Extreme As partitioning in pyrite from low-As fluids

Description

The data presented here includes all tabulated data contained in the manuscript draft entitled "Extreme As partitioning in pyrite from low-As fluid" by Martin Kutzschbach, Frederik Dunkel, Christof Kusebauch, Ferry Schiperski, Frederik Börner, Henrik Drake, and Manuel Keith and the associated supplemantary material Additionally it includes the input codes for the PhreeqC calculation of As-speciation and Mineral stabilities presented in Figure 5, all literature data used to construct Figure 7 and the detailed results of the modelling of As sequestration from fluids by formation of pyrite as a function of fluid volume and DAs (py/fluid) values. presented in Figure 8. Abstract of the manuscript draft: Pyrite, an ubiquitous sulfide mineral found in diverse geological settings, holds great significance in the formation of Au deposits and the safe utilization of groundwater due to its remarkable ability to incorporate substantial amounts of As. However, despite its importance, there remains a dearth of fundamental data on the partitioning of As between pyrite and fluid, which is key for accurately modeling the As distribution in these environments Here, we present new insights into the partitioning behavior of As between pyrite and fluid at conditions that mimic natural fluid systems. Pyrite was synthesized by replacement of natural siderite in hydrothermal experiments at 200°C and pH 5 applying a wide range of fluid As concentrations spanning from 0.001 to 100 µg/g. The As distribution and concentration in synthetic pyrite was analyzed by quantitative LA-ICP-MS mapping providing a high spatial resolution and sensitivity at 2-3 µm image pixel size at a detection limit of ~1 µg/g at the single pixel scale. Pyrite-fluid partition coefficients (DAs(py/fluid)) based on the As concentration of the synthetic pyrite and the experimental fluid agree with previously published data for high fluid As concentrations of 1 µg/g to 100 µg/g (DAs < 2000). However, at low As concentrations in the experimental fluid (<1 µg/g), a steep increase in the DAs(py/fluid) values of up to ~41,000 was detected, demonstrating a high degree of fractionation of As into pyrite. This is a yet unknown relation that holds significant implications, but which has important implications for natural fluid systems that frequently exhibit comparable low fluid As concentrations. Our findings contribute to a better understanding of As sinks and its possible mobilization, which is crucial for the formation and fingerprinting of mineral deposits and the secure utilization of groundwater resources.

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