THERMOCHRONOLOGY LAB TECHNIQUES: STANDARDIZATION TOWARDS EQUITABLE OUTCOMES

The geo/thermochronologic communities are experiencing rapid growth in method development and instrument accuracy and efficiency, which facilitate the production of more new data at an exciting rate. As infrastructure grows and more data is collected, laboratories develop innovative methods for sample processing in an efficient and effective manner. However, these innovations are hard to find through publications and are spread through word-of-mouth or lab visits. The latest international meeting on Thermochronology (Thermo2021) emphasized the need for more access to this “hidden curriculum” (Ketcham et al., 2022). In the newly created mineral separation labs at California State University, Long Beach we are working towards two innovations to help with (1) more accurate grain characterization for thermochronologic dating, and (2) reduction of water waste during mineral separation practices.

/Crystal measurement is an important aspect of grain characterization for many thermochronologic dating methods. Measurement accuracy and human error play a role in dating outcomes, however, grain size uncertainty is not propagated through age calculations or modeling efforts and is never reported as far as we know. We have made repeated measurements on 50 apatite and zircon crystals and found that variables such as time of day, caffeine consumption, and hours of sleep can contribute to grain size measurement uncertainties. With more replications of these measurements we will generate a percent error on crystal size measurements that can be used to better standardize measurement and dating outcome accuracy.

Water separation tables are commonly used for mineral separation needed in geo/thermochronology dating. Water consumption from these tables is extremely high, for example the Holman-Wilfley model 800 Laboratory Table uses 1-20 kg/hour, and water is not recycled. We have designed a water filtration system using affordable, easy to source parts, that passes the table run-off through several stages of settling and filtration, and then gets pumped back up for re-use allowing the table to function as a closed system. This set-up can save at least 50-100 gallons/sample. We emphasize that community-wide standardization compounded with sustainability can lead to a more equitable and diverse scientific community.