叶巴滩水电站坝址区“砂糖状”挤压破碎带蚀变矿物岩石学特征及成因分析

发布时间：2018-12-27 13:36

【摘要】：受区域构造作用影响,欧亚板块与印度板块间三江构造带内,广泛发育的挤压破碎带,已成为制约我国大型水电站建设和运营的主要工程地质问题。深入研究金沙江叶巴滩水电站坝址区“砂糖状”挤压破碎带的基本特征、类型及形成原因,为进一步评价“砂糖状”挤压破碎带岩体质量及可利用性奠定基础。基于野外调查、扫描电镜(SEM)、X射线粉晶衍射(XRD)和地球化学测试等方法,揭示“砂糖状”挤压破碎带的宏观地质特征与蚀变矿物岩石学特征,划分蚀变类型,探讨“砂糖状”挤压破碎带的控制因素与演化过程。研究表明:(1)“砂糖状”挤压破碎带集中位于2790~2850m范围,随高程变化规律不明显;左岸“砂糖状”挤压破碎带分布范围广、数量多,右岸“砂糖状”挤压破碎带集中发育在常规风化卸荷带,微新岩体中较少揭露此类特殊的地质现象,水平和垂向分布范围均小于左岸;“砂糖状”挤压破碎带发育深度具有随切割深度、坡形转折程度增大而加深的规律。(2)“砂糖状”挤压破碎带大多继承早期构造节理形成,力学特性呈剪性;“砂糖状”挤压破碎带总体呈弱透水性,在局部构造或裂隙密集带透水性会增强;中高程的透水率往往比低高程透水率大,具有随埋深的增大,透水率逐渐减少的规律。(3)观察石英形貌特征可得坝址区“砂糖状”挤压破碎带中,石英形貌结构有贝壳状、次贝壳状、桔皮状、苔藓状和虫蛀状5种类型;左岸石英颗粒经历的溶蚀时间、溶蚀结构的复杂程度大致与高程呈正相关;强弱卸荷带以里的“砂糖状”挤压破碎带中石英颗粒表面具有粘滑的应力痕迹;“砂糖状”挤压破碎带错动主要发生在中更新世~晚更新世。(4)坝址区蚀变是多期次的,蚀变产物形成的阶段不同,温度变化幅度大,与围岩接触的动力流体为富镁铁的氧化流体;“砂糖状”挤压破碎带内岩石富铝贫碱,这与斜长石的大量分解,浅色云母等新生矿物的形成有关;同一平硐中主量元素的变化表明,断裂构造对主量元素的重新分配具有明显控制作用。(5)结合蚀变作用的叠加,根据蚀变温度、破碎带宽度、破碎带内物质的颜色、风化状态以及地下水作用,将“砂糖状”挤压破碎带划分为轻微蚀变型、中等蚀变型、强烈蚀变型;不同蚀变类型是高温型~低温型动力构造蚀变与次生风化蚀变的不同组合叠加构成。(6)坝址区特有的岩性、地质构造与岩体结构条件为“砂糖状”挤压破碎带的形成提供物质和结构基础;河谷的快速下切造成岸坡岩体内部高应变能强烈释放,边坡岩体向临空方向发生卸荷回弹,形成“砂糖状”挤压破碎带,并产生构造动力蚀变,与围岩接触的动力热流温度由高到低,形成轻微蚀变型和中等蚀变型;经后期地下水的改造作用,局部风化加剧,带内叠加形成次生风化蚀变。
[Abstract]:Under the influence of regional tectonics, the compressional fracture zone, which is widely developed in the Sanjiang tectonic belt between Eurasian plate and Indian plate, has become the main engineering geological problem restricting the construction and operation of large hydropower stations in China. The basic characteristics, types and causes of the "sucrose" crush fracture zone in the dam site of Yipatan Hydropower Station on the Jinsha River are studied in depth, which lays a foundation for further evaluation of the quality and availability of the rock mass in the "Sugar" crush fracture zone. Based on field investigation, scanning electron microscope (SEM), X) ray powder diffraction (XRD) and geochemical measurement, the macroscopic geological characteristics and altered mineral petrological characteristics of the "Sugar" crush fracture zone are revealed, and the alteration types are classified. The controlling factors and evolution process of sugary crush zone are discussed. The results show that: (1) the "sugary" crushing zone is located in the range of 2790 ~ 2850 m, and the rule of variation with elevation is not obvious; On the left bank, the "Sugar" crush fracture zone has a wide distribution range and a large number. On the right bank, the "Sugar shaped" crush crushing zone is concentrated in the conventional weathering and unloading zone, and the special geological phenomena are seldom revealed in the micro-new rock mass. The horizontal and vertical distribution range is smaller than the left bank; The depth of development of "Sugar" crush fracture zone has the law of deepening with cutting depth and slope turning degree. (2) most of "Sugar" crush fracture zone inherits early structural joints, and its mechanical properties are shearing; The "sugary" crushing zone is weak permeable in general, and will be enhanced in local structure or fissured dense zone. The permeability of medium elevation is usually higher than that of low elevation, and the permeability decreases gradually with the increase of buried depth. (3) observing the morphology characteristics of quartz, we can find that the structure of quartz is shell-like in the "sugary" crush crushing zone of dam site area. There are 5 types of secondary shell, orange peel, moss and insect moths; The dissolution time of quartz particles on the left bank and the complexity of the dissolution structure are positively correlated with the elevation, and the surface of quartz particles in the "sugary" crush crushing zone in the strong and weak unloading zone has visco-slip stress trace. The dislocation of the "Sugar" crush fracture zone mainly occurred in the Middle Pleistocene to the late Pleistocene. (4) the alteration in the dam site is multistage, and the alteration products are formed at different stages and the temperature varies greatly. The dynamic fluid in contact with the surrounding rock is the oxidized fluid rich in magnesium and iron; The rock is rich in aluminum and alkali in the "sugary" crushing zone, which is related to the decomposition of plagioclase and the formation of new minerals such as light-colored mica. The variation of the principal elements in the same adit shows that the fault structure has obvious control over the redistribution of the principal elements. (5) combined with the superposition of the alteration, according to the alteration temperature, the width of the broken zone and the color of the material in the broken zone, In the weathering state and the effect of groundwater, the "sugary" crush fracture zone is divided into slight alteration type, moderate alteration type and strong alteration type. Different alteration types are composed of different combinations of high-temperature and low-temperature dynamic structural alteration and secondary weathering alteration. (6) the specific lithology of the dam site. Geological structure and rock mass structure conditions provide material and structural basis for the formation of "sugary" crush fracture zone. The rapid downcutting of the valley results in the strong release of high strain energy in the slope rock mass, and the unloading and rebound of the slope rock mass towards the sky, forming a "sugary" crush crushing zone and producing structural dynamic alteration. The temperature of the dynamic heat flux in contact with the surrounding rock changes from high to low, resulting in slight and moderate alteration. Local weathering intensifies during the late stage of groundwater transformation, and secondary weathering alteration is formed when the zone is superimposed.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV221.2

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