Isotope dating of rocks file profile
However, note that chemical alteration of older uraninite grains was observed and can take place during metamorphism, most probably via dissolution-reprecipitation.For a successful dating of uraninite in metamorphic rocks, it is imperative to record internal textures and high-resolution compositional profiles across single crystals.We briefly comment on the potential of the field emission–scanning electron microscopy–energy dispersive X-ray method for U–Th–total Pb uraninite dating.We propose that the special construction, particularly the high beam stability, of modern FE-SEMs is advantageous for high spatial resolution measurements, as is the ability of EDX detectors to analyze all elements simultaneously.Unravelling the full geological history of basement terranes using geochronological methods is not a simple task, because regional metamorphism may obscure, or even obliterate, older crystallization stages.
Many crystals that we measured during this study did not show Pb loss despite having been subjected to temperatures of ∼500–550 °C during a much younger, penetrative regional metamorphic event.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). Three novel points of generic geochronological importance are raised in this study. 215 Ma) age that predate medium-grade regional metamorphism were identified using high spatial resolution field emission–scanning electron microscopy–energy dispersive X-ray (FE-SEM-EDX) U-Th-Pb dating of uraninite microcrystals in basement rocks of the Tauern Window, Eastern Alps.