamorphic evolution of the shear zone and its role during spreading of the western Tethys. In addition, we used zircon U–Pb ages to date formation of the gabbroic lower crust in this sector of the Apennines. Our results indicate that the CSZ rooted below the brittle–ductile transition at temperature above 800 °C. A high-temperature ductile fabric was overprinted by fabrics recorded during progressive exhumation up to shallower levers under temperature b500 °C.Wesuggest that the CSZ may represent the deep root of a detachment fault that accomplished exhumation of an ancient oceanic core complex (OCC) in between two stages of magmatic accretion.We suggest that the CSZ represents an excellent on-land example enabling to assess relationships between magmatism and deformation when extensional oceanic detachments are at work

Mantle-Derived Corundum-Bearing Felsic Dykes May Survive Only within the Lower (Refractory/Inert) Crust: Evidence from Zircon Geochemistry and Geochronology (Ivrea–Verbano Zone, Southern Alps, Italy)

Corundum-rich (up to 55 vol.%) felsic dykes formed with albite, +/- K-feldspar, +/- hercynite and +/- biotite-siderophyllite cut the lower crustal rocks exposed in the Ivrea–Verbano Zone (NW Italy). Zircon is an abundant accessory mineral and its investigation through laser ablation-inductively coupled plasma (multi-collector)-mass spectrometer (LA-ICP-(MC)MS) has allowed results to directly constrain the timing of emplacement, as well as petrology and geochemistry of parental melts. Zircons are characterized by very large concentration in rare earth elements (REE), Th, U, Nb and Ta, and negative Eu anomaly. U–Pb analysis points to Norian emplacement ages (223 +/- 7 Ma and 224 +/- 6 Ma), whereas large positive EHf(t) values (+13 on average) indicate a derivation from depleted to mildly enriched mantle source. The mantle signature and the corundum oversaturation were preserved thanks to limited crustal contamination of the host, high-temperature refractory granulites and mafic intrusives. According to the geochemical data and to the evidence of the development of violent explosions into the conduits, it is proposed that dykes segregated from peraluminous melts produced by exsolution processes affecting volatile-rich differentiates during alkaline magmatism. This work provides robust evidence about the transition of the geochemical affinity of Southern Alps magmatism from orogenic-like to anorogenic during Norian time, linked to a regional uprising of the asthenosphere and change of tectonic regime

Atmospheric CO 2 concentrations and δ 13 C values between New Zealand and Antarctica, 1998 to 2010: some puzzling results

From 1998 to 2010, during eight cruises of the M/V Italica between New Zealand and Antarctica, sets of flask air samples were collected and atmospheric CO 2 concentrations were recorded. The δ 13 C of CO 2 from the 1998 to 2003 air samples have already been published and show large interannual variability and an increasing frequency of 13 C-depleted samples. These results were related to a mosaic of areas with positive air–sea fluxes. We report here δ 13 C results from air samples collected from four further cruises. δ 13 C values obtained during the 2004/2005 cruise show an inexplicable saw-toothed distribution. Air samples from the 2005/2006 cruise have δ 13 C values which match previous sets of samples (1998 to 2004) and show more frequent and more negative isotopic events. From 2006 until 2009, further samples could not be collected. However, during December 2009 and January 2010, two more sets of air samples were collected, the δ 13 C values of which greatly differ from previous results, being absolutely homogeneous and paralleled by flat CO 2 concentrations. The results of these last two sets of air samples may be due either to fortuitous environmental conditions or to an improbable and substantial change in oceanic and atmospheric conditions in this section of the circumpolar area. Keywords: New Zealand to Antarctica, flask air samples, atmospheric CO 2 concentrations, carbon isotopic composition of CO 2 , puzzling results (Published: 5 December 2012) Citation: Tellus B 2012, 64 , 17472, http://dx.doi.org/10.3402/tellusb.v64i0.1747

Brittle-ductile deformation effects on zircon crystal-chemistry and U-Pb ages: an example from the Finero Mafic Complex (Ivrea-Verbano Zone, western Alps)

A detailed structural, geochemical and geochronological survey was performed on zircon grains from a leucocratic dioritic dyke discordantly intruded within meta-diorites/gabbros forming the External Gabbro unit of the Finero Mafic Complex. This latter is nowadays 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 dyke consists mainly of plagioclase (An18-24Ab79-82Or0.3-0.7) with subordinate amounts of biotite, spinel, zircon and corundum. Both the leucocratic dyke and the surrounding meta-diorites show evidence of ductile deformation occurred under amphibolite-facies conditions. Zircon grains (up to 2 mm in length) occur mainly as euhedral grains surrounded by fine grained plagioclasedominated matrix and pressure shadows, typically filled by oxides. Fractures and cracks within zircon are common and can be associated with grain displacement or they can be filled by secondary minerals (oxides and chlorite). Cathodoluminescence (CL) images show that zircon grains have internal features typical of magmatic growth, but with local disturbances. However EBSD maps on two selected zircon grains revealed a profuse mosaic texture resulting in an internal misorientation of ca. 10o. The majority of the domains of the mosaic texture are related to parting and fractures, but some domains show no clear relation with brittle features. Rotation angles related to the mosaic texture are not crystallographically controlled. In addition, one of the analysed zircons shows clear evidence of plastic deformation at one of its corners due to indentation. Plastic deformation results in gradual misorientations of up to 12o, which are crystallographically controlled. Trace elements and U-Pb analyses were carried out by LA-ICP-MS directly on petrographic thin sections and designed to cover the entire exposed surface of selected grains. Such 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: in particular, the 206Pb/238U ages range from Carboniferous to Triassic within the same zircon grain. The youngest 206Pb/238U data derive from narrow axial stripes 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, likely related to a concomitant magmatic activity. Deformation related structures (cracks and fractures) within zircon grains acted as fast-diffusion pathways allowing fluids to modify the geochemistry and isotopic systems of zircon. Our results suggest that fluid-assisted brittle-ductile deformation can severely modify the trace elements and isotopic composition of zircon with unexpected patterns constrained by stress regime. In similar cases, our observations suggest that, for a more appropriate interpretation of the petrologic evolution and age variability, a direct characterization of the internal structures of zircons still placed in their microtextural site is highly recommended

Dinâmica larval do mexilhão dourado Limnoperna fortunei no reservatório de Aguas Corrientes, rio Santa Lucía, Uruguay

The golden mussel (Limnoperna fortunei) is an invasive exotic species that has several negative impacts in ecosystems worldwide. Santa Lucía River is the main drinking water source, supplying 60% of the total population of Uruguay. L. fortunei has been reported since 1996 in the basin, and nowadays is present in the three reservoirs that supply the water treatment plant. The aim of this study was to analyze the temporal dynamics of L. fortunei larvae in Aguas Corrientes reservoir (Santa Lucía River). We quantify diary L. fortunei larvae and phytoplankton, we also measure physicochemical parameters of water. L. fortunei larvae showed a seasonal dynamic and its development was promoted by temperatures up to 17°C. Temperature was the main variable controlling the presence of larvae. Once temperature was optimal for its reproduction, the reservoir level was the key variable to determine the presence of larvae. This shows the importance of flow managing in the reservoir in order to reduce golden mussel impacts during the reproductive season. We also propose two alternative regulation mechanisms of larvae, acting at two different scales: physiological and environmental.El mejillón dorado (Limnoperna fortunei) es una especie exótica invasora que causa grandes perjuicios a nivel mundial. El río Santa Lucía es la principal fuente de agua potable que abastece al 60% de la población de Uruguay. L. fortunei ha sido reportado desde 1996 en la cuenca y actualmente se encuentra en los tres embalses que abastecen a la usina potabilizadora. El objetivo de este trabajo fue caracterizar la dinámica temporal de las larvas de L. fortunei en el embalse de Aguas Corrientes (río Santa Lucía). Para esto se realizaron análisis diarios del embalse donde se midieron parámetros fisicoquímicos y cuantificaron larvas y la comunidad fitoplanctónica. Las larvas de L. fortunei presentaron una dinámica estacional y su desarrollo fue favorable a temperaturas mayores a los 17°C. La temperatura fue la principal variable moduladora de la presencia de larvas. Una vez que la temperatura fue adecuada para su reproducción, la cota del embalse resultó ser la variable clave para determinar la presencia de larvas. Esto evidencia la importancia del manejo del caudal del embalse durante la época reproductiva del mejillón para disminuir sus impactos. Se plantean dos mecanismos de regulación de las larvas que actúan a diferentes escalas: fisiológico y ambiental.O mexilhão dourado (Limnoperna fortunei) é uma espécie exótica invasora que causa grandes danos em todo o mundo. O rio Santa Lucía é a principal fonte de água potável que abastece 60% da população do Uruguai. L. fortunei é registrada desde 1996 na bacia e atualmente é encontrada nos três reservatórios principais que abastecem a estação de tratamento de água. O objetivo deste trabalho foi caracterizar a dinâmica temporal de larvas de L. fortunei no reservatório de Aguas Corrientes (rio Santa Lucía). Para isso, foram realizadas análises diárias do reservatório, onde foram medidos parâmetros físico-químicos e quantificadas as larvas e a comunidade fitoplanctônica. As larvas de L. fortunei apresentaram dinâmica sazonal e seu desenvolvimento foi favorável em temperaturas superiores a 17°C. A temperatura foi a principal variável moduladora da presença de larvas. Uma vez que a temperatura foi adequada para sua reprodução, a elevação do reservatório passou a ser a variável chave para determinar a presença de larvas. Isso mostra a importância do gerenciamento da vazão do reservatório para reduzir os impactos do mexilhão dourado. Ao mesmo tempo, dois mecanismos de regulação das larvas são propostos atuando em diferentes escalas: fisiológica e ambiental

Investigation of Adjacent Lifted Flames Interaction in an Inline and Inclined Multi-Burner Arrangement

The main objective of this research is to assess an innovative, low nitrogen oxides emission combustor concept, which has the potential to achieve the long term European emissions goals for aircraft engines. Lean lifted spray flames and their very low nitrogen oxides emissions are combined with an inclination of burners in annular combustor leading to a more compact combustor with superior stability range. The presented combustor concept was developed in the frame of the European research project CHAIRLIFT (Compact Helical Arranged combustoRs with lean LIFTed flames). CHAIRLIFT combustor concept is based on “low swirl” lean lifted spray flames, which features a high degree of premixing and consequently significantly reduced nitrogen oxides emissions and flashback risk compared to conventional swirl stabilized flames. In the CHAIRLIFT combustor concept, the lifted flames are combined with Short Helical Combustors arrangement to attain stable combustion by tilting the axis of the flames relative to the axis of the turbine to enhance the interaction of adjacent flames in a circumferential direction. A series of experimental tests were conducted at a multi-burner array test rig consisting of up to five modular burners at different burner inclination angles (0° and 45°), equivalence ratios, and relative air pressure drop at ambient conditions. For all investigated configurations, a remarkable high lean blow out for non-piloted burners (ϕLBO = 0.29–0.37), was measured. The multi-burner configurations were observed having a superior stability range in contrast to the typical decrease in stability from single to high swirl multi-burner. The unwanted flow deflection of highly swirled flames in Short Helical Combustors arrangement, could be avoided with the investigated low swirl lifted flames. Moreover, the flame chemiluminescence (OH*) measurements were used to provide a qualitative characterization of the flame topology. Complementary numerical investigations were carried out using different numbers of burners to evaluate the effect of boundary conditions