In Situ Re-Os Dating of Molybdenite Using La-Icp-Ms/Ms. Analytical protocol and standardization.
Bibliographic record
Abstract
Dating with the Re-Os isotopic system provides several advantages compared to conventional\nchronometers such as Rb-Sr. Because of the sidero- and chalcophilic nature of Re and Os, those\ncan be found as trace elements in sulfides, meaning that ages can be obtained for sulfide deposit,\ngiving valuable information of ore genesis. To ensure the quality of the analytical measurements\nneeded in isotopic dating, a reference material with known concentrations of Re and Os is\nnecessary. The aim of this study is to develop a method to produce a homogenous tablet of the\nsulfide molybdenite, and validate its use as a reference material for calibration of in situ Re-Os\ndating using LA-ICP-MS/MS. Molybdenite from Kingsgate, Australia, was used as a test\nmaterial, molybdenite from Moly Hill, Canada, as the reference material for the tablet, and\nmolybdenite from Ytterby, Sweden, as a validation of the produced tablet. The molybdenite\nwas milled by hand with ethanol in an agate mortar and pressed into a tablet in a tablet die set\nby applying 2.5 t (0.19 × 106 kPa) for 2 min. Molybdenite proved to be hard to mill due to its\nlayered structure and milling in a high power planetary ball mill was therefore unsuccessful in\nproducing fine material. The optimum pressure and corresponding time depended on several\nfactors, such as the tablet die set and material, and will affect for example numbers of cracks in\nthe tablet. The tablet was analyzed with LA-ICP-MS/MS, an analytical method that was chosen\nbecause it provides the opportunity to target specific ions, created after a reaction with a reaction\ngas, in this case CH4. This is a tool used to chemically separate the parent and daughter isotopes\nand overcome the isobaric overlap. Isotopes of Re and Os, as well as potential elements in\ninclusion, was measured. Despite signs of inclusions in the final tablets, the Re and Os signals\nseemed unaffected by this. Ratios for 187Re/187Os was calculated for the tablet of molybdenite\nfrom Moly Hill, and for Ytterby molybdenite. The literature Re-Os age for Moly Hill, 2646 Ma,\nwas used to obtain a corresponding 187Re/187Os ratio, which in turn could be used to calculate a\ncorrection factor. This was applied to the Ytterby molybdenite to obtain corrected ratios, then\ncalculating an age of 1823 ± 28 Ma, which overlaps the literature age for Ytterby, 1795 ± 2 Ma.\nThe results validate the quality of the tablet produced of molybdenite from Moly Hill and\nconfirms that it can be used for calibration of in situ Re-Os dating with LA-ICP-MS/MS, even\nif several improvements of the methods can be done in the future, both in the milling process\nand the analytical process.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.010 | 0.004 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".