鄂尔多斯盆地东北部中侏罗世直罗—安定期原始沉积面貌及后期改造

【作者】 喻林；

【导师】 刘池阳；

【作者基本信息】 西北大学 ， 构造地质学， 2007， 硕士

【摘要】 鄂尔多斯盆地东北部直罗组-安定组受后期强烈而不均匀的剥蚀影响，盆地残留地层及东部的同期地层或剥蚀殆尽，或残缺不全。总体表现为西厚东薄，南厚北薄。在大量露头和钻测井资料分析的基础上，以旋回对比法为主，结合地区性标志层和岩性、颜色特征等，将直罗组划分为上下两段。通过露头和钻井沉积相分析、区域剖面对比并结合岩矿鉴定、粒度分析和地球化学等方法，在今盆地直罗、安定组识别出辫状河、曲流河、三角洲及湖泊等沉积体系类型。物源分析是判别盆地发育的人地构造背景、沉积相分布和原盆恢复的重要依据。通过野外实测古水流方向、镜下碎屑统计、重矿物分布、阴极发光特征和稀土、微量及主量元素物源判识等方法，对盆地东北部直罗-安定期物源进行综合分析，并认为研究区榆林以北直罗-安定组的物源土要来自北部隆起(包括河套)地区，源区主要岩性是前寒武的高级变质岩，同时印支-燕山期的花岗质的侵入岩也占了一定的比例。榆林以南除了受北部物源的控制，同时受研究区东部的火山岩源区的影响。通过以上研究区的物源分析、沉积相的平面展布以及沉积相的剖面演化恢复鄂尔多斯盆地东北部直罗-安定期地层的原始沉积面貌。在直罗-安定组原始沉积面貌恢复的基础上，进行后期改造的探讨。研究区地层在沉积之后，除了东隆西降和强烈而不均匀的剥蚀外，在晚侏罗世，研究区的北部还受到河套地区变质岩基底地层由北向南逆冲推覆，造成研究区地层在挤压作用下向物源区缩短变形。物源区提供的大量的高级变质岩岩屑和花岗质的岩屑，为东胜地区直罗组的铀矿富集提供了物质保障。同时，在研究区地层遭受后期改造的过程中，由于北部和东部抬升造成的东部地层整体剥蚀，为后期铀矿富集提供了一个外部有利的构造环境。更多还原

【Abstract】 Effected by the intensity and asymmetry deudation reconstructive later, the stratum distributing of Zhiluo-Anding period in Ordos Basin and the neighbour area’s synchronal stratum disintegrated entirety, or with parts missing partly. It shows thicker in the west and thin east entirety.Based on the analysis of great deal of outcrop and well logging data, take the cycle compare as the main method, combine to the regional marker bed and the characteristic of lithology and color, the Zhiluo group in headquarters of the basin is divided into upper and lower sections. Through the analysis of the well sedimentary faces, regional section compare, and combine to the other methods, such as lithology identify, grain size analysis and geochemical, such sedimentary system types as the braid river face, meandering river face, delta face, and lake face are been identified in Zhiluo-An’ding group of today’s basin.Provenance analysis is the important reference that background of geostructure, distribute of precipitation facies, primary basin resume. Through actual measurement the paleocurrent direction outdoors, optical mode statistics, heavy mineral distributed, athodeluminescence characteristic, rare earth, trait and principal quantum element analysis, use these means analyse the provenance of Zhiluo-Anding in Northeastern part of Ordos basin,and judged that the provenance come form the northern horseback in northern of Yulin and the mother rock is igh grade rock the Eozoic mmixture the granitic irruptive rock.Region of interest in southern of Yulin controlled by the northern provenance,and affected by volcanic provenance in eastern of region of interest.Through the provenance analysis, precipitation facies distributed on the plane and precipitation facies evolved on the plane section, resumed primary sedimentary features of Zhiluo-Anding in Northeastern part of Ordos basin.On base of resuming primary sedimentary features of Zhiluo-Anding,the late-reformations can be inquired. After the stratum deposited,the eastern uplift and the western subsidence,it suffered strong and unequal exfoliation.At Late Jurassic,the metamorphic rock basement stratum of Hetao area thrust-motion form north to south,it result that the stratum curtated and deformed to the provenance at the compression.The provenance supplied the abundant high grade rock cuttings and granitic cuttings,it offered material safegrardguarantee. Simultaneously,at the process of the stratum suffered late-reformations,the northern and the southern uplifted caused the eastern stratum exfoliated entirety,it offered favor structural setting for uranium deposits concentrated at later stage.更多还原