Independently, and with postdoctoral fellows and students, I explore geological questions about the evolution of the solid Earth and the active tectonic processes that have shaped it. The formation of lithospheric and superdeep diamonds has been an area of interest and research for me for nearly two decades. My studies of mineral inclusions in these diamonds has been applied to global scale questions such as the creation of continental mantle, the onset of plate tectonics, and the recycling of surface materials into the deeper parts of the mantle to see how plate tectonics works at depth.

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" 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 support new 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) a mantle that gets progressively reduced with depth yet harbors distinct oxidized and reduced regions.

In my work, trace element and isotopic compositions of ancient minerals and rocks are employed to understand some of the deepest and oldest magmatic and geodynamic processes that have shaped Earth since its formation. This quest has led me to work on topics as diverse as arc volcanism, Archean crustal evolution, continental volcanism, meteorites and impacts, mantle heterogeneity, and  analytical method development in geochemistry. A recurring research theme has been to show how ancient episodes of mantle-derived magmatism and crust formation differ (or not!) from those today. 

Another main research emphasis of mine has been on the formation of continents and how they emerged from Earth's mantle as highligthed in papers on Archean crustal evolution and formation of the subcontinental mantle. This geologic process spans most of Earth history and holds the rock record of conditions on the ancient Earth that led to life. Earth is the only rocky planet in our Solar System with current tectonic activity that can be traced back nearly to its birth 4.5 billion years ago. Continents are the record of that activity.

But the evolution of continents is even more fundamental. Recent thinking holds that life depends on at least two critical things: 1) emergent surfaces above sea level and 2) availability of the element phosphorous at Earth's surface. Emergent surfaces allow wet–dry cycles that foster the formation of complex molecules. Phosphorous is required to make DNA and RNA as well as life's energy cycles. The process of continent formation by crustal differentiation is essential to accomplish both requirements.