Williams,M.L., Jercinovic,M.J., Goncalves,P. and Mahan,K.(2006): Format and philosophy for collecting, compiling, and reporting microprobe monazite ages. Chemical Geology, 225, 1-15.

『EPMAによるモナザイト年代を収集し、編集し、報告するための体裁と考え方』


Abstract
 Microprobe monazite dating has been increasingly used to constrain the timing of deformation and metamorphism because of the potential to date very small monazite domains (down to 5μm or less) in structural and petrologic context. This paper presents an analytical strategy, presentation format, and error considerations for microprobe monazite dating. The strategy involves high-resolution compositional mapping to delineate compositional domains within monazite crystals. Then for each compositional domain, a series of Th, U and Pb analyses are made, and a single date and error are calculated. The number of analyses in each domain is determined by the desired statistical precision of the date. Results from several monazite grains are typically combined and, along with textural relationships, are used to build an argument that the dates constrain the age of a deformation or metamorphic event. The total error involves three components: short-term random error (dominated by counting statistical uncertainty), short-term systematic error (uncertainty in background correction, conductive coating variation, and calibration), and long-term systematic error (uncertainty in standard composition, mass absorption factors, decay constants, etc.). In homogeneous compositional domains, short-term random errors (2σ) of less than 10 m.y. can be obtained from five to ten analyses. However, short-term systematic error, mainly background estimation uncertainty, would typically result in a doubling of the magnitude of random error. Microprobe dates are presented as a single Gaussian probability distribution for each domain, along with representative compositional maps. It is recommended that a consistency standard be analyzed during each analytical session and the results be reported along with those from the unknown. This proposed strategy and format are compatible with those of other geochronological techniques; they incorporate analytical limitations associated with trace, as opposed to major element, microprobe analysis, and will allow better comparisons to be made between labs and between different geochronological techniques.

Keywords: Monazite; U-Pb dating; Electron microprobe; Trace element analysis』

1. Introduction
2. Background
 2.1. Major vs. trace element analysis: distinct approaches for distinct applications
 2.2. Top-down vs. bottom-up approaches
3. Proposed analytical strategy
4. Uncertainty considerations
5. Presenting and integrating results
6. Discussion and conclusions
Acknowledgments
References


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