Lithogeochemical facies of Athabasca Basin clastics, Saskatchewan - the use of PCA as a reconnaissance and mapping tool
Bibliographic record
Abstract
This study illustrates how Principal Component Analysis (PCA) of lithogeochemical data may be used to identify and map lithogeochemical facies using a regional-scale database of ca. 40,000 samples. This database also includes ca. 11,000 samples with enough stratigraphic data to permit this to be done in three dimensions to a rudimentary degree. The facies distribution by stratigraphy and deposystems furthers the understanding of depositional, alteration history, and ore processes of the Athabasca Basin and its high-grade unconformity-related U deposits. PCA permits distinction and mapping of detrital and alteration facies, separating uraniferous detrital facies from those related to mineralization processes. The analysis helps to form working hypotheses about the ore systems in the basin, identify areas of further interest, as well as areas whose high U values suggest that they might be important, but which, in fact, are not involved in the mineralization processes. Uranium bound in minerals released during partial dissolution techniques contributes less than a third of the U signal in the non-mineralized sandstone. Thus, immobile U not related to alteration can mask the signal of hydrothermal U that still may be recognized by PCA. PCA also highlights potential large, but complex metal depleted zones around some of the major orebodies. If true, then the interpretation of low raw data element values or low U component scores from PCA in a regional context is as important as the interpretation of high values. Samples from above or very near mafic intrusive suites in the basin show anomalously high and low values for some elements, as well as for a number of PCA components. This suggests that the mafic intrusions generated hydrothermal systems of only limited extent. Consistent with recent fluid-flow modelling, differences in alteration facies above and below the Wolverine Point Formation show that the unit was an aquitard. Low levels of alteration facies in the basal unit in the Athabasca Basin imply that it was an aquifer in many areas. Both these observations reinforce long-standing field observations.
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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 | 0.002 | 0.003 |
| Science and technology studies | 0.001 | 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".