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

Fabrizio Nestola, Gabriele Zaffiro, Mattia L. Mazzucchelli, Paolo Nimis, Giovanni B. Andreozzi, Benedetta Periotto, Francesco Princivalle, Davide Lenaz, Luciano Secco, Leonardo Pasqualetto, Alla M. Logvinova, Nikolay V. Sobolev, Alessandra Lorenzetti, Jeffrey W. Harris

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number12586
Pages (from-to)12586
Number of pages8
JournalScientific Reports
Volume9
Issue number1
DOIs
Publication statusPublished - 29 Aug 2019

Keywords

  • EQUATION-OF-STATE
  • INFRARED-ABSORPTION
  • THERMAL-EXPANSION
  • SOLID INCLUSIONS
  • HIGH-PRESSURES
  • SPINEL
  • GARNET
  • TEMPERATURE
  • BEHAVIOR
  • MAGNESIOCHROMITE

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