U-Pb zircon age, geochemical, and Sr-Nd isotopic constraints on the age and origin of granodiorite porphyries in the Guilong area, southern Yunnan Province, South China
Bibliographic record
Abstract
Associated with several important polymetallic mineral deposits, the origin of the investigated Guilong area granodiorite porphyries (southern Yunnan Province) are presently poorly understood. For this reason we have undertaken a geochronological and geochemical study of these felsic intrusive rocks that includes: U-Pb zircon age-dating, whole-rock geochemical, and Sr-Nd isotopic data, and that are presented and discussed in this paper. Laser ablation inductively coupled plasma mass spectrometry, U-Pb zircon analyses yield an age of 252.5 ± 1.0 Ma for one sample of the felsic rocks. The Guilong area granodiorite porphyries are characterized by variable and high (87Sr/86Sr)i, ranging from 0.7103 to 0.7143, and relatively low εNd(t) values from -13.1 to -11.6. They also exhibit negative Nb, Ta, Ti and Sr anomalies on a primitive mantle-normalized multi-element diagram. Based upon their petrological and geochemical characteristics, we suggest that these rocks derive through the partial melting of crustal rocks at a shallow level. The parental magmas to the Guilong granodiorite porphyries underwent fractional crystallization of K feldspar, plagioclase, and ilmenite or rutile prior to emplacement. Magma generation at around 250 Ma (during Permian times) occurred in response to tectonic interactions between the Yangtze Platform and other crustal blocks, that provided the heat source and elevated geotherms required for partial melting of crust.
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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".