My fundamental research goals have been, and continue to be, the application of 40Ar/39Ar thermochronology towards solving geological problems. 40Ar/39Ar thermochronology is probably the best suited method for understanding the thermal evolution of the lithosphere in the 150-500°C temperature interval, thus making it relevant to a wide variety of geological environments. My present research is spread amongst several projects, including: the thermal evolution of Precambrian terranes in the Southwestern U.S. and Canada, thermochronology in the Colorado River Extension zone and applications of thermochronologic data in determining the timing and petrogenesis of economic gold and copper deposits in New Mexico and Nevada. Improving our knowledge of argon systematics is also vital in helping to make sound interpretations of 40Ar/39Ar results. Along this avenue, I continue experimental studies of argon diffusion in K-feldspar and evaluation of the multiple diffusion domain model, and studies of white mica with respect to age spectrum results and recoil phenomenon. Recent applications of directly dating and monitoring the thermal history at the Geysers and Tiwi geothermal systems using the 40Ar/39Ar technique on adularia have proven very insightful. Extension of the commonly dated minerals to phases such as jarosite, barite, and inclusions in quartz have led to advances in analytical techniques and have proven applicable to some geological settings. Lastly, I have become active in dating young (<100 ka) basaltic rocks at various places (most notably near Yucca Mountain) and believe we have overcome some previously established hurdles to produce reproducible and geologically relevant results for these types of samples.