Home – Home – Jornals – Russian Geology and Geophysics 2002 number 9

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 (M_HF): from 0.0153 to 0.0024 mole/dm³ at T = 800-700 ^oC. The M_HF of the deposits decreases in the sequence: 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 potassic metasomatism, and Cu/Mo in ores. We have found no correlation of M_HF 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 slightly in M_HF. 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.