Nanoscale trace-element zoning in pyrite framboids and implications for paleoproxy applications

Abstract Pyrite framboids (spherical masses of nanoscale pyrite) are among the earliest textures pyrite to form in sediments. It has been proposed that their trace-element (TE) contents can be used track TE composition water column which they formed. However, it is not clear how these TEs associated with framboidal grains. For instance, important know whether incorporated uniformly or enriched different regions framboid. We high-resolution scanning transmission electron microscopy identify chemical zoning within framboids. found initial, euhedral crystals, make up volumetric majority framboids, covered/infilled by later templates on earlier pyrite. Further, this TEs, suggesting many relatively late (during early diagenesis; column). This observation suggests although analyses may provide ocean-water chemistry trends through time, details complex. Specifically, linked adsorption onto organic matter, detrital material, and authigenic minerals such as Fe- Mn-oxide phases followed desorption sediments release via dissolution incorporation into overgrowths initial crystals While use understand past ocean conditions remains promising, even diagenetic additions preclude utility for reconstructing ancient conditions, care must taken interpretations because end concentration influenced diagenesis.