Implications of high-precision Re-Os molybdenite dating of the Navachab orogenic gold deposit, Namibia
Bibliographic record
Abstract
This paper presents and discusses the first Re-Os molybdenite dates from the Navachab orogenic gold deposit, the largest non-Witwatersrand gold resource in southern Africa. At the deposit, a late-kinematic, auriferous, quartz-vein swarm and associated Ca-Mg-Fe-Mn skarn ( sensu lato ) alteration crosscut the Neoproterozoic Damara Sequence, which comprises the upper amphibolite-facies equivalents of continental quartzites, glaciogenic mixtites and pelite – carbonate shelf rocks. Re-Os dating of rare traces of molybdenite in two different types of aplite yielded Cambrian Re-Os ages of 525 ± 2.4 Ma and 523 ± 2.1 Ma (2σ). Molybdenite-bearing, NNE-dipping, extensional auriferous quartz+bismuth+pyrite+pyrrhotite veins with garnet selvage have Re-Os ages of 520 ± 2.1 Ma and 519.4 ± 2.1 Ma (2σ). The 525–520 Ma gold-mineralizing event occurred slightly after the collisional metamorphic peak at 530 Ma, but subsequent gold redistribution and possibly ore mineral melting of the Au-Bi minerals likely occurred at the late-stage thermal peak of the Damaran High-Temperature-Low-Pressure tectonothermal event. This Re-Os dating considerably improves on previous attempts to date the gold-mineralizing event, which comprised U-Pb zircon age determinations on cross-cutting aplite/pegmatite dykes and U-Pb titanite age determinations on a lamprophyre and quartz veins.
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 | 0.001 | 0.001 |
| 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".