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S Borisov - One of the best experts on this subject based on the ideXlab platform.

  • measurement of the isotopic composition of hydrogen and Helium nuclei in cosmic rays with the pamela experiment
    The Astrophysical Journal, 2013
    Co-Authors: O. Adriani, G. A. Bazilevskaya, Roberto Bellotti, M. Boezio, E. A. Bogomolov, Massimo Bongi, V. Bonvicini, G C Barbarino, S Borisov
    Abstract:

    The satellite-borne experiment PAMELA has been used to make new measurements of cosmic ray H and He Isotopes. The isotopic composition was measured between 100 and 600 MeV/n for hydrogen and between 100 and 900 MeV/n for Helium Isotopes over the 23rd solar minimum from 2006 July to 2007 December. The energy spectrum of these components carries fundamental information regarding the propagation of cosmic rays in the galaxy which are competitive with those obtained from other secondary to primary measurements such as B/C.

David R. Hilton - One of the best experts on this subject based on the ideXlab platform.

  • Multi-level magma plumbing at Agung and Batur volcanoes increases risk of hazardous eruptions.
    Scientific reports, 2018
    Co-Authors: Harri Geiger, David R. Hilton, Valentin R. Troll, Ester M. Jolis, Frances M. Deegan, Chris Harris, Carmela Freda
    Abstract:

    The island of Bali in Indonesia is home to two active stratovolcanoes, Agung and Batur, but relatively little is known of their underlying magma plumbing systems. Here we define magma storage depths and isotopic evolution of the 1963 and 1974 eruptions using mineral-melt equilibrium thermobarometry and oxygen and Helium Isotopes in mineral separates. Olivine crystallised from a primitive magma and has average δ18O values of 4.8‰. Clinopyroxene records magma storage at the crust-mantle boundary, and displays mantle-like isotope values for Helium (8.62 RA) and δ18O (5.0–5.8‰). Plagioclase reveals crystallisation in upper crustal storage reservoirs and shows δ18O values of 5.5–6.4‰. Our new thermobarometry and isotope data thus corroborate earlier seismic and InSAR studies that inferred upper crustal magma storage in the region. This type of multi-level plumbing architecture could drive replenishing magma to rapid volatile saturation, thus increasing the likelihood of explosive eruptions and the consequent hazard potential for the population of Bali.

  • Helium Isotopes at Rungwe Volcanic Province, Tanzania, and the origin of East African Plateaux
    Geophysical Research Letters, 2011
    Co-Authors: David R. Hilton, Sæmundur A. Halldórsson, Tobias P. Fischer, Peter H. Barry, J. M. De Moor, Carlos Ramírez, F. Mangasini, Paolo Scarsi
    Abstract:

    [1] We report Helium isotope ratios (3He/4He) of lavas and tephra of the Rungwe Volcanic Province (RVP) in southern Tanzania. Values as high as 15RA (RA = air 3He/4He) far exceed typical upper mantle values, and are the first observation of plume-like ratios south of the Turkana Depression which separates the topographic highs of the Ethiopia and Kenya domes. The African Superplume - a tilted low-velocity seismic anomaly extending to the core-mantle boundary beneath southern Africa – is the likely source of these high 3He/4He ratios. High 3He/4He ratios at RVP together with similarly-high values along the Main Ethiopian Rift and in Afar provide compelling evidence that the African Superplume is a feature that extends through the 670-km seismic discontinuity and provides dynamic support – either as a single plume or via multiple upwellings – for the two main topographic features of the East Africa Rift System as well as heat and mass to drive continuing rift-related magmatism.

  • Helium Isotopes in peridotite mineral phases from hyblean plateau xenoliths south eastern sicily italy
    Chemical Geology, 2005
    Co-Authors: Giovanna Sapienza, David R. Hilton, Vittorio Scribano
    Abstract:

    Abstract Fourteen He isotope and abundance analyses have been performed on olivine, orthopyroxene, and clinopyroxene grains from selected spinel-facies peridotite xenoliths collected from the Hyblean Plateau, southeastern Sicily. These peridotites consist of protogranular-textured, spinel-facies lherzolites and lherzolitic harzburgites. Microthermometric data on olivine and pyroxenes reveal that the fluid inclusions (FIs) are nearly pure CO 2 , with densities ranging from 0.76 to 1.15 g/cm 3 . The densest inclusion trail occurs in an orthopyroxene grain and indicates a trapping-pressure of 0.98–1.14 GPa (estimated equilibration temperature of 1000 °C for pure CO 2 system) corresponding to a depth of ∼ 36–41 km (for an average estimated density of the lithospheric column of 2.85 g/cm 3 ). These are minimum estimates. The near-unimodal distribution of CO 2 densities indicates that these xenoliths have been stored at the pressure interval of 0.75–0.95 GPa—corresponding to a depth of ∼ 27–35 km (crust–mantle boundary or just below). En route to the surface, they have not had any significant interaction with shallower volatile reservoirs. He trapped in CO 2 -rich fluid inclusions ranges in abundance from 1.8 to 86.6×10 − 9 cm 3 STP/g, with clinopyroxenes usually showing higher He contents than coexisting olivines and orthopyroxenes. The inter-mineral differences are due to physical properties of minerals. In contrast, He isotope ratios cover a narrow range (∼ 7.3 ± 0.3 R A , where R A  = air 3 He/ 4 He), indicating isotopic equilibration between the mineral phases. He composition indicates a MORB-type source for the metasomatic agent(s), influenced by relatively minor radiogenic production in the source. Therefore, in closed-system conditions, the calculated Helium residence time is 790 Myr. Geophysical and geochemical studies suggest the existence of a common fluid reservoir in the mantle beneath the Central Mediterranean area. The most pristine He signature for the mantle endmember is found on Pantelleria Island (Sicily Channel): this He ratio is similar to that found in Hyblean peridotite minerals, testifying to a common source history. We conclude, therefore, that Hyblean xenoliths can be used as a powerful tool in defining the geochemical features of this portion of the upper mantle.

  • Crustal contamination processes traced by Helium Isotopes: Examples from the Sunda arc, Indonesia
    Earth and Planetary Science Letters, 1994
    Co-Authors: Massimo Gasparon, David R. Hilton, R. Varne
    Abstract:

    Helium isotope data have been obtained on well-characterised olivine and clinopyroxene phenocrysts and xenocrysts from thirteen volcanic centres located between central Sumatra and Sumbawa in the Sunda arc of Indonesia. Olivine crystals in mantle xenoliths (lherzolite) from Bukit Telor basalts are primitive (Mg# = 90), and their 3He 4He value ( R RA = 8.8) indicates that the Sumatran mantle wedge is MORB-like in Helium isotope composition. All other samples have lower 3He 4He ratios ranging from 8.5RA to 4.5RA, with most (thirteen out of eighteen) following a trend of more radiogenic 3He 4He values with decreasing Mg#. The only exceptions to this trend are phenocrysts from Batur, Agung and Kerinci, which have MORB-like 3He 4He values but relatively low Mg# (Mg# = 70-71), and two highly inclusion-rich clinopyroxenes which have 3He 4He values lower than other samples of similar Mg#. The results indicate that crustal contamination unrelated to subduction in the Sunda arc is clearly recorded in the 3He 4He characteristics of mafic phenocrysts of subaerial volcanics, and that addition of radiogenic Helium is related to low-pressure differentiation processes affecting the melts prior to eruption. These conclusions may have widespread applicability and indicate that Helium isotope variations can act as an extremely sensitive tracer of upper crustal contamination.

  • Mapping magma sources in the east Sunda-Banda arcs, Indonesia: Constraints from Helium Isotopes
    Geochimica et Cosmochimica Acta, 1992
    Co-Authors: David R. Hilton, Jurian Hoogewerff, M.j. Van Bergen, Konrad Hammerschmidt
    Abstract:

    Abstract We report new Helium isotope analyses of olivine and clinopyroxene separates from recent lavas for eleven volcanoes from Flores in the east Sunda arc through the inactive segment between the arcs to Banda Island at the extreme of the contiguous Banda arc. In the east Sunda arc, 3 He 4 He ratios (R) vary between 4.5 RA ( R A = air 3 He 4 He ) for the leucitic Batu Tara volcano to a remarkable low of pure radiogenic Helium (0.0075 RA) for Werung at the southern tip of Lomblen Island. Lavas from the inactive zone, which represents the locus of collision of the Australian continent with the arc, have a narrower range in R R A —from 3.9 for Kisu in the straits of Pantar to 1.0 for Romang Island. Our one locality (Banda Island) in the Banda arc gives the highest R R A ratio (3.1) observed along this arc to date. The results are consistent with the involvement of crustal material in magma genesis throughout the east Sunda/Banda arcs, as far west as Iya in central Flores. We combine these Helium isotope results with published and on-going strontium isotope studies, and show that the source of the Helium in the crustal component is unlikely to be terrigenous sediments derived from the Australian continent; rather, degassing of Australian continental crust appears to be the dominant process controlling the Helium budget. The He-Sr isotope systematics also provide a framework to account for the areal pattern of 3 He 4 He in this part of the arcs: the radiogenic crustal component is diluted with mantle Helium both in a down-dip direction and with increasing lateral distance from the collision zone. These factors result in an excellent first-order relationship between the 3 He 4 He ratio, degree of He Sr enrichment (relative to the postulated mantle endmember), and alkalinity of the erupted lavas. Such a relationship has a direct bearing on models of the tectonic evolution of the collision zone, and on the observation that Helium Isotopes are decoupled from strontium and other geochemical signatures along the Banda arc.

O. Adriani - One of the best experts on this subject based on the ideXlab platform.

  • Measurements of Cosmic-Ray Hydrogen and Helium Isotopes with the PAMELA experiment
    The Astrophysical Journal, 2016
    Co-Authors: O. Adriani, Giancarlo Barbarino, G. A. Bazilevskaya, Roberto Bellotti, M. Boezio, E. A. Bogomolov, Massimo Bongi, V. Bonvicini, S. Bottai, A. Bruno
    Abstract:

    The cosmic-ray hydrogen and Helium ($^1$H, $^2$H, $^3$He, $^4$He) isotopic composition has been measured with the satellite-borne experiment PAMELA, which was launched into low-Earth orbit on-board the Resurs-DK1 satellite on June 15th 2006. The rare Isotopes $^2$H and $^3$He in cosmic rays are believed to originate mainly from the interaction of high energy protons and Helium with the galactic interstellar medium. The isotopic composition was measured between 100 and 1100 MeV/n for hydrogen and between 100 and 1400 MeV/n for Helium Isotopes using two different detector systems over the 23rd solar minimum from July 2006 to December 2007.

  • measurement of hydrogen and Helium Isotopes flux in galactic cosmic rays with the pamela experiment
    Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2014
    Co-Authors: V Formato, O. Adriani, G. A. Bazilevskaya, Roberto Bellotti, M. Boezio, E. A. Bogomolov, Massimo Bongi, V. Bonvicini, G C Barbarino, S. Bottai
    Abstract:

    PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature, with particular focus on the antimatter component. The detector cons ...

  • measurement of the isotopic composition of hydrogen and Helium nuclei in cosmic rays with the pamela experiment
    The Astrophysical Journal, 2013
    Co-Authors: O. Adriani, G. A. Bazilevskaya, Roberto Bellotti, M. Boezio, E. A. Bogomolov, Massimo Bongi, V. Bonvicini, G C Barbarino, S Borisov
    Abstract:

    The satellite-borne experiment PAMELA has been used to make new measurements of cosmic ray H and He Isotopes. The isotopic composition was measured between 100 and 600 MeV/n for hydrogen and between 100 and 900 MeV/n for Helium Isotopes over the 23rd solar minimum from 2006 July to 2007 December. The energy spectrum of these components carries fundamental information regarding the propagation of cosmic rays in the galaxy which are competitive with those obtained from other secondary to primary measurements such as B/C.

F. A. J. Abernethy - One of the best experts on this subject based on the ideXlab platform.

  • A secretive mechanical exchange between mantle and crustal volatiles revealed by Helium Isotopes in 13C-depleted diamonds
    Geochemical Perspectives Letters, 2019
    Co-Authors: Sami Mikhail, Finlay M Stuart, James C. Crosby, Luigia Dinicola, F. A. J. Abernethy
    Abstract:

    Fluid inclusions trapped in fast-growing diamonds provide a unique opportunity to examine the origin of diamonds, and the conditions under which they formed. Eclogitic to websteritic diamondites from southern Africa show 13C-depletion and 15N-enrichment relative to mantle values (δ13C = -4.3 to -22.2 ‰ and δ15N = -4.9 to +23.2 ‰). In contrast the 3He/4He of the trapped fluids have a strong mantle signature, one sample has the highest value so far recorded for African diamonds (8.5 ± 0.4 Ra). We find no evidence for deep mantle He in these diamondites, or indeed in any diamonds from southern Africa. A correlation between 3He/4He ratios and 3He concentration suggests that the low 3He/4He are largely the result of ingrowth of radiogenic 4He in the trapped fluids since diamond formation. The He-C-N isotope systematics can be best described by mixing between fluid released from subducted altered oceanic crust and mantle volatiles. The high 3He/4He of low δ13C diamondites reflects the high 3He concentration in the mantle fluids relative to the slab-derived fluids. The presence of post-crystallisation 4He in the fluids means that all 3He/4He are minima, which in turn implies that the slab-derived carbon has a sedimentary organic origin. In short, although carbon and nitrogen stable isotope data show strong evidence for crustal sources for diamond-formation, Helium Isotopes reveal an unambiguous mantle component hidden within a strongly 13C-depleted system.

V. Bonvicini - One of the best experts on this subject based on the ideXlab platform.

  • Measurements of Cosmic-Ray Hydrogen and Helium Isotopes with the PAMELA experiment
    The Astrophysical Journal, 2016
    Co-Authors: O. Adriani, Giancarlo Barbarino, G. A. Bazilevskaya, Roberto Bellotti, M. Boezio, E. A. Bogomolov, Massimo Bongi, V. Bonvicini, S. Bottai, A. Bruno
    Abstract:

    The cosmic-ray hydrogen and Helium ($^1$H, $^2$H, $^3$He, $^4$He) isotopic composition has been measured with the satellite-borne experiment PAMELA, which was launched into low-Earth orbit on-board the Resurs-DK1 satellite on June 15th 2006. The rare Isotopes $^2$H and $^3$He in cosmic rays are believed to originate mainly from the interaction of high energy protons and Helium with the galactic interstellar medium. The isotopic composition was measured between 100 and 1100 MeV/n for hydrogen and between 100 and 1400 MeV/n for Helium Isotopes using two different detector systems over the 23rd solar minimum from July 2006 to December 2007.

  • measurement of hydrogen and Helium Isotopes flux in galactic cosmic rays with the pamela experiment
    Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2014
    Co-Authors: V Formato, O. Adriani, G. A. Bazilevskaya, Roberto Bellotti, M. Boezio, E. A. Bogomolov, Massimo Bongi, V. Bonvicini, G C Barbarino, S. Bottai
    Abstract:

    PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature, with particular focus on the antimatter component. The detector cons ...

  • measurement of the isotopic composition of hydrogen and Helium nuclei in cosmic rays with the pamela experiment
    The Astrophysical Journal, 2013
    Co-Authors: O. Adriani, G. A. Bazilevskaya, Roberto Bellotti, M. Boezio, E. A. Bogomolov, Massimo Bongi, V. Bonvicini, G C Barbarino, S Borisov
    Abstract:

    The satellite-borne experiment PAMELA has been used to make new measurements of cosmic ray H and He Isotopes. The isotopic composition was measured between 100 and 600 MeV/n for hydrogen and between 100 and 900 MeV/n for Helium Isotopes over the 23rd solar minimum from 2006 July to 2007 December. The energy spectrum of these components carries fundamental information regarding the propagation of cosmic rays in the galaxy which are competitive with those obtained from other secondary to primary measurements such as B/C.