Technical note: Investigation into the mechanism of chemical abrasion using SHRIMP, Raman spectroscopy and atom probe tomography
Bibliographic record
Abstract
Abstract. Chemical abrasion, a two-step process of annealing and partial dissolution, is routinely applied to zircon grains prior to U-Pb geochronology, to remove portions of the grains affected by Pb loss. The exact effect of this technique on the zircon structure and the distribution of radiogenic isotopes, however, remains elusive. Herein, grains of reference zircon OG1 were either fully or partially subjected to the chemical abrasion process and subsequently analysed by sensitive high mass resolution ion microprobe (SHRIMP) to determine the U-Pb systematics. Sputter craters from untreated, annealed, and fully chemically abraded aliquots were then mapped using Raman spectroscopy to determine the magnitude and distribution of radiation damage. For the untreated and annealed zircon, sputter craters from both concordant and discordant analyses were mapped. All chemically abraded zircon SHRIMP analyses were concordant. Raman mapping showed that the bottoms of discordant SHRIMP sputter craters generally had areas of higher and more heterogeneous Raman band width than concordant sputter pits for the same treatment. These results are consistent with previous scanning electron microscopy and micro computer tomography results. Based on the Raman maps, sputter craters with varying degrees of lattice damage and Pb loss were targeted for nanoscale analysis using atom probe tomography (APT) to assess the distribution of radiogenic isotopes at the lattice scale. APT reconstructions reveal a homogeneous distribution of all major components and radiogenic isotopes for all samples. These results indicate that APT is not able to detect elemental mobility or void formation arising from the lead loss, annealing or chemical abrasion in these samples. Thus the APT data do not provide additional constraints beyond the SHRIMP and Raman data on the mechanisms of Pb loss. Importantly, as the APT technique cannot distinguish between concordant and 5–10 % discordant zircon, it should not be used for this purpose.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".