Masanori Kurosawa

Hydrogen analysis in quartz crystals and quartz glasses by secondary ion mass spectrometry

Abstract Microanalysis of hydrogen in quartz crystals and quartz glasses has been developed by secondary ion mass spectrometry (SIMS). The secondary ion intensities of hydrogen are proportional to the hydrogen contents determined by infrared (IR) absorption over the range of 5 to 3000 ppma H/Si. The correlation between SIMS and IR results indicates that secondary ion yields of hydrogen are independent of crystal structure. This SIMS method could reveal correlations between hydrogen distribution and hydrolytic weakening at the microscopic level.

Quantitative trace element analysis of single fluid inclusions by proton-induced X-ray emission (PIXE): Application to fluid inclusions in hydrothermal quartz

Abstract Single fluid inclusion analogues with known elemental composition and regular shape were analyzed for trace element contents by particle-induced X-ray emission (PIXE)—a nondestructive method for the analysis of single fluid inclusions—to evaluate the accuracy and detection limits of this type of analysis. Elements with concentrations of 10 to 1000 ppm were measured with average estimated relative error of ±7%. For natural fluid inclusions with 30 μm radius and 20 μm depth in quartz, the total analytical errors were estimated to be ±40% relative for Ca, ±16% for Fe, ±13% for Zn, ±12% for Sr, and ±11% for Br and Rb, by considering uncertainties in microscopic measurements of inclusion depths. Detection limits of 4 to 46 ppm for elements of mass numbers 25–50 were achieved for analyses of a spherical fluid inclusion with 30 μm radius and 20 μm depth in quartz, at an integrated charge of 1.0 μC. The trace element compositions of single fluid inclusions in a hydrothermal quartz crystal were also determined. The elemental concentrations in the inclusions varied widely: 0.2–9 wt.% for Ca and Fe, 300–8000 ppm for Mn and Zn, 40–3000 ppm for Cu, 100–4000 ppm for Br, Rb, Sr, and Pb, and less than 100 ppm for Ge. Elemental concentrations of secondary fluid inclusions on the same trail varied over an order of magnitude, even though all these inclusions were formed from the same fluid. Elemental concentrations in inclusions on the same trail are positively correlated with each other, except for Cu and Rb. Ratios of almost all elements in the inclusions on the trail were essentially unchanged; thus, the elemental ratios can provide original information on trace element compositions of a hydrothermal fluid.

Development of a new sample chamber for proton microprobe analysis of mineral samples

Abstract We describe a newly developed proton microprobe sample chamber designed for analysis of heterogeneous mineral samples. The instrument features a computer-driven stage and is equipped with novel beam and sample optics, external microscope and filter exchange system. Under the employed optical geometry, axes of beam and sample optics are collinear and normal to the sample surface, an essential aspect allowing high spatial resolution of analyses and accurate micrometer-scale sample and beam positioning. Use of a long working distance in conjunction with integral reflectance mirror are the primary design constraints satisfied for successful development. Based on measurements, the presented proton microprobe is expected to enhance studies requiring effective and easy-to-perform nondestructive microanalytical analysis of minerals.

Hydrogen analysis of mineral samples at University of Tsukuba

This study reports the present status of our work on the hydrogen analysis of mineral and rock samples. The preparation of a standard material by means of ion implantation, a method of its calibration and the application of the method are described. The number of hydrogen atoms per unit volume in the standard material can be determined from the simultaneous observation of α-particles, γ rays and α–γ coincidence events for the 1H(19F,αγ) reaction at the 16.44 MeV resonance energy. The hydrogen content in a natural obsidian determined with the method mentioned above is in agreement with that obtained by FTIR. A heavy-ion microbeam system under construction, which consists of a Russian-type quadrupole magnet for beam focusing, a beam defining slit system and a γ-ray detector, is also described.

Quantitative PIXE analysis of single fluid inclusions in quartz vein: Chemical composition of hydrothermal fluids related to granite

Compositions of fluids trapped as inclusions during the growth of minerals, or during later healing of fluid-filled cracks, provide information on hydrothermal vein-type ore formation. Trace elements in fluid inclusions from hydrothermal quartz vein related to granite were determined by micro-PIXE. High concentration (wt.%) of Ca and Fe, and tens to thousands ppm Mn, Zn, Cu, Br, Rb, Sr, Pb and Ge, were observed in the inclusions, indicating higher metal contents in hydrothermal fluid released from granite.

Preliminary experiments on a laser coupling with an electron cyclotron resonance ion source for trace element analysis

We have developed a laser coupling with an electron cyclotron resonance (ECR) ion source for trace element analysis of mineral samples at University of Tsukuba. A compact Q-switched Nd:YAG laser at 1064 nm wavelength with a pulse width of 8 ns and a maximum energy of 50 mJ is employed to ablate the sample materials as a means of introducing samples into the ECR plasma. Preliminary experiments were performed to focus the laser beam on a pure metallic target (Cu). The mean kinetic energy of the laser produced Cu ions is measured to 470 eV for the laser energy of 50 mJ by a simple time-of-flight method. Design for a laser coupling with an ECR ion source as a new application of mass spectrometry are reported.

Development of the Tokai nuclear microprobe for natural analogue studies of nuclear waste

Abstract A nuclear microprobe with new sample chamber has been designed to investigate a behavior of radioactive nuclei in rocks and chemical compositions of deep underground water that is retained in minerals as fluid inclusions. Outline of the new chamber is described and preliminary micro-PIXE analyses for fluid inclusions and U–Nb minerals that is a natural analogue for high level nuclear waste deposits are also presented.

Hydrogen Analysis in Micro-area of Minerals using Secondary Ion Mass Spectrometry.

The abundance of hydrogen in olivines has been determined by secondaryion mass spectrometry (SIMS). Hydrogen implanted olivines were prepared for SIMSmeasurements as standards. A linear relationship was obtained between the relative hydrogen intensity ratio against the silicon and hydrogen concentrations overthe range of 100 to 25000 ppm H/Si.