Compositional and spectroscopic investigation of three ungrouped carbonaceous chondrites

Abstract

Ungrouped carbonaceous chondrites are not easily classified into one of the well‐established groups due to compositional/petrological differences and geochemical anomalies. Type 2 ungrouped carbonaceous chondrites represent a very small fraction of all carbonaceous chondrites. They can potentially represent different aspects of asteroids and their regolith material. By conducting a multitechnique investigation, we show that Queen Alexandra Range (QUE) 99038 and Elephant Moraine (EET) 83226 do not resemble type 2 carbonaceous chondrites. QUE 99038 exhibits coarse‐grained matrix, Fe‐rich rims on olivines, and an apparent lack of tochilinite, suggesting that QUE 99038 has been metamorphosed. Its polyaromatic organic matter structures closely resemble oxidized CV3 chondrites. EET 83226 exhibits a clastic texture with high porosity and shows similarities to CO3 chondrites. It consists of numerous large chondrules with fine‐grained rims that are often fragmented and discontinuous and set within matrix, suggesting a formation mechanism for the rims in a regolith environment. The kind of processes that can result in such chemical compositions as in QUE 99038 and EET 83226 is currently not fully known and clearly presents a conundrum. Tarda is a highly friable carbonaceous chondrite with close resemblance to Tagish Lake (ungrouped C2 chondrite). It comprises different types of chondrules (some with Fe‐rich rims), framboid magnetite, sulfides, carbonates, and phyllosilicate‐ and carbon‐rich matrix, and is consistent with being an ungrouped C2 chondrite.

Chemical composition of carbonaceous asteroid Ryugu from synchrotron spectroscopy in the mid- to far-infrared of Hayabusa2-returned samples

“…Figure 8 shows the comparison of CH 2 /CH 3 peak ratios with literature data. The CH 2 /CH 3 peak ratios in Ryugu are higher than the one typically observed for petrologic type 1 chondrites, and are comparable to the range observed for type 2 and 3 chondrites (Alexander et al 2014;Briani et al 2013;Dionnet et al 2018;Kebukawa et al 2010Kebukawa et al , 2011Kebukawa et al , 2019Kerraouch et al 2022;Merouane et al 2012;Orthous-Daunay 2011Quirico et al 2018;Yesiltas et al 2014Yesiltas et al , 2015Yesiltas et al , 2022Yesiltas & Kebukawa 2016). This does not necessarily imply a higher level of heating of Ryugu than in C1 type chondrites, and should be constrained by other petrologic estimates.…”

“…A2, page 8 of 30 E.Fig.8. Comparison of methylene-to-methyl (CH 2 /CH 3 ) intensity peak ratios for Ryugu bulk sample measurements (this work) with measurements from the literature for diffuse ISM observations(Sandford et al 1991;Pendleton et al 1994;Dartois et al 2007;Godard et al 2012), Stardust samples (comet 81P/Wild2,Keller et al 2006), IDPs(Flynn et al 2003), and meteorites bulk and IOM samples(Alexander et al 2014;Briani et al 2013;Dionnet et al 2018;Kebukawa et al 2010Kebukawa et al , 2011Kebukawa et al , 2019Kerraouch et al 2022;Merouane et al 2012;Orthous-Daunay 2011Quirico et al 2018;Yesiltas et al 2014Yesiltas et al , 2015Yesiltas et al , 2022 Yesiltas & Kebukawa 2016).…”

A sample preparation guide for clay‐rich carbonaceous chondrites

“…These clays have a hardness of ~1-3 on the Mohs scale. In contrast, embedded minerals within this soft matrix include chondrules and chondrule fragments, magnetite, dolomite, olivine, and Fe-sulfides which exhibit considerably higher Mohs hardness values up to 7 (Marrocchi et al, 2021;Yesiltas et al, 2022). 2.…”

Analytical method for stable background reduction for Raman spectra of carbon‐containing meteorite and terrestrial samples suffering from intense fluorescence

“…To overcome the problem of the intense fluorescence, mathematical data analysis has been previously discussed (Christ et al., 2022; Gao et al., 2021; Gomez‐Mascaraque & Pinho, 2021; Holmi & Lipsanen, 2022; Korepanov, 2020; Villanueva‐Luna et al., 2011; Yesiltas et al., 2022). Since the fluorescent spectra are generally asymmetric to wavelength and well described by log‐normal function (asymmetric Gaussian function) (Burstein & Emelyanenko, 1996; Siano & Metzler, 1969), a log‐normal function is often assumed to estimate the spectral shape of the broad fluorescence spectra (Addison et al., 2013; Bacalum et al., 2013; Caarls et al., 2010; Djikanovic et al., 2007; Humbs et al., 2000; Kimura et al., 2015; Lang et al., 2006; Le et al., 2017; Xiong et al., 2019).…”

“…Instead of the log‐normal fitting, some researchers tried to estimate the fluorescence background shape by a very high seventh‐order polynomial functions or by semi‐automated principal component analysis (PCA) to the region of interest (Christ et al., 2022; Gao et al., 2021; Gomez‐Mascaraque & Pinho, 2021; Holmi & Lipsanen, 2022; Villanueva‐Luna et al., 2011; Yesiltas et al., 2022). However, while these methods are advantageous for effective and reproducible removal of the background in wide wavenumber region, the high‐order polynomial fitting sometimes overestimate the fluorescence intensity, leading to over‐subtracting of the background especially when the Raman peaks are not very sharp.…”