TRACING FLUID SOURCES AND INTERACTIONS

Methods of evaluating possible sources and interactions of ancient and modern fluids are being significantly improved by the development of new isotopic and geochemical microprobe techniques. Applications of O, C, and S isotopes are benefiting from the development of laser ablati on methods capable of 0.1 permit precision on submilligram samples and ion microprobe methods capable of permit precision on nanogram region s of rock sections. The noble gases are proving themselves useful cons ervative tracers of fluid processes. The ubiquitous presence of air sa turated water patterns testifies to the dominance of water originating at the Earth's surface, while the presence of radiogenic isotopes and He-3 quantify interactions with crust and mantle respectively. The us e of resonance ionisation has increased sensitivity for Xe and Kr anal yses to the single atom level. Examples of fluid regimes currently und er study are described.