内蒙古大青山高级变质岩韧性剪切带及其流变机制

发布时间：2018-04-03 15:40

本文选题：大青山　切入点：高级变质岩　出处：《地球科学》2017年12期

【摘要】：大青山高级变质岩不仅记录华北克拉通早期大陆形成演化历史,也保留了中下部地壳岩石流变信息,它们经历了下部地壳构造层次高角闪岩相-麻粒岩相条件变质变形、深熔作用改造,形成了复杂构造样式和构造要素组合.韧性剪切带是高级变质岩中主要构造形迹,控制着早前寒武纪高级变质岩主体构造格架.依据野外地质产状、变形特征与构造要素叠加改造关系,韧性剪切带划分为早期近水平顺层伸展型和晚期陡倾韧性剪切带.近水平顺层伸展韧性剪切带呈残留状保留在后期变形改造较弱部位上,主要沿着不同地质单元或者岩性层界面上发育,是在伸展变形体制下形成的.晚期陡倾韧性剪切带呈近东西方向展布,规模较大,叠加和改造早期构造形迹,形成于晚期造山挤压构造环境中,以左行滑移为主.这两种韧性剪切带都形成于地壳中深部构造层次高角闪岩相-麻粒岩相条件下,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、条纹条带构造、熔融线理、层内流动褶皱等构造形迹,在微观上矿物晶体没有发生明显塑性变形,均匀消光,晶体为三边平衡结构,与静态变质结构相似,形成了地壳深部构造层次上变质构造岩-构造片麻岩.
[Abstract]:Daqingshan high grade metamorphic rocks not only recorded the early continental evolution history of North China Craton, but also retained the rheological information of middle and lower crustal rocks. They experienced the metamorphic deformation of high amphibolite facies and granulite facies in the lower crustal tectonics.The transformation of deep penetration resulted in the formation of complex structural styles and structural elements.The ductile shear zone is the main tectonic trace in the advanced metamorphic rocks, which controls the main tectonic framework of the early Precambrian high metamorphic rocks.According to the field geological occurrence, deformation characteristics and superposition and transformation of structural elements, the ductile shear zone can be divided into early extensional near water smooth layer and late steep dip ductile shear zone.The extensional ductile shear zone of the near water smooth layer is retained in the weaker part of the late deformation transformation and developed mainly along the interface of different geological units or lithologic layers and formed under the extensional deformation system.The late steep-dip ductile shear zone is distributed in the direction of east and west, and its scale is large. The superposition and reconstruction of the early tectonic trace were formed in the late orogenic compressional tectonic environment, with the left-line slip dominating.Both of these ductile shear zones were formed under the conditions of high amphibolite facies and granulite facies at the middle and deep tectonic levels of the crust. The deformation mechanism is mainly melt enhanced particle boundary diffusion and particle flow, resulting in large-scale plastic flow of rocks.On the macro level, there are asymmetrical flow fabric, stripe structure, melting line, flow fold in layer and so on. There is no obvious plastic deformation, uniform extinction and triangular-balanced structure in the microcosmic mineral crystal.Similar to the static metamorphic structure, metamorphic tectonite-tectonic gneiss was formed in the deep crustal structure.
【作者单位】：吉林大学地球科学学院;
【基金】：国家自然科学基金(Nos.41230206,41272223,41772212)
【分类号】：P588.3

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