40Ar/39Ar dating utilizes the radioactive decay of 40K to 40Ar in potassium-bearing rocks and minerals (e.g., basaltic groundmass, K-feldspars, plagioclases, biotites, white micas, and amphiboles etc.). The 40Ar/39Ar technique is used to determine the ages of a large range of geological processes, including volcanism, plutonic and metamorphic cooling, tectonic processes, detritus in sediments, extraterrestrial impact events, and the evolution of early humans.
The Argon Geochronology in Oceanography (ArGO) Laboratory at GEOMAR Helmholtz Centre in Ocean Research Kiel has been operational since 1993. The laboratory is mainly involved in the 40Ar/39Ar dating of < 200 Ma submarine volcanic samples. The laboratories are currently undergoing a major rebuild and upgrade (2023).
The new laboratory features a Thermofisher Scientific Helix MC Plus mass spectrometer, with a Nier source, high mass resolution capabilities, and allows simultaneous measurement of all five Ar isotopes using multiple Faraday and compact discrete dynode (CDD) detector configurations. The mass spectrometer is connected to an ultra-high-vacuum extraction line, X-Y-Z stages for movement of the sample chamber, and a 25 W Coherent argon-ion laser, to allow completely automated laser step-heating and single-crystal 40Ar/39Ar analyses.
40Ar/39Ar samples are prepared from crushed, sieved, and hand-picked samples (usually 0.25 to 1 mm grain size). The samples and age standards are fast-neutron irradiated at the Oregon State University nuclear reactor, USA. Lead times for 40Ar/39Ar analyses range from 6 months (minimum) to 12 months for hand-picked samples. This is dependent on the age of the samples, the frequency of our irradiation packages (usually every 6-9 months depending on the age of the samples), a radioactive cooldown period after irradiation, and analyses time. The costs for 40Ar/39Ar dating can be provided on request.