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.
As the extraction temperature is increased, deeper or more strongly held argon is released from the mineral lattice.
The process can reveal not only an original cooling age for disturbed samples, but often (i) the age of the later event causing the disturbance, (ii) argon diffusion characteristics of the sample and (iii) the thermal history of the later event.
18.3 Ma dike of the Mugu granite from the Upper Mustang region of central Nepal.With this technique, we calculate a mean chemical date that is consistent with isotope-dilution thermal ionization mass spectrometry (ID-TIMS) U-Pb dates obtained from seven other uraninite grains and a monazite crystal from the same sample.Electron microprobe chemical dating yields results that typically will be an order of magnitude less precise than conventional dates: in the specific case of the Mugu granite, single point chemical dates each have ca. However, the mean chemical date of 15 point analyses of the crystal we study has a 2SE (2 standard error) uncertainty of ca.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.