Diamonds & Mantle Geodynamics of Carbon

✦ Group of type IIa rough diamonds (VRL# 190894). These rough diamonds, comprising the world's most valuable gemstones based on size and clarity, are the subject of recent research that shows them to crystallize out of metallic liquids at extreme depths in the mantle. The examples shown here range from 14 to 91 carats sometimes appear to be broken fragments of once larger diamonds. Photo by Robert Weldon. © 2015 GIA. Courtesy of Gem Diamonds Ltd.

DMGC Mission

The Diamonds and Mantle Geodynamics of Carbon (DMGC) consortium was conceived at the 1st International Diamond School in 2011 as a new international infrastructure for diamond research that would be based on basic questions about the Earth's deep interior that are especially suited to diamond research. Our mission is to advance studies of natural diamonds and experiments on diamond forming fluids/melts for understanding the mobility of carbon and other volatiles in the Earth's interior now and through geologic time. The deep time aspect of the carbon cycle is a unique contribution of diamond research since diamonds are the oldest, deepest-crystallized minerals on planet Earth. Click on the official DMGC website here.

✦ DMGC -part of the Reservoirs & Fluxes Directorate of the Deep Carbon Observatory.

✦ Recent studies of large gem diamonds known as CLIPPIR diamonds (such as those in the photo at top) reveal the low redox conditions in the deep mantle allow carbon to segregate from metallic iron, thus confirming theoretical predictions of oxygen activity and providing a new carbon pathway. See Smith et al. (2016) Science 354, 1403-1405. Figure from Smith, Shirey, and Wang, Gems and Gemology 53, 388-403.

DMGC Members

The DMGC is international in scope comprising partners from 8 countries on 4 continents. A photo gallery and e-mail addresses can be found on the DMGC website.

  • Sonja Aulbach, Goethe Univeristat, Germany

  • Frank Brenker, Goethe Universitat, Germany

  • Pierre Cartigny, Inst. Physique du Globe, France

  • Daniel Frost, Beyreuth Geoistitut, Germany

  • Erik Hauri, Carnegie Inst. for Science, USA

  • Dorit Jacob, University of Melbourne, Australia

  • Fabrizio Nestola, University of Padua, Italy

  • Paolo Nimis, University of Padua, Italy

  • Graham Pearson, University of Alberta, Canada

  • Karen Smit, Gemological Inst. of America, USA

  • Steven Shirey, Carnegie Inst. for Science, USA

  • Thomas Stachel, University of Alberta, Canada

  • Emilie Thomassot, ETH, Switzerland

  • Michael Walter, University of Bristol, UK

Some DMGC Scientific Breakthroughs

  • pinpointing the onset of plate tectonics at 3.2 Ga

  • recycling through the mantle transition zone to the top of the lower mantle

  • observation of the first terrestrial ringwoodite

  • documentation of mantle methane in diamond growth fluids

  • establishing the high water carrying capacity of nominally ahnydrous minerals such as ringwoodite

  • documenting seawater subduction and recent diamond growth

  • generation of IIa diamonds from deep mantle metallic liquid

  • verification of metastable reducing conditions in the mantle transition zone

  • observation of the first terrestrial calcium perovskite

  • association of deep mantle carbon with pervasive recycling related to slab subduction

Some Questions Important to DMGC Research

  • What is the source of carbon and other volatiles returned by diamond from the deep mantle?

  • What is the mineralogy and composition the major deep mantle minerals from direct sample analysis?

  • What is the mechanism and capacity for water storage in deep mantle minerals?

  • How and why do contrasting (carbonatitic versus metallic) mantle environments exist?

  • Does the C and N isotopic composition of diamonds vary with geologic time?

DMGC Key Components

The DMGC consortium has pioneered a new way to work on diamonds and their mineral inclusions by employing different types of components:

  • cutting edge research in the highest profile journals

  • network of research labs of wide-ranging analytical capability

  • International Diamond Schools for educating the next generation and industry synergy

  • diamond database

  • diamond research collection

  • legacy project on C and N isotopic signatures of diamond-forming fluids through time

  • future Research in MIneralogy and Geochemistry (RiMG) volume on Diamonds