Insights Into Middle Crustal Processes In Magmatic Arcs, Coast Mountains, British Columbia
Bibliographic record
Abstract
This thesis explores processes occurring in the middle and lower crust of magmatic arc-settings. This study is based on observations on the Coast Mountains of British Columbia, Canada, at ~53 degree N latitude. The rocks exposed at the surface in this area represent the roots of a Mesozoic to early Tertiary magmatic arc. Transpressional deformation occurred synchronously with magmatism and metamorphism from the Late Cretaceous to the Early Eocene. Between 61 and 50 Ma, the entire Canadian Cordillera tracks a period of extension and exhumation of high-grade metamorphic rocks, synchronous with intensified magmatism. The thermal state of the crust during this time period was explored using numerical models. The models attempt to reproduce a geotherm that explains observations found in the field, such as abundance of amphibolitic migmatites, widespread magmatism, granulite facies metamorphism, and high-temperature low-pressure metamorphism. The resulting geotherm is isothermal from the pluton emplacement depth to the Moho. The temperature of the profile is buffered by the solidus temperature of the country-rock. The upper crust is characterized by a steep temperature gradient of ~50 degree C/km. The structure and petrology of three plutons was analyzed to better understand pluton emplacement processes. Two of the plutons, the Kitlope and Quottoon plutons; are characterized by steep foliations and intruded during transpression. The third pluton, the Chief Matthew's pluton; intruded as a sub-horizontal sill during extension. The transposition of the foliation from vertical to horizontal is explained by the development of melt-filled tension gashes oriented perpendicular to the sub-vertical foliation. Melt migration results in melt accumulation in the gashes. This process coupled with a change from regional transtension caused development of flat foliation localized around the Chief Mathew's pluton. The exhumation path and cooling history of the three plutons was also explored. Petrology, geothermobarometry, geochemistry, and cooling ages were analyzed to determine that: 1) exhumation of ~6 km of rock occurred between the emplacement of the Quottoon and Chief Matthew's plutons at a rate of ~2-3 mm/yr; 2) the rocks cooled at a rate of ~50 degree C/Ma; 3) the area cooled below the biotite closure temperature by 51 Ma. An exhumation model integrating the studied area with the rest of the Canadian Cordillera is also proposed.
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.004 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.010 | 0.001 |
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".