Lateral variability in the upper main zone, Bushveld Complex, owing to directional magma recharge and emplacement from north to south

Jacob B. Setera, Jill A. VanTongeren

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Recharge and magma mixing into shallow crustal reservoirs is a critical parameter in understanding magma diversity and predicting volcanic activity and hazards. Direct observation of magma mixing within the crust, however, is impossible. The solidified remnants of large magma chambers in layered mafic intrusions are therefore some of the most important natural laboratories for measuring and understanding past magma chamber dynamics. Here we provide in situ major and trace element compositions of all major mineral phases throughout a single stratigraphic section of a well-defined magma recharge interval in the ~2·06 Ga Bushveld Complex layered intrusion of South Africa. This section, the Roossenekal Traverse, is located ~75km south of a previously documented section of the same stratigraphy, the Leolo Mountain Traverse. Despite their distance, the two profiles show remarkably similar thicknesses and compositional variations; however, both resident and incoming magmas recorded in the Roossenekal Traverse are slightly more compositionally evolved. We show that the lateral compositional variability is a direct result of the locus of magma recharge originating in the north, near the Thabazimbi-Murchison Lineament. New primitive magma was emplaced in the north, mixed with more evolved magma towards the south, and fractionated as it filled the magma chamber progressively to the south.

Original languageEnglish (US)
Pages (from-to)1763-1786
Number of pages24
JournalJournal of Petrology
Volume59
Issue number9
DOIs
Publication statusPublished - Sep 1 2018

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All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Keywords

  • Bushveld Complex
  • Lateral variation
  • Magma mixing
  • Main Zone
  • Pyroxenite Marker
  • UUMZ

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