Downhole lithogeochemical patterns relating to chemostratigraphy and igneous fractionation processes in the Golden Mile dolerite, Western Australia
Bibliographic record
Abstract
The Fimiston Superpit, Kalgoorlie, Western Australia, is the largest gold mine in Australia. The main host to mineralization, the differentiated Golden Mile dolerite (GMD) sill, has undergone several episodes of deformation, metamorphism and intense deuteric and hydrothermal alteration. This has replaced the primary silicate minerals but at least partially preserved the original igneous textures in the intrusion, upon which its ten horizontally stratified units are defined. An examination of petrologic and lithogeochemical data from drill-core through the GMD sill was undertaken to identify mineralogical and geochemical parameters that confirm stratigraphic position within the igneous stratigraphy. These parameters facilitate construction of palinspastic reconstructions of cross-sections through the GMD sill, and will thus enable identification and testing of deep exploration targets. Results also provide more detailed information about the history of the intrusion. Conserved element ratio analysis indicates that the intrusion formed from a single cooling magma body. Plagioclase and pyroxene fractionation occurred throughout during cooling, but magnetite fractionation occurred only after c. 50% crystallization. Calculations reveal unbalanced enrichments and depletions of magnetite-borne Ti and V that are possibly caused by tapping of the magma chamber after magnetite saturation, or by lateral variations in the magma chamber, possibly due to turbulence. Magnetite saturation also triggered saturation of immiscible sulphide droplets, which gravitationally settled from the magma and fractionated Cu and Ni. In summary, textural and compositional variations within the GMD can be explained by simple igneous processes that affected the magma chamber during cooling. The parameters that track these processes allow a stratigraphic re-assessment of the original ten stratigraphic units. Only seven units bounded by sharp and consistent contacts defined by obvious mineralogical and lithogeochemical breaks can be confidently discerned.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 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) | 0.001 | 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".