The ca. 2.45 Ga pyritic uraniferous quartz-pebble conglomerate (UQC) of the Matinenda Formation of the Elliot Lake Group, Huronian Supergroup, was used in this study to investigate the origin of pyrite. A laser-microprobe was used for analysis of the sulfur isotopic compositions of individual pyrite grains, and an electron-probe microanalyzer was used for analysis of the trace element compositions of pyrite grains with overgrowth texture. We found a variation in δ³⁴S values among pyrite crystals (73 analyses) of various size and morphologies that occur in a small (∼1 cm³) rock chip: the total range in δ...