GRENVILLIAN METAMORPHISM OF MONOCYCLIC ROCKS, GEORGIAN BAY, ONTARIO, CANADA: IMPLICATIONS FOR CONVERGENCE HISTORY
Bibliographic record
Abstract
The objective of this paper is to represent the main features inherent to Grenville-Sveconorwegian Orogen (GSNO) and to propose a model of tectonic and geodynamic evolution of this orogen based on the results of research concerning similar Precambrian tectonic units in the East European Craton.The studies of the conditions and settings related to origin and evolution of GSNO are of special interest, because it is located geographicaly and in a certain sense ideologically in the center of Rodinia, a supposed Neoproterozoic supercontinent.GSNO originated in the Mezo-Neoproterozoic in the inner region of the Lauroscandia continent.At present, the synformal tectonic structure of GSNO is divided into two portions: Grenville sector along the southeastern margin of the Canadian Shield, and Sveconorwegian sector in the southwestern Scandinavia.The integrity of Lauroscandia was twice disturbed in the Mezo-Neoproterozoic when oceanic structures resembling the Atlantic Ocean were formed.Later on, the continuity of the continent was restored with the involvement of oceanic lithosphere subduction and accretion and obduction of the island-arc and oceanic terranes.We distinguish two stages in the GSNO history: (1) 'preparatory' stage (from ~1.90 to ~1.16 Ga), and (2) formation of GSNO proper (from ~1.19 to ~0.90 Ga).The manifestations of granulite-facies metamorphism were repeatedly recorded before the Grenville Orogeny at 1.67-1.66,1.47-1.45,1.37-1.35,and 1.20-1.18Ga.The Ottawan stage of the Grenville metamorphism proper is dated between 1.16 and 1.05-1.03Ga.Metamorphism at the base of Allochthonous Belt corresponds to high-pressure granulite facies and, in a number of places, to hightemperature eclogite facies (800-900 °C at pressure in the range between 14 and 20 kbar).The age of metamorphism of rocks within Paraautochthonous Belt is 1.05-0.95Ga; metamorphic grade increases from the greenschist facies near the Grenville front to the high-pressure amphibolite facies near Allochthon Boundary Thrust showing an inverted metamorphic zoning.High-pressure granulite-facies metamorphism is characteristic of Sveconorwegian sector; and high-temperature eclogites are observed locally at the base of the allochthonous complexes and within the paraautochthonous complexes.A distinctive feature of GNSO is the abundant occurrence of specific intrusive magmatism.Massifs of anorthosite-mangerite-charnockite-granite (AMCG) and anorthosite-rapakivi granite (ARG) complexes formed 1.8-1.5 Ga ago frame the orogen as a wide arc.In the internal region of GSNO, these complexes were formed successively at 1.16-1.13,1.09-1.05,0.99-0.96,and 0.93-0.92Ga.Later on, after the intrusion, the massifs unevenly underwent granulite-facies metamorphism.The high-temperature magmatism and metamorphism, numerous repeated thermal pulses and enormous crustal body that underwent high-temperature transformation point to a mantle plume as the most adequate source of thermal energy.The model of intracontinental development of GSNO comes GEODYNAMICS & TECTONOPHYSICS
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.023 | 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".