Algorithms and software for U-Pb geochronology by LA-ICPMS

Noah M. McLean, James F. Bowring, George Gehrels
<span title="">2016</span> <i title="American Geophysical Union (AGU)"> <a target="_blank" rel="noopener" href="https://fatcat.wiki/container/7h4lalujvjdp3d7nn3adrvs3ky" style="color: black;">Geochemistry Geophysics Geosystems</a> </i> &nbsp;
The past 15 years have produced numerous innovations in geochronology, including experimental methods, instrumentation, and software that are revolutionizing the acquisition and application of geochronological data. For example, exciting advances are being driven by Laser-Ablation ICP Mass Spectrometry (LA-ICPMS), which allows for rapid determination of U-Th-Pb ages with 10s of micrometer-scale spatial resolution. This method has become the most commonly applied tool for dating zircons,
more &raquo; ... ning a host of geological problems. The LA-ICPMS community is now faced with archiving these data with associated analytical results and, more importantly, ensuring that data meet the highest standards for precision and accuracy and that interlaboratory biases are minimized. However, there is little consensus with regard to analytical strategies and data reduction protocols for LA-ICPMS geochronology. The result is systematic interlaboratory bias and both underestimation and overestimation of uncertainties on calculated dates that, in turn, decrease the value of data in repositories such as EarthChem, which archives data and analytical results from participating laboratories. We present free open-source software that implements new algorithms for evaluating and resolving many of these discrepancies. This solution is the result of a collaborative effort to extend the U-Pb_Redux software for the ID-TIMS community to the LA-ICPMS community. Now named ET_Redux, our new software automates the analytical and scientific workflows of data acquisition, statistical filtering, data analysis and interpretation, publication, community-based archiving, and the compilation and comparison of data from different laboratories to support collaborative science. Key Points: We present new software to review, reduce, interpret, and archive U-Pb LA-ICPMS data, ET_Redux ET_Redux uses matrix-based full uncertainty propagation for "intercept" and "downhole" methods We introduce statistical techniques to handle ratios, systematic uncertainties, and overdispersion PUBLICATIONS Principles of LA-ICPMS Data Handling Despite the popularity and appeal of LA-ICPMS U-Pb dating, there is no broadly adopted data reduction and uncertainty propagation protocol in use today. Largely, each laboratory has created its own data handling protocols, specific to its instrumentation and scientific goals. An outline of the data handling process has been discussed at several recent meetings [e.g., Horstwood et al., 2010, and recent meetings of the LA-ICPMS Working Group at Goldschmidt in 2013 and 2015] and in a recent summary article by Horstwood
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