3.2 Ga detrital uraninite in the Witwatersrand Basin, South Africa: Evidence of a reducing Archean atmosphere
Bibliographic record
Abstract
Research Article| February 02, 2018 3.2 Ga detrital uraninite in the Witwatersrand Basin, South Africa: Evidence of a reducing Archean atmosphere Ian Burron; Ian Burron 1Department of Geological Sciences, University of Manitoba, Winnipeg, R3T 2N2 MB, Canada Search for other works by this author on: GSW Google Scholar Giuliana da Costa; Giuliana da Costa 2Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park, 2006 Johannesburg, South Africa Search for other works by this author on: GSW Google Scholar Ryan Sharpe; Ryan Sharpe 1Department of Geological Sciences, University of Manitoba, Winnipeg, R3T 2N2 MB, Canada Search for other works by this author on: GSW Google Scholar Mostafa Fayek; Mostafa Fayek 1Department of Geological Sciences, University of Manitoba, Winnipeg, R3T 2N2 MB, Canada Search for other works by this author on: GSW Google Scholar Christoph Gauert; Christoph Gauert 3Department of Geology, University of the Free State, 9301 Bloemfontein, South Africa4Geological Survey of Saxony-Anhalt, 06118 Halle (Saale), Germany Search for other works by this author on: GSW Google Scholar Axel Hofmann Axel Hofmann 2Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park, 2006 Johannesburg, South Africa Search for other works by this author on: GSW Google Scholar Author and Article Information Ian Burron 1Department of Geological Sciences, University of Manitoba, Winnipeg, R3T 2N2 MB, Canada Giuliana da Costa 2Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park, 2006 Johannesburg, South Africa Ryan Sharpe 1Department of Geological Sciences, University of Manitoba, Winnipeg, R3T 2N2 MB, Canada Mostafa Fayek 1Department of Geological Sciences, University of Manitoba, Winnipeg, R3T 2N2 MB, Canada Christoph Gauert 3Department of Geology, University of the Free State, 9301 Bloemfontein, South Africa4Geological Survey of Saxony-Anhalt, 06118 Halle (Saale), Germany Axel Hofmann 2Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park, 2006 Johannesburg, South Africa Publisher: Geological Society of America Received: 04 Dec 2017 Revision Received: 05 Jan 2018 Accepted: 07 Jan 2018 First Online: 01 Feb 2018 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2018 Geological Society of America Geology (2018) 46 (4): 295–298. https://doi.org/10.1130/G39957.1 Article history Received: 04 Dec 2017 Revision Received: 05 Jan 2018 Accepted: 07 Jan 2018 First Online: 01 Feb 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ian Burron, Giuliana da Costa, Ryan Sharpe, Mostafa Fayek, Christoph Gauert, Axel Hofmann; 3.2 Ga detrital uraninite in the Witwatersrand Basin, South Africa: Evidence of a reducing Archean atmosphere. Geology 2018;; 46 (4): 295–298. doi: https://doi.org/10.1130/G39957.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The evolution of oxygen levels in the Archean atmosphere is one of the most important questions in the study of early Earth environments. The presence of redox-sensitive uraninite in the Archean Witwatersrand Basin, South Africa, has been cited as evidence for a reducing Archean atmosphere; however, whether the uraninite is detrital or hydrothermal in origin has been intensely debated. Here, we present, for the first time, in situ U-Pb ages of uraninite from the Witwatersrand Basin that are significantly older than the host sedimentary rocks (the 3074 ± 6 Ma Dominion and 2872 ± 6 Ma Vaal Reefs). Uraninite grains from the Dominion Reef are 3186 ± 19 Ma and may have been eroded from 3174 ± 9 Ma granites in the immediate hinterland, while uraninite grains from the Vaal Reef formed at 2994 ± 48 Ma and 2918 ± 20 Ma and are similar in age to detrital zircon populations within the Central Rand Group, which includes the Vaal Reef. These predepositional ages conclusively prove the detrital origin of the uraninite and represent arguably the best evidence to date that the Mesoarchean atmosphere was more reducing than the modern atmosphere. The detrital origin of the uraninite strongly supports the modified paleoplacer model for uranium mineralization within the Witwatersrand Basin over the hydrothermal models. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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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 | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".