内蒙古狼山地区韧性剪切带构造特征研究

发布时间：2018-02-28 13:15

本文关键词： 狼山韧性剪切带宏微观构造地球化学　出处：《昆明理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：位于华北克拉通北缘西段的内蒙古狼山构造带,是研究华北板块与西伯利亚板块相互作用的重点地区,也是中国境内研究超大型矿床成矿作用的重要地区之一。狼山构造带内有着不同的构造形式,而韧性剪切带,是狼山构造带内主要的构造型式之一,是地壳深层次构造的反映。根据韧性剪切带内糜棱岩带的规律性分布,狼山构造带内可划分出三条规模较大的韧性剪切带和数条次级韧性剪切带。本论文在前人研究的基础上通过宏观构造与微观构造相互结合的方法,对狼山构造带内的三条主要韧性剪切带的几何学、运动学、动力学、地球化学、变形年代等方面进行了系统研究,取得了以下新的认识：1.通过韧性剪切带的几何学研究查明,狼山韧性剪切带内发育有不同类型的糜棱岩或构造片岩,糜棱岩面理产状平行于狼山山体走向,且糜棱岩面理中仅发育一组矿物拉伸线理,线理向NE或SW方向倾伏。2.通过对狼山韧性剪切带的宏观构造特征研究,发现狼山韧性剪切带内的糜棱岩中存在构造透镜体、旋转碎斑、Ω型鞘褶皱、石香肠等构造,且这些宏观构造均指示韧性剪切带的剪切指向以左行剪切为主。3.通过详细定向薄片的镜下观察,系统的对狼山韧性剪切带的显微构造特征进行了研究,发现狼山韧性剪切带的显微构造主要有核幔构造、石英的动态重结晶、波状消光、石英亚晶粒化或机械双晶、云母扭折带等构造。通过具有指示剪切方向的显微构造,如旋转碎斑系、不对称压力影、S-C组构、云母鱼等,指示了狼山韧性剪切带剪切方向以左行剪切为主,与野外确定的剪切方向一致。4.通过对狼山韧性剪切带的岩石组构分析,说明了狼山Ⅰ、Ⅱ号韧性剪切带在韧性剪切变形过程中,石英具有柱面滑移和底面滑移2种滑移机制,其中Ⅰ号韧性剪切带以高温柱面c滑移和中-高温柱面a滑移为主,Ⅱ号韧性剪切带具有中-高温柱面a和低温底面a滑移的特点,且该两条韧性剪切带石英组构特征所显示的剪切指向与野外及镜下确定的剪切方向基本一致,均为左行剪切。5.利用狼山韧性剪切带定向薄片的显微构造特征与应变间的关系,运用石英颗粒重结晶法和蠕变方程计算得到狼山韧性剪切带古差应力值为56-115mp,平均应变速率在10-13—10-14m/s。6.在地球化学方面,对狼山Ⅱ号韧性剪切带中具有明显塑性流变特征的硅质条带状灰岩进行了常量元素、微量元素和稀土元素的分析,分析结果表明不同变形强度的硅质条带状灰岩与原岩的成分存在着差异变化。条带状灰岩中的大多数常量元素和微量元素均为富集元素,随着变形程度的增加而带入,且各构造岩与原岩的稀土元素配分模式基本一致,也表明了稀土元素在剪切过程中具有一定的相对稳定性和同源性。7.对狼山韧性剪切带中Ⅱ、Ⅲ号剪切带进行了40Ar/39Ar测年,测试结果表明狼山Ⅱ、Ⅲ号韧性剪切带均形成于晚泥盆世末,说明了狼山构造带在晚泥盆世末到早石炭世发生了一次显著地构造活动。
[Abstract]:Located in the northern margin of the North China Craton of Inner Mongolia Langshan tectonic belt, is the study of the North China plate and the Siberia plate interaction in key areas, and it is also one of the important areas of research within the territory of Chinese deposits. Large super function of Langshan tectonic belt with different structure form, and the ductile shear zone, is one of the main tectonic types with Langshan structure that is a reflection of the deep crustal structure. According to the ductile shear zone in the mylonite zone distribution, Langshan tectonic belt can be divided into three large scale ductile shear zone and several secondary ductile shear zone. This paper on the basis of previous studies by means of macro structure and micro structure with each other, the Langshan tectonic belt in three major ductile shear zone geometry, kinematics, dynamics, geochemistry, makes a systematic research on the deformation in the aspects made by Under the new understanding: 1. through the study of geometry of the ductile shear zone identified Langshan ductile shear zones developed different types of mylonite or tectonic schist, mylonite foliations parallel to the strike Langshan Mountain, and the rnylonite foliation only developed a set of mineral stretching lineation, lineation to NE or SW direction of plunging.2. through the research on the macroscopic structural characteristics of Langshan ductile shear zone, mylonite are found in tectonic lens Langshan in the ductile shear zone, rotating porphyroclasts, Omega sheath fold, stone sausage structure, and the macro structure indicates shear ductile shear zone observation point to the left lateral shearing.3. with directional sheet under the microscope, on the microstructural characteristics of the ductile shear zone of Langshan Mountain was studied, found that the core mantle structure mainly Langshan microstructure of ductile shear zone, dynamic recrystallization of quartz, wavy extinction, quartz Sub grain or mechanical twinning, mica kink band structure. By having a microstructure indicating the shear direction, such as rotational porphyroclast, asymmetric pressure shadow, S-C fabric, mica fish, indicating the Langshan ductile shear to left lateral shear dominated with shear direction, shear direction and field determined by.4. agreement the rock group of Langshan ductile shear zone structure analysis shows that Langshan I, II ductile shear zone in the ductile shear deformation process, quartz has prismatic slip and the bottom surface of the 2 slip slip mechanism, the effect of ductile shear zone in high temperature and in - cylinder slip cylindrical C a slip characteristics, II the ductile shear zone with high temperature and low temperature a a cylindrical bottom slip, and the two ductile shear zone quartz fabric characteristics show the shear direction and determine the direction of shear field or under microscope are basically the same, are left shear by.5. The relationship between microstructure characteristics and strain of Langshan ductile shear zone between oriented thin sections, using quartz grain recrystallization method and the creep equation to calculate ancient Langshan ductile shear zone differential stress value is 56-115mp, the average strain rate of 10-13 - 10-14m/s.6. in geochemistry, obvious plastic rheological characteristics of No. 2 ductile shear mountain wolf with with siliceous banded limestone for analysis of major elements, trace elements and rare earth elements, the results showed that different deformation intensity of siliceous banded limestones and protolith composition differences change. Most major elements of banded limestone and trace elements are enriched with the elements, and to the increase of deformation degree, and rare earth elements in various tectonic rocks and rock distribution patterns are basically the same, also shows that the rare earth elements have a certain relative stability in the shearing process and homology .7. of Langshan ductile shear zone II, III shear bands were 40Ar/39Ar dating. The test results show that Langshan II, III ductile shear zone was formed in the late Devonian late that Langshan tectonic belt in Late Devonian to late Early Carboniferous had a significant tectonic activity.

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P542

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