【作者】 何耀宇；

【导师】 宋选民；

【作者基本信息】 太原理工大学 ， 采矿工程， 2016， 博士

【摘要】 磁组构作为一种快速、经济和无损性的岩石组构测量手段,在构造地质学等领域得到了广泛应用。以往对岩石磁组构的研究,大多停留在对岩石受力变形与磁组构关系的定性描述,或用于解决区域构造、变形演化等实际问题。探讨不同变形环境下,岩石压裂过程中磁组构对应力的响应特征仍然是当前磁组构理论研究的前沿核心问题之一。此外,山西太谷断裂带和韩城断裂带是汾渭地堑系中2条重要的边界控制断裂,该区域也是山西省重要的煤、铁、石膏等采矿工业聚集区。由于区域内缺乏有效的应变指示标志,系统的构造应力场研究较少,影响了采矿工程区域地应力场的精确构建。本文依托中国地震局地震动力学国家重点实验室与中国科学院地质与地球物理研究所古地磁与年代学实验室中的岩石力学、岩石磁学及古地磁学实验条件及设备,以火成岩为研究对象,在实验室进行了常温加载、常压变温、恒载变温与温压耦合作用下岩石磁组构对受力变形的响应特征研究。同时借鉴岩石变形破裂过程中电磁辐射机理的研究方法,进行了岩样的声发射实验,分析探讨了磁组构响应的细观机理。最后,基于岩石磁组构理论,结合野外填图过程中获得的地质构造资料与区域内地震震源机制解的应力张量反演,研究了山西太谷断裂带与韩城断裂带区域构造应力场的方向、分布及演化特征。本文主要得到以下研究结论:1)常温单轴加压过程中,随着载荷的不断增加,岩样的平均磁化率与磁化率各向异性度缓慢上升;形状因子明显升高;磁面理逐渐发育;磁化率椭球体由“铅笔型”向“扁球型”演化;磁化率椭球体最大轴和中间轴围绕最小轴快速旋转,在下半球等面积投影图中,最大轴投影向投影中心靠拢,而中间轴投影大致沿着相同方位趋于远离投影中心。2)常压变温条件下,随着温度的不断升高,在240℃以下岩样平均磁化率呈上升趋势,当温度达到240℃之后,平均磁化率总体转折下降;伴随温度的持续升高,磁化率各向异性度、形状因子、磁化率椭球主轴方位、及磁化率椭球体三个主轴的下半球等面积投影均未呈现规律性变化趋势。这表明岩石受热过程中往往存在伴随矿物的生成和转化,造成磁化率的升高或者降低;加热过程中的热作用和热蚀变在一定程度上弱化了岩石磁化率各向异性。温度对岩石磁组构的影响受其所含磁性矿物种类、含量、粒度、矿物优选方位及物化反应等共同作用的影响。3)温压耦合作用下,岩体力学特性劣化明显,内部结构变化更加剧烈,磁组构对岩样变形破坏的响应更为显著。岩石磁组构的变化主要受控于加载造成的形变,同时,载磁矿物种类的多样性,温度变化产生的热化学反应和热蚀变等因素使岩石磁组响应特征更加复杂化。4)韩城断裂带ne段邵家岭、渚北庄与上峪口3个剖面岩石磁学与磁组构特征研究揭示韩城断裂带ne段总体受控于nw-se向的拉张应力,兼有相对较弱的ne-sw向水平挤压应力作用。断裂带不同区域的应力作用存在一定的差异,上峪口与渚北庄受到的水平挤压应力相对较弱,邵家岭则表现出较强的挤压应力作用。5)太谷断裂带磁组构研究揭示该断裂带受控于NW-SE向的拉张应力,兼有相对较弱的NE-SW向水平挤压应力作用,与野外地质证据及发生在断层上的地震震源机制解吻合,也与基于震源机制解反演的应力张量结果、即原盆地及其附近区域的构造应力主要受控于NNW-SSE向的主张应力作用基本一致。与以往实验采用人工合成样品不同,本文以火成岩样品为研究对象,研究结果丰富了对磁组构理论的理解,为进一步研究岩石磁组构与应力之间的定量关系提供了参考;应用结果揭示了上述2个断裂带的区域构造应力场方向、分布及演化特征,为科学评价2个断裂带的活动性及周边工程区域地应力场提供依据。更多还原

【Abstract】 Magnetic fabric as a rapid,economical and nondestructive measurement method has been widely used in structural geology and other fields.However,the study in the past on the magnetic fabric of rocks mostly stayed on the qualitative description of the relationship between stress and deformation of rock and magnetic fabric,or used to solve practical problems such as regional structure,deformation and evolution.Under different deformation conditions,the response characteristics of the magnetic fabric in the process of rock fracturing is still one of the leading frontiers in the research of magnetic fabric theory.In addition,the Taigu and Hancheng fault zones located in the central and southern of Shanxi province is the two important boundary faults of the Fenwei graben system,where has a dense distribution of more coal,iron ore,gypsum ore mining engineering sites.Because of the lack of effective strain indicators,the systematical study on regional tectonic stress is less,which has affected the precise construction of in-situ stress field in mining engineering regions.Based on the advanced rock mechanics and magnetism test conditions andequipment in the State Key Laboratory of Earth Dynamics,Institute of Geology,China Earthquake Administration and Paleomagnetism and Geochronology Laboratory,Institute of Geology and Geophysics,Chinese Academy of Sciences,The igneous rocks,as the research object,were performed the experiments of rock magnetic fabric response to deformations under room temperature loading,atmospheric pressure heating,constant load heating and the coupling of temperature and pressure.At the same time,referred to the research method of rock deformation and failure process in the mechanism of electromagnetic radiation,the rock acoustic emission experiment was performed to discuss the microscopic mechanism of magnetic fabric variations.Finally,based on the theory of the rock magnetic fabric,combined with the stress tensor inversion of earthquake focal mechanism solutions and regional geological data obtained in the process of field mapping,we investigated the direction,distribution and evolution of regional tectonic stress field around the Taigu and Hancheng fault zones.The main conclusions of this study are as follows:1)In the uniaxial compression process at room temperature,as the increase of loading,the mean magnetic susceptibility and the degree of magnetic susceptibility anisotropy(AMS)increase slowly;the shape factor increases obviously;the magnetic foliation develops gradually;the magnetic susceptibility ellipsoid changes from the "pencil type" to "flat-ball type";the maximum and intermediate axis of magnetic susceptibility ellipsoid rotates rapidly around the minimum axis,and in the lower hemisphere equal area projection the maximumaxis moves closer to the center of projection,and the intermediate axis end away from the center of projection roughly.2)Under the atmospheric pressure heating condition and with temperature increasing,the mean magnetic susceptibility shows an upward trend below the temperature 240℃,but once the temperature reaching at 240℃,the mean magnetic susceptibility overall declines.At the same time,with the increase of temperature,the degree of AMS,shape factor,axis of magnetic susceptibility ellipsoid and their projections in the lower hemisphere equal area projection show no regularity change trend.This indicates that the generation and transformation of minerals is often accompanied in the process of rock heating,resulting in increase or decrease of magnetic susceptibility,and the heating and heat corrosion in the process of heating to a certain extent weakens the anisotropy of magnetic susceptibility of rocks.The effect of temperature on the magnetic fabric of rocks is influenced by the type of magnetic minerals,content,particle size,and the preferred orientation of minerals.3)Under the coupling of temperature and pressure,mechanical properties of rock mass deteriorate significantly,the internal structure change is more intense,and the response of magnetic fabric deformation and failure of rock is more significant.Deformation,change of magnetic fabric of rocks is mainly controlled by the load caused by the load.At the same time,the diversity of types of magnetic minerals,temperature changes produced by thermo-chemical reaction and thermal alteration factors such as the rock magnetic responsecharacteristics more complicated.4)The rock magnetism and magnetic fabric characteristics of the Shaojialing,Zhubeizhuang and Shangyukou three sites located at the NE section of Hancheng fault reveals that the NE section of Hancheng fault zone is mainly controlled by the NW-SE extension with the effect of a relatively weak NE-SW to the horizontal compressive stress.Certain differences in stress exist in different region.A relatively weak stress was observed at the sites of Shangyukou and Zhubeizhuang,while Shaojialing site shows strong extrusion stress.5)The magnetic fabric of Taigu fault zone revealed that the tensile stress of the fault zone is controlled by NW-SE,with relatively weak NE-SW trending horizontal compressional stress,which is consistent with the geological evidence,the earthquake focal mechanisms occurred nearby the fault zone,and also the stress tensor inversion based on the focal mechanism solutions.Different from previous experiments which used synthetic samples,in this paper the igneous rock samples were used as the research object.Our results enrich the understanding of the magnetic fabric theory and provide a reference for further research on the quantitative relationship between the rock magnetic fabric and stress.The application of the magnetic fabric method on the above two tectonic fault zones reveals the direction,distribution and evolution of the regional stress field,and the results contribute a scientific evaluation of the faultactivities and the in-siut stress field for the engineering sites and their surrounding areas.更多还原