Physico-chemical conditions of crystallization and ore-bearing of granitoids of the border zone of the Southern and Middle Urals

Abstract

The geological structure of the border zone of the Southern and Middle Urals (Kunashak area), as well as the composition and conditions for the formation of granitoid complexes developed here, whose age varies from Devonian to Triassic, is briefly considered. Thermobarometric studies of quartz of medium-grained biotite granites showed that in the age range ― Poletaev (D3), Shalkar (P1), Sultayev (P1), and Yugokonev (P1T2) complexes ― water pressure during the formation of melt inclusions was 2.22.7, 2.53.0, 3.94.4 and 3.64.5 kbar, and the crystallization temperature of rocks ― 800840, 900940, 840900 and 940980С. This indicates a consistent increase in the crystallization depth of the granite massifs in this series from the hypabyssal-subsurface to the hypabyssal-abyssal facies. At the same time, in the melt-fluid inclusions, a decrease in fluid volume is noted ― 14.216.8, 8.114.3, 6.27.9 and 4.36.8 vol.%, Water concentrations ― 3.74.8, 2.13.9, 1.82.3 and 1.31.9 wt.% as well as chlorine ― 0.040.08, 0.030.07, 0.030.06 and 0.020.05 wt.%.
 It is shown that the granitoids of the Sultayev and Yugokonev complexes are very promising for tantalum, niobium, tungsten, molybdenum and beryllium. Of the greatest interest in rare-metal mineralization are the leucocratic aplitic and greisen granites of the final phases of the formation of intrusions. The level of erosional slice of various structural and formation zones of the Kunashak area relative to each other has been established.