The evaluation and application of tourmaline crystal chemistry as an indicator of porphyry-style Cu-Mo-Au mineralization
Bibliographic record
Abstract
As the exploration for porphyry Cu-Mo-Au deposits becomes increasingly challenging, there \nexists a need for exploration techniques that can detect buried deposits. Tourmaline supergroup \nminerals (TSM), a chemically and physically robust phase in the surficial environment, is \ninvestigated for its indicator mineral potential to identify porphyry Cu-Mo-Au systems. Samples \nof TSM from mineralized porphyry systems (Cu, ±Au, ±Mo) including Casino (Yukon Territory, \nCanada), Coxheath (Nova Scotia, Canada), Donoso Breccia-Los Bronces (Chile), Highland \nValley Copper (British Columbia, Canada), New Afton (British Columbia, Canada), Schaft \nCreek (British Columbia, Canada), and Woodjam (British Columbia, Canada) were examined. \nResults show that TSM are generally an early hydrothermal mineral predating both \nmineralization and alteration assemblages. They form sub- to euhedral crystals that are \nexclusively black (in hand sample) and can be found throughout a porphyry system across all \nzones of alteration. Major-element chemistry of the TSM is unremarkable, with most having NaMg-Al (dravite) compositions (~80 % of grains) with lesser amounts of schorl (Fe). They exhibit \nconsistent concentrations of ~2.0 apfu Mg with most plotting along the oxy-dravite–povondraite trend reflecting the dominance of Al3+ ↔ Fe3+ substitution. An investigation of TSM \ntrace-elements (LA-ICP-MS) revealed key elements (Sr, Pb, Zn, Cu, and Ga) and select element \nratios (Sr/Pb and Zn/Cu) that can be used as discriminators of its environment of formation. \nUtilizing an understanding of both intrinsic and extrinsic controls on TSM chemistry is an \neffective approach to distinguish TSM forming in porphyry bedrock samples. A decision tree \nwas developed and applied to TSM grains recovered surrounding two known porphyry deposits \nincluding Casino-YT and Woodjam-BC to assess its effectiveness. Using both textural and \nchemical features of TSM from mineralized porphyry systems highlighted above, porphyry- related grains were identified down ice and downstream of both deposits respectively, \nhighlighting the potential for this method to be used in exploration. The crystal chemistry of \nTSM has been demonstrated to be sensitive to its environment of formation allowing for the \ndiscrimination and identification of TSM forming in porphyries from that forming in other \ngeologic environments and ore systems.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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 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".