The timing and structural evolution of the Donlin Creek gold deposit, southwest Alaska
Bibliographic record
Abstract
Lithologic and structural data from more than 220 structurally oriented diamond drill holes are used to delineate the subsurface geology, 3-D geometry and to constrain the structural evolution of the >30 million ounce Donlin Creek gold deposit. The geology of the Donlin Creek gold deposit is characterized by north-northeast – south-southwest shortening that produced structural fabrics similar to those formed in thin-skinned fold and thrust belts. This deformation consists of dominantly southwest dipping thrust faults, subordinate northeast dipping back thrusts, and associated thrust ramp anticlines in the Kuskokwim Group sedimentary rocks. The fold and thrust style deformation is locally overprinted by northeast trending, low amplitude open folds interpreted to be related to regional dextral strike-slip tectonics. Low displacement, north-northeast striking, steeply southeast dipping normal faults cut the thrust faults and both generations of folds. The normal faults, northeast trending folds, and older fold and thrust geometry are intruded by a porphyritic dyke and sill swarm. Bedding discordant intrusions are emplaced along the north-northeast striking, steeply southwest dipping normal faults. Bedding concordant intrusions are most common in the folded sedimentary rocks in the hanging walls of thrust faults. The intrusions are cut by tensional gold being quartz ± carbonate + sulphide veins, which represent the youngest structural fabric. The distribution of veins is dictated by the rheology of the host rocks. For example, the brittle intrusions are the best host to gold mineralization; however veins are also present in coarse grained sedimentary rocks. U-Pb and ⁴⁰Ar/³⁹Ar geochronology provide absolute ages for deposition of the Kuskokwim sediments (~ 88 Ma), emplacement of the felsic intrusions (~71 Ma) and timing of gold mineralization (~ 71 Ma). These data indicate approximately 14.9 million years between initial sedimentation, emplacement of intrusions, and precipitation of gold mineralization. Geochronology constrains the timing of fold and thrust style deformation, and overprinting north-northeast trending folds to between ~ 88 Ma and ~ 71 Ma. The available geologic and geochronologic data also indicates that intrusion of the post-kinematic Late Cretaceous
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| 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".