Textural features and chemical evolution of Ta-Nb-W-Sn oxides in the Jianfengling Deposit, South China
Bibliographic record
Abstract
The contribution of magmatic and hydrothermal processes to the formation of rare metal minerals in highly-evolved peraluminous systems has received great attention, yet is still debatable. The Ta-Nb-W-Sn mineralization at the Jianfengling deposit, in the Nanling range of Southeast China, occurs in a peraluminous intrusion that comprises three rock phases, namely a biotite granite, a zinnwaldite granite, and a topaz zinnwaldite granite from bottom to top. Rare metal ores occur as disseminations constrained to the zinnwaldite granite and topaz zinnwaldite granite. In this study, textural and chemical analyses of Ta-Nb-W-Sn ore minerals and zinnwaldite were conducted to address the origin of rare metal mineralization in the context of the magmatic-hydrothermal evolution at Jianfengling. Four stages of mineralizing events were identified. The Stage-I mineralization is represented by columbite-(Mn) that occurs mainly as cores overgrown by aggregates of Ta-Nb-Sn-W oxides, but also as individual crystals. The Stage II is represented by CGM overgrowths that have partially resorbed or replaced the Stage-I columbite-(Mn). The Stage-II overgrowths are much more enriched in Ta than the Stage-I columbite-(Mn). Cassiterite manifests the Stage-III mineralizing event, and occurs as replacement of or overgrowths on the Stage-II CGM aggregates. The Stage-IV mineralization is characterized by formation of wolframite that has replaced and/or overgrown on the Stage-II and –III minerals. The equilibrium boundaries shown between Stage-I columbite-(Mn) and magmatic zinnwaldite, and the gradual or no compositional zoning that the Stage-I columbite-(Mn) cores exhibit, suggest that the Stage-I CGM is magmatic. Because of the low solubility of Ta in aqueous fluids and the evidence for metasomatism observed in this study, the Ta-rich Stage-II CGM overgrowths were interpreted to have crystallized from a magmatic-hydrothermal, transitional fluid (i.e., hydrosilicate liquid) that lies compositionally in between silicate melts and aqueous fluids, and which was able to cause significant Ta enrichment, and in turn a strong decrease of the whole-rock Nb/Ta values. That the Stage-II CGM were sequentially replaced by cassiterite and wolframite marked a metasomatic Sn-W mineralizing event that postdated Ta-Nb mineralization. Fluids responsible for this Sn-W mineralization could be a compositionally evolved fluid derived from the same transitional fluid that led to metasomatic Ta-Nb mineralization, or infiltrating fluids that precipitated Sn and W, respectively.
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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 | 0.000 |
| 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) | 0.002 | 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".