Rock-forming minerals of manganese silicate rocks in the Triassic siliceous formation of the Sikhote-Alin
E. V. Perevoznikova, V. T. Kazachenko
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 5. P. 81-95
Manganese silicate rocks of the Sikhote-Alin’ (contact metamorphozed metal-bearing sediments) have in general the complicated mineral composition. It includes, besides Mn, Si and Al, diverse chemical admixtures from initial sediments, first of all Mg, Ca, Fe, and alkalis, Ti and Ba. It has been influenced by the lowering temperature of mineral formation due to distance from the contacts of granitoid intrusions, resulted in replacement of the high-temperature associations by the middle- and lowtemperature ones (carbonate-, chlorite-, amphibole-, and manganopyrosmalite-bearing ones). Together with jaspers and silicate-magnetite ores these rocks compose a single packet of lenses and beds replacing each other by facies. Parageneses of the manganese silicate rocks of Olginsky, Malinovsky, and Dalnegorsky ore districts of the Sikhote-Alin are dominated by silicates of bivalent Mn (rhodonite, pyroxmangite, bustamite, and tephroite), along with which there were found hyalophane, celsian, Ba- or Ni-bearing phlogopite, manganous amphiboles of the cummingtonite-grunerite and tremolite-ferroactinolite composition, pyrosmalite, alabandite, and other rare in nature minerals and mineral varieties. Differences in the mineral composition of parageneses of these manganese silicate rocks are conditioned, mainly, by the variations of the content of Ca, Fe, and alkalis in the initial deposits and by the temperature conditions of the contact metamorphism.
Key words: Mn silicates, manganese silicate rocks, Triassic, Sikhote-Alin.