Petrographic and Geochemical Characterization of the Moncou Zinc Mineralization: An Example of a Polyphase Zn Remobilization in the Central Grenville Province (Lac Saint-Jean, Quebec)
Bibliographic record
Abstract
Abstract The carbonate-dominated supracrustal sequences of the western Grenville Province formed between ∼1200 and ∼1300 Ma and are well-known for high-grade metamorphosed SEDEX and VMS deposits. However, there is limited information on base metal mineralization hosted in the clastic-dominated supracrustal sequences in the Allochthonous Medium to Low Pressure Belt of the central Grenville Province. The Moucou zinc occurrence (>1.3 wt.% Zn), located 50 km NW of Lac Saint-Jean, Quebec, provides an example of such mineralization. This zinc occurrence is hosted in metavolcanic rocks interbedded with quartzite layers of the Barrois Complex, a clastic-dominated supracrustal sequence, and metamorphosed under granulite facies. We present geochemical data, titanite geochronology, and petrographic observations for the Moncou zinc occurrence. The metavolcanic rocks have a transitional signature, Nb and Ta negative anomalies, and Ba and Th enrichments suggesting a back-arc setting comparable to the well-mineralized carbonate-dominated supracrustal sequences of the western Grenville Province. Zinc mineralization consists of (i) a first sphalerite generation (Sp1) systematically surrounded by a thin layer of plagioclase+quartz (Pl+Qz); (ii) deformed Zn-rich biotite crosscut by the titanite grains dated at ∼1000 Ma, indicating the minimum age for the first zinc remobilization; and (iii) Zn-rich chlorite spatially associated with a second sphalerite generation (Sp2). These observations suggest that Zn mineralization occurred following this sequence: a pre-metamorphic event crystallizing Sp1 as it is surrounded by anatectic melt (Pl+Qz) and shows typical high-temperature crystallization textures, then a syn- to post-metamorphic event characterized by the Zn-rich biotite, and finally a low-temperature hydrothermal event crystallizing the Zn-rich chlorite and the second sphalerite generation. This study reveals the potential for Zn mineralization of the clastic-dominated supracrustal sequences of the Medium to Low Pressure Belt such as the Barrois Complex.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| 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".