The application of LA-ICP-MS for quantified, high spatial resolution imaging of Pb isotopes in ferromanganese crusts Nathan Westwood 1 , Amy J. Managh 1 , Matthew S.A. Horstwood 2 , David N. Douglas 3 1 Loughborough University, UK, 2 British Geological Survey, UK, 3 Elemental Scientific Lasers, UK Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) combines the low detection limits, near-full mass range coverage, and wide linear dynamic range of ICP-MS with in-situ sampling by laser ablation. Over the last decade, there have been advances in both LA and ICP-MS instrumentation, as well as the introduction of accessories which improve sample transport speed and efficiency. Analyses are now performed 50x faster than previous generation technology with double the sensitivity. These developments were predominantly driven by demand for high spatial resolution, higher throughput imaging in the biosciences, thus their capabilities are poorly quantified for geoscientific applications. This study focuses on the application of modern LA-ICP-MS technology for the precise imaging of discrete Pb-Pb domains in ferromanganese crusts, identified in the previous works of Josso et al 1 . Elemental and isotope ratio data were acquired using Elemental Scientific Lasers NWR193UC and imageGEO193 LA systems, coupled to a Thermo Fisher Scientific Neptune Plus MC-ICP-MS. Coupling between the laser and ICP-MS was achieved using low dispersion, high-efficiency transport accessories ( e.g. , DCI, TV2- and TV3- ablation chambers). Several data collection parameters were adjusted between experiments to optimise the balance between image quality, data quality, and spatial resolution. These parameters included laser repetition rates, translation speed, spot size, fluence and integration times. Data reduction, processing, and generation of the final images was achieved using the post data collection processing package Iolite 2 . Results to date predominantly include the detailed characterisation of a series of Pb isotope ratio imaging methods for complex samples previously unapproachable by earlier generation technology. The capability of Iolite’s map interrogation tools ( e.g., regions of interest and transects) for the extraction and representation of data directly from LA-ICP-MS images has also been documented. Future work aims to fully quantify the uncertainty and spatial resolution of the data, and continue to optimise data extraction and representation workflows using Iolite. The data collection and processing methods will be drafted into a series of decision trees designed for laboratories and interested researchers performing laser ablation mapping of geomaterials, to optimise experimental design and quantitative interpretation of data. These methods have a wider reaching potential and could ultimately be applied to other sample types found in bio- and material sciences. References 1. P. Josso, T. van Peer, M. S. A. Horstwood, P. Lusty and B. Murton, Earth Planet. Sci. Lett. , 2021, 553, 116651 2. C. Paton, J. Hellstrom, B. Paul, J. Woodhead and J. Hergt, J. Anal. At. Spectrom. , 2011, 26, 2508–2518
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