EXTREME COMPOSITIONAL VARIATION OF PYROCHLORE-GROUP MINERALS AT THE OKA CARBONATITE COMPLEX, QUEBEC: EVIDENCE OF MAGMA MIXING?
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Bibliographic record
Abstract
Pyrochlore-group minerals are relatively common accessory constituents of calcite carbonatite at the Oka Carbonatite Complex, Quebec. This complex is a member of the Cretaceous Monteregian petrological province, and consists predominantly of calcite carbonatite and feldspathoidal silicate rocks. Mineralogical studies of the complex have identified ceroan pyrochlore, ceriopyrochlore, uranoan pyrochlore, uranpyrochlore, thorian pyrochlore and “thoriopyrochlore ” as occurring within the NIOCAN and Bond Zone deposits. At Oka, pyrochlore [general structural formula: A16–xB16O48(O,OH,F)8–y] typically occurs as euhedral to subhedral crystals, rarely as aggregates and clusters. Back-scattered electron images, coupled with results of energy-dispersion analyses, reveal complex compositional zoning in pyrochlore, which reflects changes in magma composition during growth. Uranium-rich pyrochlore from Oka exhibits either strong zonation or is devoid of zoning. Large compositional variations were observed for the major oxides of the pyrochlore: CaO (ranging from 4.1 to 34.8 wt. % oxide), TiO2 (2.3–40.4%), Nb2O5 (20.1– 58.1%), ThO2 (0.3–18.2%), and UO2 (0.1–28.0%). Ceriopyrochlore, ceroan pyrochlore and uranpyrochlore exhibit the greatest A-site vacancies, ranging from 8.1 to 62.5%. Of the rare-earth elements, only Ce is present at high levels of concentration (ranging from 2.1 to 15.8 % Ce2O3). Of note is the significant content of ZrO2, which ranges from 0 to 16.3 wt.%. An A-site substitution in the pyrochlore-group minerals has been identified between (REE + U + Th) and (Na + Ca), as well as a B-site substitution between (Nb + Ti) and Zr. The wide variety of pyrochlore-group minerals at Oka, coupled with their textural features, indicate
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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 | 0.001 | 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 | 0.001 |
| 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)
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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 it