Acid Be Solutions at the Orot Deposit and Their Relation to the Intrusion of Alkaline Granites

摘要

As is known, acid leaching, typical of granitoid intrusions, is virtually absent in the alkaline and mafic massifs. This empirical regularity is quite consistent with experimental results, which showed that the pH value of aqueous solutions in equilibrium with granite magmas depends on the molecular ratio A/NKC = Al_2O_3/(Na_2O + K_2O + CaO) in the melt: the higher the A/NKC ratio, the lower the pH value. Therefore, it is not surprising that Be metasomatites of the Yermak-ovka F-Be deposit (western Baikal region), which is genetically related to the intrusion of aegirine (alkaline) leucogranites, mainly consist of feldspathic (+fluo-rite, phenakite, ± quartz) rocks without muscovite and other indicators of highly acid solutions.