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), which can contain very high concentrations of radiogenic Pb after only a few million of years of U and Th decay.Although uraninite is regarded as a rare accessory mineral, it is relatively abundant in leucogranitic rocks such as those found in the Himalayan orogen.Concentration gradients in U, Th, and Y across the boundary imply diffusive modification.We estimate the diffusivity of U, Th, and Y in uraninite at ca. In contrast, Pb shows no distinctive concentration gradient across the core-rim boundary, implying that Pb has a much higher diffusivity in uraninite than U, Th, or Y. 8.9% has occurred in the uraninite grains we analyzed by ID-TIMS.Abstract : High spatial resolution dating of monazite by the electron-probe microanalyzer (EPMA) enables systematic and detailed studies of small minerals.Like zircon, monazite records the complex history undergone by the host rocks. If you desire of African seniors in roughly one owes me think again. Dating Tips Dating in the Digital Age: Create an account to start this course today. Optical performance The key criterion for excellent sharpness, contrast and light intensity is the quality of the prisms and lenses.
The aim of this study is to constrain a meta-morphic history using EMP dating of monazite on example of the Tatra Mts.
We compare our results with those obtained from single-grain, cathodoluminescence-controlled, U-Pb dating of zircons (Poller et al., 2000, Poller and Todt, 2000).
The beam diameter varied from 2 to 6 µm according to the possibili-ties to analyse only single phase in the monazite.
The Ar-Ar dating technique was developed by Merrihue and Turner (1966) and proved to be an extremely powerful geochronological tool even before the advent of laser extraction techniques.
Analytical procedure and age determination Analyses of monazites were carried out using the Cameca SX-100 microprobe.