Provenance and Tectonic Implications of Archean Fig Tree Group Siliciclastic Rocks in the East-Central Barberton Greenstone Belt, South Africa

Abstract:

The 3.5 to 3.2 Ga Barberton Greenstone Belt (BGB), South Africa, is a structurally and stratigraphically complex greenstone terrain divided into multiple structural blocks by faulting and folding. The complex structure and poor geochronological constraints often make correlation among the structural blocks difficult. To overcome structural complexities and to better understand the depositional relationship between the various blocks, provenance proxies such as sandstone petrography, shale geochemistry, and detrital zircon geochronology are here used to estimate the similarity of the source terrains in a number of the different structural blocks made mostly of Mapepe Formation, Fig Tree Group strata in the southeastern part of the greenstone belt, the East-Central Domain (ECD). Two of the five blocks have similarities in stratigraphy and sedimentology, but the other sequences show differences. The proximity and stratigraphy of these structural blocks in the ECD could suggest deposition in a single large basin; however, the contrasts in provenance suggest the sediments were deposited in different basins or in a single, complex basin with provenance partitioning. The structural blocks likely had locally different sources, which implies the sequences were not part of a single large source, transport, and depositional fairway. Despite the local differences, there is a regional signature consistent with sediment derivation from rocks of the underlying Onverwacht Group. Overall, this suggests a regional landscape of shallow uplifts resulting in source partitioning of the basin(s) where the sediments represented by the Mapepe Formation in the various ECD blocks were deposited.