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Starting the recycling engine: how far back in time can we fingerprint crust in Earth’s mantle?

Sebastian Tappe , Katie A. Smart & Richard A. Stern
The nature of the tectonic processes that shaped the early Earth remain unresolved, hampered not only by the sparse Early Archaean crustal rock record, but also by the dearth of tangible mantle samples (e.g., xenoliths and diamonds) older than 3 Ga. Investigating the Archaean mantle provides a complementary foil to the knowledge gleaned from the early Earth crust, and can be used to trace the onset of crustal recycling, but also to evaluate the secular...

Reasons for extreme Th/U zoning of zircon in magmatic rocks: examples from the Bushveld Complex

Armin Zeh , Dominik Gudelius & Allan H Wilson
Zircons of magmatic rocks can show enormous variations in Th/U ratios (0.2 to 100) and extreme Th/U zoning. We present data from felsic and mafic rocks of the Bushveld Complex in South Africa. Zircon grains in mafic cumulate rocks reveal Th/U ratios up to 70, those in felsic rocks barely exceed 1.0. In mafic rocks zircon mostly occur together with Rt-Bt-Kfs-Qtz in intercumulus domains, and crystallized during final magma cooling between 900 and 700°C, after...

Registration Year

  • 2022

Resource Types

  • Text


  • University of the Witwatersrand
  • University of Alberta
  • Karlsruhe Institute of Technology
  • University of Johannesburg