The Thores volcanic island arc of the Pearya Terrane from Ellesmere Island formed on Precambrian continental crust
Bibliographic record
Abstract
We report on U-Pb zircon dating and bulk rock geochemistry results of intermediate to felsic rocks of the Thores Suite of the Pearya Terrane, northern Ellesmere Island (Arctic Canada). Our new results together with the previously published data show that the Thores Suite was formed in the Early Ordovician (c. 490-470 Ma) as a part of an island arc. Some of the dated samples revealed common xenocrystic zircon. The latter yielded ages ranging between c. 2690 Ma and c. 520 Ma. The obtained ages of xenocrystic zircon are interpreted to be typical of Laurentia. We propose that the youngest obtained cluster of ages c. 580-570 Ma expresses a component typical for the Timanide Orogen, which is conventionally tied to Baltica. The newdataset sheds light on the history and understanding of the Thores Suite, which used to be explained as an effect of the M’Clintock orogenesis. The latter event was commonly presented as foreign to the major Caledonian orogenesis sensu stricto. In our view, the Thores Suite represents an island arc, which was formed on a fragment of continental crust dismembered during Iapetus opening. Importantly, the age of the Thores island arc is coeval with other island arcs and high pressure metamorphic units of the Scandinavian and Svalbard Caledonides. Thus, it is likely that the Thores volcanic island arc was a part of the larger arc system operating within northern Iapetus. The juxtaposition of the Thores arc with the other successions of the Pearya Terrane is ascribed to a major sinistral strike-slip escape fault-system developed along the northeastern margins of Baltica and Laurentia, broadly concurrent with the main Scandian collision between the two aforementioned continents. This crustal scale fault structure enabled the juxtaposition of numerous crustal blocks of different Precambrian ancestry that can be found in various regions of the current High Arctic, including Svalbard, Greenland and Ellesmere Island. This research was supported by the National Science Centre (Poland) project no. 2015/17B/ST10/03114 and the internal AGH-UST funding to J. Majka, the internal grant of the Polish Geological Institute - NRI no. 62.9012.2014.00.0 to J. Bazarnik and the National Science Foundation (USA) grant EAR1650022 to J. Gilotti and W. McClelland.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| 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 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".