Issue 10, 2017

Double-spike data reduction in the presence of isotopic anomalies

Abstract

The double-spike technique is one of the most robust and commonly used methods for high precision isotopic mass fractionation analyses by either TIMS or MC-ICPMS. It involves measuring the isotopic compositions of the pure sample, as well as a mixture of the sample and a double-spike made of an artificial mixture of isotopes. If isotopic variations follow the laws of mass-dependent fractionation, one does not need to measure the pure sample and a single measurement of the sample–spike mixture is sufficient. This approach is invalid, however, if the isotopic composition of the sample is not related to that of the standard by mass fractionation because nucleosynthetic anomalies are present, the sample is affected by cosmogenic effects, or one or several of its isotopes are produced by the decay of a radioactive parent. Extraterrestrial materials, in particular, often display isotopic anomalies of nucleosynthetic origin that can be troublemakers in double-spike data reduction if not properly accounted for. In the present publication, we derive an analytical equation to calculate the correction that needs to be applied to the isotopic composition if one erroneously assumes that samples and standards are related by the laws of mass dependent fractionation when in reality isotopic anomalies are present (by anomaly, we mean any departure from mass-dependent fractionation). This formula is applied to previous Mo, Ti and Cr isotopic analyses and demonstrated to yield an accurate correction. The newly derived formula also provides a straightforward means of propagating errors arising from the presence of anomalies in the isotopic composition calculated by the double-spike technique.

Graphical abstract: Double-spike data reduction in the presence of isotopic anomalies

Article information

Article type
Paper
Submitted
16 May 2017
Accepted
08 Aug 2017
First published
08 Aug 2017

J. Anal. At. Spectrom., 2017,32, 2024-2033

Double-spike data reduction in the presence of isotopic anomalies

J. Y. Hu and N. Dauphas, J. Anal. At. Spectrom., 2017, 32, 2024 DOI: 10.1039/C7JA00187H

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements