Mantle source of the Archean Panozero pluton, Karelia: evidence from isotope-geochemical study of rocks and minerals
Bibliographic record
Abstract
This work considers geochemical and isotopic characteristics of the source of the Archean Panozero pluton derived from LILEand LREE-enriched lithospheric mantle. Sr and Nd isotopic data on clinopyroxenes and augites define a source with Sri = 0.7017 and ɛNd(t) varying within a narrow range from + 0.7 to + 1.4 (averaging + 1.1), which is close to previously obtained whole-rock isotopic data. Similar ɛNd(t) were obtained for the Archean alkaline rocks of Canada, whereas the Archean mafic rocks of the Baltic and Canadian Shields formed from depleted mantle have ɛNd(t) ∼2. Lead isotope measurements on K-feldspars (KFsp) and monzonite showed that the source of the pluton has μ = 8.98 for the Stacey-Kramers two-stage model, at low U/Pb and high Th/U ratios. Different lead isotope composition corresponding to μ = 10.43 was determined in KFsp from quartz monzonites. Diverse interpretations of obtained data have been proposed. It was noted that the Pb-Pb isotopic system was disturbed by a later (∼ 1.9 Ga) thermal event. The ratios of elements of similar compatibility were used to determine the geochemical specifics of source of the Panozero pluton. Their comparison with numerous literature data on metasomatized mantle xenoliths and minerals in them showed that the mantle source strongly differed from primitive mantle in ratios of elements, whose mineralmelt partitioning coefficients considerably differs from mineral-fluid partitioning, for instance, Nb/La. Mantle source that was responsible for geochemical peculiarities of the Panozero pluton was made up of Phl, CPx, and Ap.
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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 | 0.001 | 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 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".