Geochemist Steven Shirey is researching how Earth's continents formed. Continent formation spans most of Earth's history, continents were key to the emergence of life, and they contain a majority of Earth’s resources. Continental rocks also retain the geologic record of Earth's ancient geodynamic processes.
Shirey’s past, current, and future studies reflect the diversity of continental rocks, encompassing a range of studies that include rocks formed anywhere from the deep mantle to the surface crust. His work spans a wide range of geologic settings such as volcanic rocks in continental rifts (giant crustal breaks where continents split apart), ancient and present subduction zones (where the tectonic plates slide under one another), the mantle keels to the continents (root-like structures that penetrate to great depths), and rocks from the present oceanic mantle (an analog to pre-continental era of the Hadean to Paleoarchean, 4500 to 3200 million years ago).
Studying continents from the deepest samples led to Shirey’s recent research on diamonds carried to the surface in volcanic eruptions of kimberlite. Diamonds carry mineral “inclusions” which are the deepest, oldest, and most pristine mantle samples known. Diamonds with these inclusions are like tiny time-capsules from about 90-430 miles (150-700 km) deep within the Earth. The included minerals are often in their original condition and their analysis can reveal information on deep mantle mineralogy, the migration of carbon-bearing fluids, and ultimately sub-continental mantle keel formation and mantle geodynamics.
To conduct his work, Shirey uses Carnegie’s extensive chemistry and mass spectrometry labs to analyze the isotopes (different atoms of the same element with differing numbers of neutrons) of naturally occurring radioactive elements. These radioactive decaying elements, critical to his work and the work of all the geochemists at Carnegie, are like atomic clocks and decay at predictable rates.
Shirey received his B.A. from Dartmouth College, his M.S. from the University of Massachusetts Amherst and his Ph.D. in geochemistry from SUNY Stony Brook. Before joining the Carnegie staff in 1985 he was a postdoctoral researcher at Carnegie. For more see http://home.dtm.ciw.edu/users/shirey