A high throughput Rb-Sr dating method using solution tandem ICP-MS/MS (87Sr/86Sr) and standard addition calibration ICP-MS (Rb/Sr)
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Bibliographic record
Abstract
Routine generation of large Rb-Sr age datasets has been limited by the time-consuming requirement of chromatographic isolation of Sr from Rb to avoid the isobaric interference of 87Rb+ on 87Sr+. Recently, direct measurement of interference-free 87Sr/86Sr has become possible with the advent of tandem quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS). Here, we describe a method that uses ICP-MS/MS to measure 87Sr/86Sr combined with a standard addition calibration for precise determination of Rb/Sr, allowing efficient generation of Rb-Sr ages. The method is demonstrated on a suite of ~50 to 90 Myrs (million years) old celadonite samples that are dated with age uncertainties typically of ±2 to 5 Myrs provided the sample Rb/Sr is >2. A method to separate the phyllosilicate fraction from the bulk sample, because it commonly has a higher Rb/Sr more suitable for dating, using differential settling is also described. Differential settling allows high Rb/Sr phyllosilicates to be separated from other phases ICP-MS/MS allows 87Sr/86Sr measurement without chromatographic isolation of Sr+ from Rb+ Single-spike standard addition ICP-MS was used for Rb/Sr measurement
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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 | 0.004 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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 it