Minerals of the crichtonite group in metarhyolites and apobasite rocks at the Chudnoe Au-Pd deposit (Subpolar Urals)

Complex Fe-Ti oxides of the crichtonite group have been identified at the Chudnoe Au-Pd deposit. The species diversity of minerals is determined by the balance between Pb and Sr, and between Zn, Mn and Y. Metarhyolites contain almeidaite, crichto-nite, senaite and minerals of intermediate composition. The composition of almeidaite, which is the richest in zinc, — (Pb0.44Sr0.38)S0.82(Mn0.65Y0.30)S0.95Zn1.23(Ti13.67Fe3+5.01)S18.68O38. The mineral association includes muscovite, hematite, rutile, zircon, aeschynite-(Y), monazite-(Ce), allanite-(Ce). In apobasite hematite-sericite rocks, gramaccioliite-(Y) was found at the contact with metarhyolites. The composition of gramaccioliite-(Y), which is the richest in yttrium, — Pb0.91(Y0.50Mn0.45)S0.95(Ti13.13Fe3+6.25 Zn0.25)S19.63O38. Associated minerals: muscovite, hematite, titanite, rutile, zircon and allanite-(Ce). Minerals of the crichtonite group are found in the contours of ore zones with vein gold-fuchsite mineralization, but they are localized not in ore veins, but in the rock matrix. The formation of minerals of the crichtonite group is associated with metamorphic processes in rhyolites and contacting basic rocks.