Evolution of the neoarchean Kola alkaline granites, northeastern Fennoscandian Shield: insights from SHRIMP-II titanite and zircon U–Pb isotope and rare earth elements data
Bibliographic record
Abstract
Abstract An U–Pb isotopic investigation combined with rare earth element data for titanites, zircons and coexisting accessories has been undertaken to gain insight into the formation of the Archean peralkaline granites of the northeastern Fennoscandian Shield and to test the stability of titanite during metamorphic and hydrothermal processes. The obtained set of isotope data shows that whereas more stable zircon retains a memory of the major episodes of granite evolution, the coexisting titanite provides additional information on crystallization, subsequent growth, cooling and alteration of the plutonic complexes. In addition to titanites formed at the magmatic stages of c. 2710 and c. 2650 Ma, the peralkaline granites contain titanite populations which have undergone major resetting at c. 1870 Ma during the burial metamorphism related to the Svecofennian orogeny and the 1760 Ma hydrothermal alteration near contemporaneous with regional metamorphism of c. 1780 Ma. The peralkaline granites which contain c. 2710 Ma titanites also include inherited titanite grains of an age of 2795 Ma. These data support the concept that the titanite can remain a closed system to Pb diffusion at temperatures of peralkaline granite melt (<800°C) as long as the crystals escape magmatic or metamorphic recrystallization.
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".