Etching characteristics of fission fragment tracks in chlorite from central Sierra Nevada Batholith, California, USA, are studied using HF as the track etchant. Systematic annealing experiments are carried out in order to obtain correction factor for the age of chlorite, which has suffered annealing during its geological history. Complete erasure of fission tracks in chlorite occurs for 4 hrs annealing at 600°C. Extrapolation of experimental annealing data suggests that a temperature of 155°C would remove all fission tracks in chlorite in 1 Ma. The annealing correction of 15% determined by the age-plateau method gives the corrected age as 161±30 Ma for this mineral. Uranium content in chlorite is quite low (∼0.315 ppm). The mean value of activation energy is 1.6 eV.
A simple thin-section holder equipped with selector apertures for the selected area X-ray diffraction has been designed for four-circle diffractometer. In making thin-section, an acrylic resin plate was employed instead of a conventional slide glass to reduce the absorption of X-rays. The selector aperture is easily moved and placed on an aimed area in thin-section under the microscope. Single crystal diffraction data from the selected area with diameter as small as 60 μm have been successfully obtained, although the measurable diffraction area is smaller than the case of usual single crystal method. The holder can also be applicable to X-ray cameras using universally used single crystal goniometer heads.
Binocular scanning electron microscope (SEM) has been developed. A pair of coils is set between the objective lens and a specimen of the ordinary SEM. The upper coil deflects the electron beam outward. The lower coil return it to the original focus. For this detour of the path, the beam irradiates a specimen from the direction oblique to the optical axis. The binocular SEM has double scanning lines, as compared with the ordinary one. The beam leans leftward at odd scans, while rightward at even scans. The odd scanning image is displayed on the left CRT, while the even image on the right CRT. Looking both images using a stereoscope, we can observe the 3-D shape of an object in real time. When we cannot observe a 3-D shape in real time, we must decide whether to take a stereophoto pair or not, on the basis of 2-D image. Unless by chance, we may fail to find such an interest 3-D pattern that is recognizable only by the stereography. On the contrary, the binocular SEM enable to keep out this failure. Consequently, the binocular SEM surely contributes to give more interesting informations to the research works using the SEM.
Compressibilities of pyrite and cattierite have been examined by the single-crystal X-ray diffraction method up to 42 kbar and 36 kbar, respectively. Both S–S and M–S (M: Fe, Co) bonds in both of the minerals are contracted linearly with pressure within the experimental pressure ranges. However, contraction of the S–S bond in cattierite is much smaller than that in pyrite, whereas the Co–S bond shows a larger contraction than Fe–S. Bonding strength (or hardness) of the S–S bond is estimated to be about 60% of that for Fe–S in pyrite.
Stibnite, getchellite, wakabayashilite, and orpiment were synthesized by hydrothermal treatment of (Sb1−X, AsX)2S3 glass (0<x<1) with solvent of Na2S aqueous solution at 250–400°C, and 1000 kg/cm2 pressure to determine their formation conditions and solid solution ranges. The As–Sb substitution occurred up to x=0.24 in the above formula for stibnite, 0.54–0.64 for getchellite, 0.84–0.86 for wakabayashilite, and up to 0.83 for orpiment, respectively. Substitution of As for Sb in stibnite caused the elongation of the a axis and shortening of the b and c axes of the unit cell, and finally the a and b lengths became equal at about 25 mol% As. Wakabayashilite, synthesized for the first time in the present experiment, does not have the superstructure known for natural materials and its powder diffraction data are presented.