Age and geochemistry of Karoo dolerite dykes from northeast Botswana

M. Elburg, A. Goldberg

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)

Abstract

The Botswana Dyke Swarm is a prominent 800 km long and 100 km wide feature on aeromagnetic maps of southern Africa, but little has been published on its exact age or geochemical composition. New age, trace element and isotope data for this dyke swarm show that its magmatism is indistinguishable from Karoo continental flood basalts. Ar/Ar dating gives an age of 178.9 ± 1.4 Ma. Both high Ti-Zr and low Ti-Zr dolerites occur, but the high Ti-Zr rocks appear to be the dominant type of magmatism. Low Ti-Zr mafic rocks have isotopic and trace element characteristics similar to a combination of a normal mid-ocean ridge basalt source with sedimentary and fluid-enriched components, which are thought to reside in the sub-continental lithospheric mantle. A lithospheric component seen in the high Ti-Zr mafic rocks is similar to that in nephelinites from Zimbabwe.

Original languageEnglish
Pages (from-to)539-554
Number of pages16
JournalJournal of African Earth Sciences
Volume31
Issue number3-4
DOIs
Publication statusPublished - 2000
Externally publishedYes

ASJC Scopus subject areas

  • Geology
  • Earth-Surface Processes

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