⁴⁰Ar/³⁹Ar Age Determinations Using ARGUS-VI

Making Sample Dating Requests

The OSU Argon Geochronology Lab carries out ⁴⁰Ar/³⁹Ar analyses for researchers, post-docs, students and outside clients against a service fee as defined in the OSU Fee Book. If you are interested in getting your samples dated in our laboratory, download the Sample Dating Request Spreadsheet below, fill it out completely in Microsoft Excel, and email the forms to geochronology@oregonstate.edu. You can also contact us at geochronology@oregonstate.edu to discuss your project and geochronology goals and to receive further instructions for completing the sample dating service request. Your samples to be-dated should be shipped to the address on the Contact Us page with a photocopy of the dating request spreadsheet inside each of the shipped boxes.

Geological Materials that we can date, and pricing and typical turnaround times for the different level of services provided are indicated below. All experiments are carried out using 30W Synrad CO2 Lasers in a raster-scanning mode and the argon gas samples extracted are cleaned using customized Thermo Scientific NG Prep Systems and analyzed using one of two Thermo Scientific ARGUS VI Multi-Collector Mass Spectrometers.

Geologic Materials

Here is a list of phases that we can separate and analyze:

Amphibole, Anorthoclase, Biotite, Clinopyroxene, Glass, Glauconite, Groundmass, Hornblende, Illite, K-Feldspar, Mica, Muscovite, Nepheline, Orthopyroxene, Phlogopite, Plagioclase, Pyroxene, Sanidine, Sericite, Tourmaline

Phases that we do not analyze:

Alunite, Jarosite

⁴⁰Ar/³⁹Ar Bulk Incremental Heating Age Determinations

Incremental heating for bulk mineral or groundmass samples ranging in weight from sub-milligram to maximally 40 mg of prepared material. Included in this service are up to 30 heating steps, up to 15 blanks, sample irradiation, flux monitor measurements, air short calibrations, and other related age standard measurements. A minimal data report, along with a description of our mineral separation protocol, acid leaching cleaning procedures, and mass spectrometry analyses will be included when the data is delivered via email. This service includes full mineral separation and acid leaching protocols.

⁴⁰Ar/³⁹Ar Single Crystal Total Fusion Age Determinations

For total fusion experiments we apply the same service levels and turnaround times as listed in the table above. In that case, a total fusion experiment will include up to 30 fusion steps. However, for detailed single crystal (provenance) studies requiring, for example, the dating of 100 single crystals per sample, the pricing is calculated as one standard service that covers 30x single fusions plus 70x additional fusions at $30 per fusion, totaling $3,400 per sample for an 8-12 month turnaround time. This service includes full mineral separation and acid leaching protocols.

⁴⁰Ar/³⁹Ar Single Crystal Incremental Heating Age Determinations

Incremental heating for in total 5 single crystals from one sample. Included in this service are up to 12 heating steps per crystal, up to 6 blanks per crystal, sample irradiation, flux monitor measurements, air short calibrations, and other related age standard measurements. A minimal data report, along with a description of our mineral separation protocol, acid leaching cleaning procedures, and mass spectrometry analyses will be included when the data is delivered via email. This service includes full mineral separation and acid leaching protocols.

Collaborative Rates

We offer several collaborative rates for researchers, post-docs, students and our non-OSU clients who would like to collaborate with the OSU Argon Geochronology Lab on scientific publications, for students who visit Oregon State University and prepare their own samples, and for our colleagues and non-OSU clients who provide us with high quality and cleanly pre-prepared samples.

Other Services

We also offer per-hour services that are in addition to the above standard services. These include additional or special mineral separation fees for more difficult samples or special projects, more in depth reporting, software user instruction, or software development in support of new data reduction protocols or software features.

OSU TRIGA Irradiations

Samples are neutron-irradiated at the OSU Radiation Center in the TRIGA experimental reactor, typically at 1 MW power for periods that are optimal for the age and composition of samples being dated (typically from 1 to 12 hours). The neutron fluxes during irradiation can be monitored with a variety of standard samples (Mmhb-1 hornblende, FCT-3 biotite, TCR sanidine) but we use FCT-NM sanidine as our default flux monitor. There are two different locations in the TRIGA reactor where samples can be irradiated and we use the Cd-shielded irradiation location CLICIT as our default as this is designed to block slow (thermal) neutrons in preference to fast neutrons. Irradiated materials are disposed through the OSU Radiation Safety Office. All workers in our laboratory are trained in the safe handling of radioactive materials.