Delineation of multiple metamorphic events in the Himalayan Kathmandu Complex, central Nepal
Bibliographic record
Abstract
Abstract Quartz‐inclusion geothermobarometry of texturally and chemically zoned garnet, together with U–(Th)–Pb accessory phase petrochronology, phase equilibria modelling, and major element thermobarometry delineates two metamorphic events within the Kathmandu Complex in central Nepal. Combined titanium‐in‐quartz thermometry (TitaniQ) and quartz‐in‐garnet barometry (QuiG) of quartz inclusions in garnet cores yields temperatures and pressures (555–580°C, 0.89–0.91 GPa) statistically higher than those estimated for both garnet rims and secondary garnet neoblasts (535–545°C, 0.81–0.84 GPa). Comparison of these temperatures and pressures with the results from phase equilibria modelling indicates that the garnet cores nucleated after overstepping the equilibrium garnet isograd. Estimation of the degree to which overstepping may have occurred, however, is complicated by uncertainty in the estimated reactive bulk compositions. Major element thermobarometry of the garnet rims returns temperatures and pressures lower than those preserved by the garnet cores but are consistent with previous estimates of Cenozoic metamorphism in the frontal portion of Kathmandu thrust sheet. Two generations of titanite are recognized on the basis of mineral morphology, chemical zoning, and U–Pb date (c. 500 Ma versus 29 ± 5 Ma). Trace‐element systematics of the two titanite populations indicate varying co‐stability with allanite and are consistent with Th–Pb dates of allanite growth (c. 489 Ma) and breakdown to clinozoisite (c. 30 Ma). Inclusion patterns within titanite indicate that the younger group formed following breakdown of rutile that originally coexisted with the older generation of titanite at pressures and temperatures similar to those determined from the garnet cores. Application of the Zr‐in‐titanite and Zr‐in‐rutile thermometers yields temperatures 100–150°C in excess of those indicated by both TitaniQ‐QuiG and major element thermobarometry. This discrepancy is interpreted to reflect disequilibrium partitioning of Zr and limited zircon reactivity during metamorphism. Collectively, these observations are consistent with previous estimates of the timing and conditions of metamorphism associated with the Palaeozoic Bhimphedian and Cenozoic Himalayan orogenies in central Nepal. The estimated temperatures and pressures for growth of the garnet cores are consistent with rapid burial during thrust stacking.
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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".