Factors of 18O/16O fractionation in garnets: Evidence from calculations of isotope frequency shifts

Based on the density functional theory (DFT), frequency shifts of garnet end-members upon isotope substitutions (O-18/O-16, as well as "non-traditional" stable isotopes) were calculated. According to the calculations, the temperature dependencies of fractionation factors (beta-factors) suggested for garnets: 1000ln beta(prp) = 9.68511x-0.19204x (2) + 0.00567x (3); 1000ln beta(grs) = 9.14697x-0.15682x (2) + 0.00412x (3); 1000ln beta(adr) = 8.72470x-0.15092x (2) + 0.00402x (3); 1000ln beta(uvr) = 8.71526x-0.14749x (2) + 0.00385x (3); 1000ln beta(sps) = 9.33600x-0.17598x (2) + 0.00499x (3); 1000ln beta(alm) = 9.45295x-0.18465x (2) + 0.00539x (3), x = 10(6)/T (K)(2). The values obtained combined with with the known values of beta-factors may be applied in geothermometry of garnet-bearing rocks.