Analysis of nano-quantities of geo-materials by Total-Reflectance X-Ray Fluorescence

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Geoscience research takes place at progressively smaller scales, either out of necessity, for example in the simulation of high-pressure high-temperature domains in the Earth where pressure inversely scales with experiment sample size, or by design, for example to interrogate the geological record at increasingly finer time-resolution. This trend produces significant analytical challenges related to the need to quantify the complete periodic table in ever smaller sample quantities. The Total Reflectance X-Ray Fluorescence Spectrometer (TXRF) requested here is ideally suited to overcome these issues. TXRF uses a grazing angle (0.1°) primary X-Ray beam to generate secondary fluorescence X-rays in a thin film of evaporated fluid, suspended solid or rock wafer. The thin-film grazing-angle configuration eliminates element interferences and matrix effects, and allows the detector to be mounted very close to the sample to optimize count rates. As a result, TXRF is characterized by very low backgrounds and can detect elements down to ppb-levels. Moreover, it is non-destructive, can analyse most of the periodic table, and can handle concentrations ranging from mass % to ppb simultaneously. The TXRF instrument will enable a wide diversity of research projects conducted by the co-applicants, including their Discovery Grant research programs. It will allow for the small quantities of fluids and solids synthesized in experiments to be analysed for major and trace elements. This experimental research aims to develop tools to reconstruct the compositions of fluids from the minerals that precipitated from them, and constrain the stability of metals in aqueous fluids to allow for thermodynamic modelling of ore-fluid evolution. The ability to analyse complex fluids and brines without any dilution or other sample pre-processing will be used in studies to determine the cycling of elements between marine sediments and seawater, and to determine whether the sediment acts as a net sink or source of these elements. It will also be applied to understand the environmental impact of acidic metal-laden brines released by Kawah Ijen volcano in Indonesia and to explore the mobility of metals in geothermal fluids in Iceland. Studies of zoned crystals and bedded meta-sediments benefit from the improved sampling resolution enabled by TXRF, which allows for the evolution of magmatic systems and sedimentary basins, respectively, to be investigated at much finer temporal scales. This research greatly enhances our understanding of element cycles and human's impact on these, it allows for past environments to be reconstructed and used as a proxy in forward modelling of climate change, and will provide insights into ore formation, all of which address key societal uncertainties for the future related to pollution, climate change and dwindling natural resources.