@techreport{oai:jaxa.repo.nii.ac.jp:00006105,
 author = {中村, 智樹 and 野口, 高明 and 田中, 雅彦 and Nakamura, Tomoki and Noguchi, Takaaki and Tanaka, Masahiko},
 month = {Mar},
 note = {Applying a combined analytical method specialized for cosmic-dust research, we have characterized mineralogy of individual mineral particles in 2A and 2B powder test samples that were prepared for the second analysis competition of the Hayabusa mission. Thirty-eight mineral particles mostly less than 300 micrometer in diameter and ten fine-grained mineral aggregates less than 200 micrometer in diameter were picked out from the test samples. Individual samples were X-rayed using synchrotron radiation to have powder X-ray diffraction patterns for identification of constituent minerals. The relative abundances of major constituent minerals in individual samples were determined by applying the Rietveld refinement to diffraction patterns. The X-rayed samples were polished and analyzed by a Scanning Electron Microscope (SEM) for imaging and an Electron-Probe MicroAnalyzer (EPMA) for quantitative concentrations of thirteen elements. Finally, ten selected samples were thinned by ultramicrotomy, argon ion bombardment, or Focused Ion Beam (FIB) method for detailed mineralogical characterization by Transmission Electron Microscopy (TEM). Small plagioclase compositions are determined by Analytical Electron Microscopy (AEM) using a cold sample stage. The bulk mineralogy, chemical composition, and nano-scale textures were all obtained from a single small particles less than 300 micrometer and the total mass of each test sample we used for the present study was only 100 microgram. Therefore, we can accomplish complete mineral characterization using very small quantity of regolith materials of the asteroid Itokawa, when the initial analysis of the returned samples is undertaken. The results showed that 2A powder sample consists mainly of olivine (Fa(sub 15.1+/-0.6) on an average), low-Ca pyroxene (Fs(sub 13.9+/-0.7) on an average), plagioclase, troilite, and kamacite with minor amounts of high-Ca pyroxene, taenite, chromite, Ca-phosphate, and alkali feldspar. The compositions and compositional variations of silicates and the minor element abundances in FeNi metals indicate that the 2A sample bears a close resemblance to H chondrites with petrologic type four to five. Fe/Mg ratios of both olivine and low-Ca pyroxene in the 2A sample correspond to the lowest-end of Fe/Mg variation for H chondrites, suggesting that it is a sample of most reduced type of H chondrites. In addition, the 2A samples contain small amounts of artificial contamination such as quartz-calcite composites, Ni-free Mn-bearing iron metals, and carbonaceous particles like epoxy resin. These particles probably got mixed during preparation of the 2A sample powder from a meteorite. The 2B sample is coarse particles that are composed mainly of metallic phases such as kamacite. Olivine and low-Ca pyroxene are also contained, but metal/silicate ratio of the 2B test sample is apparently higher than that of the 2A test sample. However, Mg/Fe ratios of silicate (Fa(sub 15.8+/-0.5) and Fs(sub 14.4+/-0.7) on an average) and the presence of well-defined chondrules suggest that the 2B sample is also similar to H chondrites with petrologic type four to five. All mineralogical characteristics, except for the mode of occurrence of FeNi metals, are very similar between 2A and 2B test samples. This may indicate that the two test samples were prepared from the same meteorite. The high metal/silicate ratio of the 2B test sample is therefore artifact, most probably the results of mechanical separation of magnetic components from a powder of an H chondrite., 資料番号: AA0063920001, レポート番号: JAXA-SP-05-021E},
 title = {Mineralogy of 100-micrograms powder test samples},
 year = {2006}
}