Early Mesoproterozoic intrusive breccias in Yukon, Canada: \nthe role of hydrothermal systems in reconstructions of \nNorth America and Australia
Bibliographic record
Abstract
In northern Yukon, Canada, numerous breccia zones of early Mesoproterozoic age (ca. 1.6 Ga) are targets for \nmineral exploration. Collectively termed Wernecke Breccia, they are characterized by disseminated specular hematite \nand local enrichment of Cu, Co, U and Au. The breccias are hosted mainly by the Paleoproterozoic Wernecke \nSupergroup, a 13-km thick basinal to platformal succession of carbonate and fine-grained clastic rocks. Brecciation \noccurred after the Wernecke Supergroup was fully lithified, deformed, and locally metamorphosed. \nThe breccia zones were generated by forceful explosions of volatile-rich fluids within the crust. The source of the \nfluids is uncertain, but may be related to igneous intrusions at depth. Rapid expansion of the fluids shattered large volumes of country rock, mainly sedimentary rocks of the Wernecke Supergroup, and dioritic to syenitic rocks of the Bonnet Plume River intrusions. In the central parts of the breccia zones, fragments underwent considerable motion, and in some cases became rounded from abrasion. Venting of brecciated rock and fluid is considered likely, but surface deposits are nowhere preserved. At one locality, large blocks of country rock foundered into open space near the top of a breccia zone, forming a fallback megabreccia. Faulting may have been active concurrently with brecciation. \nBreccia fragments are cemented together by hematite, quartz, carbonate, chlorite, feldspar, mica, and other \nminerals. In most cases, clasts and wallrocks were hydrothermally altered, leading to metasomatic growth of \nsecondary minerals including flecks of hematite or rhombs of dolomite. Widely disseminated earthy hematite and \nlocal potassic alteration in the breccia clasts resulted in color changes from original drab hues of gray and brown to \nstriking pink and red. Clasts with embayments rimmed with secondary minerals such as specular hematite are \nevidence for the dissolution of clasts or their diagenetic cements by hydrothermal fluids. The main phase of \nbrecciation and metasomatism occurred at ca. 1.6 Ga, as indicated by a 15955 Ma U-Pb date on titanite. \nSubsequent minor hydrothermal events related to emplacement of the Hart River intrusions and Bear River dykes \noccurred at 1382.87.4 Ma (U-Pb rutile) and ca. 1270 Ma (U-Pb baddeleyite), respectively. \nMineralized breccias at and near the Olympic Dam deposit in South Australia mineralogically and texturally \nresemble, and have nearly the same age as, the Wernecke Breccias. These similarities suggest that both breccia \nprovinces developed from related systems of hydrothermal activity, and provide additional evidence for models \nlinking the cratons of North America and Australia in Proterozoic time.
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 | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".