Precious metals at magnetite skarn deposits of the Kaz and Sukharinskii ore fields in Gornaya Shoriya, Russia

The distributions of Au, Ag, Pt, and Pd were examined in the ore-hosting rocks, magnetite and skarn bodies, and sulfide associations of contact-metasomatic deposits at the main iron ore fields of Gornaya Shoriya. Magnetite skarns of the Kaz and Sukharinskii ore fields are demonstrated to bear economic concentrations of Au and Ag (1.0-5.3 ppm Au, 5-40 ppm Ag) and low contents of Pt and Pd (0.3-0.5 ppm Pt and 0.02-0.05 ppm Pd on average at usual variations from 0.01 to 5 ppm). The maximum concentrations of precious metals were found in blocks of sulfidized and silicified magnetite skarn bodies, particularly their pinching-out parts. The main minerals concentrating Au, Ag, Pt, and Pd are sulfides, first of all, pyrite and pyrrhotite: up to 6-8 ppm Au, 11-29 ppm Ag, 1.41 ppm Pt, and 0.21-0.27 ppm. Pd. The ore Au-Ag mineralization was produced during the early pyrite-pyrrhotite and late quartz-polysulfide stages of the contact metasomatic process at the Tel'bes granitoid intrusion. The accompanying Pt-Pd mineralization is of low economic significance (1.41 ppm Pt and 0.2 ppm Pd) and was produced simultaneously with the deposition of magnetite and late sulfide mineralization.