Raman spectra of tridymite modifications: MC, MX–1, and PO–10

Abstract

In order to facilitate identification of tridymite modifications using micro-Raman spectroscopy, the Raman spectra of synthetic and natural tridymite modifications (MC, MX-1, and PO-10) including low frequency region (ν = 15-200 cm −1) are measured. The Raman spectrum of MX-1 is reported for the first time. All modifications revealed the characteristic peaks below 150 cm −1. Using the compiled Raman spectra, tridymite modifications of the reported Raman spectra from meteorites in the literature were identified. It revealed that not only MC, but PO-10 modification exists in the meteorites.

Phase transitions of tridymite MC: A low frequency Raman spectroscopic study

“…We noted that most major peaks can be assigned to those of MC, but there are additional peaks. There is a peak at 256 cm −1 , which is diagnostic for MX-1 (Kanzaki, 2019b). Other strong peaks of MX-1 also exist.…”

“…A synthetic tridymite used in this study is same sample reported in our previous study (Kanzaki, 2019b) and was synthesized from a mixture of silica sand and 3 wt% K 2 CO 3 at 1400°C. The sample consists of mostly MC with minor cristobalite and MX-1, as detected by micro-Raman spectroscopy.…”

“…New generation Raman notch filter (Lebedkin et al, 2011) now allows us to measure the lower frequency region even using a conventional single monochromator-based Raman system as demonstrated in our previous studies (Kanzaki, 2018;Kanzaki, 2019a). Recently, Raman spectra of tridymite modifications (MC, MX-1, and PO-10) stable at room temperature including the low frequency region were reported (Kanzaki, 2019b), and the low frequency peaks were found for all phases studied. In this paper, a preliminary result of in-situ high-temperature low frequency Raman spectroscopic observation of tridymite MC is reported.…”

Association of silica phases as geothermobarometer for eucrites: Implication for two‐stage thermal metamorphism in the eucritic crust

“…Therefore, when a rock was slowly cooled and enough impurities were concentrated, we consider that tridymite crystallized directly from melt instead of cristobalite or quartz in a wide range of temperature. Almost all previous studies except for Kanzaki (2019) used powdered monoclinic tridymite for starting materials different from single crystals of monoclinic tridymite in 1-2 mm eucrite fragments in our study. Powdered samples transform more quickly because of the larger surface area compared with single grains in eucrite.…”

“…More than 23 polymorphs, including metastable phases, are known within a wide temperature range (<110 to >1470°C; e.g., Kihara 2001). In particular, tridymite has more than seven metastable phases, and three different polymorphs are metastable at room temperature: low-monoclinic tridymite (MX-1), high-monoclinic tridymite (MC), and pseudo-orthorhombic tridymite (PO) (Graetsch and Fl€ orke 1991;Graetsch 2000;Kanzaki 2019). We have previously studied three cumulate eucrites focusing on silica minerals clarifying that tridymite polymorphs represent low-temperature thermal histories (Ono et al 2019).…”