The Devonian massive sulfide orebodies of the West Shasta district in N California are composed primarily of pyrite, with lesser amounts of other sulfide and gangue minerals. Examination of polished thin sections of more than 100 samples from the Mammoth, Shasta King, Early Bird, Balaklala, Keystone, and Iron Mountain mines suggests that mineralization may be divided into 6 paragenetic stages, the last 5 each separated by an episode of deformation: 1) precipitation of fine-grained, locally colloform and framboidal pyrite and sphalerite; 2) deposition of fine-grained arsenopyrite and coarse-grained pyrite; 3) penetration and local replacement of sulfide minerals of stages 1 and 2 along growth zones and fractures by chalcopyrite, sphalerite, galena, tennantite, pyrrhotite, bornite, and idaite; 4) recrystallization and remobilization of existing minerals; 5) deposition of quartz, white mica, chlorite, and calcite; and 6) formation of bornite, digenite, chalcocite, and covellite during supergene enrichment of several orebodies at the Iron Mountain mine. Mineralogic and textural evidence do not support a second major episode of massive sulfide mineralization during the Permian. -from Author
Additional publication details
Mineralogy, textures, and relative age relationships of massive sulfide ore in the West Shasta district, California ( USA).