Nanostructure reveals REE mineral crystallization mechanisms in granites from a heavy REE deposit, South China
Bibliographic record
Abstract
Abstract Weathering crusts after granites are the most important source of heavy rare-earth elements (HREE) worldwide. Although HREE in these deposits is known to be inherited from parental rocks, the origin of HREE enrichment and the reasons why it is rare outside of China remains unclear. Here, we report the occurrence of variably organized nanoparticles of Ce-poor (<0.2 wt%), Nd-Y-rich bastnäsite-(La), and associated cerianite in parental granites from a HREE deposit, South China. The mineral contains high-HREE abundances (up to 13 wt% Y2O3). Synchrotron radiation-induced X-ray diffraction and high-resolution transmission electron microscopy analyses suggest that the mineral grew as disordered nanocrystals and (nearly) coaligned nanoparticle aggregations, thus supporting “nonclassical” crystallization mechanisms by particle attachment under hydrothermal conditions. The nanocrystal-line Ce-poor, Nd-Y-rich bastnäsite-(La) precipitated at rapidly decreasing temperature related to the influx of externally derived fluids, which caused CO2-H2O immiscibility and REE supersaturation. This interpretation is supported by petrographic data and microthermometric analysis of fluid inclusions in quartz. Unusually high fO2 resulted in Ce oxidation and decoupling from trivalent lanthanides, producing polycrystalline mineralization.
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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 | 0.001 |
| 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 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".