The research programs in geochemistry at Brown address a wide variety of geological problems, utilizing observational, analytical, and experimental approaches. The principal active research areas presently are: geochronological and isotope tracer studies of tectonic processes in orogenic belts, including direct dating of deformational fabrics and shear zones; time-dependent aspects of a number of major long and short-term geological processes, especially mass transport and isotope diffusion rates in mineral structures and along mineral grain boundaries.
Igneous and metamorphic events are emphasized in studies of the behavior of elements and nuclides during the process of rock and mineral formation. Kinetic studies include diffusion and exchange of elements and isotopes in a fluid system (hydrothermal or magmatic), and application of oxygen and cation diffusion kinetics to cooling rates (and associated uplift and denudation rates) of igneous and metamorphic rocks in the Alps, Rockies, and New England. Geochronological methods are being developed to determine the ages and thermal histories of deformational events in the orogenic belt. Trace element and isotope geochemical studies are used to reconstruct the evolution of plutonic rock systems.
Solid State Mineralogy
The mechanisms and kinetics of mineralogical processes on a microscopic scale give insight into large scale geological processes. Experimental samples, subjected to desired temperature, pressure, and chemical conditions, are analyzed by a combination of optical, x-ray diffraction, transmission electron microscopy, and chemical-isotopic methods. Current interests include grain boundary transport mechanisms and effects of crystal growth and interrelations of mineral deformation and kinetics during metamorphism. The latter involves collaborative studies with structural geologists Professors Jan Tullis and Greg Hirth.
Petrology research investigations include: field and experimental studies of the evolution of magmas under varying temperature, pressure and fugacities of oxygen, carbon dioxide and water; theoretical and experimental studies of the structure & solution characteristics of silicate melts; lab and theoretical studies of transport properties of silicate melts and transport processes in crystal-melt systems. Also being studied: origin and differentiation of lunar, Martian and terrestrial magmas, chemistry of magmas in equilibrium with sulfide & sulfate phases, magma ascent in calc-alkaline volcanic complexes, and controls on mineral-liquid element distributions.
Planetary petrology and volcanology at Brown focuses on petrological and volcanological processes that occur on the terrestrial-type planets other than Earth. This research compli-ments studies of similar processes that occur on Earth, and graduate students often add a planetary project to thesis research that is focused on Earth. The planetary science research is conducted on Earth’s Moon, Venus, Mars and the parent bodies of various igneous meteorites.