The Endako Batholith: Episodic Plutonism Culminating inFormation of the Endako Porphyry Molybdenite Deposit, North-Central BritishColumbia
Bibliographic record
Abstract
The Endako batholith is a composite batholith that consists of early foliated hornblende ± biotite diorites, intermediate-age unfoliated hornblende ± biotite diorites, and late granodiorites to monzogranites. These latter plutons host the Endako molybdenite deposit, a major porphyry deposit located in the central Canadian Cordillera. Extensive K-Ar dating on the batholith had given relatively reproducible ages centered on 140 Ma, indicating a short life span for magmatic activity. However, a combined U-Pb and 40Ar/39Ar study has resulted in a substantial reappraisal of the age and time span of intrusive activity and its association with molybdenite mineralization. The new data show that the batholith had a protracted emplacement history, covering ~75 m.y., with clear evidence for periods of magmatic quiescence. The oldest magmatic suite of the Endako batholith, the Stern Creek suite, is dated at ~220 Ma and comprises foliated gabbros and diorites. Mafic to intermediate plutons of the Stag Lake suite range in age from 180 Ma to 161 Ma. The Francois Lake suite is divided into two subsuites: the Glenannan subsuite dated at 157 Ma to ~155 Ma and the 149 to 145 Ma Endako subsuite that hosts the Endako molybdenite deposit. 40Ar/39Ar dating of hydrothermal biotite indicates molybdenite mineralization is genetically associated with terminal stages of magmatic activity. Biotite within the mine had its 40Ar/39Ar systematics reset at ~145 Ma by hydrothermal fluids with temperatures in excess of 300°C. This resetting is associated with intrusion of the 145.1 ± 0.2 Ma Casey phase monzogranite, the youngest phase within the Endako subsuite. A further partial resetting of biotite is interpreted to be coeval with Eocene intrusion of the high-level, miarolitic Sam Ross Creek phase and numerous mafic dikes that cut through the region. Hydrothermal fluids associated with this latter event were below biotite closure temperature and do not appear to have any relationship to molybdenite mineralization within the Endako deposit. The new geochronologic data, coupled with detailed mapping, show a general age progression from mafic plutonism at the margins to a central core of high-level granodiorite to monzogranite. The data document the existence of a long-lived, relatively stationary magmatic center. Pulsed magmatism, evident even within individual magmatic suites, may play a major role in concentrating and ultimately depositing molybdenite in some porphyry systems. At Endako, molybdenite would have formed within the higher level portions of the batholith, a position that would normally have rendered the deposit prone to erosional removal. However, subsequent Eocene extensional block faulting may explain the preservation of this Jurassic deposit, which is the oldest economic molybdenite deposit in the Cordillera of North America.
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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 | 0.000 |
| 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) | 0.003 | 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".