Sapphire-bearing magmatic rocks as indicators of the continental collision tectonic events: a case study of Uralian orogenic belt
Bibliographic record
Abstract
Gem corundum (mainly ruby) occurrences are commonly associated with orogenic belts. Corundum deposits of metamorphic origin are known as robust indicators of continent-continent collision tectonic events. Although sapphire-bearing primary magmatic deposits are also found in orogenic belts, their link to continental collision process remains poorly understood. Here we show that primary igneous blue sapphire occurrences in the Ilmenogorsky alkaline complex of Ilmen Mountains in Uralian orogenic belt are indicative of the continent-continent collision processes among Kazakhstania, Laurussia, and Siberia 330 – 250 Ma ago (Sorokina et al. 2017). The results of geochemical, mineralogical, and geochronological research of corundum syenite pegmatites demonstrate that in situ primary magmatic corundum-bearing mineral assemblages can be used to evaluate the formation conditions and the time constraints of magmatic processes imposed by tectonic activity during orogenesis. Thus, the corundum syenite pegmatites have recorded a multistage evolution of the Ilmenogorsky complex. They crystallized at temperatures of 700 – 750°C at 275 and 295 Ma ago (in situ LA-ICP-MS U-Pb zircon dating) within the timeframe of the continental collision of the Uralian orogeny. The isotopic signatures show a geochemical link of these deposits to nepheline syenites – miaskites of the main igneous body in Ilmenogorsky complex. While, some corundum syenite-pegmatites express the metamorphic overprint at temperatures of 700 – 780°C occurred 249 ± 2Ma ago (TISM Rb-Sr isotopy) during limited post-collision stretching period in the area of Ilmenogorsky complex (Sorokina et al. 2021). Hence, these results imply that primary magmatic corundum deposits can be used as an important indicator of continental collision events. References: 1. Sorokina E.S., Botcharnikov R., Kostitsyn Yu.A., Rösel D., Häger T., Rassomakhin M.A., Kononkova N.N., Somsikova A.V., Berndt J., Ludwig T., Medvedeva E.V., Hofmeister W. (2021). Sapphire-bearing magmatic rocks trace the boundary between paleo-continents: a case study of Ilmenogorsky alkaline complex, Uralian collision zone of Russia. Gondwana research 2021 (in press). 2. Sorokina, E.S., Karampelas, S., Nishanbaev, T.P., Nikandrov, S.N., Semiannikov, B.S., (2017). Sapphire Megacrysts in Syenite Pegmatites from the Ilmen Mountains, South Urals, Russia: New Mineralogical Data. Canadian Mineralogist 55, 823–843
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".