Geology, Geophysics, and Geochemistry Science Center Stable Isotope Laboratory


Security Lab



6th Avenue, Kipling Blvd
Building 95
Denver, CO 80225
United States


Stable isotope geochemistry involves isotopic analysis of carbon, hydrogen, nitrogen, oxygen, and sulfur. These elements are abundant in common minerals and rocks, and they are the building blocks of most geologic fluids (surface waters, magmatic waters, hydrocarbon fluids, and others) and most biological compounds. Geologic metal deposits are in most cases precipitates from hot fluids. Stable isotope measurements can help to determine the source of the fluids, the sources of dissolved constituents, physicochemical parameters of ore formation such as temperature, and the trigger for metal precipitation. Stable isotope analysis can also reveal the broader geologic environment of ore formation, an essential part of any mineral deposit model.

The Stable Isotope Laboratory is located on the Denver Federal Center within the Geology, Geophysics, and Geochemistry Science Center. This facility is the descendant of a USGS laboratory that was established in the 1950s when the field of stable isotope geochemistry was in its infancy. Building on a long history, the laboratory covers a broad array of analytical capabilities and has a wealth of accumulated experience in isotope applications spanning Earth science research.

Specifications/Capabilities: The Laboratory includes five mass spectrometer systems, several vacuum extraction lines, and a Ni-vessel extraction line for fluorination analyses. The mass spectrometers are as follows:

  1. Finnigan MAT 252
  2. Micromass Optima with Multiprep Device and CE Instruments NC 2500 Elemental Analyzer
  3. Micromass Optima with HP 6890 Gas Chromatograph-Combustion System
  4. Thermo Finnigan Delta Plus XL with TCEA and Gas Bench II Devices
  5. Thermo Finnigan Delta Plus XP with Thermo Scientific Flash 2000 Elemental Analyzer and Gas Bench II Device

Analyses performed routinely are listed below. Numerous other types of analyses are performed less frequently.


  • carbonate minerals
  • organic carbon, oils, and graphite
  • compound specific carbon
  • dissolved organic carbon


  • hydrous minerals
  • organic hydrogen
  • water, including fluid inclusion water


  • inorganic nitrogen salts
  • organic nitrogen

Oxygen-18/oxygen-16 and oxygen-17/oxygen-16:

  • carbonate minerals
  • silicate and oxide minerals
  • sulfate minerals
  • organic oxygen
  • water


  • sulfide and sulfate minerals
  • organic sulfur
  • dissolved sulfate

Scientific Opportunities/Applications: The primary applications are genesis of mineral resources, environmental impacts of mining, animal diet and other ecosystem studies.


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