Volatiles and hydrogen isotopes in apatite reveal slab tearing-induced high-temperature S-type granitic magmatism in South China
Bibliographic record
Abstract
Abstract The formation of sediment-derived granitoids often occurs at relatively low temperatures during incongruent melting or muscovite dehydration. However, the petrogenesis of high- to ultrahigh-temperature S-type granites remains enigmatic. Volatile compositions can be powerful tracers of fluid origins and can provide insights into granite petrogenesis. We present data on the chlorine (Cl), fluorine (F), and water (H2O) contents, along with hydrogen and oxygen isotopic compositions, of apatite from the Darongshan-Shiwandashan granitic belt in South China. The petrogenesis and geodynamic setting responsible for the formation of this largest Mesozoic granitic complex in South China are highly debated. Various interpretations include those related to the collision between South China and Indochina in the southwest, subduction and tearing of the Paleo-Pacific oceanic slab in the southeast, and heating by the Emeishan mantle plume. The Cl/F ratio of melt, calculated from apatite data, decreases from southwest to northeast, which suggests halogen inputs from a northeastward-subducting slab. The δ18O value of apatite is relatively uniform across the granite suites, ranging from 9.7‰ to 12.1‰, and indicates a common metasedimentary source. The δD value of apatite varies widely, with the lowest hydrogen isotopic ratios (−238.6‰ ± 27.2‰) being comparable to those in the mantle transition zone, which possibly indicates H2O contributions from a deep mantle that was transferred into the upper crust. Based on these results, we propose a unified model involving the subduction of the Paleo-Tethyan oceanic crust and subsequent slab tearing, which favors the underplating of basaltic magmas from both the mantle wedge and deep mantle at the mantle-crust transition. These mafic magmas released fluids and heat into the overlying continental crust, inducing partial melting of metasedimentary rocks and formation of the high- to ultrahigh-temperature Darongshan-Shiwandashan granitic belt. Apatite is a powerful recorder of magmatic, metamorphic, and metasomatic processes occurring in complex geodynamic scenarios.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 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".