Structural Data and Thermometry Indicate That the Tso Morari UHP Nappe (Indian Himalaya) Was Emplaced as a Large‐Scale, Structurally Coherent Sheet
Bibliographic record
Abstract
Abstract Ultrahigh‐pressure (UHP) nappes provide important opportunities to investigate the processes that exhume rocks from upper mantle depths. Here, we investigate the UHP Tso Morari nappe (TMN) in the Indian Himalaya to test competing models for the construction of UHP nappes via detachment of single, structurally coherent sheets, accretion of multiple sheets, or chaotic accretion of km‐scale rock packages. We collected Raman spectroscopy of carbonaceous material (RSCM) temperatures and thin section‐scale finite strain, quartz crystallographic preferred‐orientation (CPO) and shear‐sense data sets from three transects, which we combine with published data to quantify trends across the 120 km by 40 km extent of the TMN. A laterally continuous tectonostratigraphy of metasedimentary rocks overlying granitic orthogneiss, a lack of field evidence for internal shear zones, uniformly high strain (3.4 average lineation‐parallel Rs, 65% average lineation‐parallel stretching) and CPO intensity (0.64 average cylindricity, 3.80 average J PF ), dominant top‐to‐east kinematics, and overall similar temperature conditions vertically and laterally are all consistent with detachment of the TMN as a single, structurally coherent sheet. The TMN lacks field evidence for partial melting, which is consistent with RSCM and maximum thermobarometric temperatures generally ≤700°C, and limits the importance of diapiric rise as an exhumation mechanism. Distributed top‐down‐to‐east, normal‐sense ductile shearing was an important process that facilitated exhumation of the TMN from mid‐crustal depths at ∼51–46 Ma to upper‐crustal depths at ∼45–29 Ma. This extensional shearing was contemporaneous with regional, SW‐NE‐directed shortening in the Himalayan fold‐thrust belt, which could be the consequence of strain partitioning during oblique convergence.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 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 teacher head, 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".