Geochemistry of trace elements in rock-forming minerals of gneisses and granites of the Murzinka granite area, Central Urals
S.V. Pribavkin, N.S. Borodina, M.V. Chervyakovskaya
The Murzinka granite area (Central Urals), which combines Murzinka granite pluton and underlying rocks of the Murzinka-Adui metamorphic complex, exhibits an evident wetrending geochemical zonation of magmatism with increasing of Rb, Li, Nb and Ta contents and decreasing ba and Sr contents and K/Rb, zr/Hf and Nb/Ta ratios from vein granites of the Yuzhakovo complex to granites of the Vatikha complex and further to granites of the Murzinka complex (Fershtater et al., 2019). To develop the ideas about geochemical zonation of the Murzinka granite magmatism, as well as about the role of gneisses of the Murzinka-Adui metamorphic complex in the formation of granites, we studied the distribution of trace elements in biotite and feldspars of gneisses and granites. Biotite shows an increase in Li, Rb, Cs, Nb, Ga, zn, Mn, Sc, Sn and Tl contents and a decrease in V, Cr, Co, Ni, Y, zr and ba contents from vein biotites of the Yuzhakovo granites to two-mica granites of the Murzinka complex. The composition of feldspars also changes in this direction: plagioclase is enriched in Li, Rb, Cs, be, zn and depleted in Sr, ba, Ga and Pb and K-feldspar is enriched in Rb and depleted in Sr and ba. The varying trace element composition of rock-forming minerals of gneisses and granites is explained by We-trending change in the composition of a crustal protolith, as well as the formation conditions of granites.
Figures 6. Tables 4. References 18.
Key words: granite, gneiss, biotite, feldspar, geochemistry, rare elements, Murzinka
MINERALOGY № 3 2020