Ildikó Gyollai

Non-luminescent nature of the planar deformation features in shocked quartz from the Ries impact structure, Germany: A new interpretation

Quartz grains from the Ries impact structure containing shock-induced microstructures were investigated using Scanning Electron Microscopy in cathodoluminescence (SEM-CL), secondary electron (SEM-SE) and back-scattered electron (SEM-BSE) modes as well as Mott–Seitz analysis. The purpose of this study is to evaluate the mechanism by which CL detects Planar Deformation Features (PDFs) in quartz, which is one of the most important indicators of shock metamorphism in rock-forming minerals. PDFs are micron-scale features not easily identified using optical microscopy or scanning electron microscopy. The CL spectrum of PDFs in quartz that has suffered relatively high shock pressure shows no or a relatively weak emission band at around 385 nm, whereas an emission band with a maximum near 650 nm is observed independent of shock pressure. Thus, the ~385 nm intensity in shocked quartz demonstrates a tendency to decrease with increasing shock metamorphic stage, whereas the 650 nm band remains fairly constant. The re...

A Combined Petrographic and Micro-Raman Study of Meteoritic Microdiamond in ALH-77257 Ureilite and ALH-78113 Aubrite

ABSTRACT Two diamond-bearing meteorites (ALH-77257 and ALH-78113) were investigated by petrographic microscope and micro-Raman spectroscopy. The meteoritic diamonds can be found in fractures or veins cross-cutting the original minerals (olivine, pyroxene, feldspar) and inside the host minerals. The micro-Raman spectral features of microdiamonds in two studied meteorites are very similar to each other. The diamond peak was found at 1329 in ALH-77257 and 1332 cm−1 in ALH-78113. Hexagonal diamond was not present. However, we observed the D and G bands of graphite or amorphous carbon at 1322 and 1582 cm−1 wavenumbers, indicating an origin of the meteoritic microdiamonds by magmatic processes.

Cathodoluminescence and Raman Spectromicroscopy of Forsterite in Tagish Lake Meteorite: Implications for Astromineralogy

The Tagish Lake meteorite is CI/CM2 chondrite, which fell by a fireball event in January 2000. This study emphasizes the cathodoluminescence (CL) and Raman spectroscopical properties of the Tagish Lake meteorite in order to classify the meteoritic forsterite and its relation to the crystallization processes in a parent body. The CL-zoning of Tagish Lake meteorite records the thermal history of chondrules and terrestrial weathering. Only the unweathered olivine is forsterite, which is CL-active. The variation of luminescence in chondrules of Tagish Lake meteorite implies chemical inhomogeneity due to low-grade thermal metamorphism. The blue emission center in forsterite due to crystal lattice defect is proposed as being caused by rapid cooling during the primary crystallization and relatively low-temperature thermal metamorphism on the parent body of Tagish Lake meteorite. This is in a good agreement with the micro-Raman spectroscopical data. A combination of cathodoluminescence and micro-Raman spectroscopies shows some potentials in study of the asteroidal processes of parent bodies in solar system.

Thermal metamorphism of the Mócs meteorite (L6) revealed by optical microscopy and BSE imaging

The Mocs chondrite was studied by optical microscopy, element mapping, as well as scanning electron microscope backscattered electron (SEM—BSE) imaging, in order to gain a better understanding of the thermal metamorphic as well as post-shock annealing evolution and the mineralogical signatures in this meteorite. The studied thin section of Mocs meteorite contains 26 chondrules with a variety of chondrule textures, which are characterized by a blurry rim. The chondrules mostly consist of pyroxene and olivine, whereas feldspars occur only in the recrystallized groundmass, chondrule mesostasis, and mineral melt inside and beyond the shock veins. It was found that the matrix was completely recrystallized. According to the scanning electron microscope and optical microscope observations mentioned above, it can be concluded that the Mocs chondrite is a 6.5 petrographic type.