Kimberlite genesis from a common carbonate-rich primary melt modified by lithospheric mantle assimilation

Andrea Giuliani; D Graham Pearson; Ashton Soltys; Hayden Dalton; David Phillips; Stephen F Foley; Emilie Lim; Karsten Goemann; William L Griffin; Roger H Mitchell

doi:10.1126/sciadv.aaz0424

Kimberlite genesis from a common carbonate-rich primary melt modified by lithospheric mantle assimilation

Sci Adv. 2020 Apr 24;6(17):eaaz0424. doi: 10.1126/sciadv.aaz0424. eCollection 2020 Apr.

Authors

Affiliations

¹ KiDs (Kimberlites and Diamonds), School of Earth Sciences, The University of Melbourne, Parkville, 3010 Victoria, Australia.
² Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC, Department of Earth and Planetary Sciences, Macquarie University, North Ryde, 2109 New South Wales, Australia.
³ Institute of Geochemistry and Petrology, Department of Earth Sciences, ETH Zurich, Clausiusstrasse 25, Zurich 8092, Switzerland.
⁴ Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada.
⁵ Central Science Laboratory, University of Tasmania, Hobart 7001 Tasmania, Australia.
⁶ Department of Geology, Lakehead University, P7B 5E1 Ontario, Canada.

Abstract

Quantifying the compositional evolution of mantle-derived melts from source to surface is fundamental for constraining the nature of primary melts and deep Earth composition. Despite abundant evidence for interaction between carbonate-rich melts, including diamondiferous kimberlites, and mantle wall rocks en route to surface, the effects of this interaction on melt compositions are poorly constrained. Here, we demonstrate a robust linear correlation between the Mg/Si ratios of kimberlites and their entrained mantle components and between Mg/Fe ratios of mantle-derived olivine cores and magmatic olivine rims in kimberlites worldwide. Combined with numerical modeling, these findings indicate that kimberlite melts with highly variable composition were broadly similar before lithosphere assimilation. This implies that kimberlites worldwide originated by partial melting of compositionally similar convective mantle sources under comparable physical conditions. We conclude that mantle assimilation markedly alters the major element composition of carbonate-rich melts and is a major process in the evolution of mantle-derived magmas.

Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).