部分熔融与高级变质岩流变机制——以内蒙古大青山高级变质岩为例

部分熔融作用与高级变质岩变形作用是相互制约,变形作用能够提高岩石部分熔融程度,降低熔融温度。熔体存在影响和制约岩石强度和变形机制。大青山高级岩经历了下部地壳构造层次变质变形和深熔作用改造,形成了复杂构造要素组合。宏观与微观构造特点表明:高级变质岩变形机制主要为熔体增强颗粒边界扩散和颗粒流动,使岩石发生大规模的塑性流动。在宏观上形成了不对称流动组构、熔融线理、岩石和矿物条带、层内底辟褶皱和大型穹窿构造。但是,在微观上矿物颗粒变形不明显,晶内变形组构不发育,表现为三边平衡结构,与静态结晶变质岩结构相似,形成了地壳深部构造层次上变质构造岩-构造片麻岩。

Partial melting and the rheologic mechanism of high-grade metamorphic rock-a case study on Daqingshan high-grade metamorphic rock in Inner Mongolia.

There is a restricted relationship between the partial melting and the deformation of high-grade metamorphic rock; the deformation enhances the degree of rock partial melting and decreases the partial melting temperature. Melt influences rock strength and deformation mechanism. The Daqingshan high-grade metamorphic rocks were modified by metamorphism, deformation and anatexite in the lower crust, and developed a complex assemblage of structural elements. The characteristics of macrostructures and microtectonics show that the main deformation mechanism of high-grade metamorphic rock is the melt-enhanced grain side diffusion and the grain flow, which caused a large scale plastic flow of rock. Some macrostructural elements, such as asymmetry flow folds, melted lineations, rock and mineral bands, intrastratal diapiric folds and a large dome, were formed in partially melted high-grade metamorphic rocks. The microfabrics features of rock are equilibrium textures of triple sides, similar to the metafabrics of rocks by static crystalline metamorphism; the deformation of mineral grain is not obvious and the intracrystalline deformation textures did not develop; the metamorphic tectonite of lower crustal tectonic level, the tectonic gneiss, was formed.