Identification and pairing reassessment of unequilibrated ordinary chondrites from four Antarctic dense collection areas

Righter, K.; Schutt, J. W.; Lunning, N. G.; Harvey, R. P.; Karner, J. M.; Yamaguchi, A.

doi:10.1111/maps.13707

Cited by 4 publications

(3 citation statements)

References 27 publications

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“…There are five 3.00, seven 3.05, five 3.1, six 3.2, four 3.3, four 3.4, two 3.5, seven 3.6, five 3.7, three 3.8, two 3.9, two 4, and eight non‐subtyped 3. We note that some Elephant Moraine (EET) and Meteorite Hills (MET) meteorites we studied have recently been re‐classified (Righter et al., 2021). In addition, we studied three Rs which have petrologic type 3/4 (1) and 3.8 (2).…”

Section: Methodsmentioning

confidence: 99%

Calcium–aluminum‐rich inclusions in non‐carbonaceous chondrites: Abundances, sizes, and mineralogy

Dunham,

Sheikh,

Opara

et al. 2023

Meteorit & Planetary Scien

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As the Sun was forming, calcium-aluminum-rich inclusions (CAIs) were the first rocks to have condensed in the hottest regions of the solar nebula disk. Carbonaceous chondrites (CCs) contain abundant CAIs but are thought to have accreted in the outer Solar System, requiring that CAIs must have been transported outward. Curiously, CAIs are rare in ordinary, enstatite, rumuruti, and kakangari chondrites, non-carbonaceous chondrites (NCs), that likely formed in the inner Solar System. Thus, CAI abundances and characteristics can provide constraints on the early dynamical evolution of the disk. In this work, we address whether the hypothesis of an early-formed proto-Jupiter "opening a gap" in the disk can explain the dichotomy in the relative abundance of CAIs in CC and NC chondrites. We searched 76 NC meteorite sections to find 232 CAIs which have an average apparent diameter of 46 μm and comprise 0.01 area%, about half the size of and ~200 times less abundant than CC CAIs on average. Unlike CC CAIs, only 4% of the NC CAIs contain melilite and most contain alteration features suggesting that NC CAIs underwent pervasive fluid-assisted thermal metamorphism on asteroidal parent bodies. However, based on NC CAI populations correlating with meteorite metamorphic grade, we argue that disk dynamics is likely the primary reason behind the existence of small (<100 μm) and rare NC CAIs. Our data support astrophysical models which suggest that, after outward transport of CAIs, formation of a gap in the disk trapped CAIs in the outer Solar System.

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Section: Methodsmentioning

confidence: 99%

Calcium–aluminum‐rich inclusions in non‐carbonaceous chondrites: Abundances, sizes, and mineralogy

Dunham,

Sheikh,

Opara

et al. 2023

Meteorit & Planetary Scien

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“…Moreover, most entries in the database represent individual specimens, as only the most obviously fragmented proximal stones are usually paired as one single meteorite in the field (50). Despite the importance of considering pairing of meteorite specimens (12,51), to our knowledge, no systematic pairing campaigns on Antarctic meteorites have been performed (50,52,53), and pairing data are often not updated in the database. Therefore, the (reprojected) observations are used as provided in the database, notwithstanding the limitation this imposes on the results.…”

Section: Data For Observationsmentioning

confidence: 99%

Unexplored Antarctic meteorite collection sites revealed through machine learning

et al. 2022

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Meteorites provide a unique view into the origin and evolution of the Solar System. Antarctica is the most productive region for recovering meteorites, where these extraterrestrial rocks concentrate at meteorite stranding zones. To date, meteorite-bearing blue ice areas are mostly identified by serendipity and through costly reconnaissance missions. Here, we identify meteorite-rich areas by combining state-of-the-art datasets in a machine learning algorithm and provide continent-wide estimates of the probability to find meteorites at any given location. The resulting set of ca. 600 meteorite stranding zones, with an estimated accuracy of over 80%, reveals the existence of unexplored zones, some of which are located close to research stations. Our analyses suggest that less than 15% of all meteorites at the surface of the Antarctic ice sheet have been recovered to date. The data-driven approach will greatly facilitate the quest to collect the remaining meteorites in a coordinated and cost-effective manner.

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“…Twenty‐three CO3 chondrites have been recovered in the Dominion Range (DOM) during the 2003–2004, 2008–2009, 2010–2011, 2014–2015, 2018–2019, and 2019–2020 ANSMET (Antarctic Search for Meteorites) seasons (e.g., Righter et al., 2019; Satterwhite & Righter, 2009, 2011, 2014; Figure 1). Initial characterization led to the suggestion that many of the DOM CO3 could be paired, that is, individually recovered pieces of the same meteoroid that broke up in the atmosphere or subsequently on the ground.…”

Section: Introductionmentioning

confidence: 99%

Pairing relations within CO3 chondrites recovered at the Dominion Range and Miller Range, Transantarctic mountains: Constraints from chondrule olivines, noble gas, and H, C, N bulk and isotopic compositions

Righter,

Alexander,

Foustoukos

et al. 2024

Meteorit & Planetary Scien

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The Dominion Range (DOM) and Miller Range (MIL) dense collection areas (DCAs) have yielded more than 20 and 200 CO3 chondrites (carbonaceous chondrites of the Ornans chemical group), respectively, over multiple field seasons. Several samples have exhibited primitive characteristics and have been the focus of interest. With so many CO3s recovered from this area, a natural question is if there are multiple pairing groups (where pairing refers to two or more meteorites that are part of a single fall) and if there is additional primitive material that would interest the meteorite community. This comprehensive study looks at all samples using several approaches: field and macroscopic observations; magnetic susceptibility; Cr in ferroan olivine; bulk elemental and isotopic analysis of H, C, N, and noble gas analyses to determine cosmic ray exposure (CRE) ages. Magnetic susceptibilities (measured as logχ) for all samples correlate with their type II (i.e., FeO‐rich) olivine Cr contents, with the most primitive CO3s (3.00) have logχ values near 5, while the higher grade CO3s have logχ values as low as 4.17. Altogether, there appear to be two distinct CO3 pairing groups and five other unpaired CO3s recovered at the Dominion Range: (a) the main DOM 08004 pairing group (16 specimens with a CRE age of 10–16 Ma), (b) the DOM 08006 group (2 specimens incl. DOM 10847 with a CRE age of 25 Ma), (c) DOM 14359 with a CRE age of 6 Ma, (d) DOM 18070 with a CRE age of 8 Ma (these two samples have similar ages but distinct trapped 20Ne contents), (e) DOM 10900 with a CRE age of 5.5 Ma, (f) DOM 18286 (with a CRE age of ~59 Ma), and (g) DOM 19034 (with a CRE age of ~43 Ma). There are three distinct age groupings of 3.00–3.05 COs, highlighting the diverse pristine CO3 materials present in the DOM area. There is one large MIL pairing group (MIL 07099; n = 199; 9–14 Ma CRE age where measured) and one smaller pairing group with distinctly lower Cr2O3 in type II olivines (8 samples of unknown CRE age), and five unpaired or unique CO3s. Notably, the large DOM and MIL pairing groups have 9–16 Ma exposure ages that could have been delivered in a single large fall event spanning ~200 km, two separate falls that were ejection paired, or two separate falls from two separate ejections. Finally, we recommend reclassifying several CO3 to CM2 based on new data and that from previous studies.

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Identification and pairing reassessment of unequilibrated ordinary chondrites from four Antarctic dense collection areas

Cited by 4 publications

References 27 publications

Calcium–aluminum‐rich inclusions in non‐carbonaceous chondrites: Abundances, sizes, and mineralogy

Calcium–aluminum‐rich inclusions in non‐carbonaceous chondrites: Abundances, sizes, and mineralogy

Unexplored Antarctic meteorite collection sites revealed through machine learning

Pairing relations within CO3 chondrites recovered at the Dominion Range and Miller Range, Transantarctic mountains: Constraints from chondrule olivines, noble gas, and H, C, N bulk and isotopic compositions

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