| 1. |
- Kristiansson, Per, et al.
(författare)
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The implementation of a DSSSD in the upgraded boron analysis at LIBAF for applications in geochemistry
- 2014
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 332, s. 207-211
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Tidskriftsartikel (refereegranskat)abstract
- Interest in high spatial resolution boron analyses from a geochemical perspective is related to the recognition of boron as an important tracer of chemical recycling in the Earth, due to the high solubility of boron in aqueous fluids and silicate melts. Although boron is not a nominal component in common silicates they may still contain significant B-concentrations and hence constitute important boron reservoirs in the deeper parts of the Earth. Boron analyses have been performed at the Lund Ion Beam Analytical Facility for almost 20 years. For the analysis the nuclear reaction p+B-11 is used with beam energy just below 700 keV where the reaction has a broad resonance. In this paper we describe an upgrade of the system with a double sided silicon strip detector, which allows for much higher count rates compared to the old annular surface detector based system. A gain close to 20 in the data rate allows for high resolution mapping of boron distributions in crystals. This is illustrated by a number of examples. In addition, the detection limits for boron in geological samples are improved, now around 5 ppmw. In this work we address issues with data quality, especially charge normalization, lifetime correction and subtraction of different background components. (C) 2014 The Authors. Published by Elsevier B.V.
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| 2. |
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| 3. |
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| 4. |
- Hålenius, Ulf, et al.
(författare)
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Coordination of Boron in Nominally Boron-Free Rock Forming Silicates: Evidence for Incorporation of BO3 groups in Clinopyroxene
- 2010
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 74, s. 5672-5679
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Tidskriftsartikel (refereegranskat)abstract
- To explore mechanisms of B-incorporation in common chain silicates we have investigated synthetic diopside samples produced under boron-saturated conditions by 11B and 29Si magic-angle spinning (MAS) NMR and single-crystal NRA, FTIR, EMP and XRD/SREF techniques. Our samples contain 0.14–0.65 wt.% B2O3. NMR reveals that B is predominantly present in trigonal coordination in the clinopyroxene structure. This observation is supported by vibrational bands characteristic for B–O stretching in BO3 groups in the range 1250–1400 cm−1 in polarised single crystal FTIR-spectra. Single crystal structure refinements suggest that boron replaces Si at the T site. Combined, these results suggest that boron replacement for Si at the T-site leads to disruption of one of the T–O bonds of the nominal clinopyroxene structure resulting in replacement of SiO4 tetrahedra by BO3 groups. Our results show that high concentrations of boron can be incorporated in the nominally boron-free diopside. Elevated B-concentrations in the present calcic clinopyroxenes are accompanied by modifications of the diopside crystal structure involving the breaking of one T–O bond and simultaneous formation of vacancies at the octahedral M2 site. These structural modifications destabilize the structure and constitute thereby limiting factors for incorporating higher boron concentrations in diopside.
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| 5. |
- Nikolopoulos, Anna, et al.
(författare)
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BIAS Implementation Plan : Monitoring and assessment guidance for continuous low frequency sound in the Baltic Sea
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The BIAS Implementation Plan describes a regional programme for monitoring underwater ambient noise in the Baltic Sea. The programme combined measurements and modelling and was successfully implemented in 2012-2016 within the EU LIFE+ project Baltic Sea Information on the Acoustic Soundscape (BIAS) by Sweden, Denmark, Germany, Poland, Estonia and Finland.In 2014, one year of sound measurements was performed at 36 locations with the purpose of establishing the baseline state of ambient noise levels in the Baltic Sea. The measurements, as well as the post-survey processing of the data, were subject to standardized field procedures, quality control and signal processing routines were all developed within BIAS.BIAS dealt exclusively with monitoring continuous low frequency sound as referred to by the Marine Strategy Framework Directive indicator 11.2.1. Therefore, the study focused on the 1/3 octave frequency bands of 63 and 125 Hz, as specified by the indicator, and a third frequency band (2 kHz) which was added to strengthen the ecological relevance of the BIAS results.The measured sound data were used to model the soundscape for the entire project area, providing the first results for the Baltic Sea on a monthly basis. Soundscape maps were produced for the three targeted frequency bands, and three depth intervals: the surface layer (0 to 15m deep), the deep layer (30m to the bottom), and the full water column of the Baltic Sea.A large number of soundscape maps were produced constituting the base for future management of noise in the Baltic Sea. To facilitate an efficient handling of these, and future, results a GIS-based soundscape planning tool was created for visualizing the measured data and the modelled maps in a management friendly concept. BIAS identified two useful statistical measures for characterizing the soundscape which were incorporated into the soundscape planning tool. The year-by-year change of these measures directly relate to the current definition of the indicator.Based on the experiences made in the project, the BIAS implementation plan also outlines a plausible strategy for the future monitoring and the elements needed for maintaining a joint implementation for underwater ambient noise in the Baltic Sea region.
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| 6. |
- Nyquist, Susanne, et al.
(författare)
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An EELS study of near edge structures of the oxygen K-edge in spinels
- 2014
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Ingår i: Physics and chemistry of minerals. - : Springer Science and Business Media LLC. - 0342-1791 .- 1432-2021. ; 41:4, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- Spectra of seven aluminate, ferrite and chromate spinels were collected at the oxygen K-edge in order to examine the effect of octahedral ion composition on the near edge structures and explore whether these may shed some light on previously reported major variations in the optical absorption coefficient (epsilon) for the spin-allowed d-d band transitions due to tetrahedrally coordinated Fe2+ in optical spectra of oxide spinels. Interpretation of the energy loss near edge structure (ELNES) spectra was aided using the multiple scattering code FEFF8.40. For the chromate samples spin polarised calculations were included. Gold's iterative deconvolution method was utilized to improve on energy resolution, resulting in spectra equal in merit to those recorded by technically superior instruments. Results include absolute energy positions and interpretation of ELNES features in terms of transitions to available states. We conclude that the major causes of differences in the optical absorption coefficient mentioned above are hybridization between oxygen p- and octahedral metal orbitals. Our study does not support the idea presented by other authors that there exists a local antiferromagnetic ordering in MgCr2O4 at room temperature.
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| 7. |
- Nilsson, Charlotta, et al.
(författare)
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A nuclear geochemical analysis system for boron quantification using a focused ion beam
- 2017
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 311:1, s. 355-364
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Tidskriftsartikel (refereegranskat)abstract
- Ion beam analysis has for decades been used as a tool for geochemical analysis of trace elements using both X-rays (particle induced X-ray emission) and nuclear reaction analysis. With the geoanalytical setup at the Lund Ion Beam Analysis Facility, the boron content in geological samples with a spatial resolution of 1 µm is determined through nuclear reaction analysis. In the newly upgraded setup, a single detector has been replaced by a double sided silicon strip detector with 2048 segments. After optimization, boron content in geological samples as low as 1 µg g−1 can be measured.
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| 8. |
- Demidova, S. I., et al.
(författare)
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A micrometeorite from a stony asteroid identified in Luna 16 soil
- 2022
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 6:5, s. 560-567
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Tidskriftsartikel (refereegranskat)abstract
- Despite the intense cratering history of the Moon, very few traces of meteoritic material have been identified in the more than 380 kg of samples returned to Earth by the Apollo and Luna missions. Here we show that an ~200-µm-sized fragment collected by the Luna 16 mission has extra-lunar origins and probably originates from an LL chondrite with similar properties to near-Earth stony asteroids. The fragment has not experienced temperatures higher than 400 °C since its protolith formed early in the history of the Solar System. It arrived on the Moon, either as a micrometeorite or as the result of the break-up of a bigger impact, no earlier than 3.4 Gyr ago and possibly around 1 Gyr ago, an age that would be consistent with impact ages inferred from basaltic fragments in the Luna 16 sample and of a known dynamic upheaval in the Flora asteroid family, which is thought to be the source of L and LL chondrite meteorites. These results highlight the importance of extra-lunar fragments in constraining the impact history of the Earth–Moon system and suggest that material from LL chondrite asteroids may be an important component.
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| 9. |
- Nemchin, Alexander, et al.
(författare)
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Pb-Pb ages of feldspathic clasts in two Apollo 14 breccia samples
- 2017
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 217, s. 441-461
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Tidskriftsartikel (refereegranskat)abstract
- Pb-Pb isochron ages of ca. 3.92 Ga for three K-feldspar-rich clasts from Apollo 14 breccias 14303 and 14083 were determinedusing Secondary Ion Mass Spectrometry (SIMS). These ages are interpreted to represent the resetting of the U-Pb systemin the clasts as a result of brecciation during the Imbrium impact. One of the clasts contains zircon grains that record asignificantly older crystallization age (ca. 4.33–4.35 Ga) for the rock represented by that clast. Initial Pb compositions determinedfor the clasts, combined with the previously measured Pb isotopic compositions of K-feldspar grains from severalApollo 14 breccia samples, constrain a range of initial Pb compositions in the ca. 3.9 Ga Fra Mauro formation at the Apollo14 landing site. This range in initial Pb compositions indicates that the rocks represented by these clasts, or the sources ofthose rocks, evolved with a high 238U/204Pb (µ-value) for substantial periods of time, although the precise crystallization agesof the rocks represented by at least two of the clasts investigated here are unknown.
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