Stable isotope (C, O, S, and Zn) geochemistry of marble-hosted exhalative zinc deposits in the Central Metasedimentary Belt, Grenville Province, Canada: Insights into ore deposition and tectonic setting
Bibliographic record
Abstract
Mesoproterozoic marbles of the southwestern Grenville Province contain numerous stratiform zinc deposits, which include the world-class Balmat-Edwards Zn-Pb district in the Adirondack Lowlands and the Franklin-Sterling Zn-Fe-Mn district in the New Jersey Highlands. Ten small deposits in the Central Metasedimentary Belt (CMB) of Ontario and Quebec were selected for stable isotope study (C and O in carbonates and S and Zn in sulfides) to help constrain depositional conditions, ore genesis, and tectonic setting. These deposits and the Balmat-Edwards and Franklin-Sterling districts are interpreted to have formed in contemporaneous back-arc basins associated with rifting of the Andean-style margin of Laurentia. Stable isotope systematics and the geology of these deposits indicate two distinct sedimentary exhalative (Sedex) settings: marble-hosted deposits associated with volcanic rocks, and marble-hosted deposits that are not associated with volcanic rocks and sometimes occur with evaporites. Volcanic-associated Sedex deposits (the Long Lake, Slave Lake, Wilkinson, Lafontaine, Bouchette, and Leitch deposits, and the Franklin-Sterling district) have COS isotope systematics that are consistent with water/rock interaction between marine carbonate protoliths and fluids having an igneous component at ca. 150 ± 25 °C. In contrast, Sedex deposits not associated with volcanic rocks (the Cadieux, Spry, Thirty Island Lake, and Salerno Lake deposits, and the Balmat-Edwards district) have C and O isotope ratios that are consistent with formation at ambient or low (<80 °C) temperatures. Sulfur isotopes of sulfides in some evaporite-associated deposits are similar to those of other Proterozoic Sedex deposits (δ34S = 5–15 ‰ VCDT), with the Cadieux and Spry having lower values (δ34S ≈ 0‰) which might reflect differences in depositional settings. Zinc isotope ratios of CMB Zn deposits are relatively constrained (δ66Zn = 0.17 ± 0.04 ), and are similar to other seafloor deposits. An exception to this is the Thirty Island Lake deposit in the Frontenac terrane, which has δ66Zn = 0.46 ± 0.05 ‰, which may indicate an exotic origin relative to other CMB deposits. The recognition of the volcanic association for some Grenville Sedex deposits and not for others (and the relationship with evaporites for this group) has implications for Zn exploration programs in this region.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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 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".