The course deals with advanced topics in stable and radiogenic isotope geo-/cosmochemistry and builds on Ge 140 a and b, with emphasis on non-traditional isotope systems (Mg, Fe, Ti, Mo, U, etc.). Starting with close examination of seminal papers, each topic will build up to a discussion of the remaining outstanding questions. Topics to be covered will be guided by class interests. Example subjects could include: the early solar system, nucleosynthetic anomalies, the early Earth, planetary differentiation, paleoredox reconstructions, medical use of stable isotopes. All participants will lead discussions of papers and present a lecture on a relevant subject. Grades will include participation, a review/proposal paper, and oral examination(s).