PII S0016-7037(01)00768-2 190Pt–186Os and 187Re–187Os systematics of the Sudbury Igneous Complex, Ontario
Bibliographic record
Abstract
Abstract—We measured by negative thermal ionization mass spectrometry (NTIMS) Re, Os and 186Os/188Os and 187Os/188Os in 26 samples of 18 Ni–Cu sulfide ores from the Falconbridge, McCreedy West, and Strathcona mines at Sudbury, Ontario. At McCreedy West and Falconbridge, the isochron Re–Os ages are 1835 70 Ma and 1827 340 Ma, and the initial 187Os/188Os ratios 0.514 0.019 and 0.550 0.024, respectively. The ages agree with the canonical value of 1850 1 Ma for the Sudbury Igneous Complex (SIC). For Hangingwall and Deep Zone ores at Strathcona, the age of 1780 7 Ma may reflect resetting by dyke activity. The high initial 187Os/188Os of 0.934 0.005 in these ores is distinct from those at McCreedy West and Falconbridge. Strathcona Deep Copper Zone ores have highly radiogenic Os giving a mean model age of 1883 54 Ma that is similar to ages at McCreedy West and Falconbridge, but distinct from other Strathcona sulfides. Initial 186Os/188Os in two Strathcona ores with low 190Pt/188Os average 0.119 826 0.000 009 (n 3) and 0.119 827 0.000 004 (n 3), respectively, with a grand mean of 0.119 827 0.000 003. This ratio may be slightly lower than the chondritic value at that time. Similar ores at Falconbridge and McCreedy West show more scatter, averaging 0.119 855 0.000 008 (n 6) and 0.119 867 0.000 020 (n 3), respectively. These values are substantially suprachondritic. The Re–Os isotope systematics of Sudbury ores are clearly of crustal origin and may be derived from a binary mixture of Superior Province and
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.068 | 0.014 |
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 source (direct Gemma or distilled Codex), 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".