晋蒙交界孔兹岩系熔体参与变质反应的结构特征及其动力学意义

Textural Characteristics and Dynamic Significance of Metamorphic Reaction Involving Melt in Khondalite Series on the Border of Shanxi and Inner Mongolia

晋蒙交界孔兹岩系变质反应结构与矿物相转变机制研究结果表明，在麻粒岩相变质及其与之相伴随的重熔作用过程中，存在一类特殊的有熔体参与的变质反应，即未熔矿物与熔体之间的反应。结合天然块状岩石高温高压实验，确定研究区孔兹岩系熔体参与变质反应如下：①２Ｇｔ＋（９ＳｉＯ２＋４Ａｌ２Ｏ３）熔体＝３Ｃｒｄ；②Ｇｔ＋（２ＳｉＯ２＋２Ａｌ２Ｏ３）熔体＝Ｓｐ＋Ｃｒｄ；③２Ｇｔ＋（３ＳｉＯ２）熔体＝２Ｏｐｘ＋Ｃｒｄ；④１４Ｇｔ＋（２５ＳｉＯ２＋４Ｈ２Ｏ）熔体＝４Ｃｕｍ＋７Ｃｒｄ。这类熔体参与变质反应不仅受控于温压条件，而且与寄主岩石脱水熔融、长英质矿物部分熔融存在密切成因关系。该项理论与实验研究对于深化变质反应理论、探讨孔兹岩系矿物相转变成因机制及其动力学过程有着重要的意义。

The widespread Archean khondalite series is distributed on the margin of Shanxi and Inner Mongolia. According to the characteristics of metamorphic reaction textures and mineral phases transformation in khondalite series, the metamorphic reaction involving melt (reaction between unmelted minerals and melt) is one of the most important reactions in granulite facies metamorphism and its attendant remelting besides the traditional solid+solid phase (or fluid phase) reaction and dehydration reaction. With high temperature and pressure experimental results on natural block rock, the following metamorphic reactions involving melt have been determined in the khondalite series of the studied region: ①2Gt+(9SiO 2+4Al 2O 3) Melt = 3Crd; ②Gt+(2SiO 2+2Al 2O 3) Melt = Sp+Crd; ③2Gt+(3SiO 2) Melt = 2Opx+Crd; ④14Gt+(25SiO 2+4H 2O) Melt = 4Cum+7Crd. These reactions involving melt are not only controlled by PT conditions, but also genetically associated with dehydration melting, partial melting of felsic minerals in host rocks. These theoretical and experimental results have important significance for an in depth study on the feature of metamorphic reaction and the genetic mechanism of mineral phases transformation in granulite facies metamorphism of khondalite series.