Tectonic history of the Grenville-age Trenton Prong inlier, Central Appalachians, USA: evidence from SHRIMP U–Pb geochronology
Bibliographic record
Abstract
New zircon U–Pb geochronologic data from the Grenville-age Trenton Prong provide information on the age of magmatism, timing of metamorphism, and post-metamorphic history of the inlier. Diorite gneiss (1318 ± 13 Ma) of the Colonial Lake Suite temporally correlates to magmatic arc sequences that formed along the eastern margin of Laurentia at <1.4 Ga. Metasedimentary gneisses yielded detrital zircon ages of ca. 1319–1133 Ma and ca. 1370–1207, consistent with sediment derived from a similar local source of Laurentian affinity. A small population of zircon (either detrital or igneous in origin) in one sample yielded ages of ca. 1074–1037 Ma. Possible interpretations for their formation are explored. Ca. 1060 Ma overgrowths on zircon in the northern part of the inlier constrain the timing of granulite-facies metamorphism to the Ottawan phase of the Grenvillian Orogeny. The undeformed Assunpink Creek Granite (1041 ± 6 Ma) intruded country rocks as small bodies of late-orogenic syenogranite. It provides a minimum age for amphibolite-facies metamorphism and Ottawan orogenesis elsewhere in the inlier. Regionally, zircon rim ages of ca. 1010–960 Ma record continued thermal activity during the Rigolet phase of the orogen that resulted in migmatization of paragneiss at ca. 1004 Ma and juxtaposition of upper- and mid-crustal rocks during orogenic collapse. The lithologic ages and tectonic history of the Trenton Prong correlate to those in other Appalachian Mesoproterozoic inliers and parts of the Canadian Grenville Province, confirming it is not an exotic terrane that was accreted to eastern Laurentia during Grenvillian orogenesis.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".