磷对过铝质岩浆液相线温度影响的实验研究

Experimental study of effect of phosphorous on liquidus temperature of peraluminous magmatic system

以宜春414岩体中的钠长花岗岩作为实验初始物,利用"RQV-快速内冷淬火"高温高压装置实验研究了100MPa压力、含5%H2O条件下,P对过铝质花岗岩液相线温度的影响。实验结果表明,碱性长石是最早结晶的矿物;随着体系中P2O5含量从0.27%增加到7.71%,液相线温度从最初的810℃降低到740℃,表明P有效地降低了过铝质岩浆体系的液相线温度。在过铝质岩浆体系中,P5+与Al3+的结合形成AlPO4,降低了熔体中碱性长石组分的活度,很可能是液相线温度降低的机制。

The effect of phosphorous on liquidus temperature of peraluminous granite was experimentally studied in rapid-quenched cold ＋ sealed vessels （RQV） at 100 MPa in this paper. The albite granite of Yichun stock was closed as the initial composition for experiments with 5% H2O. The experimental result shows that alkali feldspar is the initial liquidus crystalline phase. Phosphorus can effectively reduce the liquidus temperature of the peraluminous magrnatie systems. With increasing phosphorus content in melt from 0. 27% to 7.71% P2O5, the liquidus temperature of the granite decreases from 810 ℃ to 740 ℃. The depression of the activity of alkali feldspar-forming components by the association of P^5＋ with Al^3＋ in the melt is a probable mechanism for the reduction of the liquidus temperature of peraluminous magmatic system.