Magmatic–hydrothermal evolutionary processes in highly evolved granitic systems: Insights from zircons of the Baishitouquan pluton, NW China
Bibliographic record
Abstract
Abstract As a robust accessory mineral in igneous rocks, the mineralogical and geochemical characteristics of zircon can record the lithological differentiation and magmatic–hydrothermal evolution of highly evolved granitic systems. The F-Rb–rich, highly evolved Baishitouquan pluton of NW China exhibits gradual lithological changes from leucogranite, amazonite-bearing granite, and amazonite granite in the lower levels of the pluton to topaz-bearing amazonite granite, topaz albite granite, and pegmatite in the upper levels. In this study, three types of zircon grains were identified in five lithological zones based on textural and chemical characteristics. Type I zircon, which mostly occurs in leucogranite and amazonite-bearing granite, exhibits oscillatory zoning in cathodoluminescence images and experienced low degrees of radiation damage (0.21–0.68 × 1015 α-decay events/mg), which is indicative of its magmatic origin. Type II zircon, which mostly occurs in amazonite granite and amazonite pegmatite, exhibits textures that are indicative of hydrothermal alteration (e.g., spongy texture, porosity, and microcracks), and has elevated concentrations of some cations, such as Ca and Al. Type II zircon contains a higher concentration of non-formula elements, including rare earth elements (REEs), and Hf, Th, and U, than Type I and III zircons. Additionally, Type II zircon exhibits a significant M-type lanthanide tetrad effect and experienced varying levels of radiation damage (3.75–11.72 × 1015 α-decay events/mg). These characteristics suggest that Type II zircon has a hydrothermally altered origin. Type III zircon, which is restricted to the topaz-albite granite, has the smallest crystal size among all types of zircon grains, shows a euhedral to anhedral mottled appearance, and is characterized by patchy, cloudy, or irregular zoning, with numerous fluid inclusions. This type of zircon contains higher concentrations of Ti (110–1030 μg/g) than other types of zircon grains. Additionally, this type of zircon experienced limited radiation damage (2.18–3.69 × 1015 α-decay events/mg), and has a smooth surface and homogeneous internal textures. These characteristics suggest that Type III zircon is the product of fluid interaction with hydrothermally altered Type II zircon. Accordingly, this type of zircon crystallized directly from a Zr-saturated hydrothermal fluid during the later stages of magmatic–hydrothermal evolution. These contrasting textural and compositional features of the three types of zircon grains are indicative of three stages of magmatic–hydrothermal evolution of the Baishitouquan pluton: magmatic, magmatic–hydrothermal transition, and hydrothermal. These magmatic and hydrothermal processes were involved in the enrichment, transport, and precipitation of rare metals, such as Rb. Accordingly, this contribution demonstrates that the textures and chemistry of zircon grains can serve as petrogenetic indicators for assessing magmatic–hydrothermal evolution and rare-metal mineralization in highly evolved granitic systems. Furthermore, this study presents a model of the magmatic–hydrothermal evolution of F-rich, highly evolved granitic systems through the lens of zircon.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.000 | 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 source (direct Gemma or distilled Codex), 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".