SHRIMP U-Pb zircon dating of the South Mountain Batholith, Nova Scotia: timing and duration of crystallization and evidence for inheritance
Bibliographic record
Abstract
The South Mountain Batholith (SMB) is the largest (7300 km2) granitoid body in the Appalachian Orogen. It is a composite peraluminous intrusion with early stage biotite-granodiorite to biotite-monzogranite and later leucomonzogranite to leucogranite plutons. The latter are associated with subeconomic to economic polymetallic mineral deposits, including the past-producing (1985-1992) East Kemptville Sn-Cu-Zn-Ag(-In) deposit. Sensitive High-Resolution Ion Microprobe (SHRIMP) analyses of zircon were used to constrain the timing of emplacement for phases across the SMB and to investigate potential sources of contamination to the magma. Zircon from four granodiorite to monzogranite samples and one from a more evolved leucogranite were analyzed to complement our previous SHRIMP U-Pb zircon dating of the more evolved phases (ca. 377-370 Ma). The granodiorite samples yielded ages between 384.9 ± 4.4 Ma and 375.9 ± 4.5 Ma whereas the leucogranite yielded an age of 377.7 ± 5.2 Ma (2? errors). A late monzogranitic phase on the edge of the SMB also yielded an age of 367.7 ± 4.0 Ma. Collectively, the data sets indicate an apparent span of ca. 11 to 23 Ma for emplacement and assembly of the SMB, but with most ages between ca. 378 to 370 Ma. The abundance of xenocrystic zircon cores varies throughout the complex; from common in less evolved granodiorite samples to rare in the more evolved leucogranite samples. The relative age population density pattern for the inherited cores is very similar to the detrital zircon signature for the upper stratigraphy of the Meguma Supergroup that hosts the SMB.
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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 | 0.001 |
| 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 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".