【作者】 黄喜峰；

【导师】 钱壮志；

【作者基本信息】 长安大学 ， 矿产普查与勘探， 2009， 博士

【摘要】 贺兰山地区地处我国北方东、西部不同大地构造单元的枢纽地区，是我国北方构造、地貌以及各种地球物理的分界带，也是我国逆冲推覆构造较为发育的地区之一。因其独特的地质构造特征和构造作用而为地质学者所重视。不同学者对贺兰裂谷、推覆滑脱构造、祁连造山带与贺兰裂谷边界等存在不同的理论和认识分歧，特别是贺兰山地区的显生宙具何种构造特征的研究比较缺乏。本次研究基于地质大调查项目《银川市幅、吉兰泰幅1：25万区域地质调查》对贺兰山地区的显生宙构造格局及演化进行了重点解剖和研究，取得了大量野外实际材料和科研数据。论文从野外构造特征、岩石建造进行调研分析，结合岩石地球化学数据，对贺兰山地区的推覆构造和滑脱构造研究、早古生代贺兰裂谷作用、贺兰山构造格局与演化及祁连造山带与贺兰“冷”裂谷界线等方面取得了新的认识。野外的地质观测及室内研究表明，贺兰山地区在构造属性上与陆间或陆缘造山带明显区别，属于陆内(大陆板内)造山带。其主体部分，尤其是在祁连造山带与华北板块分界线的北侧，清晰地保存和展现了华北板块的地壳结构，显示了史密斯地层区的建造特点，与典型的板内造山带有强烈构造变形及岩浆活动差异。大量野外地质事实显示贺兰山地区逆冲推覆构造较为发育，并反映为贺兰构造带显生宙多个构造演化阶段(加里东、印支、燕山、喜马拉雅期)的构造变形，其动力学机制与中祁连-柴达木陆块与华北陆块间、特提斯海(洋)以及印度板块与欧亚板块间碰撞挤压构造远程效应相关，并对其形成的楔顶效应进行了有意义的力学机理补充。汝箕沟滑脱褶皱属典型的侏罗山式构造，其滑脱构造底板断层具有单层和双层结构模式，论文对其形成机理进行了研讨，这也是贺兰构造带滑脱断层的典型结构。研究区中南段“米”字形构造是贺兰山-六盘山两大逆冲构造系统双重作用之下，经过加里东期-喜马拉雅期等多期构造演化过程的叠加，即“米”字形构造是不同演化阶段的线性断裂叠加的结果。本次研究确认了贺兰山地区在地质构造演化历史中裂谷作用是存在的，其沉积建造记录所在就是米钵山组。该裂谷的时限为早奥陶世牯牛潭期至中奥陶世庙坡期，其构造属性为被动型“冷”裂谷。依据陆架和陆坡转换地带、前陆盆地及边界断裂分析，并结合地球物理资料，本文认为土井子-青铜峡断裂代表了祁连造山带与华北板块界线。围沟井断裂南侧的上泥盆统地层标志祁连褶皱系影响范围的北东部边界。依据沉积建造和构造变形特征，贺兰山显生宙区域构造演化可以划分为陆内“冷”裂谷-陆缘盆地、隆升夷平、陆盆坳陷-陆表海、板内变形(伸展-挤压)和盆岭构造五个阶段，进而探讨了各演化阶段的构造格局、变形特征及相应的构造-岩浆事件，特别是对板内变形阶段(J-K)、盆岭构造阶段(E-Q)和“冷”裂谷阶段的研究和认识也是本文的主要新进展所在。同时论文还分析了研究区显生宙构造格局下矿产资源分布规律及大战场一带的成矿远景。依据最新的小松山杂岩体岩石地球化学数据分析，在加里东构造旋回中期，贺兰山北段处于拉张环境。更多还原

【Abstract】 Helan Mountain is located at the nodal region of geotectonic element of East and West China, where is the tectonic, geomorphic and also geophysical boundary in North China and also one of the region that thrusting nappes is well developed. Even attention has been paid to it for its special characteristics of geological structure and tectonism, the viewpoints about the Helan rift, thrusting nappe structure, orogenic belt of Qilian Mountains and the boundary of Helan-Mountains rift, have not reached to a consistent understanding, especially lacking the Phanerozoic structural characteristics of Helan Mountains. Supported by the project of "1:250000 regional geological survey of Yinchuan map and Jilantai map ", we obtained more understanding from field and also fundamental data to focus on the tectonic framework and evolution of Helan mountain in phanerozoic period.Here based on new dataset from aspects of field structure characteristics, rock formations and geochemical data, new light has been reached on thrust nappe structure in Helan Moutains, Helan rift effect in Early Palaeozoic, tectonic framework and evolution of Helan Moutains, the boundary of Qilian Orogenic Belt and Helan cold rift.Our geological survey showed that Helan moutain belongs to the intra-plate orogenic belt, which is obviously different from that of marginal or intercontinental orogen. Its main body remains the crustal structure of North China plate, showing remarkable Smith stratigraphic characteristics, especially in the north part of the boundary between Qilian Orogenic Belt and North China plate. This is different from the typical intra-plate orogenic belt with strong tectonic deformation and magmatic activity.Our geological survey further proved that the thrusting nappe structures are relatively well developed in Helan Mountains, reflecting multiple phases of the tectonic evolution and deformation of the Caledonian, Indo-Chinese, Yanshanian and Himalayan periods during Phanerozoic era. The dynamic mechanism is related to the remote effect of collision tectonics between Mid-Qilian - Qaidam continental block with North China block, and between Tethys Sea and Indian plate with Eurasian plate. Here our results contribute to the remote effect.The Rujigou detachment fold is the typical Jura-type structure; and its floor fault has one or two layers structure, which is typical structure of detachment fault in Helan-Mountains tectonic belt. The Mi-zi Type tectonics in the south-middle part of the studied area experiences double effects from thrusting nappe systems of Helanshan Mountains-Lioupanshan Mountains, and superposition of multi-stage tectonic evolutions from Caledonian period to Himalayan period. That is, the Mi-zi Type tectonics, is the superposition of linear fractures in different evolution stages.Our study confirmed the existence of Helan Mountain rift, the record of sedimentary formation is Miboshan Group, and its tectonic pattern can be regarded as the passive mode of cold rift, and its timing can be stricted from Guniutan period of Early Ordovician to Miaopo period of Middle Ordovician.According to the analysis of continental shelf, continental slope transfer zone, foreland basin and boundary faults, and also with respects to th geophysical data, it is suggested that Tujingzi-Qingtongxia Fault could be regarded as the boundary belt of Qilian Orogenic Belt and North China block, the Upper Devonian series on the south side of Weigoujing Fault marks the northeast boundary of Qilian fold system.Based on the characteristics of sedimentary formation and tectonic deformation, the regional tectonic evolution of Helan Mountains in Phanerozoic can be divided into five stages: intra-plate cold rift-continental margin basin, uplifting and planation, depression of continental basin-epicontinental sea, intraplate deformation (extension-compression) and basin-range structure. In this thesis the tectonic framework, deformation features and corresponding tectonic-magmatic event of each evolution stage has also been studied. Especially, progress are made in new understanding on the stages of intraplate deformation (J-K) ,basin-range structure (E-Q) and cold rift. Meanwhile, the analysis and summary of distribution of mineral resources in the studied area by the control of tectonic framework of Phanerozoiceon and sedimentary formation are also presented in this thesis.更多还原