Birimian crustal growth in the West African Craton: U-Pb, O and Lu-Hf isotope constraints from detrital zircon in major rivers

Research output: Contribution to journalArticle

Abstract

Combined U-Pb, O and Lu-Hf isotope analyses of detrital zircon grains from five major rivers in Ghana are used to investigate the growth and evolution of the Birimian terrane of the West African Craton. The majority of the analysed zircon yields supra-chondritic εHf values, suggesting derivation from primarily juvenile host magmas. Zircon grains from the Birim River in southwestern Ghana deviate from the generally juvenile trend, where the sub-chondritic εHf but mantle-like δ18O of the 2.15 Ga population suggest reworking of ancient, but unweathered, meta-igneous crust. Hf-O isotope data from detrital zircons of the remaining rivers are consistent with sequential crust generation between ca. 2.2 and 2.1 Ga. Oxygen isotope data suggest that the contribution from Archaean sedimentary material to felsic magmas was below 30%, and in most cases below 10%. Zircon with strongly positive εHf values and elevated δ18O indicate rapid reworking of juvenile crust within southern Ghana. An increase towards heavier oxygen isotope signatures over time suggests a maturing arc system with rapid recycling of juvenile supracrustal material during the evolution of the Birimian terrane.

Details

Authors
Organisations
External organisations
  • Swedish Museum of Natural History
  • University of Western Australia, Crawley
  • Lund University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Geology
  • Geochemistry

Keywords

  • Baoulé Mossi, Detrital zircon, Lu-Hf, Oxygen, U-Pb, West African Craton
Original languageEnglish
Pages (from-to)259-271
JournalChemical Geology
Volume479
Early online date2018 Jan 31
Publication statusPublished - 2018 Feb
Publication categoryResearch
Peer-reviewedYes