Assessing the U‐Pb, Sm‐Nd and Sr‐Sr Isotopic Compositions of the Sumé Apatite as a Reference Material for LA‐ICP‐MS Analysis
Bibliographic record
Abstract
This study has determined the trace element and the U‐Pb, Sm‐Nd and Sr‐Sr isotope composition of the Sumé apatite (from NE Brazil) to assess its suitability as a primary/secondary reference material for LA‐ICP‐MS. Reproducibility tests demonstrate that one batch (~ 100 g) of the Sumé apatite (Sumé‐570) is uniform in terms of Nd‐Nd and U‐Pb isotope compositions. Bulk isotope dilution TIMS/ICP‐MS and LA‐MC‐ICP‐MS analyses confirm that the apatite is well suited for use as quality control material for Nd isotopes and U‐Pb geochronology. U‐Pb ID‐TIMS analyses yield weighted mean ratios of 0.09211 ± 0.00053 (2 s ; 206 Pb*/ 238 U) and 0.06120 ± 0.00063 (2 s ; 207 Pb*/ 206 Pb*) and a weighted mean 206 Pb*/ 238 U date of 568 ± 3 Ma (95% c.l.). U‐Pb LA‐(SF/MC)‐ICP‐MS runs using Sumé‐570 as a primary RM and reproduces the dates of other established RMs within 1% deviation (except for Durango 2–4%). Major and trace element abundances show that Sumé‐570 is a fluorapatite derived from a syenitic source. It also strongly shows LREE‐enriched chondrite‐normalised REE patterns with significant negative Eu anomalies, due to crystallisation of plagioclase in the residue.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot 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.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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 teacher head, 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".