【作者】 陈丹敏；

【导师】 冯乔；

【作者基本信息】 山东科技大学 ， 矿产普查与勘探， 2009， 硕士

【摘要】 研究区构造现象复杂、特征各异,中生代的构造属性及其演化不同学者认识有别,尤其是对晚三叠世的构造属性尚存较大分歧。本文在广泛收集前人资料基础上,对研究区平凉、陇县的等地进行了野外剖面观测,在此基础上重点分析了大量该区的钻井资料,结合锆石和重矿物等测试分析资料,从区域地球动力学背景和盆地耦合的思路入手,对鄂尔多斯盆地西南缘的构造特征及其对沉积的控制演化进行详细分析。由于受三叠纪末晚印支运动弱挤压的影响,研究西部和南部边缘晚三叠世地层翘倾抬升并遭受剥蚀;越向边缘,抬升幅度越大,地层缺失越多,与上覆侏罗系为微角度不整合接触。研究中部和东北部,地壳主要表现为垂直隆升,河流下切侵蚀,形成许多河谷、边坡、河堤,侏罗纪早期为填平补齐的沉积,上三叠统与侏罗系之间为平行不整合或侵蚀不整合接触。本研究区的物源具有多样性,及包括前震旦纪的变质岩和火山岩,也有加里东和海西期的火山岩和变质岩,其中以前者来源为主。这些岩石主要分布在中祁连构造带和北祁连构造带中。自长8到长6再到长3稳定重矿物锆石和白钛石及电气石的含量在增加,而不稳定重矿物石榴石的含量明显减少。自盆地边部向盆地内部不稳定的矿物石榴子石含量在逐渐减少,而稳定重矿物锆石含量增加。物源可能主要来自盆地西南方向祁连一西秦岭造山带。研究区沉积体系以辫状河和辫状河三角洲沉积体系为主。辫状河沉积主要发育在层序1(长10)的早期,而且主要分布在研究区西南边部,分布范围有限;而辫状河三角洲沉积是研究区的主要沉积类型,靠近研究区西南部以辫状河三角洲平原沉积为主,而且三角洲平原主要以分流河道垂向加积为主,砂体厚度大。靠近研究区中部以辫状河三角洲前缘沉积为主,三角洲前缘主要以水下分流河道和分流间湾沉积为主,砂体厚度与三角洲平原相比较薄;在层序3(主要是长7—长6)靠近湖盆中心大量发育浊积砂体沉积。更多还原

【Abstract】 Phenomena of structure in the southwest edge of the Ordos Basin is complicated with different chatacteristics.To different scholars,their views about the structure attribute and the evolution in Mesozoic of this region are not the same,espicially in the structure attribute in late Triassic.In this paper,on the basis of wildly collecting the imformation about this region and observating the field profiles of Pingliang and Longxian,the author utmost analysised the logging data,with the test data about Zircon and other heavy minerals,then analysised the structure features of the southwest edge of Ordos Basin and its effection on controling the evolution of deposition from the background of regional geodynamics and the ideas of coupling basin.Affecting the weak extrusion bu the Indo-Chinese Movement in late Triassic,formation of late Triassic in the edge of southern and western area Alice dumping uplifted,suffered form dendation with the Jurassic formations overlying by micro-perpective unconformity.The more reached the edge,its uplifted range is larger and the formation missed more.In the central and eastern part of the study area,eatth crust uplifted vertically,rivers down incised and eroded, forming many valleies、slopes and embankments.In early Jurassic,it deposited with filled and level up.The.contact relationships between upper Triassic and Jurassic was parallel unconformity or erosion unconformity.The source of this region are diversity,including metarmorphic rocks and volcanic rocks in Pre-Sinian、Caledonian and Hercynian.That came form Pre-Sinian was the main source. This rocks mainly distributed on the middle and the north of Qilian Tectonic Belt.From Chang 8 to Chang 6 to Chang 3,the contention of the stability heavy minerals,such as Zircon、Titanium white stone and Tourmaline,was increased,but the conten of Garnet-one kind of heavy minerals was significantly reduced fome the edge of the basin to the center.The source main major came from the orogeny belt of Qilian and Qinling-west,which direction is in the southwest of the study area.The main sedimentary system of this region was braid river and braid river delta sedimentary system.Braid river sediment mainly developed in sequence one,its distribution was limited on the southwest of the study region.While braid river delta sediment was the main deposition type in this region.Next to the southwest part it mainly deposited the braid river delta plain sediments which vertical aggradated with distributary channel,and the sand body was very thick.Braid river delta front deposition was distributed on the central part of the study area.The braid river delta front was maily deposited two kind of sedments,the subaqueous distributary channel sediment and inter-bay sediment.The sand body was thicker than that of delta plain.In sequence 3(maily developed in Chang 6 to Chang 7) which next to the center of the basin,the turbidite sediment had a great development.更多还原