Diamond-inclusion system recording old deep lithosphere conditions at Udachnaya (Siberia)

Nestola, F. et al. (2019) Diamond-inclusion system recording old deep lithosphere conditions at Udachnaya (Siberia). Scientific Reports, 9, 12586. (doi: 10.1038/s41598-019-48778-x) (PMID:31467318) (PMCID:PMC6715805)

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Diamonds and their inclusions are unique fragments of deep Earth, which provide rare samples from inaccessible portions of our planet. Inclusion-free diamonds cannot provide information on depth of formation, which could be crucial to understand how the carbon cycle operated in the past. Inclusions in diamonds, which remain uncorrupted over geological times, may instead provide direct records of deep Earth’s evolution. Here, we applied elastic geothermobarometry to a diamond-magnesiochromite (mchr) host-inclusion pair from the Udachnaya kimberlite (Siberia, Russia), one of the most important sources of natural diamonds. By combining X-ray diffraction and Fourier-transform infrared spectroscopy data with a new elastic model, we obtained entrapment conditions, Ptrap = 6.5(2) GPa and Ttrap = 1125(32)–1140(33) °C, for the mchr inclusion. These conditions fall on a ca. 35 mW/m2 geotherm and are colder than the great majority of mantle xenoliths from similar depth in the same kimberlite. Our results indicate that cold cratonic conditions persisted for billions of years to at least 200 km in the local lithosphere. The composition of the mchr also indicates that at this depth the lithosphere was, at least locally, ultra-depleted at the time of diamond formation, as opposed to the melt-metasomatized, enriched composition of most xenoliths.

Item Type:Articles
Additional Information:The European Research Council is thanked for supporting this research (ERC Starting Grant No. 307322). GZ e MLM received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 714936 for the project TRUE DEPTHS to M. Alvaro).
Glasgow Author(s) Enlighten ID:Harris, Dr Jeff
Authors: Nestola, F., Zaffiro, G., Mazzucchelli, M. L., Nimis, P., Andreozzi, G. B., Periotto, B., Princivalle, F., Lenaz, D., Secco, L., Pasqualetto, L., Logvinova, A. M., Sobolev, N. V., Lorenzetti, A., and Harris, J. W.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Scientific Reports
Publisher:Nature Research
ISSN (Online):2045-2322
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Scientific Reports 9: 12586
Publisher Policy:Reproduced under a Creative Commons License

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