Localized metasomatism of Grenvillian marble leading to its melting, autoroute 5 near Old Chelsea, Québec
Why this work is in the frame
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Bibliographic record
Abstract
The recent (2009) opening of an extension of Autoroute 5 north of Old Chelsea, Quebec, has produced striking road cuts over a length of 2 km, with a wide variety of rock types and a very complex and bewildering juxtaposition of igneous, metamorphic, and metasomatic assemblages of minerals. The focus here is on the mineralogy of the "regional" white marble; it is compared to calcite-dominant rocks, orange, pink, yellow, and blue in color. The orange to pink calcite is dominant in phenocryst-bearing dikes with a selvage of euhedral crystals of diopside. pargasite, phlogopite, titanite and betafite are the dominant phenocrysts. The orange calcite in those dikes [δ13C â â1â°, δ18O â 16â°] is isotopically intermediate between the regionally developed white marble [δ13C â 3â°, δ18O â 24â°] and a typical mantle-derived carbonatite [δ13C â â5â°, δ18O â 6â°]. The evidence points to the local metasomatism of regional marble by an alkaline fluid of mixed crust + mantle derivation, then melted, possibly at the end of the Ottawan orogenic phase, at approximately 1020 m.y., or the Rigolet orogenic phase, at approximately 980 m.y. The orange pigment in the calcite is possibly bastnäsite-(Ce) or hydroxylbastnäsite-(Ce), and the pink calcite may well be due to exsolution-induced blebs of ferroan dolomite. Above the dikes are diffuse zones of fracture-controlled reddening of the gray gneiss, in which the original mineralogy is replaced by a K-feldspar-dominant "syenitic" material. There are signs of rheomorphism of fenites developed at the expense of the gray gneiss. The road cut displays the products of melting of marble in the crust, leading to a crustal silicocarbonatite. The phenomenon is widespread but localized in the Central Metasedimentary Belt of the Grenville Province.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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 it