Genetic features of tourmaline from the magnesian skarns of Kuhilal deposit, Southwestern Pamir

Background. Although the Kuhilal deposit of Mg skarns has been thoroughly studied, tourmaline in their composition never considered [5, 6, 16]. Uvite, a variety, was mentioned list rare minerals only with its crystallochemical formula [17]. L.N. Shabynin, great connoisseur skarns, noted rarity various deposits. Tourmaline this type is characterized by strong variation ferruginosity and significant content Ca. At same time, Ca:Na varies from 2:3 to 20:1 [15]. According N.N. Pertsev, another major specialist mineral skarn deposits [11]. The boron-iron ore Tayozhnoe, Aldan shield, an exception. This belongs where widespread development [12]. (dravite) found silicate metamorphic rocks containing marbles skarns. Aim. To determine paragenesis, crystal morphology, chemical composition, genetic characteristics Materials methods. Large aggregates (more than 10 cm across) crystals apple-green were investigated. Samples collected documented authors during fieldwork research at 2017. samples examined mineralogical petrographic methods, X-ray diffraction analysis using DRONE-3M (analyst A.V. Fedorov, Sergo Ordzhonikidze Russian State University for Geological Prospecting), microprobe Cameca SX 100 15 kV 30 nA shooting mode V.I. Taskaev, IGEM RAS), fluorescence AXIOS advanced spectrometer tube equipped 3 kW Rh anode Philips PW-2400 sensitivity 10-4% A.I. Yakushev, RAS). majority studies conducted Department Mineralogy Gemology Prospecting. Results. studied first time. rocks. Two associations identified: spinel forsterite, chlorite serpentine. In terms isattributed fluorine-containing uvite close zero ferruginosity. Uvite lenticular shape rarely observed, underdeveloped prism. Its properties, formation conditions analyzed. can be used make inexpensive jewelry inserts. Conclusion. crystallization occurred under granulite facies regional metamorphism. For boron formation, apo-sedimentary, evaporite source assumed.