Highly accurate dating of micrometre-scale baddeleyite domains through combined focused ion beam extraction and U–Pb thermal ionization mass spectrometry (FIB-TIMS)
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.
Bibliographic record
Abstract
Abstract. Baddeleyite is a powerful chronometer of mafic magmatic and meteorite impact processes. Precise and accurate U–Pb ages can be determined from single grains by isotope dilution thermal ionization mass spectrometry (ID-TIMS), but this requires disaggregation of the host rock for grain isolation and dissolution. As a result, the technique is rarely applied to precious samples with limited availability (such as lunar, Martian, and asteroidal meteorites and returned samples) or samples containing small baddeleyite grains that cannot readily be isolated by conventional mineral separation techniques. Here, we use focused ion beam (FIB) techniques, utilizing both Xe+ plasma and Ga+ ion sources, to liberate baddeleyite subdomains directly, allowing their extraction for ID-TIMS dating. We have analysed the U–Pb isotope systematics of domains ranging between 200 and 10 µm in length and from 5 to ≤0.1 µg in mass. In total, six domains of Phalaborwa baddeleyite extracted using a Xe+ plasma FIB (pFIB) yield a weighted mean 207Pb∕206Pb age of 2060.1±2.5 Ma (0.12 %; all uncertainties 2σ), within uncertainty of reference values. The smallest extracted domain (ca. 10×15×10 µm) yields an internal 207Pb∕206Pb age uncertainty of ±0.37 %. Comparable control on cutting is achieved using a Ga+-source FIB instrument, though the slower speed of cutting limits potential application to larger grains. While the U–Pb data are between 0.5 % and 13.6 % discordant, the extent of discordance does not correlate with the ratio of material to ion-milled surface area, and results generate an accurate upper-intercept age in U–Pb concordia space of 2060.20±0.91 Ma (0.044 %). Thus, we confirm the natural U–Pb variation and discordance within the Phalaborwa baddeleyite population observed with other geochronological techniques. Our results demonstrate the FIB-TIMS technique to be a powerful tool for highly accurate in situ 207Pb∕206Pb (and potentially U–Pb in concordant materials) age analysis, allowing dating of a wide variety of targets and processes newly accessible to geochronology.
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 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 | 0.001 |
| Science and technology studies | 0.000 | 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) | 0.007 | 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