Wagner 2024 Thesis Data- Zircon U-Pb and Trace Element

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Trace Element and U-Pb Geochronology Data for Rhyolites from the Mogollon area, southwest New Mexico

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Zircon U-Pb Geochronology and Trace Element Analysis Zircons were separated using standard manual mechanical crushing techniques, and density separation methods at Missouri State University. Optical picking was used to ensure purity and individual grains were placed on tape mounts. U/Pb isotope ratios within zircon were obtained at the University of Arkansas using an ESI NWR 193 nm Excimer Laser Ablation System coupled with a Thermo Scientific iCapQ Quadrupole Mass Spectrometer during two sessions, the first during November 2020, and the second in June, 2023. The first session analyzed one sample of the Fanney Rhyolite (53 zircon), two samples of the Apache Spring Tuff (45 zircon), and one sample of the Bloodgood Canyon Tuff (41 zircon). All zircons were analyzed for U-Pb ages, 10 zircon from the Fanney Rhyolite, 20 zircon from the Apache Spring Tuff, and 10 zircon from the Bloodgood Canyon Tuff were analyzed for trace elements. The second session analyzed four samples, one from the Apache Spring Tuff (41 zircons), one from the Fanney Rhyolite (41 zircons) one from the Deadwood Gulch (45 zircons), and one from the Rhyolite of Hay canyon (36 zircons). All zircons from the second session were analyzed for U-Pb ages and trace elements. All zircons were analyzed on a tape mount and had one spot per crystal. Laser ablation was accomplished with a 25 μm diameter spot size with laser fluence of 2.0-2.2 J/Cm2 at 10 Hz for 15 seconds of integration. On peak dwell times were adjusted to give the best precision on the U-Pb and Pb-Pb ratios for an average zircon composition. The value, uncertainty, and scatter of zircon standards during the analytical session was 1%–2% (2 standard deviations [2σ]). The primary zircon reference material analyzed was 91500 (1062.4 ± 0.8 Ma; Weidenbeck et al. 1995). Plesovice (337.1 ± .0.1 Ma; Slama et al., 2008) and Mud Tank (732 ± 0.2 Ma; Woodhead and Hergt, 2007) were used as secondary zircon reference materials. Systematic uncertainty was propagated using quadratic addition incorporating the internal and external reproducibility of the reference materials and data was reduced using the Iolite4 software (Paton et al., 2011). Since all samples possessed Mesozoic or younger crystallization ages, 206Pb-238U ratios and IsoPlot 4.0 software (Ludwig, 2003) were used to calculate weighted mean ages. Zircon trace element contents were collected during the same session as U-Pb isotope analysis using the same conditions at the University of Arkansas. External calibration standards used were the NIST610 and NIST612 glasses along with the 91500-zircon reference mineral as a secondary calibration standard. Quantitative results for 23 elements were obtained through calibration of relative element sensitivities of the calibration standards. Off-line selection and integration of background and analyte signals, and time-drift correction and quantitative calibration were performed using the Iolite4 reduction software (Paton et al., 2011).

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