PROJECT DETAILS ONLY - NO DATA. Sandstones in hydrocarbon basins are usually cemented by quartz: this frequently infills porosity by 50%, and so dramatically reduces reservoir quality. Predictive models for spatial patterns of cementation require to know the sources of silica, and the hydrogeology of cement-forming fluids. The ion microprobe has recently proved capable of in-situ micro analysis (0.02mm), to decipher the record of palaeo-fluids. To date 18O/16O has provided an effective tracer of fluid source, but sources of silica remain obscure. We will use the ion microprobe to investigate new geochemical tracers - B, Li, Al, 11B/10B (sigma11B), 30Si/28Si (sigma30Si) - to simultaneously discriminate silica sources, fluid sources, and fluid migration. This is a key step to more comprehensive predictive cementation models. Tracers will be tested in known hydrogeological settings, and by laboratory experiments.