Published In

Nature

Document Type

Post-Print

Publication Date

7-26-2023

Subjects

Geology, Geodynamics, Geochemistry, Volcanism, Mantle plumes, Plate tectonics, Kimberlite, Diamonds

Abstract

Kimberlites are volatile-rich, occasionally diamond-bearing magmas that have erupted explosively at Earth’s surface in the geologic past1,2,3. These enigmatic magmas, originating from depths exceeding 150 km in Earth’s mantle1, occur in stable cratons and in pulses broadly synchronous with supercontinent cyclicity4. Whether their mobilization is driven by mantle plumes5 or by mechanical weakening of cratonic lithosphere4,6 remains unclear. Here we show that most kimberlites spanning the past billion years erupted about 30 million years (Myr) after continental breakup, suggesting an association with rifting processes. Our dynamical and analytical models show that physically steep lithosphere–asthenosphere boundaries (LABs) formed during rifting generate convective instabilities in the asthenosphere that slowly migrate many hundreds to thousands of kilometres inboard of rift zones. These instabilities endure many tens of millions of years after continental breakup and destabilize the basal tens of kilometres of the cratonic lithosphere, or keel. Displaced keel is replaced by a hot, upwelling mixture of asthenosphere and recycled volatile-rich keel in the return flow, causing decompressional partial melting. Our calculations show that this process can generate small-volume, low-degree, volatile-rich melts, closely matching the characteristics expected of kimberlites1,2,3. Together, these results provide a quantitative and mechanistic link between kimberlite episodicity and supercontinent cycles through progressive disruption of cratonic keels.

Rights

This is the accepted version. The definitive version is available from the publisher: https://doi.org/10.1038/s41586-023-06193-3

© The Author(s), under exclusive license to Springer Nature Limited 2023

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Locate the Document

This is the accepted version. The definitive version is available from the publisher: https://doi.org/10.1038/s41586-023-06193-3

Data Availability

All data generated and analysed during this study are provided as Source Data files and as Supplementary Datasets 1 and 2, available in the online version of the paper. All associated files and georeferenced data are available from the Zenodo open repository (developed under the European OpenAIRE programme and operated by CERN) at https://doi.org/10.5281/zenodo.7849141. Source data are provided with this paper.

Code availability

The input file, custom source code and ASPECT installation details for the thermomechanical simulations are available from the Zenodo repository at: https://doi.org/10.5281/zenodo.7825780. The software, calculation and plotting scripts for the decompressional hydrous melting calculations in Fig. 3c are freely available at https://github.com/smj75/mormel. The input files, output files and source code for the kimberlite tectonic analysis are available at https://doi.org/10.5281/zenodo.7849141.

DOI

10.1038/s41586-023-06193-3

Persistent Identifier

https://archives.pdx.edu/ds/psu/40565

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