南极拉斯曼丘陵高级区假蓝宝石及有关矿物组合的形成过程

通过对南极拉斯曼丘陵含假蓝宝石矿物及有关组合的研究，得知假蓝宝石的成分以富镁、铁、铝但贫硅为特征，其粒间及粒内成分的变化均较为明显，这种变化主要表现为以钙契尔马克代换(Mg, Fe) + Si = 2Al为主的类质同象置换。在形成假蓝宝石的高级变质-深熔作用过程中，岩石矿物组合的变化主要是多阶段变质造成的，如浅-暗色组分发生了分离，其中含镁铁组分多的矿物较早结晶，而镁铁组分的分离使得相对富Fe的矿物较早结晶，即晚期形成的镁铁质矿物更富Mg组分，并形成递进演化的不同阶段的组合。假蓝宝石的出现与组分的活动有关，而不仅仅是由岩石成分决定的。变质矿物组合的多次递进演化，反映了活动组分的不断变化，以及体系组分相当程度的开放性。含假蓝宝石的变质岩石之原岩未必是富镁泥质岩。本区假蓝宝石成分的多变性主要是环境成分而不是pT变化所引起的，假蓝宝石形成于840~880℃，并没有达到超高温（>1 000℃）的条件，其形成与高级变质-深熔作用过程中组分渗透和扩散的共同作用有关。

Formation Process of Sapphirine and Related Mineral Association in the High-grade Region of the Larsemann Hills, East Antarctica

Study of sapphirine and related mineral association in the high-grade region of the Larsemann Hills, East Antarctica, shows that sapphirine of the area is characterized by its magesio, iron-and aluminum-rich, but silico-poor feature, and the substantial intra-and intergrain changes in compositions. The change is mainly manifested by the Tschermark substitution (Mg, Fe) + Si = 2Al. In the high-grade metamorphism and anatexis process, in which sapphirine was formed, the multistage crystallization of minerals resulted in the complexity of the mineral association, such as the differentiation of leuco-and melano-components. Generally, the mafic-rich minerals formed earlier, and the differentiation of magnesio-and iron-components is responsible for the earlier presence of iron rich minerals, i.e., magnesio-rich minerals crystallized later, thus the successive associations of multistage occurred. The rock composition is an important but not the only critical factor for the occurrence of sapphirine. It is the mobilization of components that accounts for the formation of sapphirine. The multistage evolution of mineral association to some degree reflects the changing composition and opening of the setting. It can therefore, be deduced that the protolith from which sapphirine was derived is not necessarily magnesio rich pelite. The heterogeneity of sapphirine in composition is related to the composition changes of the settings, not to the changes in pT condition. Sapphirine was formed at 840-880℃, not at the ultrahigh temperature condition（>1000℃）previously thought. Its formation is thought to be related both to the filtration and diffusion processes during high grade metamorphism and anatexis.