U-Pb laser ablation geochronology has become the most commonly applied tool for dating zircons. Despite the widespread application of this tool to a host of geological problems, there is little consensus with regard to analytical strategies and data reduction protocols. The result is inter-laboratory bias and both under- and over-estimation of errors on calculated dates. This limits our ability to compare results from different labs and limits rigorous compilations from databases such as EarthChem. This project will remedy this situation by developing cyber infrastructure tools in support of Laser-Ablation ICP-Mass Spectrometry (LA-ICP-MS). The project will develop open-source, free, software in consultation with the international community to treat with statistical rigor all aspects of data reduction, from calculation of ratios to correction for interferences and drift. Our approach will follow that used in developing similar software as part of the EARTHTIME project and requires the integration of the fields of software engineering and geochemistry. The resulting software will eliminate large sources of interlaboratory bias and serve as a teaching tool showing clearly how raw ratios are converted into dates and uncertainties.
Creating the software for connecting the LA-ICP-MS community with the developing EarthChem database for geochronology and thermochronology will provide the integration of data from this important technique into the larger data structure of geochemistry and geology. These data will play an important role in far-ranging fields such as understanding the growth of continents, chronology of evolutionary changes, timing of early hominid evolution, and linkages between climate and tectonics. During all phases of the planned work, we will involve a broad cross section of the community from undergraduates to post-doctoral scientists to help develop the next generation of analysts and software engineers. In particular, the systematic evolution of the collaboration between software engineers and earth scientists will be advanced as it produces robust and reliable workflow tools.
The primary objective of this project has been to develop improved cyberinfrastructure for U-Pb geochronology by Laser-Ablation ICP Mass Spectrometry (LA-ICPMS). There have been six main activities: 1. Develop a mathematically rigourous data reduction scheme. 2. Adapt a software system developed by the ID-TIMS community (Redux) to incorporate this new LA-ICPMS data reduction scheme. 3. Test the system and create new capabilities with data from the Arizona LaserChron Center. 4. Develop capabilities for Redux to feed data direcly into Geochron, which is a geochronology database operated by the EarthChem initiative. 5. While Redux is being developed, populate Geochron with legacy data such that the database will eventually contain all published data. 6. Encourage the broader LA-ICPMS geochronology community to become familiar with Redux and participate in its development. These activities have been conducted as a collaboration between four PI's: -- Jim Bowring (College of Charleston): responsible for Redux programming, and organizer of 2013 workshop for Redux development -- Sam Bowring (Massachusetts Institute of Technology): develop data reduction scheme with robust error propagation (together with PhD student Noah MacLean) -- Doug Walker (University of Kansas): maintain Geochron database and develop linkages with Redux -- George Gehrels (University of Arizona): Test Redux with data from the Arizona LaserChron Center, upload data into Geochron, and co-organize 2011 and 2013 workshops for Redux development Excellent progress has been made on all objectivities. Outcomes from activities at the University of Arizona are as follows: 1. U-Pb data from the Arizona LaserChron Center have now been processed through Redux with accurate results and robust error propogation. Continuing development efforts focus on enhanced visualizations, accomodation of variable data-acquisition formats, and creation of training materials. 2. Uploading of U-Pb data from over 1200 legacy samples from around the world. This is a significant percentage of the previously published geochronologic data. 3. Co-organized two international workshops (August 2011 in Prague and 2013 in Charleston) that have highlighted the develpoment of Redux and the Geochron database. In terms of Broader Impacts, the primary contribution has been the involvement of three MS students (Clare Tochilin, Chen Li, and Intan Yokelson) in developing Redux and using it to upload legacy U-Pb data into the Geochron database.
