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Ulf Söderlund

Ulf Söderlund

Professor

Ulf Söderlund

Neoarchean large igneous provinces on the Kaapvaal Craton in southern Africa re-define the formation of the Ventersdorp Supergroup and its temporal equivalents

Author

  • Ashley Gumsley
  • Joaen Stamsnijder
  • Emilie Larsson
  • Ulf Söderlund
  • Tomas Naeraa
  • Michiel De Kock
  • Anna Sałacińska
  • Aleksandra Gawȩda
  • Fabien Humbert
  • Richard Ernst

Summary, in English

U-Pb geochronology on baddeleyite is a powerful technique that can be applied effectively to chronostratigraphy. In southern Africa, the Kaapvaal Craton hosts a well-preserved Mesoarchean to Paleoproterozoic geological record, including the Neoarchean Ventersdorp Supergroup. It overlies the Witwatersrand Supergroup and its world-class gold deposits. The Ventersdorp Supergroup comprises the Klipriviersberg Group, Platberg Group, and Pniel Group. However, the exact timing of formation of the Ventersdorp Supergroup is controversial. Here we present 2789 ± 4 Ma and 2787 ± 2 Ma U-Pb isotope dilution- thermal ionization mass spectrometry (ID-TIMS) baddeleyite ages and geochemistry on mafic sills intruding the Witwatersrand Supergroup, and we interpret these sills as feeders to the overlying Klipriviersberg Group flood basalts. This constrains the age of the Witwatersrand Supergroup and gold mineralization to at least ca. 2.79 Ga. We also report 2729 ± 5 Ma and 2724 ± 7 Ma U-Pb ID-TIMS baddeleyite ages and geochemistry from a mafic sill intruding the Pongola Supergroup and on an east-northeast-trending mafic dike, respectively. These new ages distinguish two of the Ventersdorp Supergroup magmatic events: the Klipriviersberg and Platberg. The Ventersdorp Supergroup can now be shown to initiate and terminate with two large igneous provinces (LIPs), the Klipriviersberg and Allanridge, which are separated by Platberg volcanism and sedimentation. The age of the Klipriviersberg LIP is 2791-2779 Ma, and Platberg volcanism occurred at 2754-2709 Ma. The Allanridge LIP occurred between 2709-2683 Ma. Klipriviersberg, Platberg, and Allanridge magmatism may be genetically related to mantle plume(s). Higher heat flow and crustal melting resulted as a mantle plume impinged below the Kaapvaal Craton lithosphere, and this was associated with rifting and the formation of LIPs.

Department/s

  • Lithosphere and Biosphere Science

Publishing year

2020

Language

English

Pages

1829-1844

Publication/Series

Geological Society of America Bulletin

Volume

132

Issue

9-10

Document type

Journal article

Publisher

Geological Society of America

Topic

  • Geology

Status

Published

ISBN/ISSN/Other

  • ISSN: 0016-7606