Fine-grained volatile components ubiquitous in solar nebula: Corroboration from scoriaceous cosmic spherules |
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| Authors: | N G Rudraswami D Fernandes A K Naik M Shyam Prasad S Taylor |
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| Institution: | 1. National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa, 403004 India;2. Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, New Hampshire, 03755–1290 USA |
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| Abstract: | The scoriaceous cosmic spherules (CSs) that make up to a few percent (for sizes >150 μm size) of total micrometeorite flux are ubiquitous and have remained enigmatic. The present work provides in-depth study of 81 scoriaceous CSs, from observed ~4000 CSs, collected from Antarctica (South Pole water well) and deep-sea sediments (Indian Ocean) that will allow us to analyze the nature of these particles. The fine-grained texture and the chemical composition of scoriaceous particles suggest that they are formed from matrix materials that are enriched in volatiles. The volatile components such as water, sulfide, Na, K, etc. have vanished due to partial evaporation and degassing during Earth's atmospheric entry leaving behind the vesicular features, yet largely preserving the elemental composition. The elemental ratios (Ca/Si, Mg/Si, Al/Si, Fe/Si, and Ni/Si) of interplanetary dust particles (IDPs) are compatible with the scoriaceous CSs, which in turn are indistinguishable from the matrices of CI and CM chondrites signifying similarities in the nature of the sources. Furthermore, the texture of cometary particles bears resemblance to the texture of the scoriaceous particles. The compilation of petrographic texture, chemical, and trace element composition of scoriaceous CSs presents a strong case for matrix components from hydrated and volatile-rich bodies, such as CI and CM chondrites, rather than chondrules. We conclude that the fine-grained scoriaceous CSs, the matrix materials of hydrated chondrites, IDPs, and cometary particles that overlap compositionally were widespread, indicating a dominant component in the early solar nebula. |
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