Zircon diffusion chronometry reveals brief ultrahigh-temperature metamorphism in a prolonged Paleoproterozoic orogen
Bibliographic record
Abstract
Abstract Ultrahigh-temperature (UHT) metamorphism (≥900 °C) represents the most extreme thermal regime in the continental crust. Whether such conditions occurred as brief pulses (<1 m.y.) during the Precambrian, as observed in some Phanerozoic orogens, remains unresolved. Here we integrate phase equilibria modeling, thermobarometry, high-resolution nanoscale secondary ion mass spectrometry (NanoSIMS) trace-element mapping, and diffusion modeling in zircon from pelitic granulites in the Paleoproterozoic Jiao-Liao-Ji orogen, North China craton. The rocks record peak pressures of ~1.30 GPa at ~850 °C, followed by heating during decompression to ≥940 °C and ~0.65 GPa, and subsequent cooling to ~600 °C. Zircons preserve Archean detrital cores with oscillatory Dy, Yb, and Ti zoning, overgrown by ca. 1.85 Ga metamorphic rims. Diffusion modeling of these elemental profiles within the detrital cores reveals heating durations of 0.02–0.62 m.y. and UHT residence times within 0.05–1.3 m.y., providing the first robust evidence for ultrafast (~0.1 m.y.) UHT pulses in the Paleoproterozoic. Ti zoning further yields the first empirical constraints on Ti diffusivity in natural zircon at crustal temperatures, showing rates three to five orders of magnitude faster than experimental extrapolations. The spatial and temporal links to ca. 1.85 Ga mafic intrusions suggest transient mantle upwelling as the heat source. These findings demonstrate that vigorous Paleoproterozoic crust-mantle interactions generated short-lived UHT events comparable to those in modern orogens, highlighting the power of NanoSIMS-guided zircon diffusion chronometry in resolving the tempo of Precambrian thermal and tectonic processes.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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) | 0.001 | 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".