Helium-based thermochronometry and cosmogenic noble gas geochemistry in the Thermochronology @ Purdue (T@P) noble gas mass spectrometry facility

The Thermochronology @ Purdue (T@P) noble gas mass spectrometry facility was established at Purdue University between 2020 and 2023. In this presentation, we will detail the T@P laboratory’s instrument configuration and demonstrate the facility’s capabilities for both helium-based thermochronometry and cosmogenic noble gas geochemistry. The primary instrument in the T@P laboratory is an Isotopx NGX, a multi-collector sector field mass spectrometer with a Nier-type source, which has a custom detector configuration consisting of three discrete dynode electron multipliers, including one fitted with an electrostatic filter, and two Faraday cups with ATONA® amplifiers. The NGX is connected to a custom-built, fully automated, ultra-high vacuum extraction line that includes an activated charcoal cryogenic trap and two getters for gas purification, two manometrically-calibrated gas standards for sensitivity calibration (air and ³He-enriched helium), and a manometrically-calibrated ³He spike for measurements of radiogenic ⁴He by isotope dilution. Gases are extracted by heating samples under vacuum using a diode laser system in a feedback control loop with either a calibrated optical pyrometer (better than ± 10 ºC precision), or a bare, thin-wire thermocouple in contact with the sample (better than ± 3 ºC precision). We will present isotopic analyses made in the T@P laboratory of reference materials for both helium-based thermochronometry (Durango apatite) and cosmogenic noble gas geochemistry (CRONUS-P, CRONUS-A, CREU-1) as well as from example applications in Earth and planetary surface processes.