My research focuses on the use of radiogenic and heavy stable isotopes to study the evolution of the crust and mantle through time, the genesis of ore deposits, paleogeography, and environmental and archeological problems. I have collaborative research on the genesis of the goldfields of the Witwatersrand basin of South Africa using Os isotopes, mantle metasomatism and crustal contamination in arc magmatism in Chile, Mexico, and the Cascades of the western US using Sr, Nd, and Os isotopes, tracing archeological objects in Mesoamerica using Pb and Os isotopes, tracing contamination in rivers in Mexico and Arizona, US, using Pb isotopes, understanding Cu leaching in base metal deposits using Fe and Cu isotopes, understanding soil formation in Hawaii using Fe and Cu isotopes, understanding the tectonic evolution of Mexico during the formation of Rodinia and Pangea using laser ablation Inductively Coupled Plasma Mass Spectrometry MC-ICPMS) U-Pb geochronology. All my projects are interdisciplinary and involve collaborations with researchers and students from many parts of the world. A current biography see Recent CV below) lists the papers that have been written from these collaborations.