Paper No. 35-11
Presentation Time: 4:20 PM
ALGORITHMS AND SOFTWARE FOR U-PB GEOCHRONOLOGY BY LA-ICPMS: ET_REDUX
MCLEAN, Noah M., Department of Geology, University of Kansas, Lawrence, KS 66045, BOWRING, James F., Department of Computer Science, College of Charleston, Charleston, SC 29424 and GEHRELS, George E., Department of Geosciences, University of Arizona, Tucson, AZ 85721, noahmc@ku.edu
Numerous recent innovations in geochronology, including laboratory and analytical methods, instrumentation, and software are revolutionizing the acquisition and application of geochronological data. In particular, exciting advances are being driven by Laser-Ablation ICP Mass Spectrometry (LA-ICPMS), which performs rapid determination of U(-Th)-Pb ages with high spatial resolution. This method has become the most commonly applied tool for dating zircons, informing a host of geological problems. The LA-ICPMS U-Pb community is now faced with archiving these data with their associated analytical results and, more importantly, ensuring that data meet the highest standards for precision and accuracy and that interlaboratory biases are minimized. Unfortunately, there is little consensus with regard to both analytical strategies and data reduction protocols for LA-ICPMS U-Pb geochronology. The likely result is systematic interlaboratory bias and both underestimation and overestimation of uncertainties on calculated dates that, in turn, decrease the value of data found in repositories such as EarthChem.
ET_Redux is free open-source platform-independent software that implements existing approaches and new algorithms for evaluating, implementing, and interpreting user-defined choices in LA-ICPMS U-Pb data reduction. This software is the result of a collaborative effort to extend ‘U-Pb_Redux,’ designed for the ID-TIMS community, to the LA-ICPMS community. Our new software automates the analytical and scientific workflows of data acquisition, statistical filtering, data analysis and interpretation, publication, community-based archiving in online databases, and the download, compilation and comparison of data from different laboratories to support collaborative science. Innovations include allowing users to implement and compare both ‘intercept’ and ‘downhole’ data reduction techniques, recognition of sample-to-sample uncertainty correlations deriving from sample-standard bracketing, and implementation of log-ratio analysis for handling compositional data.
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