STABLE ISOTOPE OXYGEN 18 Technique

Element: Oxygen delta18O (SMOW - PDB) Material: carbonate minerals organic compounds (organic oxygen) gases (CO2, CO, molecular O2, H2O vapor) oxides and silicates water oxygen trace atmospheric gases- ozone, NOx aerosols- atmospheric SO4 sulfate minerals oxygen (anhydrite, gypsum, barite, celestite) soluble sulfates/evaporites in mine drainage aqueous nitrate oxygen phosphate oxygen (phosphate minerals, teeth, bones, etc.) Form: extract and process to carbon dioxide, analyze as CO2 on mass spectrometer (molecular O2 into mass spectrometer to analyze 17O directly) Precision: Typically ± 0.04 to 0.1 per mil Applications: Temperature, kinetics, sources and tracers, reaction pathways Instruments: Finnigan 252, Finnigan 251, VG Optima Speciality Peripherals: Kiel devise, Multiprep, extraction lines, CO2 and Nd:YAG laser microbeam sampling, auto trapping/gas separation, fluorination line using F2 and BrF5 reagents to liberate oxygen Automation: Yes - Kiel (46/day), Trapping box cleaning (24/day), Multiprep (60/day) Sample Size: minimum: 1 nanomole as CO2 extracted from sample typical: 20-60 micromole as CO2

| Capabilities | | Geochronology, Geochemistry, and Tracer Studies  | | Geochemistry, and Tracer Studies  |

URL http://geology.cr.usgs.gov/capabilities/gronemtrac/geochem/stablei/oxygen/tech.html