Bibliographic record
Abstract
The worldclass Hemlo deposit is one of Canada's largest gold producers, containing 95 million tons of ore grading ~8 g/t Au; the mineralization is hosted mainly by two sub-parallel shear zones. However, unlike most Archean lode gold deposits, the ore occurs as finely disseminated Hg- and Ag-bearing native gold in potassically altered rocks, and is associated with molybdenite, stibnite and realgar. Mineralization occurred at greenschist conditions (400 to 500°C), and was subsequently overprinted by a single metamorphic event that peaked at ~630°C and 5 to 7 kb, which recrystallized the ore and alteration assemblages. Retrograde cooling lasted for ~80 m.y., with temperature decreasing on average ~5°C per m.y. Ore formation involved three reactions that affected ∫S2,∫O2, and pH: the dissolution of sedimentary barite, the precipitation of pyrite, and the replacement of muscovite by K-feldspar. During sulfidation, caused by the dissolution of barite, iron partitioned preferentially into pyrite, which prevented the formation of Fe-bearing metamorphic index minerals (such as garnet and staurolite), oxides (e.g., magnetite, hematite, ilmenite), and low- ∫S2 sulfides (e.g., pyrrhotite). In addition, K-alteration strongly enriched the ore zones in K-feldspar (microcline) and muscovite, which buffered pH, and prevented formation of aluminosilicates. Hemlo is an example of a mesothermal deposit which formed from metamorphic fluids with a significant magmatic component. Deposition of native gold and molybdenite occurred due to decreases in pH and ∫O2 that accompanied potassic alteration and pyrite precipitation. Other elements, such as Sb and As were adsorbed initially onto pyrite growth surfaces. Near peak metamorphism, the deposit evolved a sulfide melt that formed through release of As and Sb from pyrite during metamorphic recrystallization, partial decomposition of primary minerals (such as native gold), and interaction of the melt with sulfur-bearing aqueous metamorphic fluids. The mineral assemblages that crystallized from this melt are similar to those predicted by experimental data for the As-Sb-S and related systems, and are interpreted to have formed by fractional crystallization.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 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) | 0.003 | 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".