Project title: Refining multi-isotope, micro-analytical imaging methodologies (LA-ICP-MS silicate and geochronology)
Researcher: Dr Foteini Drakou
This project in part of the Geochemistry Platform and is related to the TCD LA-ICP-MS silicate and geochronology facility (an Agilent 7900 quadrupole ICP-MS coupled to a Teledyne Photon Machines ArF Excimer laser) and involves undertaking novel method development research and technical support in assisting user in the lab The research to be undertaken will broadly encompass LA-ICP-MS method development in both U-Pb geochronology and LA-ICP-MS trace element mapping, which are the main applications of the instrumentation. Method development will encompass both i) developing both new applications for iCRAG2 users from within the challenges, while also ii) developing analytical and data reduction strategies that substantially improve the sample throughput of the facility.
Research questions or hypothesis a) Sediment tracking Sedimentary provenance studies provide key constraints on sediment dispersal pathways, reservoir quality and hinterland exhumation, but are often hampered by non-unique provenance determinations (e.g. due to multiple phases of sedimentary recycling of refractory minerals such as zircon). (Aim 1) Can we expand the iCRAG multi-proxy toolkit to incorporate other single grain varietal approaches for more diagnostic provenance determinations? Additionally, single-grain sediment fingerprinting studies are more diagnostic and statistically robust when large grain sets are employed, and such an approach enables detection of minor but geologically important age components such as the youngest detrital zircon population. (Aim 2) Can we improve our ability to automatically identify large amounts of grains from heavy mineral fractions for more diagnostic provenance determinations? (Aim 3) Can we then rapidly analyse these grain populations by LA-ICP-MS and efficiently reduce these large amounts of data? b) Imaging approaches The recent significant uptake in LA-ICP-MS imaging in the Geosciences has only be made possible by several key developments in instrumentation and data reduction approaches. These include fast washout cells which minimize signal smearing, and data reduction approaches which facilitate the construction and extraction of data from LA-ICP-MS maps. Outstanding issues remain, including i) imaging artefacts (spectral skew) caused by interaction between the laser pulse rate and the total sweep cycle time in fast washout cells and ii) accurate standardization of LA-ICP-MS maps when the internal standard element does not exhibit constant concentration across the sample (due to elemental zoning or the sample is comprised of multiple mineral phases with differing concentrations of the internal standard). This project (Aim 4) investigates the minimization of imaging artefacts.