Columbite U-Pb Geochronology of Kalu’an Lithium Pegmatites in Northern Xinjiang, China: Implications for Genesis and Emplacement History of Rare-Element Pegmatites
Bibliographic record
Abstract
The Kalu’an-Azubai pegmatite field, one of the most important rare-metal metallogenic regions in China, contains a large number of pegmatite dikes belonging to spodumene and lepidolite subtypes. Columbite-group minerals (CGMs) collected from three spodumene subtype pegmatites (No. 802, No. 803, and No. 805 pegmatites) were analyzed for major element contents using EPMA (electron probe micro-analyzer) and dated using LA-ICP-MS (laser ablation-inductively coupled plasma mass spectrometer). The crystallization ages of the CGMs from No. 802, No. 803, and No. 805 pegmatites are 209.5 ± 1.4 Ma (2σ), 198.3 ± 2.0 Ma (2σ), and 224.3 ± 2.9 Ma (2σ), respectively. Oscillatory zoning and/or sector zoning along with the associated mineral assemblages suggest that the dated columbite is of magmatic origin. The crystallization ages of the columbite grains thus represent the emplacement ages of the Li pegmatites. Therefore, our dating results indicate that there were three emplacement events of the Li-rich pegmatite-forming melts in a timeframe of ~30 Ma. In combination with previous studies, we conclude that the Li pegmatites were formed before the Be-Ta-Nb pegmatites (~194–192 Ma), which precludes the genesis of rare-metal pegmatites via fractional crystallization of a granitic magma in the Kalu’an-Azubai region.
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How this classification was reachedexpand
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 | 0.000 | 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 | 0.000 | 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) | 0.003 | 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 teacher head, 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".