Barium feldspars of the Ilmeny-Vishnevogorsky complex (South Urals)

The results of studying barium feldspars from different metasomatic rocks of the complex are summarized in the article. Studies of minerals were performed using a scanning electron microscope РЭММА-202М with a microanalyzer. Forms of barium feldspars, features of composition and conditions of formation are considered. Barium-potassium feldspar is characterized by heterogeneity of composition, an increase in the amount of Ba to the grain edge, and a high content of Ab minal (12-17 %). The composition of celsian, developed in the basic plagioclase, shows significant variations in the CaO content of 0.4-3.6 wt. %. The temperature of formation of barium-potassium feldspar is 610-660 °C, celsian 560-610 °C. In a barite vein, celsian with a high Ba content was formed at T » 450 °C. The formation of barium minerals is associated with postmagmatic processes that occurred after the formation of the alkaline-carbonatite rocks of the complex. Rocks with barium-containing minerals are usually confined to zones of faults, along which barium was introduced.