Mineralogy of spessartine-quartz rocks of the Sikhote-Alin

Research subject. The article is devoted to the study of spessartine-quartz rocks of the Triassic chert formation of the Sikhote-Alin. The research objects involved the outcrops of spessartine-quartz rocks of the Gornaya and Shirokaya Pad areas from Malinovka and Olga ore districts (in the Samarka and Taukha terranes respectively). Materials and methods. The selection of stone materials was performed manually. The diagnostic of minerals was performed using the microscope in transmitted and reflected light and carried out by the determination of their composion. The polished sections of the minerals were investigated at the FEGI FEB RAS using JXA8100 microanalysers. Results. Spessartine-quartz and manganese silicate rocks occupy the same position in the section of the Triassic deposits of the Taukha and Samarka terrains. This indicates a synchronous accumulation of sediments (protoliths of these rocks) in a single sedimentary basin. The rocks formed by contact metamorphism in the Late and Early Cretaceous large granitoid massifs. This process is manifested in the presence of a variety of such minerals, as spessartine, members of the ilmenite-pyrophanite series, titanite, monazite, bastnesite, allanite, apatite, zircon, baddeleyite, torianite and others. The rocks under study also include such rare minerals, as cheralite, greyite and a rare variety of fluorine-aluminous titanite. Conclusion. The occurrence (during contact metamorphism of siliceous-rhodochrosite rocks) of spessartine-quartz or manganesesilicate rocks composed mainly of pyroxenoids, was determined by both the relative amounts of carbonate and clay matter, as well as the concentrations of Ba and alkalis in the initial sediments.