Abstract:

This paper describes in detail the features of mineralogy and mineral chemistry about tourmaline from peraluminous granite in south Tibet(PGST)．The analysis results show that(Fe+Mg)/Mg ratio is between 2.32-5.37 in tourmaline. It indicates the tourmaline in granite and pegmatite is iron tourmaline series, belongs to pierrepontite in magnesium tourmalineiron tourmaline series. FeO/(FeO+MgO)ratio of 0.70-0.89 is similar to the feature of Li-poor  granite. The Al-Al₅₀Fe₅₀ -Al₅₀Mg₅₀ diagram and the Fe-Mg-Ca diagram spots are also locating in lean Li-poor granite area. TiO₂-MnO/CaO-MgO/FeO diagram indicates the tourmaline is as type Ⅰ, in which MgO content is synchronous ebb and flow with FeO, and the tourmaline has low Mg and high Fe content. But MnO is opposed to TiO₂ in content, which represent same implication as FeO/(FeO+ MgO)ratio in tourmaline. It indicates the tourmaline in PGST is hydrothermal genesis during post-magmatic stage of acid intrusion with the features of geology mineralogy and mineral chemistry.

Key words: tourmaline, peraluminous granite, mineral chemistry, genesis, south Tibet