西藏松宗—八宿地区蚀变岩发育规律及工程分级研究
发布时间：2019-01-18 07:03
【摘要】：青藏高原是欧亚板块与印度板块碰撞挤压隆升而成,因此地质构造及岩浆活动复杂而强烈。又因青藏高原特殊的高海拔、高地应力、高地热和高昼夜温差影响,在岩浆活动强烈的区域,火成岩侵入围岩时形成了特殊而复杂的火成岩蚀变带。本文以西藏松宗～八宿地区的蚀变岩体为研究对象,针对蚀变岩的分布规律、组合特征、蚀变成因和力学性质展开了系统的研究,取得了如下成果：(1)对研究区内蚀变岩的资料进行分析,总结出主要的蚀变岩种类和空间分布特征；通过现场的调查和室内试验分析出蚀变岩的组合特征,得到调查区内花岗岩的侵入大致是沿着区域性大断裂发生,从平面上沿着断裂带走向呈带状分布。蚀变组合关系主要分为两种：一、古新世(E1)花岗岩侵入早石炭世(C1)砂岩；二、早白垩世(K1)花岗岩侵入中晚侏罗世(J2-3)砂岩。(2)查明了蚀变带内岩体的蚀变成因,调查区蚀变岩的矿物蚀变主要包括黑云母绿泥石化,斜长石绢云母化,微斜长石白云母化和石英晶体的重结晶作用。其中绿泥石交代黑云母在黑云母花岗闪长岩中比较常见；绢云母交代斜长石在黑云母花岗闪长岩和侏罗系变质砂岩中比较常见；白云母交代微斜长石主要发生在早白垩世的花岗岩中;石英的重结晶作用主要发生在热液作用下的侏罗系细砂岩和长石石英砂岩中。(3)根据岩石中石英和长石的含量将侏罗系砂岩蚀变带岩体中矿物间连接结构分为三种：石英—石英—石英结构(石英含量75%-90%,长石含量10%)；石英—长石—石英结构(石英含量40%-50%,长石含量25%-40%)；长石—石英—长石结构(石英含量400%,长石含量40%-60%)。(4)通过室内单轴压缩变形试验,得到了蚀变带内各岩体的力学参数。认为蚀变岩属于高压缩性、高强度的脆性变质岩类,岩体内部孔隙非常发育。采用岩块单轴抗压强度和割线模量两个指标将研究区内蚀变岩体强度分为三个等级：高强度岩体,单轴抗压强度100-200MPa,割线模量4.5～5.0×104MPa；中等强度岩体,单轴抗压强度在50～100MPa,割线模量2.5～4.5×104MPa；低强度岩体,单轴抗压强度在25-50MPa,割线模量1～2.5×104MPa。
[Abstract]:The Qinghai-Xizang Plateau is formed by collision and uplift of Eurasian plate and Indian plate, so geological structure and magmatic activity are complicated and strong. Because of the special high altitude, high ground stress, high geothermal and high diurnal temperature difference in the Qinghai-Tibet Plateau, the igneous rock formed a special and complex igneous rock alteration zone in the area with strong magmatic activity. In this paper, the altered rock mass in Songzong ~ Bashu area, Tibet is taken as the research object. The distribution law, assemblage characteristics, alteration cause and mechanical properties of the altered rock mass are systematically studied. The results are as follows: (1) the data of altered rocks in the study area are analyzed and the main types and spatial distribution characteristics of altered rocks are summarized. Based on the field investigation and laboratory tests, the authors analyze the assemblage characteristics of altered rocks. It is concluded that the granite intrusions in the investigation area occurred roughly along the large regional faults and distributed in a zonal pattern along the strike of the fault zone in the plane. Alteration assemblages are mainly divided into two types: first, the Paleocene (E1) granite intruded into the early Carboniferous (C1) sandstone; Second, the early Cretaceous (K1) granite intruded into the Middle and late Jurassic (J2-3) sandstone. (2) the causes of alteration of the altered rock mass in the altered zone were identified. The mineral alteration of the altered rocks in the investigation area mainly included biotite greenstone and plagioclase sericite. Microplagioclase Muscovite and recrystallization of quartz crystals. Chlorite metasomorphic biotite is common in biotite granodiorite, sericite metasomorphic plagioclase is common in biotite granodiorite and Jurassic metamorphic sandstone. Muscovite metasomorphic microplagioclase mainly occurred in early Cretaceous granite; The recrystallization of quartz mainly occurs in Jurassic fine sandstone and feldspar quartz sandstone under hydrothermal action. (3) according to the content of quartz and feldspar in the rock, the mineral connection structure in the Jurassic sandstone alteration zone is divided. There are three types: quartz-quartz structure (quartz content 75-90), Feldspar (10%); Quartz feldspar quartz structure (quartz content 40% -50%, feldspar 25% -40%); The mechanical parameters of each rock mass in the alteration zone were obtained by laboratory uniaxial compression deformation tests with feldspar quartz feldspar structure (quartz content 400 and feldspar content 40-60%). (4). It is considered that altered rocks belong to brittle metamorphic rocks with high compressibility and high strength, and the internal pores are very developed. According to the uniaxial compressive strength and Secant modulus of rock blocks, the strength of altered rock mass in the studied area is divided into three grades: high strength rock mass, uniaxial compressive strength 100-200MPa, Secant modulus 4.5mg 5.0 脳 104MPa; The uniaxial compressive strength of medium strength rock mass is 50 ~ 100MPa, the Secant modulus is 2.54.5 脳 104MPa, and the uniaxial compressive strength of low-strength rock mass is 25-50MPa, and the Secant modulus is 12.5 脳 104MPa.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.1;TU45
本文编号：2410451
[Abstract]:The Qinghai-Xizang Plateau is formed by collision and uplift of Eurasian plate and Indian plate, so geological structure and magmatic activity are complicated and strong. Because of the special high altitude, high ground stress, high geothermal and high diurnal temperature difference in the Qinghai-Tibet Plateau, the igneous rock formed a special and complex igneous rock alteration zone in the area with strong magmatic activity. In this paper, the altered rock mass in Songzong ~ Bashu area, Tibet is taken as the research object. The distribution law, assemblage characteristics, alteration cause and mechanical properties of the altered rock mass are systematically studied. The results are as follows: (1) the data of altered rocks in the study area are analyzed and the main types and spatial distribution characteristics of altered rocks are summarized. Based on the field investigation and laboratory tests, the authors analyze the assemblage characteristics of altered rocks. It is concluded that the granite intrusions in the investigation area occurred roughly along the large regional faults and distributed in a zonal pattern along the strike of the fault zone in the plane. Alteration assemblages are mainly divided into two types: first, the Paleocene (E1) granite intruded into the early Carboniferous (C1) sandstone; Second, the early Cretaceous (K1) granite intruded into the Middle and late Jurassic (J2-3) sandstone. (2) the causes of alteration of the altered rock mass in the altered zone were identified. The mineral alteration of the altered rocks in the investigation area mainly included biotite greenstone and plagioclase sericite. Microplagioclase Muscovite and recrystallization of quartz crystals. Chlorite metasomorphic biotite is common in biotite granodiorite, sericite metasomorphic plagioclase is common in biotite granodiorite and Jurassic metamorphic sandstone. Muscovite metasomorphic microplagioclase mainly occurred in early Cretaceous granite; The recrystallization of quartz mainly occurs in Jurassic fine sandstone and feldspar quartz sandstone under hydrothermal action. (3) according to the content of quartz and feldspar in the rock, the mineral connection structure in the Jurassic sandstone alteration zone is divided. There are three types: quartz-quartz structure (quartz content 75-90), Feldspar (10%); Quartz feldspar quartz structure (quartz content 40% -50%, feldspar 25% -40%); The mechanical parameters of each rock mass in the alteration zone were obtained by laboratory uniaxial compression deformation tests with feldspar quartz feldspar structure (quartz content 400 and feldspar content 40-60%). (4). It is considered that altered rocks belong to brittle metamorphic rocks with high compressibility and high strength, and the internal pores are very developed. According to the uniaxial compressive strength and Secant modulus of rock blocks, the strength of altered rock mass in the studied area is divided into three grades: high strength rock mass, uniaxial compressive strength 100-200MPa, Secant modulus 4.5mg 5.0 脳 104MPa; The uniaxial compressive strength of medium strength rock mass is 50 ~ 100MPa, the Secant modulus is 2.54.5 脳 104MPa, and the uniaxial compressive strength of low-strength rock mass is 25-50MPa, and the Secant modulus is 12.5 脳 104MPa.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.1;TU45
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