Petrochemistry and U–Pb (zircon) age of porphyry dykes at the McKenzie Gulch porphyry–skarn Cu–Ag–Au deposit, north-central New Brunswick, Canada: implications for emplacement age, tectonic setting, and mineralization potential
Bibliographic record
Abstract
North- to northeast-trending intermediate to felsic porphyry dykes in the McKenzie Gulch (MG) area intrude Upper Ordovician through Silurian calcareous sedimentary rocks of the Matapédia Group. These dykes are spatially associated with numerous copper–silver skarn occurrences. In this area, two distinct suites of dykes are recognized: plagioclase–hornblende porphyry (P–H) and quartz–plagioclase porphyry (Q–P). These suites yielded U–Pb (zircon) ages of 386.2 ± 3.1 Ma and 386.4 ± 3.3 Ma, respectively, indicating a coeval relationship and similar genesis despite slight geochemical and petrographical differences. Geochemical data indicate that the dykes are granodioritic to granitic to slightly tonalitic in composition with I-type and slab failure signatures. When compared with other granitoids in the region, the Murdochville suite in Gaspésie, Québec, is the only intrusion that exhibits slab failure magmatic signatures similar to the MG dykes. Magmas with slab failure signatures are compositionally similar to tonalite–trondhjemite–granodiorite (TTG) suites and adakites. They exhibit low Y and Yb concentrations and subsequent high Sr/Y and La/Yb ratios, which are interpreted to be the result of melting of subducting slab and mantle during the waning stages of collision and consequent slab failure. These processes were followed by assimilation and fractional crystallization of minerals such as hornblende and clinopyroxene (± titanite), which preferentially partition Y and heavy rare earth elements (HREE) in the absence of significant plagioclase. Magmas with similar geochemical characteristics worldwide have been proposed to be an important source for metals in most porphyry Cu and skarn deposits and consequently are a target during mineral exploration.
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 | 0.000 |
| Scholarly communication | 0.001 | 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".