Crustal Geophysics and Geochemistry Science Center

Isotope and chemical methods for mineral and geoenvironmental assessments

Development of continuous flow IRMS stable isotope techniques


Task Objectives

The development of continuous flow isotope ratio monitoring mass spectrometry (IRMS) has revolutionized our ability to analyze large quantities of small samples of almost any natural material for C, N, O, H and S isotope composition. This ability has in turn revolutionized our ability to apply stable isotopes to the study of all aspects of ore deposits. This task develops stable isotope techniques using combustion flow IRMS combined with microsampling techniques to ensure that the enormous potential of stable isotope geochemistry is made available to scientists in this project and throughout the Mineral Resources Program.

The objective of the task is to develop state-of-the-art continuous flow IRMS stable isotope techniques for C, H, N, O, S, analyses of small samples of minerals solutions species, liquids, and organic matter.

Statement of Work

The development of continous flow IRMS techniques which increase productivity and create opportunities for new science in support of USGS Strategic Science will continue as follows:

  1. Attempts to refine direct sulfur isotope analyses of organic matter and other matrices containing small amounts of sulfur will continue.
  2. Efforts to integrate LA-ICP-MS analyses of the chemistry of single fluid inclusions, noble gas isotope chemistry, active gas chemistry and stable isotope compositions of inclusion fluids from the same sample will continue.
  3. Development of techniques to analyze sulfur isotope compositions of conodonts will continue as will attempts to improve measurment of the sulfur isotope composition of organic material using a gas bench on the Thermo Delta XP mass spectrometer.
  4. Continuous flow techniques for 18O analyses of silicates have proven extremely difficult. We are currently working with scientists at Yale University to develop this technique for oxides such as hematite and magnetite and silicate minerals other than quartz.

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Mineral Resources Program
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