Geochemistry and mineralogy of sediments from the Ventersdorp and Transvaal supergroups, South Africa: Cratonic evolution during the early proterozoic
- New Mexico Institute of Mining and Technology, Socorro (USA)
Approximately 100 pelite and 12 quartzite samples from the Ventersdorp ({approx} 2.7 Ga) and Transvaal Supergroups ({approx} 2.6-2.1 Ga) have been analyzed to monitor the early Proterozoic evolution of the Kaapvaal Craton, southern Africa. From oldest to youngest, pelites were sampled from the Ventersdorp-Bothaville (BOT), Transvaal-Selati (SEL), Black Reef (BR), Timeball Hill (TH), Strubenkop (STR), and Silverton (SIL) Formations. Paleocurrent measurements in Transvaal quartzites indicate sources lying predominantly to the north and east. Compositions of TH-STR-SIL pelites suggest a provenance similar to average Phanerozoic upper-continental crust. This source is more evolved than that of BOT-SEL-Br pelites, indicating a transformation from primitive (mafic-rich) to evolved (felsic-rich) upper-crust at 2.2 Ga. This transition follows earlier primitive to evolved trends in Moodies-Pongola (3.3-3.0 Ga) and Witwatersrand ({approx} 2.8 Ga) successions. These data suggest that several cycles of changing upper-continental crust occurred in the Kaapvaal craton between 3.3-2.1 Ga.
- OSTI ID:
- 6991225
- Journal Information:
- Geochimica et Cosmochimica Acta; (USA), Vol. 54:2; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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