In order to understand the source of magma under Ascension, and how much interaction the magma has with surrounding rock as it ascends to the surface can be understood by measuring the isotopic composition of the rocks erupted. In this first round of isotope work, Katy has powdered up whole samples of both lava flows and pyroclastic material, and then dissolved them to liquids, in order to isolate the two elements on interest for us: lead (Pb) and strontium (Sr). While a lot of whole rock (WR) isotope work has been carried out on Ascension previously, we have new samples which haven’t been examined in detail before, so we are aiming to fill in a few gaps in our understanding of the source of volcanism on Ascension Island.
Once Katy has cuts of Pb and Sr from each sample, the cuts are taken up into a dilute acid solution, and analysed using a multi-collector (MC) inductively coupled plasma mass spectrometer (ICPMS) at Durham University. Data to come soon!
MC-ICP-MS at Durham University.