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英云闪长质—奥长花岗质成分的高Na/K比的片麻岩在苏格兰和东格陵兰太古代高级变质区中占优势。片麻岩的成分从超镁铁质变化到奥长花岗岩,但成分的分布是双模式的,特别是在角闪岩相的片麻岩带中尤是如此。英云闪长质片麻岩的Al_2O_3偏高(平均大于15%),CaO也高,但SiO_2多数低于70％,而以小型奥长花岗岩体和脉体为例外。Ba和Sr的含量高,而Sr甚至在硅质片麻岩中仍居高位。在Y与SiO_2间和TiO_2与SiO_2之间显然存在着负相关。CeN/YN比值随SiO_2而增加,主要是较富硅质片麻岩中重稀土元素大大减低的结果,其比值可以超过100。然而有些奥长花岗质岩石中,稀土总量和Ce/Yb比值是较低的。虽然Eu异常之量与总稀土的含量有关,但许多硅质片麻岩具有显著正Eu异常,而有一些奥长花岗质岩石具不明显的负Eu异常。地球化学有力地表明,假如片麻岩成分范围与分离结晶作用有关,那么角闪石则已是一种主要控制矿物相,整个片麻岩杂岩可以在地壳深部高PH_2O条件下演化而来。然而包含着初源物质的角闪岩,特别是柘榴角闪岩的部分熔融模式,看来是最能解释地球化学特征和野外关系的。片麻杂岩的较深部分在地壳矿物相生成时或稍后,转化为干的麻粒岩相组合,可能相应有变化的流体成分(富CO_2)。驱逐含水流体要伴随着K、Rb、Th和U的丢失,从而增进了片麻岩杂岩的英云闪长质一奥长花岗质的特点。
The high Na / K ratio gneisses of the Yingyun dioritic-olivine granulosities dominate the Archean high-grade metamorphic zones in Scotland and East Greenland. The composition of gneisses changes from ultramafic to anorthogenic granite, but the compositional distribution is bimodal, especially in the gneisses of amphibolite facies. The Al 2 O 3 of the Ying-diorite gneisses is high (average more than 15%), CaO is also high, but the majority of SiO 2 is less than 70%, with the exception of small-scale granodiorites and veins. Ba and Sr are high, whereas Sr is still high even in siliceous gneiss. There is obviously a negative correlation between Y and SiO 2 and between TiO 2 and SiO 2. The CeN / YN ratio increases with SiO 2, mainly due to the greatly reduced heavy rare earth elements in the siliceous gneiss, which can exceed 100%. However, some of the dolomitic granites have a lower REE and Ce / Yb ratio. Although the amount of anomalies of Eu is related to the total RE content, many of the siliceous gneisses have significant positive Eu anomalies, whereas some of the granodiorites show negligible negative Eu anomalies. Geochemistry strongly suggests that amphibole is already a dominant mineral phase provided that the compositional range of gneiss is related to segregation and crystallization, and that the entire gneisse complex can evolve from the deep high pH 2O crust. However, the partial melting patterns of amphibolite, and especially gypsum amphibolite, which contain precursors, appear to best explain geochemical characteristics and field relationships. The deeper part of the gneiss is converted to a dry granulite assemblage at or after crustal mineral phase formation, possibly with varying fluid composition (CO 2 -rich). The expulsion of hydrous fluids accompanied by the loss of K, Rb, Th and U enhanced the characteristics of the Ying-diorite-magmatic granodiorite in the gneisses.