Isotope dating of rocks file profile
Furthermore, repeated analyses of two in-house uraninite age standards have confirmed the validity of the calculated dates (Fig. In conclusion, we assume that state of the art FE-SEM-EDX techniques (with large-area silicon-drift detectors) provide sufficient accuracy for uraninite dating owing to the circumstance that radiogenic Pb is abundant in uraninite.
The study received support through the Austrian Science Fund project P 22480 (to Finger). Geiger and Noreen Vielreicher for style and linguistic improvements of the text, and C. Williams, and an anonymous reviewer for helpful comments.
We are aware that quantitative EDX spectral analysis is viewed by many with skepticism, and considered inferior compared to wavelength dispersive analysis (WDX).
However, in our study the EDX results have proved reproducible in several control measurements using WDX microprobe analysis (see the Data Repository).
The accuracy of the dating procedure was monitored by two in-house uraninite age standards: hydrothermal uraninite from Mitterberg, Austria, previously dated as 90 ± 5 Ma (Paar and Köppel, 1978), and uraninite-bearing granite from the Erzgebirge, Germany, dated as 326 ± 4 Ma (Förster, 1999) and 330 ± 5 Ma (Kempe, 2003).
At 15 k V, the electron beam excitation volume in uraninite is slightly minerals that were produced at that time were obliterated by the penetrative Paleogene regional metamorphism.
The use of microcrystals for geochronology presents a challenge because state of the art in situ dating methods such as sensitive high-resolution ion microprobe (SHRIMP) or laser-based U-Pb isotope dating involve spot-sizes of 5 µm, which do not allow for precise targeting of minute grains.Background, line interference, and matrix corrections are automatically carried out by the INCA Energy software.A Pb-free synthetic UO crystal was measured to control the Pb background, which is one of the most critical parameters for U–Th–total Pb dating (Williams and Jercinovic, 2002).Notably, metamorphic or hydrothermal minerals from the Permian–Triassic Periods have very rarely been reported in the Tauern Window, despite the numerous multimethod geochronological studies.Here, uraninite dating may provide a completely new and powerful approach.