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Sökning: LAR1:nrm > Bellucci Jeremy

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  • Bellucci, Jeremy, 1984-, et al. (författare)
  • A scanning ion imaging investigation into the micron-scale U-Pb systematics in a complex lunar zircon
  • 2016
  • Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 438, s. 112-122
  • Tidskriftsartikel (refereegranskat)abstract
    • The full U-Pb isotopic systematics in a complex lunar zircon ‘Pomegranate’ from lunar impact breccia 73235 have been investigated by the development of a novel Secondary Ion Mass Spectrometry (SIMS) scanning ion imaging (SII) technique. This technique offers at least a four-fold increase in analytical spatial resolution over traditional SIMS analyses in zircon. Results from this study confirm the hypothesis that the Pomegranate zircon crystallized at 4.302 ± 0.013 Ga and experienced an impact that formed, U-enriched zircon around primary zircon cores at 4.184 ± 0.007 Ga (2σ, all uncertainties). The increase in spatial resolution offered by this technique has facilitated targeting of primary zircon that was previously inaccessible to conventional spot analyses. This approach has yielded results indicating that individual grains with a diffusive distance of less than ~4 μm have been reset to the young impact age, while individual grains with a diffusive distance larger than ~6 μm have retained the old crystallization age. Assuming a broad range in cooling rate of 0.5–50 °C/year, which has been observed in a suite of similar lunar breccias, a maximum localized temperature generated by the impact that reset small prima- ry zircon and created new, high-U zircon is estimated to be between 1100 and 1280 °C.
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3.
  • Bellucci, Jeremy, et al. (författare)
  • Direct Pb Isotopic Analysis of a Nuclear Fallout Debris Particle from the Trinity Nuclear Test
  • 2017
  • Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 89, s. 1887-1891
  • Tidskriftsartikel (refereegranskat)abstract
    • The Pb isotope composition of a nuclear fallout debris particle has been directly measured in post-detonation materials produced during the Trinity nuclear test by a secondary ion mass spectrometry (SIMS) scanning ion image technique (SII). This technique permits the visual assessment of the spatial distribution of Pb and can be used to obtain full Pb isotope compositions in user-defined regions in a 70 μm × 70 μm analytical window. In conjunction with backscattered electron (BSE) and energy-dispersive spectroscopy (EDS) mapping of the same particle, the Pb measured in this fallout particle cannot be from a major phase in the precursor arkosic sand. Similarly, the Pb isotope composition of the particle is resolvable from the surrounding glass at the 2σ uncertainty level (where σ represents the standard deviation). The Pb isotope composition measured in the particle here is in excellent agreement with that inferred from measurements of green and red trinitite, suggesting that these types of particles are responsible for the Pb isotope compositions measured in both trinitite glasses. 
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4.
  • Bellucci, Jeremy, et al. (författare)
  • Geochronology of Hadean zircon grains from the Jack Hills, Western Australia constrained by quantitative scanning ion imaging
  • 2018
  • Ingår i: Chemical Geology. - : Elsevier. - 0009-2541 .- 1872-6836. ; 476, s. 469-480
  • Tidskriftsartikel (refereegranskat)abstract
    • Five Hadean (> 4 Ga) aged zircon grains from the Jack Hills metasedimentary belt have been investigated by a secondary ion mass spectrometry scanning ion image technique. This technique has the ability to obtain accurate and precise full U-Pb systematics on a scale < 5 μm, as well as document the spatial distribution of U, Th and Pb. All five of the grains investigated here have complex cathodoluminescence patterns that correlate to different U, Th, and Pb concentration domains. The age determinations for these different chemical zones indicate multiple reworking events that are preserved in each grain and have affected the primary crystalized zircon on the scale of < 10 μm, smaller than conventional ion microprobe spot analyses. In comparison to the spot analyses performed on these grains, these new scanning ion images and age determinations indicate that almost half of the spot analyses have intersected several age and chemical domains in both fractured and unfractured parts of the individual crystals. Some of these unfractured, mixed domain spot analyses have concordant ages that are inaccurate. Thus, if the frequency of spot analyses intersecting mixed domains here is even close to representative of all other studies of the Jack Hills zircon population, it makes the interpretation of any trace element, Hf, or O isotopic data present in the literature tenuous. Lastly, all of the grains analysed here preserve at least two distinguishable 207Pb/206Pb ages. These ages are preserved in core-rim and/or complex internal textural relationships in unfractured domains. These secondary events took place at ca. 4.3, 4.2, 4.1, 4.0, 3.7, and 2.9 Ga, which are coincident with previously determined statistically robust age peaks present in this zircon population.
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5.
  • Bellucci, Jeremy, et al. (författare)
  • Halogen and Cl isotopic systematics in Martian phosphates: Implications for the Cl cycle and surface halogen reservoirs on Mars
  • 2017
  • Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 458, s. 192-202
  • Tidskriftsartikel (refereegranskat)abstract
    • The Cl isotopic compositions and halogen (Cl, F, Br, and I) abundances in phosphates from eight Martian meteorites, spanning most rock types and ages currently available, have been measured in situ by Secondary Ion Mass Spectrometry (SIMS). Likewise, the distribution of halogens has been documented by x-ray mapping. Halogen concentrations range over several orders of magnitude up to some of the largest concentrations yet measured in Martian samples or on the Martian surface, and the inter-element ratios are highly variable. Similarly, Cl isotope compositions exhibit a larger range than all pristine terrestrial igneous rocks. Phosphates in ancient (>4 Ga) meteorites (orthopyroxenite ALH 84001 and breccia NWA 7533) have positive d37Cl anomalies (+1.1 to +2.5 ‰).  These samples also exhibit explicit whole rock and grain scale evidence for hydrothermal or aqueous activity. In contrast, the phosphates in the younger basaltic Shergottite meteorites (<600 Ma) have negative d37Cl anomalies (-0.2 to -5.6 ‰).  Phosphates with the largest negative d37Cl anomalies display zonation where the rims of the grains are enriched in all halogens and have significantly more negative d37Cl anomalies indicating interaction with the surface of Mars during the latest stages of basalt crystallization. The phosphates with no textural, major element, or halogen enrichment evidence for mixing with this surface reservoir have an average d37Cl of -0.6 ‰, which suggests a similar Cl isotope composition between Mars, the Earth, and the Moon. The only process known to fractionate Cl isotopes, both positively and negatively, is formation of perchlorate, which has been detected in weight percent concentrations on the Martian surface. The age range and obvious mixing history of the phosphates studied here suggest perchlorate formation and halogen cycling via brines, which have also been observed on the Martian surface, has been active throughout Martian history. 
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6.
  • Bellucci, Jeremy, et al. (författare)
  • Pb evolution in the Martian mantle
  • 2018
  • Ingår i: Earth and Planetary Science Letters. - : Elsevier. - 0012-821X .- 1385-013X. ; 485, s. 79-87
  • Tidskriftsartikel (refereegranskat)abstract
    • The initial Pb compositions of one enriched shergottite, one intermediate shergottite, two depleted shergottites, and Nakhla have been measured by Secondary Ion Mass Spectrometry (SIMS). These values, in addition to data from previous studies using an identical analytical method performed on three enriched shergottites, ALH 84001, and Chassigny, are used to construct a unified and internally consistent model for the differentiation history of the Martian mantle and crystallization ages for Martian meteorites. The differentiation history of the shergottites and Nakhla/Chassigny are fundamentally different, which is in agreement with short-lived radiogenic isotope systematics. The initial Pb compositions of Nakhla/Chassigny are best explained by the late addition of a Pb-enriched component with a primitive, non-radiogenic composition. In contrast, the Pb isotopic compositions of the shergottite group indicate a relatively simple evolutionary history of the Martian mantle that can be modeled based on recent results from the Sm–Nd system. The shergottites have been linked to a single mantle differentiation event at 4504 Ma. Thus, the shergottite Pb isotopic model here reflects a two-stage history 1) pre-silicate differentiation (4504 Ma) and 2) post-silicate differentiation to the age of eruption (as determined by concordant radiogenic isochron ages). The μ-values (238U/204Pb) obtained for these two different stages of Pb growth are μ1 of 1.8 and a range of μ2 from 1.4–4.7, respectively. The μ1-value of 1.8 is in broad agreement with enstatite and ordinary chondrites and that proposed for proto Earth, suggesting this is the initial μ-value for inner Solar System bodies. When plotted against other source radiogenic isotopic variables (Sri, γ187Os, ε143Nd, and ε176Hf), the second stage mantle evolution range in observed mantle μ-values display excellent linear correlations (r2 > 0.85) and represent a spectrum of Martian mantle mixing-end members (depleted, intermediate, enriched).
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7.
  • Bellucci, Jeremy, 1984- (författare)
  • Pb Isotopic Composition of Panamanian Colonial Majolica by LA-ICP-MS
  • 2016
  • Ingår i: Recent Advances in Laser Ablation ICP-MS for Archaeology. - Berlin, Heidelberg : Springer Berlin/Heidelberg.
  • Bokkapitel (refereegranskat)abstract
    • Panama ́ Viejo, founded in 1519 by the Spanish explorer Pedrarias Da ́vila, was the first permanent European settlement on the Pacific Ocean, and became a city, by royal decree, in 1521. Shortly after its creation, the city became an important base for trade with Spain. In 1671, the English pirate Henry Morgan waged an attack on Panama ́ Viejo, which resulted in a fire that destroyed the entire city. A new settlement built a few miles west, called Casco Antiguo or San Felipe, is now the historic district of modern Panama City. The Pb isotopic compositions of the glazes on the surface of sixteenth to seventeenth century majolica pottery sherds from Panama Viejo and Casco Antiguo (both in Panama), and Lima (Peru) were determined via non-destructive laser ablation multi-collector ICP-MS (LA-MC-ICP-MS). The contrast in Pb isotopic compositions in the glazes on ceramics recovered in different locations demonstrate that early majolica pottery production during this period used Pb obtained from the Andes. However, the Pb used in later majolica production in Panama is of Spanish origin. After Panama ́ Viejo was burned to the ground, Panamanian majolica production ended.
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8.
  • Bellucci, Jeremy (författare)
  • Pb-isotopic evidence for an early, enriched crust on Mars
  • 2015
  • Ingår i: Earth and Planetary Science Letters. - 0012-821X .- 1385-013X. ; 410, s. 34-41
  • Tidskriftsartikel (refereegranskat)abstract
    • Martian meteorite NWA 7533 is a regolith breccia that compositionally resembles the Martian surface measured by orbiters and landers. NWA 7533 contains monzonitic clasts that have zircon with U–Pb ages of 4.428 Ga. The Pb isotopic compositions of plagioclase and alkali feldspars, as well as U–Pb isotopic compositions of chlorapatitein the monzonitic clasts of NWA 7533 have been measured by Secondary Ion Mass Spectrometry (SIMS). The U–Pb isotopic compositions measured from the chlorapatitein NWA 7533 yield an age of 1.357 ±81Ga(2σ). The least radiogenic Pb isotopic compositions measured in plagioclase and K-feldspar lie within error of the 4.428 Ga Geochron. These data indicate that the monzonitic clasts in NWA 7533 are a product of a differentiation history that includes residence in areservoir that formed prior to 4.428 Ga with a μ-value (238U/204Pb) of at least 13.4 ±1.7 (2σ)and aκ-value (232Th/238U) of ∼4.3. This μ-value is more than three times higher than any other documented Martian reservoir. These results indicate either the Martian mantle is significantly more heterogeneous than previously thought (μ-value of 1–14 vs. 1–5) and/or the monzonitic clasts formed by the melting of Martian crust with a μ-value of at least 13.4. Therefore, NWA 7533 may contain the first isotopic evidence for an enriched, differentiated crust on Mars.
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