内蒙古大青山-乌拉山地区高级变质杂岩中的陡倾叶理带——造山作用的产物

    THE STEEP FOLIATION BELT IN THE HIGH-GRADE METAMORPHIC COMPLEX OF THE DAQINGSHAN-WULASHAN AREA, INNER MONGOLIA: Product of orogeny

    • 摘要: 内蒙古大青山-乌拉山地区的高级变质杂岩是华北克拉通北缘西段怀安-贺兰山麻粒岩相地体的一部分,以孔兹岩系的发育为特征.这些高级变质杂岩经历了十分复杂的变形变质作用改造,构造特征十分复杂.近年来的研究发现,近东西向陡倾叶理带是该区高级变质杂岩中保存完好的一种主要构造形式,规模巨大,以密集的近东西向陡倾叶理和直立褶皱的发育为特征,反映了地壳挤压收缩环境下的纯剪切变形,其上叠加了深构相右行走滑剪切带.陡倾叶理带形成于角闪岩相-角闪麻粒岩相构造环境中,叠加在早期近水平顺层滑脱变形和穹形构造之上,是古元古代末期叠加造山作用的产物.

       

      Abstract: The high-grade metamorphic complex in Daqingshan-Wulashan area, Inner Mongolia is a part of Huai'an Helanshan terrain of granulite facies, which lies in the western segment of the north margin of North China craton. The complex, characterized by well developed khondalite series, is seriously metamorphosed and deformed with complicated structures. Study shows that the E-W-trending steep foliation belt (ETSFB) is one of the major structural patterns, which is well-preserved in the complex. The large-scaled ETSFB is characterized by well-developed E-W-trending steep-dipping foliations and sub-vertical folds, suggesting pure shearing under the condition of crust contraction. The ETSFB, superimposed by dextral shear belts of deep structural phase, is formed in the tectonic environment of amphibole phase to amphibole-granulite phase during late Paleoproterozoic orogenesis, overprinting on the early sub-horizontal bedding detachment and dome structures.

       

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