A simple method for in-situ U–Th–He dating

Vermeesch, Pieter; Sherlock, Sarah C.; Roberts, Nick; Carter, Andy. 2012 A simple method for in-situ U–Th–He dating. Geochimica et Cosmochimica Acta, 79. 140-147. 10.1016/j.gca.2011.11.042

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Official URL: http://www.sciencedirect.com/science/journal/00167...

Abstract/Summary

This paper presents a significantly simplified method for in-situ U–Th–He dating removing the need to know any absolute concentrations. 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.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.gca.2011.11.042
Programmes:	BGS Programmes 2010 > NERC Isotope Geoscience Laboratory
ISSN:	0016-7037
Date made live:	10 Apr 2012 15:37 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/17636

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1016/j.gca.2011.11.042

Programmes:

BGS Programmes 2010 > NERC Isotope Geoscience Laboratory

ISSN:

0016-7037

Date made live:

10 Apr 2012 15:37 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/17636