Fig. 3.

Three-dimensional APT reconstructions of localized ⁵⁷Fe enrichment. (A) The 3D APT reconstruction of goethite particle MR1 reacted with ⁵⁷Fe(II); 5-nm cube is used for 3D scale. Arrows indicate regions 1 and 2 highlighting (B) nonenriched and (C) ⁵⁷Fe-enriched regions, respectively. (D) Comparison with ⁵⁷Fe(II)−(001) hematite surface from Taylor et al. (26). Note that the ⁵⁶Fe/⁵⁷Fe values correspond to the y axis on the left-hand side, while the Cr and Fr concentrations correspond to the y axis on the right-hand side. The onset of the goethite phase is set to 0 nm, and the vertical, gray dashed lines mark the onset of the nominally nonrecrystallized phase (i.e., where ⁵⁶Fe/⁵⁷Fe reaches NA).