Diamonds and Crustal Recycling into Deep Mantle
Two main occurrences of diamonds are currently known in the Earth: kimberlites and their xenoliths from the deep continental lithospheric mantle and ultrahigh-pressure metamorphic rocks. Recently recognized diamonds and other ultrahigh pressure (UHP) and crustal minerals in ophiolitic peridotites and chromitites demonstrate the occurrence of a new type of diamond in the Earth that forms at mantle depths of 150-300 km, or perhaps deeper, near the mantle transition zone or in the lower mantle. These ophiolite-hosted diamonds raise a series of fundamental questions regarding the mantle dynamics and deep Earth processes. What is the source of carbon producing these diamonds? How do diamonds form and become incorporated into peridotites and chromitites? What is the redox state of the upper mantle, and how are the highly reduced phases and diamonds brought from the Mantle Transition Zone to shallower levels? These questions require a re-evaluation of the existing models for the formation of podiform chromites and the ophiolites containing these diamonds and ultrahigh-pressure minerals. Contributions are welcome on any aspects of: mantle compositions and heterogeneities based on mantle xenolith, ophiolite, and Deep Ocean drilling studies; UHP metamorphic rocks; and the occurrence of different types of diamonds and their geodynamic settings of formation. This session is an IGCP-649 contribution.
Jingsui Yang, Yildirim Dilek, Julian Pearce, Hans-Peter Schertl and Cong Zhang