This award provides one-half of the funding required for the support of a laboratory technician to assist in the operations of the stable isotope mass spectrometry laboratory in the Department of Geological Sciences at the University of Southern California. The University is committed to providing the remaining funding required. The stable isotope laboratory at USC is primarily engaged in research projects investigating the role of aqueous fluids in geological processes of the Earth's crust. Specific goals of current projects include: (1) To determine the depth to which surface (meteoric) water penetrates the crust. (2) The nature of fluid-rock interactions across the lithostatic-hydrostatic transition zone. (3) The role of fluids in faulting and shear zones. (4) Understanding the influence of fluids escaping from cooling magmatic plutons within the crust. These general goals are investigated through detailed study of isotope variations (primarily oxygen, carbon, hydrogen, and sulfur) in rocks of the Mojave desert of California and Arizona.