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Record W3097778711

Sm-Nd Systematics of Chondrites

2004· article· en· W3097778711 on OpenAlex
Yuri Amelin, E. Rotenberg

Why this work is in the frame

A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.

affAt least one author lists a Canadian institution in the pinned OpenAlex snapshot.

Bibliographic record

VenueLunar and Planetary Science Conference · 2004
Typearticle
Languageen
FieldPhysics and Astronomy
TopicAstro and Planetary Science
Canadian institutionsUniversity of Toronto
Fundersnot available
KeywordsIsochronChondriteChondruleIsochron datingGeologyGeochemistryMineralogyMeteoriteAstrobiologyPhysics
DOInot available

Abstract

fetched live from OpenAlex

We have studied the 147Sm–143Nd and 146Sm–142Nd isotopic systems in phosphate fractions and chondrules from six ordinary chondrites and one carbonaceous chondrite, previously dated with Pb–Pb method. 147Sm/144Nd ratios vary between 0.182 and 0.191 in phosphates, and between 0.179 and 0.243 in chondrules. The 147Sm–143Nd isochron regression through all 34 phosphate and chondrule analyses yields a date of 4588±100 Ma and is in good agreement with more precise Pb–Pb dates of the same chondrites. The initial 143Nd/144Nd is 0.50665±0.00014. The same analyses define a 146Sm–142Nd isochron with a slope corresponding to 146Sm/144Sm=0.0075±0.0027. Initial 142Nd/144Nd=1.14160±0.00011 corresponds to e142Nd=−2.62±0.93. Compilation of the published chondritic whole rock Sm–Nd analyses yields the median 147Sm/144Nd=0.1964+0.0003/−0.0007, which is our preferred Chondritic Uniform Reservoir (CHUR) value. Using this value and its error limits, we find the present-day CHUR 143Nd/144Nd=0.512637+0.000009/−0.000021 from the chondritic Sm–Nd isochron that includes all available data for whole rocks, chondrules and phosphates. This value is identical within error with the currently accepted number. An estimate of the bulk earth 147Sm/144Nd=0.1941±0.0059 is obtained from intercept of chondritic 146Sm–142Nd isochron with the terrestrial value of 142Nd/144Nd. This estimate is independent of measured Sm/Nd ratios in chondrites. The same approach was applied to published 146Sm–142Nd internal isochrons for differentiated meteorites and yielded similar, although less precise, values. Our data are completely consistent with the currently accepted CHUR parameters and substantiate their use as terrestrial reference values.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.

Full frame distilled prediction

Teacher imitation

Not calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.

metaresearch head score (Codex)0.000
metaresearch head score (Gemma)0.000
Version: codex-gemma-dda1882f352aValidation status: machine_predicted_unvalidated
Candidate categoriesnone
Consensus categoriesnone
DomainCandidate signal: none · Consensus signal: none
Study designCandidate signal: Observational · Consensus signal: Observational
GenreCandidate signal: Empirical · Consensus signal: Empirical
Teacher disagreement score0.102
Threshold uncertainty score0.467

Codex and Gemma teacher scores by category

CategoryCodexGemma
Metaresearch0.0000.000
Meta-epidemiology (narrow)0.0000.000
Meta-epidemiology (broad)0.0000.000
Bibliometrics0.0000.000
Science and technology studies0.0000.001
Scholarly communication0.0000.000
Open science0.0000.000
Research integrity0.0000.000
Insufficient payload (model declined to judge)0.0000.000

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.

Opus teacher head0.011
GPT teacher head0.208
Teacher spread0.197 · how far apart the two teachers sit on this one work
Validation statusscore_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it