From results of microprobe analysis and experimental data on biotite systems of ore-bearing porphyry complexes (stocks, dikes) and the host granitoids (massifs), we have calculated concentrations of HF in magmatogene fluids coexisting with biotite. Porphyry complexes of Cu-Mo deposits of Siberia and Mongolia are characterized by low concentrations of HF (MHF): from 0.0153 to 0.0024 mole/dm3 at T = 800–700 °C. According to decreasing MHF, the deposits are ordered as follows: Sora–Vykhodnoe–Zhireken, Aksug–Erdenetuin-Obo–Shakhtama. This sequence (except for the Shakhtama deposit) is to a certain extent correlated with the silica content of ore-bearing porphyries, intensity of potassium metasomatism, and Cu/Mo in ores. We have found no correlation of MHF with (87Sr/86Sr)0 of porphyries, abundance of mineralization, and contents of ore-forming components. The ore-bearing porphyries and more ancient host granitoids (except for the large Erdenetuin-Obo deposit and Vykhodnoe ore occurrence) differ little in MHF. Therefore, the elevated activity of HF in porphyry Cu-Mo ore-magmatic systems is related not only to the concentration of F in magmas but also to the evolution of porphyry melts in more open settings. The great spread in (87Sr/86Sr)0 values of ore-bearing porphyry complexes at different deposits (from 0.70393 to 0.70774) suggests mantle-crustal sources of fluorine.

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