Bid document

Data turnaround time, quality and continuity are essential for these geochronological analyses. U-Pb samples must be prepared (mineral separates made) and analyzed at the same lab on the same instrument. Previous experience utilizing different labs for data sets that are to be a part of the same study has shown lab-based differences in the number of discordant grains, adding new variables to data and preventing data sets from being directly comparable. The USGS has utilized the Arizona LaserChron lab for U/Pb dating from 2021-2026. During this time, Arizona Laserchron completed over
worth of analyses for Alaska and Gulf Coast
projects at the USGS. The data produced from analyses included in this PR would be a continuation of that effort, and this data needs to be directly compared to our existing data set. Additionally, ALC offers several services not available from other labs:

ALC has been an NSF National Facility for geochronology since 2005, and the offers a complete service including zircon extraction, mounting, polishing, SEM imaging (backscatter and cathodoluminescence), Raman analysis, U-Pb, T/REE, and Hf isotopic analysis. ALC has 4 ICPMS coupled to 3 excimer lasers to ensure rapid turnaround times. The lab exclusively uses excimer lasers for the ablation of zircon whereas many labs use less effective lasers (effectiveness is due to light coupling characteristics between the light wavelength and zircon crystals).
ALC measures 204Pb during each U-Pb measurement so each analysis can be corrected for common Pb.
ALC U-Pb data is reduced using in-house data reduction protocols (AgeCalcML (LA-SCICPMS) or AgeCalcN3 (LA-MC-ICPMS)). This is highly desirable to ensure data reductions are completed appropriately/similarily for ALL samples, including those we have run to date. Many other labs use Iolite which allows users an extremely high degree of subjectivity when reducing datasets, which is highly undesireable.
ALC is a full-service lab where ALC staff not only separate and process samples but accurately select spots for laser ablation, analyze samples and collect data, and reduce data down to best collected in this way, it is imperative that future data analysis and processing be conducted using the exact same methods.