First data on chemical composition of zircon from lithium-fluorine granite of the Severnyi pluton, Chukchi Peninsula

Wolframoixiolite and niobian ferberite from zinnwaldite granitic rocks of the Chukchi Peninsula

“…Wolframoixiolite was detected at more than ten observation points in the northern part of the main cupola of the Severny pluton about 30 km 2 in area. All the findings were exclusively related to the fine grained zinnwaldite granite and ongonite con taining topaz and fluorite, which are the main ore bearing rocks in the area (Alekseev, 2005). Under a microscope, wolframoixiolite is observable much more often than zircon (up to 5-20 grains per thin section) and is one of the main accessory minerals in zinnwaldite bearing granites.…”

“…The study of accessory tungsten and asso ciated Ta-Nb minerals are helpful in this respect. The microcline-albite granitic sills and ongonite dikes with zinnwaldite and topaz were found during special ized geological mapping of the Severny pluton near the eastern coast of the Chaun Gulf of the Chukchi Peninsula (Alekseev, 2005). The study of the accessory minerals resulted in the first finding of a rare min eral-wolframoixiolite-in granites of the Far East.…”

Zircon as a Mineral Indicating the Stage of Granitoid Magmatism at Northern Chukotka, Russia

“…The anomalies of Eu (Eu/Eu* = 0.01-0.05) and Ce (Ce/Ce* = 2.73-42.5) are clearly pronounced (Table 2; Figure 4). In the rims enriched in rare metals, light REE are concentrated (mainly Ce, Sm, and Nd): Sm N /La N decreases to 1.7-2.7 [5,9]. 1: (a) Euhedral, oscillatory zoned zircon of the second type in BG (coarse-grained equigranular granite, sample 4063, Table 1); (b) subhedral zircon of the second type with a bright rim enriched in U-Hf in MG (porphyric quartz monzonite, sample 2739, Table 1); (c) euhedral zoned zircon of the first type with a parental core, two bright rims strongly enriched in U and Hf in ZG (medium-grained zinnwaldite granite, sample 4447, Table 1); (d) subhedral patchyzoned porous zircon of the second type rich in U, Hf, Y, and REE in ZG (microgranular albite-rich zinnwaldite granite, sample 4193, Table 1).…”

“…The average values of the anomalies are Eu/Eu* = 0.02 and Ce/Ce* = 2.03 (Table 2, Figure 4). In the uranium zone of the crystals, the content of Ce, Pr, and Nd increases: the Sm N /La N ratio decreases to 3.15-16.6 [5,9].…”

“…The mineral is relatively poor in uranium (Figure 5) and has a high (up to 1.79) Th/U ratio. It was formed by crystallization in a granite melt depleted in rare elements [1,9,12]. The zircon crystallization temperature was determined by the Ti-in-Zrn thermometer [10].…”