Saikia, Bhaskar J and Parthasarathy, G and Saikia, Binoy K and Bordoloi, Puja and Borah, Rashmi R
(2025)
First observation of coexistence of crystalline and amorphous mineral phases in the Bhawad LL6 chondrite: Evidence from Micro-Raman spectroscopic studies.
Geoscience Frontiers.
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| Abstract: |
We report here for the first time the detailed spectroscopic investigations on Bhawad meteorite using micro-Raman spectroscopic and high-resolution transmission electron microscopy (HR-TEM) investigation of the Bhawad LL6 ordinary chondrite, focusing on its mineralogical composition and carbonaceous phases. Raman spectroscopy reveals crystalline silicates including olivine, pyroxene, and plagioclase, along with accessory chromite containing ≤20 % of Al. Carbonaceous material exhibits broad ID (∼1336 cm−1) and IG (∼1587 cm−1) bands with an ID/IG ratio of ∼1.04, indicative of disordered graphite and nanocrystalline carbon, reflecting shock-induced metamorphism. High-pressure TiO2 polymorphs are identified by characteristic Raman modes at 146, 394, 446, and 610 cm−1. HR-TEM imaging confirms the presence of nanocrystalline TiO2 particles embedded within amorphous carbonaceous matrices, demonstrating the coexistence of crystalline and amorphous phases. The Raman spectra of the Bhawad meteorite reveal the presence of high-temperature plagioclase phases, characterized by these distinct vibrational features. This observation indicates possible quenching of the melts having feldspar components, representing the complex thermal and shock metamorphic history of the meteorite. This coexistence of crystalline and amorphous phases highlights the complex thermal and shock history of the Bhawad meteorite, revealing insights into phase transitions and structural order–disorder phase transition induced by impact processes. |
| Item Type: |
Journal Paper
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| Subjects: |
School of Natural and Engineering Sciences > Geology |
| Divisions: |
Schools > Natural Sciences and Engineering |
| Date Deposited: |
16 Dec 2025 09:04 |
| Last Modified: |
16 Dec 2025 09:04 |
| Official URL: |
https://www.sciencedirect.com/science/article/pii/... |
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| Funders: |
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| Projects: |
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| DOI: |
https://doi.org/10.1016/j.gsf.2025.102236 |
| URI: |
http://eprints.nias.res.in/id/eprint/3013 |
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