A simple method for in-situ U-Th-He dating
Vermeesch, Pieter and Sherlock, S.C. and Roberts, N.M.W. and Carter, Andrew (2012) A simple method for in-situ U-Th-He dating. Geochimica et Cosmochimica Acta 79 , ISSN 0016-7037.
This paper presents a significantly simplified method for in-situ U-Th-He dating removing the need to know any absolute concentrations or ablation pit volumes. This is done by calculating the normalised U, Th, and He concentrations of a conventionally dated calibration standard from its measured Th/U ratio and known U-Th-He age, and scaling these concentrations to the raw U, Th, and He signals of the sample. The Th/U ratio of the standard can be determined from its measured 208Pb/206Pb ratio, removing the need to use NIST glass as a reference material. We introduce an LA-ICP-MS-based method to correct for variable ablation depths between the standard and the unknown, using the strength of the ablated 29Si signal. Finally, we propose a pseudo-depth profile method to assess the effects of compositional zoning on the accuracy of in-situ U-Th-He data. The effectiveness of the proposed method has been demonstrated on three samples of gem-quality Sri Lanka zircon, which yield ages that are in agreement with previously published conventional U-Th-He measurements.
|School:||Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences|
|Date Deposited:||09 Dec 2011 09:25|
|Last Modified:||11 Oct 2016 12:01|
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