The economically important sulfide deposits of Precambrian age can be subdivided into two principal groups. The first group is represented by Ni- and Cu-bearing differentiates within either layered intrusions of the Sudbury-Bushveld type or within smaller ultramafic bodies (sometimes of greenstone belt association). The relatively narrow spread around the meteorite standard of the δ34S values of these deposits suggests a mantle provenance of the sulfide sulfur.