Arsenic-poor fluids promote strong As partitioning into pyrite

The data presented here includes all tabulated data contained in the manuscript draft entitled "Extreme As partitioning into pyrite from low-As fluids" by Martin Kutzschbach, Frederik Dunkel, Christof Kusebauch, Ferry Schiperski, Frederik Börner, Henrik Drake, and Manuel Keith and the associated supplementary material (in .pdf "_Data_repository_Kutzschbach_etal_2024")

Additionally, it includes:

-the location of all investigated transects across the pyrite rims (.png_files; name is the # of the experiment)

- the location of all segments assigned to the core phase assemblage (.png files; name is the # of the experiment + _core)

-The elemental distribution across the transects (.xlxs file "transet locations")

-The input code for the PhreeqC calculation of As-speciation presented in Figure 5 (.pqi file)

-All literature data used to construct Figure 8  (in .pdf "_Data_repository_Kutzschbach_etal_2024")

-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 9 (in .pdf "_Data_repository_Kutzschbach_etal_2024")

-This is the abstract of the manuscript draft:

Pyrite is a ubiquitous sulfide mineral found in diverse geological settings and holds great significance in the formation of Au deposits as well as 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 (D_As^(py/fluid)) between synthetic pyrite and experimental fluid agree with previously published data for high fluid As concentrations of 1 µg/g to 100 µg/g (D_As < 2000). However, at low As concentrations in the experimental fluid (<1 µg/g), a steep increase in the D_As^(py/fluid) values of up to ~30,000 was detected, demonstrating even stronger As partitioning into pyrite. This previously unknown relation holds significant implications for natural fluid systems which frequently exhibit similar As concentrations. Our findings contribute to a better understanding of As mobility and scavenging, which in turn is important for understanding the formation and fingerprinting of mineral deposits as well as for secure utilization of groundwater resources.