Zircon of rhyolite is enclosed in biotite or leucoxene-product of biotite alteration. It shows low reflectivity. Kazancev et al. The rest of uranium should be present in form of small inclusions of uranium oxides and silicates. Clastic allogenic, authigenic and vein tourmaline occurs in studied rocks.
Tourmaline is an accessory mineral of volcanic and sedimentary rocks.
Rounded allogenic clastic grains can be seen in sedimentary rocks. Authigenic tourmaline is often orientated in conformity with sericite in volcanic and sedimentary rocks. They form radial aggregates and they are accompanied by chlorite, barite and sulphides in quartz-carbonate veinlets. Tourmaline is especially abundant in mineralized rocks with intensive carbonatization and pyritization. It rims larger fragments of volcanoclastic rocks accompanied by pyrite.