Welcome to the School of Ocean and Earth Science, Tongji University

The 45th Ocean Fest | Superdeep diamonds: sampling plate tectonics at 400 to 700 km depths in Earth's mantle


 Tuesday, November 2, 2021 9:00-11:00

 ZOOM Meeting ID810 780 06286  Code541099


Seminar Speaker:  Prof. Steven B Shirey 

Earth and Planets Laboratory, Carnegie Institution for Science


Abstract: Diamonds are the premier container for mineral inclusions, effectively isolating them completely from reactions with fluids and magmas. A special class of diamond, estimated to comprise less than 10% of diamonds mined from kimberlite, derives from hundreds of kilometers below the lithospheric mantle. These so-called superdeep or sublithospheric diamonds carry distinctive retrograded mineral assemblages that give a valuable look at deep mantle mineralogy not attainable any other way.  Recent studies of microscopic mineral inclusions extracted from diamond hosts and pressure/temperature modeling of subducted slabs provide new support for these findings: 1) the recycling of surface-derived constituents to the top of the lower mantle, 2) a measurably high water content for nominally anhydrous high-pressure minerals, and 3) evidence for fluid release in the mantle transition zone that may be a cause of deep focus earthquakes.


Academic positions: A geologist for more than 50 years, Steve Shirey is the senior staff member of the Geochemistry and Cosmochemistry Group at the Earth and Planets Laboratory (EPL). His main interests are in diamonds as the deepest probe of plate tectonics, the igneous evolution of the Earth, and the emergence of Earth's continents. Steve conducts his own research in these areas but equally important is the teaching and training he does of young scientists for their research careers. Steve is currently mentoring 3 postdoctoral fellows; over his career he has advised some 32 additional postdoctoral fellows and 21 PhD students, who have gone on to successful careers as university professors or in industry. Steve is a Fellow of the American Geophysical Union, the Geochemical Society, the Geological Society of America, and the Mineralogical Society of America (MSA). He was 96th President of MSA and the 100th President of the Geological Society of Washington.


Scientific Specialization:

Igneous petrology

Isotope geochemistry

Trace element geochemistry

Geochemical evolution of the Earth's crust and mantle