Ｔａ、Ｎｂ花岗岩是一种含黄玉和萤石的锂（白）云母钠长花岗岩，它的主要矿物与含Ｆ矿物之间的平衡关系是理解其岩石成因的关键。本文进行的有关反应热力学计算表明：在等温等压下（６００℃，１ｋｂ），含Ｆ花岗岩体系中斜长石牌号随共存流体中ｆＨＦ增高而减小，高ｆＨＦ体系只能形成钠质斜长石或钠长石；在含Ｆ花岗岩体系中，白云母的温压稳定域相对无Ｆ体系增大，使得白云母可以在富Ｆ低熔花岗岩的固相线之上形成。这些结果解释了Ｔａ、Ｎｂ花岗岩中钠长石、锂（白）云母岩浆成因的可能性 Ta, Nb granite is a kind of lithium (Ba) mica sodium granite with topaz and fluorite. The balance between its major minerals and F minerals is the key to understand its rock genesis. The thermodynamic calculations in this paper show that plagioclase grades decrease with increasing fHF in the co-existent fluids at isothermal isobaric (600 ℃, 1kb) Rock or albite. In the F-containing granite system, the temperature-pressure stable region of muscovite increases relative to the non-F system so that muscovite can form on the solidus of F-rich low-grade granite. These results explain the possibility of the genesis of albite and lithium (white) mica in Ta and Nb granites