Pyrophyllite and pyrophyllite raw materials in the sulfide-bearing areas of the Urals

Abstract

Pyrophyllite, Al 2(Si 4O 10) (OH) 2, was discovered for the first time in the Urals, in 1829, occurring in quartz veins of the Berezovsk gold-beresite deposit. At present, 6 types of pyrophyllite mineralization occurrences are known in the region. Pyrophyllite-containing metasomatites in areas with massive sulfide mineralization are the most interesting for practical purposes. They are confined to Devonian palaeo-island arcs formed on the margin of the Urals palaeo-ocean. While studying the Gay and Kul-Yurt-Tau deposits, it was discovered that productive metasomatites occur in the flanks and roofs of rhyolite-dacite domes. Depending on the ratio of pyrophyllite, diaspore, sericite, kaolinite and quartz, several types of pyrophyllite raw material can be distinguished. Quartz-sericite-pyrophyllitic rocks are the most suitable for ceramic production. They have an elevated content of alkalis that promote sintering in the range of 1100 to 1200°C. Pyrophyllitic, pyrophyllite-diasporic, and pyrophyllite-quartz varieties can be used for production of fireproof materials. Sometimes, besides ordinary pyrophyllite of the 2M + 1Tc polytype, chromiferous pyrophyllite of the 1Tc polytype is present. Processes like synvolcanic metasomatism, dynamometamorphism and atmospheric weathering have played an important role in the formation of pyrophyllite ore bodies.