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Keywords:

  • SIMS;
  • hydrogen isotopes;
  • high mass resolution;
  • energy filtering;
  • high precision;
  • D/H ratio;
  • turquoise;
  • O primary beam

Abstract

SIMS offers spatial resolution on the scale of micrometers and consumes an exceedingly small amount of sample. In addition, easy sample preparation, rapid analysis and high sensitivity allow SIMS to be applied to hydrous minerals. Hydrogen isotopes normally can be measured as negative or positive secondary ions using either a Cs+ or an O primary ion beam, respectively. The hydrogen negative secondary ion yields are only marginally higher than hydrogen positive secondary ion yields. There are advantages and disadvantages to using either method to analyze hydrogen isotopes by SIMS. For insulating samples, O is commonly used to avoid using the electron gun. The main disadvantage in using an O beam is hydride interference (H2+) associated with deuterium (D) that must be resolved using a mass resolving power of ∼1000–2000. We have developed a method where we combine a lower mass resolution and a small voltage offset to obtain rapid (12 min), high-precision (∼2‰, 2σ) D/H ratios in turquoise using a Cameca IMS-7F ion microprobe. This technique can be applied to a variety of hydrous minerals in geological materials. Copyright © 2010 John Wiley & Sons, Ltd.