Recent authors have successfully conducted age dating on monazite using calibrated sample using SEM-EDX. It exhibits almost the same results compared to EMPA. I am interested to conduct the same measurement, but the samples contain monazite which is expected younger than 100 Ma, even 30-50 Ma. Has anyone conducted the age dating on younger ages? Thank you for your precious suggestion.
Thank you Mrs @Ariadne Tsambani. I appreciate your questions. I am considering to read and understanding your article. Warm regards.
It is worth noting that young monazite typically contains 'excess' 206Pb as a result of disequilibrium in the 238U decay chain (in particular incorporation of 'excess' 230Th). See attached paper by U. Scharer for details. As an example, in this paper (http://www.jstor.org/stable/10.1086/605994) we found that 206Pb/238U dates are 50% older than Pb/Th dates. A 'total' age cannot resolve the presence or absence of such an affect and will likely overestimate the true date. I would strongly caution against using such a method on 'young' monazite, unless it can be demonstrated that 'excess' 206Pb does not exist in the samples.
Article The effect of initial 230Th disequilibrium on young U-Pb age...
I agree with John. Even if this problem with excess 206Pb would not exist, SEM-EDX would not provide ages sufficiently accurate in this young age range. Moreover, chemical dating of monazite is confronted with several problems and one has to take extremely care to consider all of the many influences that potentially affect the result of microprobe analyses. I personally would not consider the SEM-EDX way as perspective for your purpose.
Dear Dr Cottle and Dr Förster, I would like to express gratitude for your comment. I have tried to quantify the chemical compositions, but the result suggest that only a maximum of 2wt% of Th were detected. Most of the monazite has an irregular shape with the maximum size of 30-40 micron.
Based on this evidence, we suspect this monazite is a hydrothermal in origin and age dating on monazite is not possible. However, all results had been documented for further study. Thank you for your consideration.
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