Chemical Mapping of Trace Elements in Pyrite Provides Insight into Mineralizing Processes: the Example of the Neoarchean Cu–Au Porphyry System of the Chibougamau Area, Canada
Bibliographic record
Abstract
Abstract Archean porphyry-style mineralization is one of the sources of Au and Cu in greenstone belts. Archean porphyries have been modified by regional deformation and late fluid circulation, and questions remain on the timing of Au mineralization. Indeed, Au may have been introduced at the magmatic-hydrothermal (porphyry) stage, or by a post-magmatic hydrothermal fluid (overprinting orogenic gold system), or a combination of these two processes. Using the Cu–Au Corner Bay deposit as a case study and high-quality chemical mapping performed using laser ablation coupled to a time-of-flight mass spectrometer (LA-FF-ICP-ToF-MS), this study demonstrates that pyrite chemistry has the potential to reconstitute the metallogenic model for Archean porphyry systems. The Corner Bay deposit is associated with the ~2718–2715 Ma Chibougamau pluton, located in the northeastern corner of the gold-endowed Abitibi greenstone belt. Pyrite chemistry points to the following succession of events at Corner Bay: (1) an early porphyry stage that produced pyrite-mineralized quartz-anhydrite veins associated to chloritization and sericitization; (2) followed by a porphyry stage that includes brecciation in response to fluid overpressure and deposition of Cu-Au mineralization by magmatic-hydrothermal fluids with a multi-metal signature (Cu, Ag, Bi, Te, etc.); and (3) a post-porphyry deformation event(s) that induced parallel fracturing and minor carbonatization. This study proposes that, at Corner Bay, Au was introduced during the porphyry-stage of mineralization and was neither remobilized, nor further introduced, during the ~2700 Ma regional deformation stage that is coeval with most orogenic gold-style of mineralization in the southern part of the Abitibi greenstone belt.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".