Light noble gases and cosmogenic radionuclides in Estherville, Budulan, and other mesosiderites: Implications for exposure histories and production rates
Bibliographic record
Abstract
Abstract—We report measurements of26AI,10Be,41Ca, and36Cl in the silicate and metal phases of 11 mesosiderites, including several specimens each of Budulan and Estherville, of the brecciated meteorite Bencubbin, and of the iron meteorite Udei Station. Average production rate ratios (atom/atom) for metal phase samples from Estherville and Budulan are26Al/10Be = 0.77 ± 0.02;36Cl/10Be = 5.3 ± 0.2. For a larger set of meteorites that includes iron meteorites and other mesosiderites, we find26Al/10Be = 0.72 ± 0.01 and36Cl/10Be = 4.5 ± 0.2. The average41Ca/36Cl production rate ratio is 1.10 ± 0.04 for metal separates from Estherville and four small iron falls. The41Ca activities in dpm/(kg Ca) of various silicate separates from Budulan and Estherville span nearly a factor of 4, from <400 to >1600, indicating preatmospheric radii of >30 cm. After allowance for composition, the activities of26Al and10Be (dpm/kg silicate) are similar to values measured in most ordinary chondrites and appear to depend only weakly on bulk Fe content. Unless shielding effects are larger than suggested by the36Cl and41Ca activities of the metal phases, matrix effects are unimportant for10Be and minor for26Al. Noble gas concentrations and isotopic abundances are reported for samples of Barea, Emery, Mincy, Morristown, and Marjalahti. New estimates of36Cl/36Ar exposure ages for the metal phases agree well with published values. Neon‐21 production rates for mesosiderite silicates calculated from these ages and from measured21Ne contents are consistently higher than predicted for L chondrites despite the fact that the mesosiderite silicates have lower Mg contents than L chondrites. We suggest that the elevation of the21Ne production rate in mesosiderite silicates reflects a “matrix effect,” that is, the influence of the higher Fe content of mesosiderites, which acts to enhance the flux of low‐energy secondary particles and hence the21Ne production from Mg. As10Be production is relatively insensitive to this matrix effect,10Be/21Ne ages give erroneously low production rates and high exposure ages. By coincidence, standard22Ne/21Ne based “shielding” corrections give fairly reliable21Ne production rates in the mesosiderite silicates.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".