Steven B. Shirey, Senior Scientific Staff, geochemistry
Steven B Shirey
I am 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.
Research Interests
PhD 1984, Geochemistry, SUNY Stony Brook
MS 1975, Geology, University of Massachusetts, Amherst
AB 1972, Geology, Dartmouth College
Department of Terrestrial Magnetism (DTM)
Carnegie Institution of Washington
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E-mail address: shirey_at_dtm_dot_ciw_dot_edu
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These figures represent the wide range in scale that research on continents involves, from the large scale to the microscopic. The left panel shows correspondence of diamond type with seismic structure of the Kaapvaal craton. The middle panel is a field photograph of an Archean mantle xenolith hosted in diamondiferous lamprophyre from Wawa, Ontario. The right panel is a sulfide inclusion in rough diamond (~3 mm across) from Orapa, Botswana. Click on the ‘Research’ tab above for more details on these images. A gallery of sulfide inclusion photos can be seen here.
The study of continents from the deepest samples led to my 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.
Our own, well-equipped DTM chemistry and mass spectrometry labs allow us 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). Select the Research menu above to get an idea of what we do or the Facilities and Opportunities menu to learn about our analytical capabilities and our visitor and postdoctoral programs.
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