Geochronology and Geochemical Characteristics of Mineralized and Barren Intrusions in the Fengyan Porphyry‐Skarn Zn‐Pb‐Mo Deposit, Central Fujian Region, and their Metallotectonic Implications
Bibliographic record
Abstract
Abstract Porphyry‐skarn deposits are genetically associated with multistage intrusive complexes. However, their ore fertility varies markedly, as exemplified by the coexistence of mineralized and barren intrusions within a single pluton. The factors controlling this disparity, particularly whether high oxygen fugacity ( f O 2 ) and volatile‐rich magmas are essential, remain poorly constrained. This study investigates the Fengyan Zn‐Pb‐Mo deposit in the central Fujian region by comparing geochronological and geochemical features of ore‐associated granite porphyry and barren monzogranite. SIMS zircon U‐Pb dating reveals the mineralized intrusion crystallized at 142.5 ± 1.6 Ma, significantly later than the barren monzogranite (150.3 ± 1.3 Ma). The ore‐associated porphyry exhibits higher magma temperatures and sulfur contents, yet lower f O 2 and water content relative to the barren monzogranite. Hf‐O isotopes reveal greater mantle input in the ore‐related granite porphyry ( ε Hf ( t ) = –11.5 to –7.5; δ 18 O = 6.50‰ to 7.11‰) than in the ore‐barren monzogranite ( ε Hf ( t ) = –16.0 to –9.5; δ 18 O = 6.81‰ to 8.00‰). Furthermore, elevated f O 2 and volatile‐rich conditions are not prerequisites for Zn‐Pb‐Mo mineralization, implying other factors are key. The barren rock formed during low‐angle subduction of the Paleo‐Pacific plate, whereas the mineralized porphyry originated during slab rollback and lithospheric extension. This study highlights that medium–low f O 2 (mean ΔFMQ +0.39 in granite porphyry vs. +1.80 in monzogranite), volatile‐poor magmatic systems in extensional settings can form significant mineralization, offering new insights for exploration in central Fujian and analogous regions.
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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) | 0.001 | 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 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".