U–Pb geochronologic constraints on the crustal evolution of the Long Range Inlier, Newfoundland
Bibliographic record
Abstract
The Long Range Mountains of Newfoundland expose the northeastern most basement inlier of the Appalachian Orogen. UPb results for two samples of basement gneiss reveal crustal formation ages of 1466 ± 10 Ma (Western Brook Pond charnockite) and 1530 ± 8 Ma (Cat Arm Road gneiss), indicating an affinity with Pinwarian magmatism (15101450 Ma) in Labrador. A third sample of basement gneiss from the Cat Arm Road dam site yielded a minimum formation age of 1631 Ma. These basement gneisses were intruded by granite plutons during two periods of Grenvillian magmatism; Group I at 10321022 Ma and Group II at 993985 Ma. Group I intrusions include the 1032.0 ± 1.5 Ma Lomond River granite and the 1022.0 ± 2.0 Ma Lake Michel igneous suite; Group II intrusions include the 999 ± 4 Ma Potato Hill charnockite, 993 ± 7 Ma Horse Chops granite, 984.9 ± 1.6 Ma Cloud River granite, and may include the Apsy granite. The metamorphic history of the Long Range Inlier is complex and three discrete Proterozoic metamorphic events can be delineated on the basis of field relationships and UPb dates for metamorphic minerals. M 1 metamorphism is a regional high-grade event that occurred prior to 1032 Ma, the emplacement age for the unmetamorphosed Lomond River granite. M 2 and M 3 occurred at 1022 and 989 Ma, respectively; coinciding with the two main periods of Grenvillian magmatism. The Precambrian crustal evolution of the Long Range Inlier is very similar to the Pinware terrane of Labrador, consistent with a single contiguous terrane presently separated by the Gulf of St. Lawrence. A surprising discovery from this study is identification of the first known occurrence of Silurian mafic magmatism in the Long Range Inlier, the 430.5 ± 2.5 Ma Taylor Brook gabbro.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.021 | 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".