| 1. |
- Bosi, Ferdinando, et al.
(författare)
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Late magmatic controls on the origin of schorlitic and foititic tourmalines from late-Variscan peraluminous granites of the Arbus pluton (SW Sardinia, Italy) : Crystal-chemical study and petrological constraints
- 2018
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Ingår i: Lithos. - : Elsevier BV. - 0024-4937 .- 1872-6143. ; 308-309, s. 395-411
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Tidskriftsartikel (refereegranskat)abstract
- Tourmalines from the late-Variscan Arbus pluton (SW Sardinia) and its metamorphic aureole were structurally and chemically characterized by single-crystal X-ray diffraction, electron and nuclear microprobe analysis, Mössbauer, infrared and optical absorption spectroscopy, to elucidate their origin and relationships with the magmatic evolution during the pluton cooling stages. The Arbus pluton represents a peculiar shallow magmatic system, characterized by sekaninaite (Fe-cordierite)-bearing peraluminous granitoids, linked via AFC processes to gabbroic mantle-derived magmas. The Fe2+-Al-dominant tourmalines occur in: a) pegmatitic layers and pods, as prismatic crystals; b) greisenized rocks and spotted granophyric dikes, as clots or nests of fine-grained crystals in small miaroles locally forming orbicules; c) pegmatitic veins and pods close to the contacts within the metamorphic aureole. Structural formulae indicate that tourmaline in pegmatitic layers is schorl, whereas in greisenized rocks it ranges from schorl to fluor-schorl. Tourmalines in thermometamorphosed contact aureole are schorl, foitite and Mg-rich oxy-schorl. The main substitution is Na + Fe2+ ↔ □ + Al, which relates schorl to foitite. The homovalent substitution (OH) ↔ F at the O1 crystallographic site relates schorl to fluor-schorl, while the heterovalent substitution Fe2+ + (OH, F) ↔ Al + O relates schorl/fluor-schorl to oxy-schorl. Tourmaline crystallization in the Arbus pluton was promoted by volatile (B, F and H2O) enrichment, low oxygen fugacity and Fe2+ activity. The mineralogical evolutive trend is driven by decreasing temperature, as follows: sekaninaite + quartz → schorl + quartz → fluor-schorl + quartz → foitite + quartz. The schorl → foitite evolution represents a distinct trend towards (Al + □) increase and unit-cell volume decrease. These trends are typical of granitic magmas and consistent with Li-poor granitic melts, as supported by the absence of elbaite and other Li-minerals in the Arbus pluton. Tourmaline-bearing rocks reflect the petrogenetic significance of contribution from a metapelitic crustal component during the evolution of magmas in the middle-upper crust.
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| 2. |
- de La Rosa, Nathaly
(författare)
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Investigation of lithium and fluorine content in geological materials using Nuclear Reaction Analysis (NRA)
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work focuses on the optimization of the Nuclear Reaction Analysis (NRA) technique to determine the content of lithium and fluorine in geological materials. Measuring low concentration of these isotopes is of great relevance in many fields such as geological, astrophysical, biological and material sciences. Light elements as lithium and fluorine are considered as geochemical tracers in various geological processes such as the crust-mantle recycling. In these applications, precise measurements are required.Our interest in geological applications is part of an interdisciplinary collaboration with geologists who provide us with samples and are interested in our results. The development of this project has enabled the Lund Ion Beam Analysis Facility (LIBAF) group to establish a technique for lithium and fluorine measurements that can be used in many fields.NRA is part of a family of analysis techniques known as Ion Beam Analysis (IBA). The advantages offered by IBA techniques are non-destructiveness, short measurement time, and very good sensitivity over the hole periodic table. Equipment such as particle accelerators and radiation detectors are needed to carry out IBA techniques. These types of equipment have been utilized at the LIBAF in order to perform NRA using Li-bearing and F-bearing materials. In NRA, the samples are scanned by energetic ions such as protons or deuterons to induce reactions with the sample elements. Many reactions can take place producing charged particles, X-rays and gamma rays. The 7Li(p,α)4He and 19F(p,α)16O reactions were utilized to obtain lithium and fluorine detection limits below 1~ppm and 50~ppm respectively.
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| 3. |
- De La Rosa, Nathaly, et al.
(författare)
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Lithium analysis using a double-sided silicon strip detector at LIBAF
- 2017
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 404, s. 29-33
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Tidskriftsartikel (refereegranskat)abstract
- Quantification and mapping possibilities of lithium in geological material, by Nuclear Reaction Analysis (NRA), was evaluated at the Lund Ion Beam Analysis Facility (LIBAF). LiF and two Standard Reference Materials, (SRM 610 and SRM 612) were used in the investigation. The main part of the data was obtained at the beam energy 635keV studying the high Q-value reaction 7Li(p, α)4He, but reaction yield and detection limits were also briefly investigated as a function of the energy. A double-sided silicon strip detector (DSSSD) was used to detect the α-particles emitted in the reaction in the backward direction. The combination of the high Q-value, a reasonably good cross-section and the possibility to use a high beam current have been demonstrated to allow for measurement of concentrations down below 50ppm. Proton energies below 800keV were demonstrated to be appropriate energies for extracting lithium in combination with boron analysis.
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| 4. |
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| 5. |
- de la Rosa, Nathaly, et al.
(författare)
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Quantification of lithium at ppm level in geological samples using nuclear reaction analysis
- 2018
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 317:1, s. 253-259
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Tidskriftsartikel (refereegranskat)abstract
- Proton-induced reaction (p,α) is one type of nuclear reaction analysis (NRA) suitable especially for light element quantification. In the case of lithium quantification presented in this work, accelerated protons with an energy about of 850 keV were used to induce the 7Li(p,α)4He reaction in standard reference and geological samples such as tourmaline and other Li-minerals. It is shown that this technique for lithium quantification allowed for measurement of concentrations down below one ppm. The possibility to relate the lithium content with the boron content in a single analysis was also demonstrated using tourmaline samples, both in absolute concentration and in lateral distribution. In addition, Particle induced X-ray emission (PIXE) was utilized as a complementary IBA technique for simultaneous mapping of elements heavier than sodium.
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| 6. |
- 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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| 7. |
- Pallon, Jan, et al.
(författare)
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A new quantitative X-ray system for micro-PIXE analysis
- 2017
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Ingår i: X-Ray Spectrometry. - : Wiley. - 0049-8246. ; 46:5, s. 319-324
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Tidskriftsartikel (refereegranskat)abstract
- Particle Induced X-ray Emission is a well-established technique for quantitative elemental analysis down to trace levels. During microbeam analysis, where the beam is collimated and focused into a small spot, the beam current reduces to nA or less. The generation of characteristic X-rays is reduced in the same proportion, leading to long data-acquisition times. This can partly be compensated for by using detectors with a large solid angle. In this work, the performance of an annular eight-element silicon drift detector with a total solid angle of 261 msr is described. The initial calibration of the detector was performed using thin elemental standards. Charge measurement was carried out both in a Faraday Cup positioned after the sample and by a pre-sample electrostatic deflection system sampling the beam charge into another Faraday Cup. The two methods were used in parallel and compared during the calibration measurements. A recently installed Versa Module Europe (VME) based data acquisition system equipped with, for example, multi-hit time-to-digital converters, amplifiers, and 32-channel scalers, was used to record data in event-by-event mode for simultaneous data evaluation on multiple computers. Off-line dead time and pile-up corrections were made on the event data that was sorted into spectra and fitted with the GeoPIXE software. The pre-sample deflection charge measurement gave consistent values for the calibration, and this is an important observation implying that non-conductive and thick samples will be able to quantify without the use of internal standards.
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| 8. |
- Sala, Simone, et al.
(författare)
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Dose-efficient multimodal microscopy of human tissue at a hard X-ray nanoprobe beamline
- 2022
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Ingår i: Journal of Synchrotron Radiation. - 1600-5775. ; 29:3
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Tidskriftsartikel (refereegranskat)abstract
- X-ray fluorescence microscopy performed at nanofocusing synchrotron beamlines produces quantitative elemental distribution maps at unprecedented resolution (down to a few tens of nanometres), at the expense of relatively long measuring times and high absorbed doses. In this work, a method was implemented in which fast low-dose in-line holography was used to produce quantitative electron density maps at the mesoscale prior to nanoscale X-ray fluorescence acquisition. These maps ensure more efficient fluorescence scans and the reduction of the total absorbed dose, often relevant for radiation-sensitive (e.g. biological) samples. This multimodal microscopy approach was demonstrated on human sural nerve tissue. The two imaging modes provide complementary information at a comparable resolution, ultimately limited by the focal spot size. The experimental setup presented allows the user to swap between them in a flexible and reproducible fashion, as well as to easily adapt the scanning parameters during an experiment to fine-tune resolution and field of view.
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| 9. |
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