Discharge of Hydrothermal Fluids from a Magma Chamber and Concomitant Formation of a Stratified Breccia Zone at the Questa Porphyry Molybdenum Deposit, New Mexico
Bibliographic record
Abstract
The fluorine-rich Questa porphyry Mo deposit, New Mexico, comprises several orebodies with different mineralization styles, including thick veins (decimeter- to meter-scale), thin veinlets (millimeter-scale), and very unusual breccia bodies. In the Goat Hill orebody, a >6 × 106-m3 breccia body hosts 30 to 40 percent of the contained Mo and has an elongated lens shape. It is <100 m thick, 200 m wide, and 650 m long, and is located above and southward of an aplitic stock apex. Based on detailed core relogging, the breccia body was divided into seven facies, five of which define a breccia stratigraphy on a longitudinal section. Differences between breccia facies in terms of matrix paragenesis, fragment alteration, and breccia textures can be explained by the evolution of a magmatic-hydrothermal fluid away from its source, different intensities of water-rock interaction, and different breccia-forming processes. Breccia formation was initiated when premineral dikes and surrounding andesitic country rocks were hydraulically fractured by ore-forming fluids evolved from crystallizing water-saturated magma. Fractures propagated from the stock apex along preexisting volcanic bedding or a fracture zone dipping gently toward the north. Oxygen isotope geothermometry indicates that the breccia matrix precipitated at temperatures near 550°C. The isotopic composition of this matrix is δ D = –138 to –110 per mil (phlogopite) and δ 18O = 6.8 to 10.3 per mil for quartz, and 2.8 to 5.7 per mil for phlogopite. At 550°C, the calculated water composition is δ 18O = 5.1 to 8.6 per mil and δ D = –121 to –93 per mil. The isotopic study confirms that breccia-forming water had little to no meteoric component, as evidenced by the aplite matrix in the breccia and the proximity with the source intrusion. The interpretation that magmatic fluids were dominant in ore-forming processes is in contrast with some other Mo systems that show involvement of significant meteoric water.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 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) | 0.000 | 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 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".