A petrological and geochronological study of a 360 Ma metallogenic event in Maritime Canada with implications for lithophile-metal mineralization in the Canadian Appalachians
Bibliographic record
Abstract
The occurrence of ca. 360 Ma greisen-related molybdenite mineralization in the Clayton Hill biotite–muscovite leucomonzongranite (<1 km2) is unusual for the southwestern Meguma terrane of the Maritime Appalachians, where 380 Ma granite-related Sn mineralization dominates. The presence of extensive hornfelsing and occurrence of mineralized (Sn–W–Cu–Zn) skarns in the area suggests a larger intrusion occurs at depth. The intrusion and mineralization are constrained to 361 Ma based on concordant Re–Os (molybdenite) and 40Ar/39Ar (muscovite) ages, which equates to other ca. 360 Ma granites in the area, hence magmatism of this age is more widespread than previously considered. The intrusion is highly evolved (74 wt.% SiO2), metaluminous (A/CNK = 1–1.05; A/CNK = molar ratio [Al2O3/(CaO + Na2O + K2O)]) and depleted in cafemic and transition elements. Rare-earth elements (∑REE = 106–23 ppm) are strongly fractionated with light rare-earth elements (LREE) enriched (La/LuN = 10), and negative Eu anomalies. Biotite is Fe-rich (Fe/(Fe + Mg) = 0.75), and both biotite and muscovite are F deficient. These geochemical features indicate affinity to the other 360 Ma granites and suggest a similar petrogenesis with some A-type affinity. Mineralization occurs as molybdenite-bearing greisens and rusty miaroles lined with pyrite and enrichment in Cu–As–Bi–Au. Stable isotopes (O, S) indicate greisen formation at 450 °C from fluids with δ18OH2O = 7‰ and δ34SH2S = 2‰–3‰, which suggests an A- or I-type magmatic reservoir rather than a peraluminous magma. These data indicate the presence of a widespread magmatic event that is 20 Ma younger than the 380 Ma Sn-base metal event in southern Nova Scotia (e.g., East Kemptville). That this event is the same age as the world class Mount Pleasant Mo–Sn–W–Zn–In deposit of southern New Brunswick indicates additional potential for significant granite-related mineralization in this part of Atlantic Canada.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.004 |
| Science and technology studies | 0.004 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".