岩浆熔体中的挥发性组分及其岩石学意义

文章论述了挥发性组分在岩浆熔体中的溶解行为及其在岩浆熔体中溶解的限制条件，在此基础上讨论了挥发性组分对岩浆演化及岩石学成因方面的意义：溶解在岩浆中的水可明显地改变矿物从岩浆中结晶出的顺序，改变岩浆熔体的演化轨迹。含水玄武岩浆在其早期结晶出铁的氧化物并与Ｓｉ和富碱质组分分异从而使其成为Ｆｅ亏损的钙－碱性系列的岩浆，而无水玄武岩浆演化的早期不能结晶出磁铁矿，因而演化成富Ｆｅ且具中等Ｓｉ含量的拉斑玄武岩系列。溶解于岩浆中Ｈ２Ｏ的离解将产生高ｆＯ２环境，从而导致Ｆｅ的氧化物在岩浆演化早期沉淀。

VOLATILE IN MAGMA AND ITS PETROLOGIC SIGNIFICANCE

The solution and states of volatile in magma, as well as the constraints on the solubility of H 2O in melts, are discussed in this paper. The significance of volatile for magma evolution and its petrogenesis is considered. H 2O dissolved in magma can influence the crystallization consequence and the evolution trace of melts. For water contained basalt magma, iron oxides crystallize early and separate from SiO 2 and alkali rich components, which convert basalt magma to Fe deficient calc alkaline magma, but to more H 2O basalt magma, magnetite can not precipitate in early stage, so it evolves to be Fe rich, medium Si content tholeiite. The decomposition of H 2O in magma results in high f O 2 environment, under which iron oxides precipitated early in the magma evolution.