ХРОМСОДЕРЖАЩИЕ ГРАНАТЫ ИЗ РОДИНГИТОВ ДЛИННОГОРСКОГО МАССИВА, ПОЛУОСТРОВ ВАЛИЖГЕН, КОРЯКИЯ

Abstract

New data are reported on Cr-rich garnet occurrence in calc-silicate contact metasomatic rock — rodingites, located in peripheral zones of Dlinnogorsky mafic-ultramafic massif, Valizhgen Peninsula, SW Koryakia. The following garnet minerals are described: bright emerald-green colored Cr-Ti uvarovite; and two groups of grossularite (1) weak light-green colored Cr-rich; and (2) colorless Cr-free. Chemical composition of uvarovites varies in a wide limit and composed a range of Uv33_$2Gr7_64And2-25-Mineral is characterized by uncommon composition, concerned with relatively high ТЮ2 content (1.3—1.69 wt%). Uvarovite formation is related to process of primary accessory Cr-spinel decomposition during rodingitization of gabbro inclusions in serpentinite. High alkalinity of metasomatic fluids led to increase of Cr and Ti mobility (bom are usually immobile) with their release, redistribution and accumulation in newly formed mineral phases: uvarovite and Cr-chlorite (kemme-rerite).