The Konse Group on the SE margin of the Tanzania Craton: a Paleoproterozoic passive margin succession of the Usagaran Orogen : constraints from metamorphic monazite ages and isotopically heavy carbon in marbles
The Konse Group is a 2-3 km thick succession of quartzites, metaconglomerates, micaschists, marbles, Mn-rich metasediments and mafic metavolcanics deposited over >200 km in a narrow basin along the SE margin of the Archean Tanzania Craton. The timing of basin formation with respect to the Paleopr...
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| Main Authors: | , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
1 September 2025
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| In: |
Precambrian research
Year: 2025, Volume: 427, Pages: 1-14 |
| ISSN: | 0301-9268 |
| DOI: | 10.1016/j.precamres.2025.107874 |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.1016/j.precamres.2025.107874 Verlag, kostenfrei, Volltext: https://www.sciencedirect.com/science/article/pii/S0301926825002001 
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| Author Notes: | Schenk V., Bekker A., Schmitt A.K. |
| Summary: | The Konse Group is a 2-3 km thick succession of quartzites, metaconglomerates, micaschists, marbles, Mn-rich metasediments and mafic metavolcanics deposited over >200 km in a narrow basin along the SE margin of the Archean Tanzania Craton. The timing of basin formation with respect to the Paleoproterozoic Usagaran orogeny is controversial: it is interpreted either as post-orogenic, overlying folded Usagaran gneisses, or as pre-orogenic, developed on the craton margin. In the latter case, the Konse Group is regarded as a lower-grade, time equivalent of the tectonically overlying Usagaran gneisses, which represent the deeper part of the same basin. Nearly U-free monazite from oxidized Mn3+-rich Konse Group micaschists yielded a Th-Pb age of 2028 ± 15 Ma (95 % confidence) for metamorphism, which argues against a post-orogenic depositional age. The low U content and Mn3+-enrichment are attributed to oxidizing conditions in the precursor sediment. The pre-Usagaran depositional age is supported by highly positive δ13C values, +12.6 and +9.3 ‰, for marbles of the Konse Group and correlative Mpwapwa Group to the northeast, respectively, indicating sedimentation during the ca. 2.22-2.06 Ga Lomagundi Event. Both groups share a similar depositional age and tectonic setting with marginal successions of other southeastern African cratons, which were deposited at early stages during the assembly of the Paleoproterozoic Columbia/Nuna supercontinent. The Konse and Mpwapwa groups represent cratonic passive margin successions, which belong to the Usagaran Orogen. The latter contains essential lithological members of a Wilson cycle, suggesting that modern-style plate tectonics operated during the Paleoproterozoic. |
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| Item Description: | Online veröffentlicht: 8. Juli 2025 Gesehen am 21.11.2025 |
| Physical Description: | Online Resource |
| ISSN: | 0301-9268 |
| DOI: | 10.1016/j.precamres.2025.107874 |