青海疏勒河地区奥陶系吾力沟组厘定及其构造意义

发布时间：2018-08-28 12:53

【摘要】：研究区位于青藏高原东北缘祁连山脉,主体属于中祁连陆块。本文以疏勒河地区出露的奥陶系吾力沟组为研究对象,通过野外路线调查、实测剖面,薄片鉴定,岩石地球化学分析及室内综合研究,厘定吾力沟组的地层特征和构造属性,为进一步探讨中南祁连构造属性及地质演化过程提供新的约束材料。论文取得的主要认识如下:1、疏勒河地区发育一套早古生代地层,地层由老到新分别是奥陶系吾力沟组(O1w)、盐池湾组(O2y)及志留系巴龙贡嘎尔组(Sb)。2、厘定出研究区吾力沟组主要为远洋硅泥质沉积和细复理石沉积,夹水下扇砾岩与玄武岩夹火山碎屑岩,垂向上由2个沉积-喷发旋回构成,硅质岩和紫红色硅泥质岩主要发育于下部旋回的底部,两个旋回的中部表现为复理石沉积夹水下扇砾岩;旋回的顶部为玄武岩、火山角砾岩、火山碎屑岩和灰岩、大理岩化灰岩。3、根据吾力沟组的发育位置、岩石组合与区域地质对比分析,推断吾力沟组的发育背景为盆地建造中稳定性与活动性交替变换,呈动荡环境。4、通过岩石地球化学分析,得出吾力沟组中基性火山岩属于钙碱性系列和高钾钙碱性系列。球粒陨石标准化稀土元素配分曲线总体变化规律一致,轻重稀土分馏特征较明显;基性火山岩的稀土总量高于中性火山岩稀土总量,且两者轻稀土元素较重稀土富集,呈现轻稀土元素富集的右倾曲线,无明显Eu异常。5、通过对吾力沟组火山岩大地构造环境的判别,分析出其形成环境为洋岛环境。
[Abstract]:The study area is located in the Qilian Mountains in the northeast margin of the Qinghai-Xizang Plateau and belongs to the Middle Qilian block. Taking the Ordovician Wuligou formation exposed in Shule River area as the research object, the stratigraphic characteristics and structural attributes of the Ordovician Wuligou formation are determined by field route investigation, measured profile, thin section identification, rock geochemistry analysis and laboratory comprehensive study. It provides a new constraint material for the further study of tectonic attributes and geological evolution process of Qilian in central and southern China. The main knowledge obtained in this paper is as follows: 1. A set of early Paleozoic strata developed in the Shule River area. The strata from Lao to Xin are Ordovician Wuligou formation (O1w), Yanchi Bay formation (O2y) and Silurian Baronggaer formation (Sb). 2. It is determined that the Wuligou formation in the study area is mainly oceanic siliceous muddy sedimentary and fine claystone deposit. The subaqueous fan conglomerate and basalt intercalate volcanic clastic rocks, which are composed of two sedimentary eruptive cycles vertically. The siliceous rocks and purplish red siliceous mudstones are mainly developed at the bottom of the lower cycle. The central part of the two cycles is represented by the flysch sedimentary intercalated underwater fan conglomerate, the top of the cycle is basalt, volcanic breccia, pyroclastic rock and limestone, marble limestone. 3, according to the development position of Wuligou formation, Rock assemblage and regional geological correlation analysis, it is inferred that the development background of Wuligou formation is the alternation of stability and activity in the formation of the basin, with a turbulent environment of .4.Through rock geochemistry analysis, It is concluded that the middle and basic volcanic rocks of Wuligou formation belong to calc-alkaline series and high-potassium calc-alkaline series. The distribution curve of standardized rare earth elements of chondrites is consistent, and the fractionation characteristics of light and light rare earth elements are obvious, the total amount of rare earth elements in basic volcanic rocks is higher than that in neutral volcanic rocks, and both light rare earth elements are enriched in heavy rare earths. There is no obvious Eu anomaly. 5. By discriminating the tectonic environment of volcanic rocks in Wuli Gou formation, it is found that the formation environment is an oceanic island environment.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P534.42

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