Oxygen isotopic and chemical composition of chromites in micrometeorites: Evidence of ordinary chondrite precursors

Rudraswami, N. G.; Marrocchi, Yves; Prasad, M.M.; Fernandes, D.; Villeneuve, Johan; Taylor, Susan

doi:10.1111/maps.13281

Cited by 10 publications

(6 citation statements)

References 49 publications

(149 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, Fe‐sulfides (troilite, pyrrhotite, and pentlandite) are also ruled out because they suffer thermal decomposition at low temperatures (<800°C; King et al., 2015; Taylor et al., 2011) under open system conditions and would, therefore, not survive unmelted in a cosmic spherule. By contrast, chromite has both a higher average atomic weight than magnetite and is a refractory mineral, likely to survive atmospheric entry without significant melting (Heck et al., 2016; Rudraswami et al., 2019). Although, resorption textures are present on at least two sides of the grain, they are limited in extent, indicating only incipient melting at the grain margins.…”

Section: Discussionmentioning

confidence: 99%

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

et al. 2022

View full text Add to dashboard Cite

Cosmic dust grains sample a diverse range of solar system small bodies. This includes asteroids that are not otherwise represented in our meteorite collections. In this work we obtained 3D images of micrometeorite interiors using tomography before collecting destructive high‐precision oxygen isotope measurements. These data allow us to link textures in unmelted micrometeorites to known chondrite groups. In addition to identifying particles from ordinary chondrites, CR and CM chondrites we report two micrometeorites derived from an anomalous 16O‐poor source (δ17O: +16.4‰, δ18O: +28.4‰, and Δ17O: +1.4‰). Their compositions overlap with a previously reported micrometeorite (TAM50‐25) from Suttle et al. (2020), https://doi.org/10.1016/j.epsl.2020.116444 (EPSL: 546:116444). These particles represent hydrated carbonaceous chondrite material derived either from a new group or from the CY chondrites (thereby extending the isotopic range of this group). In either scenario they demonstrate close petrographic and isotopic connections to the CO‐CM chondrite clan. Furthermore, their position in O‐isotope space makes them the most likely candidate for the parent body of the anomalous “group 4” cosmic spherules previously reported by Suavet et al. (2010), https://doi.org/10.1016/j.epsl.2010.02.046 (EPSL: 293:313‐320) and several subsequent isotopic studies. We conclude that the “group 4” cosmic spherules originate from hydrated C‐type asteroid parents.

show abstract

Section: Discussionmentioning

confidence: 99%

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

et al. 2022

View full text Add to dashboard Cite

show abstract

“…Most cosmic spherules are in the size range of less than a few hundred μm; thus, the instrument can perform a detailed study of specific areas in particles. Chemical analyses were performed using electron microprobe on selected cosmic spherules phases with accelerating voltage ~15 kV, beam current ~12 nA, ~1–2 μm beam diameter for spot analyses, and ~5 μm beam diameter for bulk analyses (Rudraswami et al, 2019). Multiple measurements obtained using different standards are <1% error for major elements and within a few percent for minor elements.…”

Section: Instrumental Techniquesmentioning

confidence: 99%

“…The instrumental mass fractionation in olivine grains was corrected using San Carlos olivine, and for I‐type and some G‐type spherules that were dominated by magnetite we have used an internal terrestrial magnetite standard. Further, detailed technical description of the SEM, electron microprobe, and ion microprobe is given elsewhere (Rudraswami et al, 2019).…”

Section: Instrumental Techniquesmentioning

confidence: 99%

The Oxygen Isotope Compositions of Large Numbers of Small Cosmic Spherules: Implications for Their Sources and the Isotopic Composition of the Upper Atmosphere

et al. 2020

Self Cite

View full text Add to dashboard Cite

Cosmic spherules are micrometeorites that melt at high altitude as they enter Earth's atmosphere, and their oxygen isotope compositions are partially or completely inherited from the upper atmosphere, depending on the amount of heating experienced and the nature of their precursor materials. In this study, the three oxygen isotope compositions of 137 cosmic spherules are determined using 277 in situ analyses by ion probe. Our results indicate a possible correlation between increasing average δ 18 O compositions of silicate-dominated (S-type) spherules along the series scoriaceous < porphyritic < barred < cryptocrystalline < glass < CAT (calcium-aluminum-titanium) spherules (~12‰, 20‰, 22‰, 25‰, 26‰, and 50‰). This is consistent with the evolution of oxygen isotopes by mass fractionation owing to increased average entry heating and thus suggests mass fractionation dominates changes in isotopic composition, with atmospheric exchange being less significant. The Δ 17 O values of spherules, therefore, are mostly preserved and suggest that~80% of particles are samples of C-type asteroids. The genetic relationships between different S-types can also be determined with scoriaceous, barred, and cryptocrystalline spherules mostly having low Δ 17 O values (≤0‰) mainly derived from carbonaceous chondrite (CC)-like sources, while porphyritic spherules mostly have positive Δ 17 O (>0‰) and are largely derived from ordinary chondrite (OC)-like sources related to S (IV)-type asteroids. Glass and CAT spherules have variable Δ 17 O values indicating they formed by intense entry heating of both CC and OC-like materials. I-type cosmic spherules have a narrow range of δ 17 O (~20-25‰) and δ 18 O (~38-48‰) values, with Δ 17 O (~0‰) suggesting their oxygen is obtained entirely from the Earth's atmosphere, albeit with significant mass fractionation owing to evaporative heating. Finally, G-type cosmic spherules have unexpected isotopic compositions and demonstrate little mass fractionation from a CC-like source. The results of this study provide a vital assessment of the wider population of extraterrestrial dust arriving on Earth.

show abstract

“…Particle density is a variable parameter, since the densities of interplanetary dust particles (IDPs) captured in the stratosphere, although peaked at ∼2 g cm −3 similar to CI chondrites, exhibit a spread up to 3.5 g cm −3 , i.e., similar to the densities of ordinary chondrites (Flynn & Sutton 1990;Love et al 1994;Flynn et al 2018;Rojas et al 2021). Previous studies on MMs have assumed that their precursors are essentially either CI or CM chondrites, though other chondrites need to be treated for completion (e.g., Brownlee et al 1997;Taylor et al 2000;Prasad et al 2013Prasad et al , 2015Rudraswami et al 2019). (Clayton et al 1986;Engrand et al 1999Engrand et al , 2005Taylor et al 2005;Suavet et al 2010;Cordier et al 2011;Rudraswami et al 2015Rudraswami et al , 2020Van Ginnekan et al 2017;Suttle et al 2020;Goderis et al 2020;Fischer et al 2021).…”

Section: The Chemical Ablation Model (Cabmod)mentioning

confidence: 99%

Oxygen Ablation during Atmospheric Entry: Its Influence on the Isotopic Composition of Micrometeorites

Rudraswami

Pandey

Fernandes

et al. 2022

ApJ

Self Cite

View full text Add to dashboard Cite

Micrometeorites (MMs) offer glimpses of the diverse nature of parent bodies that accreted during the first few million years after the formation of the proto-Sun. The present work explores this by evaluating the ablation of oxygen from MMs during atmospheric entry, and the resulting effect on the oxygen isotopic composition. A Chemical ABlation MODel (CABMOD) combined with the measured oxygen isotope composition of MMs, shows that at temperatures below 2000 K a relatively small percentage (∼0%–5%) of oxygen ablates; the temperature is nevertheless sufficient to induce diffusion among the different silicate phases of MMs. The large δ 18O composition found within different MM types with low oxygen ablation indicates that exchange with atmospheric oxygen is insignificant during entry. Therefore, to explain the large δ 18O values existing in heated MMs, where oxygen ablation is less than a few percent, we propose that these particles are from distinct C-type asteroids that have undergone nebular gas exchange and/or aqueously altered in their parent bodies. This is supported by the evidence from unmelted MMs that have not exchanged oxygen during atmospheric entry or undergone ablation, but have large δ 18O values. However, the oxygen isotope composition of different types of cosmic spherules does not appear to vary systematically with temperature and could be due to the heterogeneity of their precursors. This investigation overall provides insights into the oxygen ablation of the particles during atmospheric entry, oxygen isotopic alteration, and the reservoirs of the diverse extraterrestrial objects that prevailed in the early solar system.

show abstract

Oxygen isotopic and chemical composition of chromites in micrometeorites: Evidence of ordinary chondrite precursors

Cited by 10 publications

References 49 publications

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

The Oxygen Isotope Compositions of Large Numbers of Small Cosmic Spherules: Implications for Their Sources and the Isotopic Composition of the Upper Atmosphere

Oxygen Ablation during Atmospheric Entry: Its Influence on the Isotopic Composition of Micrometeorites

Contact Info

Product

Resources

About