Geochemical and isotopic characteristics of Youanmi terrane volcanism: the role of mantle plumes and subduction tectonics in the western Yilgarn Craton

Abstract

New geochemical and isotopic data for volcanic and shallow-level intrusive rocks of the Murchison Domain in the Youanmi Terrane of the Yilgarn Craton help to clarify some of the stratigraphic ambiguities in the area and are consistent with the most recent lithostratigraphic model. The results reveal the presence of previously unrecognised examples of the boninite-depleted tholeiite suite that, based on εNd_T > 4, were likely derived from refractory mantle following plume melting. These new findings support the conclusions of previous studies that magmatism in Archean volcanic successions, including mantle plume-associated and arc sequences, display geochemical evidence of refractory plume-related magma sources throughout their development. The presence of well-preserved boninites in the Polelle Group indicates a significant role for subduction tectonics during the 2825–2700 Ma evolution of the Youanmi Terrane. The subduction zone is tentatively linked to the accretionary processes proposed along the Youanmi Terrane–Narryer Terrane boundary. This model also implies that in the eastern Yilgarn Craton, the initial phases of craton re-assembly may have been driven by this subduction zone prior to the development of an arc off the eastern edge of the craton at ca 2715 Ma.

KEY WORDS:

• Archean
• Yilgarn
• Murchison Domain
• boninite
• geodynamics.

ACKNOWLEDGEMENTS

We appreciate the invitation to contribute to this Special Volume of AJES, stemming from the 5IAS, by Kevin Cassidy and Steven Wyche. Ali Polat, an anonymous reviewer and Kevin Cassidy are thanked for genuinely helpful comments that significantly improved the paper. The authors would like to thank David Champion and Kevin Cassidy for permission to use Figure 10 and Tony Crawford for discussions on boninites and Figure 3d. Geoff Clarke is thanked for use of boninites samples from the Népoui ophiolite (Figure 3c). DW gratefully acknowledges the assistance provided by Bryan Krapež in the early stages of this study. This study was partially supported by ARC research funds. R.K. acknowledges research support from an NSERC Discovery Grant, and the George McLeod endowment to the Department of Geological Sciences, University of Saskatchewan.