Steven B. Shirey
Igneous petrology; isotope geochemistry; trace element geochemistry; geochemical evolution of the Earth's crust and mantle
B.A., Dartmouth College, 1972 M.S., Geology, University of Massachusetts, 1975 Ph.D., Geochemistry, State University of New York, Stony Brook, 1984
Steve is interested in how Earth's continents formed. Although Earth is called the water planet it also could be called the continent planet. Continent formation spans most of Earth history, continental rocks retain a geologic record of Earth's geodynamic processes, and continents were the key to the emergence of subaerial life and concentration of Earth's resources. Understanding continent formation requires the study of rocks whose ages range from very ancient to very young and could have formed anywhere from the deep mantle to the upper crust. It requires thinking on microscopic as well as global scales. It encompasses a wide range of studies: continental volcanic rocks, ancient and present subduction zones, crust-mantle evolution now and in the past, and the deep mantle keels to the continents. Even the present oceanic mantle can be viewed an analog to pre-continental, oceanic mantle (Hadean to Paleoarchean; 4500 to 3200 million years ago) -the original source of continental crust.
The study of continents from the deepest samples led to his recent interest on diamonds. The exhumation of diamonds in erupted kimberlite magmas brings up the deepest, oldest, and most pristine mineral inclusions from the mantle that are known. Diamonds and these inclusions present an remarkable chance to study deep mantle mineralogy and the migration of carbon-bearing fluids which will lead to a unique constraints on sub-continental mantle keel formation and mantle geodynamics.
DTM's well-equipped chemistry and mass spectrometry labs allow him to develop and refine in-house the many geochemical tools used for this research: the radiogenic isotope systems (Re-Os, Sm-Nd, and Pb-Pb), the stable isotopes systems (C, N, B, and S), and the trace elements (the highly siderophile elements or HSE and the large ion lithophile elements or LILE).