Overprinting of primary magmatic features by fluid-mediated processes in a F-bearing felsic rare-metal system: the Mueilha granite (Eastern Desert, Egypt)
Bibliographic record
Abstract
• Granite evolution as a result of magmatic-hydrothermal and subsolidus processes. • The magmatic evolution in granitic systems is overprinted by fluid-mediated processes. • Fluids and F play a crucial role for rare metal redistribution. • F facilitates autometasomatism. • F promotes the formation of disseminated style Nb-Ta-REY-mineralization. Fluids are major fractionation agents in granitic systems because they partly control the behaviour and partitioning of elements, including rare metal, during the magmatic-hydrothermal transition and their subsequent redistribution during the later subsolidus stage. The exsolution of magmatic fluids from a volatile-saturated magma and their subsequent circulation commonly result in important textural and geochemical changes with primary magmatic features being entirely overprinted and earlier minerals chemically re-equilibrated. The changes documented herein serve as a basis for tracking the equilibration of a rare-metal granite with interacting fluids. The Mueilha F-Nb-Ta-REE-Y granitic system (Eastern Desert of Egypt) is composed of different facies such as the “red granite”, representing the main volume of the intrusion, and the “border facies”, occurring along the red granite south-western margin. Detailed mineralogical and textural studies of the latter facies document the pervasive and intense transformation of the original highly-evolved granite primarily via coupled dissolution-precipitation. Based on these observations, and complementary whole rock, and mineral major and trace element chemistry, a complex five-stage model of evolution from magmatic to metasomatic is proposed and discussed. As part of this evolution, the border facies represents residual melts extracted at a very late stage of crystallization of the red granite. This process led to a selective enrichment in Nb and Ta, and a corresponding depletion in Li, F, REEs, and Y within the border facies, highlighting the critical role of extraction timing in shaping the composition of residual melts. It is suggested that the weak peraluminous character of the intrusion combined with its F content, albeit low (<0.2 wt%), facilitated the observed autometasomatism and associated redistribution of rare metals and REE-Y within the intrusion to form magmatic and hydrothermal disseminated style mineralization that is typically encountered in rare-metal granite and pegmatite worldwide. We suggest that this study may serve as a useful reference point for investigating comparable settings elsewhere.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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".