Granitoid-Hosted Orogenic Gold Mineralization: Genetic Constraints on the 7.4 Moz Archean Gruyere Gold Deposit, Yilgarn Craton, Western Australia
Bibliographic record
Abstract
Abstract The genetic link between granitic intrusions and orogenic gold deposits is a contentious topic, and their spatial association is often cited as evidence for the involvement of local magmatic fluids in gold mineralization. The 7.4 Moz Gruyere gold deposit, located in the far-east Yilgarn craton and entirely hosted within the Gruyere monzogranite, offers an excellent opportunity to investigate such a relationship. This study combines mineralogical, structural, geochemical, and geochronological data to develop a genetic model for Gruyere, providing further insights into granitoid-hosted orogenic gold formation. At Gruyere, steeply dipping, auriferous quartz-calcite vein arrays (V3) crosscut the host monzogranite as well as metamorphic S1 foliation, and they consist of quartz-calcite-chlorite-albite ± pyrite ± pyrrhotite ± arsenopyrite ± gold ± telluride mineral assemblages. Wall-rock hydrothermal alteration zones associated with these V3 veins overprint pervasive, autometasomatic hematite-dusting and consist of quartz–white-mica–albite–calcite–chlorite ± pyrite ± pyrrhotite ± arsenopyrite ± gold ± telluride mineral assemblages. These zones are characterized by low base metal concentrations (Cu-Pb-Zn: <0.1 wt %) and a lack of vertical zonation. Geothermometry of V3 chlorite and arsenopyrite in V3 veins yields temperatures of 350° ± 50° and 395° ± 35°C, respectively, while the stability of hydrothermal white-mica–albite suggests slightly acidic fluid conditions (pH: ~5.0–5.5). Absolute and relative timing constraints indicate that gold mineralization (2675 ± 66 Ma; arsenopyrite Re-Os) occurred after magmatic activity associated with the Gruyere monzogranite (2830 ± 4 Ma; zircon U-Pb) and postpeak regional greenschist facies metamorphism (ca. 2665–2650 Ma). Trace element geochemistry and multiple S-isotopes of V3 pyrite (Δ33S: +0.01 ± 0.13‰; δ34S: +1.66 ± 1.35‰) point toward a single mineralizing fluid derived from a magmatic and/or mantle source at depth, although S isotope systematics are also interpreted as being influenced by proximal fluid–wall-rock interactions. These data indicate that the Gruyere monzogranite is unlikely to represent the source of fluid or gold for the Gruyere gold deposit. Instead, structural controls—such as the positioning at a shear zone jog and rheological contrasts created by the competent granitic body within more ductile supracrustal rocks—played a key role in localizing mineralizing fluids. Gruyere is therefore interpreted as a classic, granitoid-hosted, mesothermal, orogenic gold deposit similar to other deposits in the Yilgarn craton and globally, which highlights the significance of granitoid-hosted orogenic gold deposits as a valuable exploration targets.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.001 |
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".