Our project partners at the Department of Earth Sciences, University of Minnesota, received a shiney new piece of kit this week in the form of a Thermo Scientific Neptune Plus. The new mass spectrometer arrived in thirteen very large heavy boxes, which proved quite a challenge to get from the -16°C temperatures outside, and up several floors onto the 4th floor of the laboratory building. Over the next few weeks, this high-precision instrument will be carefully put together and tested before being used to meet the ever increasing demands of uranium-series geochemistry.
The Northeast Greenland Caves Project will use this machine to date samples of calcite deposits from the caves in Greenland. First of all, we will trial a well-established method known as uranium-thorium dating. The method works as follows:
1. At the time of formation, uranium but not thorium, is incorporated into the calcite.
2. With time, the uranium that is contained within the calcite decays radioactively and turns into thorium.
3. At some point after formation, the calcite is collected and samples are taken for dating and climate reconstruction.
4. The samples that are required for dating are put through a chemical procedure in order to separate the uranium and thorium from the calcite.
5. The samples are analysed on a Thermo Scientific Neptune [mass spectrometer] and the age of the sample is calculated from the ratio of thorium to uranium.