M. Mosbah

PIGME fluorine determination using a nuclear microprobe with application to glass inclusions

Abstract Fluorine quantitative microanalysis was performed on geological samples, using the 19 F (p, p ′ γ) 19 F reaction, with a 30 (μm proton microbeam at an energy of 3.4 MeV. We have detailed the analytical procedure and the calibration method in relation to a large range of fluorine concentrations in natural glasses and some minerals. This procedure was applied to study the fluorine distribution in melt inclusions trapped in minerals of different origins. The potential of this nuclear microanalysis method is discussed.

Lithium, boron and beryllium in volcanic glasses and minerals studied by nuclear microprobe

The detection of lithium, boron and beryllium was performed using a nuclear microprobe. The γ-emission yields have been measured for the most favourable nuclear reactions: 7Li(α, α′γ)7Li, 7Li(p, p′γ)7Li, 10B(p, αγ)7Be and 7Li(p, nγ)7Be. The possible interferences and the minimum detection limits (MDL) are presented, at different energies and for a total integrated charge of 1 μC. Lithium and boron, studied by the reactions (p, p′γ) and (p, α), respectively, have been determined in silicated glasses, as trace elements and on the scale of few micrometers. In the case of beryllium, using the 9Be(p, αγ)6Li reaction, the MDL is calculated to be 1100 ppm for beryllium. This element has not been further studied in our glass samples. PIGE (Proton Induced Gamma-ray Emission) allows the simultaneous measurement of lithium, fluorine and sodium. Standardization curves were made for lithium and boron on the basis of natural and synthetic glasses and minerals. Our results point out high boron contents in rhyolitic obsidians from Eolian Islands (Italy), compared with other rhyolites. Concentrations in lithium, fluorine and boron were determined, for the first time, in glass inclusions trapped within primitive minerals of the 1906 eruption of Vesuvius (Italy).

Study of hydrogen in melt inclusions trapped in quartz with a nuclear microprobe

Abstract Elastic recoil spectrometry induced by a 3 MeV 4He microbeam has been used to determine the hydrogen distribution within melt inclusions trapped in quartz. These minerals were selected from different geological environments: Guadeloupe (West Indies), Pantelleria Island (South Sicily, Italy) and San Pietro (South Sardinia, Italy). Bulk hydrogen contents are calculated (H assumed to be in H2O form). The knowledge of hydrogen distribution assists both in a better understanding and in the establishment of volcanic dynamism hypotheses. Finally, hydrogen-rich fluid inclusions are evidenced, the H concentration profile was obtained from simulation of the data and reported for the first time in a glass inclusion.

Micro-XANES with synchrotron radiation: a complementary tool of micro-PIXE and micro-SXRF for the determination of oxidation state of elements. Application to geological materials

Abstract Micro-PIXE and micro-Synchrotron X-ray fluorescence (SXRF) are powerful techniques dedicated to the study of trace elements in different matrices. However they do not give access to the chemical states of elements. By combining micro-X-Ray Absorption Near Edge Structure (XANES) and micro-SXRF using synchrotron radiation, the point analysis of an element and its proportion in different chemical states become possible. Moreover the shape and fine structures of the edge give information concerning its local structure (inter-atomic distances and coordination number). After a short presentation of both the experimental and the basic principles of μ-XANES, the study of iron oxidation states will be given to illustrate the case of geological samples. Such a study at a micrometer scale on coexisting minerals remains a fundamental goal in geochemistry. Particularly in glass inclusions trapped in volcanic minerals, this information enables one to infer the physical and chemical conditions which control the evolution of the magmas. A practical method of quantification has been employed and theoretical simulations are in development simultaneously. First results as well as the capabilities of the method are presented.

Nuclear microprobe analysis of 14N and its application to the study of ammonium-bearing minerals

Nuclear microprobe technique has been applied to the study of ammonium-bearing feldspar, biotite and muscovite crystals selected from metamorphosed black shales and pegmatite veins cross-cutting the shales sampled in the Central Jebilet (Morocco). 14N is easily detected by the nuclear reactions (d, p0) and (d, α0) with deuteron energy > 1.6 MeV for a better detection limit (14N ⩽ 50 ppm). The experimental procedure has been developed and is detailed herein. TiN has been used for calibration. The nitrogen content measured in feldspar, biotite and muscovite crystals by the nuclear microprobe is perfectly consistent with quantitative nitrogen analysis by catharometry and semiquantitative analysis by Fourier transform infrared microspectrometry. The nuclear microprobe results can be used to calibrate complementary methods such as ion microprobe and IR microspectrometry.

Nuclear reaction microanalysis and electron microanalysis of light elements in minerals and glasses

Abstract Electron microprobe analysis (EMA) and nuclear microanalysis (NMA) have been used to determine light elements (Z ⩽ 30) in minerals and glasses. Optimum NMA reaction conditions for the detection of various elements are presented and detection limits are estimated for both micro- and macrobeams. A comparison is made between results of EMA and NMA analyses for several elements. Peculiarities of both methods are emphasized. While EMA is convenient in fast routine measurement for most elements in the periodic table above Na, with analytical sensitivities ranging from 100 to 1000 wt. ppm, NMA in charged-particle or prompt gamma-ray nuclear reaction analysis (NRA) mode allows the analysis of all the isotopes between 1H and 19F (except 4He and 20Ne), with a sensitivity often better than 50 ppm. In addition, proton-induced gamma-ray emission (PIGE) enables the determination of heavier elements (from Na to Zn) with relatively good performances. Furthermore, depth profiling and local isotopic ratio measurements constitute some new interesting applications for NMA.

Micro PIXE and micro SXRF: comparison of the two methods and application to glass inclusions from Vulcano (Eolian Islands — Italy)

PIXE with a 2.5 MeV proton beam of 10 × 10 μm2 beam size and Synchrotron Radiation Induced X-ray Emission (SXRF) with photons of 11.8 keV energy and a focal spot of 5 × 2.5 μm2 with especially high intensity of 2 × 109 photons/s have been performed on synthetic and natural volcanic glasses. A comparison of the possibilities and performances of these microanalytical methods is made. MDLs are given from the acquisitions obtained on synthetic glasses. Micro PIXE and micro SXRF were jointly applied to the study of trace elements in glass inclusions from the active volcanological system of Vulcano (Eolian Islands — Italy).

Seven years of research using the Bruyeres le Chatel microprobe facility: A review

Abstract After a brief description of different research topics which have been explored between 1983 and 1988, we show several original results obtained using the Bruyeres le Châtel nuclear microprobe facility. Then we discuss the instrumental improvements carried on in the middle of 1988, by presenting recent works conducted in the new analysis chamber. Finally, looking forward to the starting of the second-generation French nuclear microprobe (beginning of 1991) at Laboratoire Pierre Sue in Saclay, we mention the 1989–1990 research projects of our Nuclear Microanalysis Group.

The characterization of glass inclusions through nuclear microprobe

Abstract In the last decade, nuclear microanalytical methods have been developed in order to study the distribution of elements of specific interest in natural glasses involving melt (or glass) inclusions trapped in minerals of magmatic origin. The study of these small objects represent a very original application of the microbeam techniques in general. With the nuclear microprobe, we have focused our research in two main directions: (1) the determination of light elements by nuclear reaction analysis (C, N, F, Li, B) and elastic recoil detection analysis in transmission mode (H), contributing to the knowledge of the magmatic thermodynamic conditions (pressure, temperature, gas solubility), to the quantification of volatile budget and to the volcanoes atmospheric contribution; (2) the determination of trace elements as geochemical markers with PIXE, contributing to the knowledge of magmatic processes. In this paper, after a brief review of the methods developed for light elements and their application in volcanology, we present with more details simultaneous use of microPIXE-microPIGE to characterize strontium and fluorine in melt inclusions. The experiments were carried out both with the Bruyeres Le Châtel nuclear microprobe (of first generation) and with the new nuclear microprobe of the Pierre Sue laboratory.

Hydrogen microdetermination in geological materials using elastic recoil detection analysis (ERDA)

Abstract For the first time, hydrogen has been determined (by means of nuclear microanalysis) within glassy inclusions trapped in volcanic minerals. Elastic recoil detection of protons has been used by means of the transmission and reflection geometry. The two major originalities of this work consist in the quantitative absolute method and the application of this technique to natural materials. Some of our results are close to those obtained with other methods. We reached a detection limit smg g within the San Carlos olivine.