摘要
鄂尔多斯盆地的发育时限为中晚三叠世—早白垩世,晚白垩世以来为盆地的后期改造时期;盆地主体具克拉通内盆地特征;现今盆地为经过多期不同形式改造的残留盆地。该盆地叠加在早、晚古生代大型盆地之上,又属多重叠合型盆地。鄂尔多斯盆地集油气、煤和铀于一盆,多种能源矿产丰富。根据盆地及周缘地区主要地质构造特征和地质事件,结合对盆地各区裂变径迹年龄的综合研究认为,在盆地发育时期(T2—K1)至少发生了4期明显的构造变动,将盆地的沉积-演化过程划分为4个阶段:中晚三叠世和早中侏罗世富县—延安期为盆地发育的两个鼎盛阶段,广泛接受沉积,湖盆宽阔,沉积范围为今残留盆地面积的2倍多;形成重要的含油和成煤岩系。这两个阶段被期间发生的区域抬升变动(J1)所分隔。抬升导致沉积间断,延长组顶部遭受强烈而不均匀的侵蚀下切,形成起伏较大的侵蚀地貌。延安期末盆地抬升变动不强烈,沉积间断和剥蚀延续时间短。随后又复沉降,进入盆地发育的第三阶段中侏罗世直罗-安定期:沉积范围仍较广阔,但湖区面积明显减小。晚侏罗世构造变动强烈,在盆地西缘形成逆冲-推覆构造带,在其东侧前渊局限堆积厚度不等的砾岩,盆地中东部地区遭受剥蚀改造;今黄河以西地区初显东隆西坳格局。在早白垩世阶段,沉积分布仍较广阔,不整合超覆在前期西缘冲断带和南、北边部隆起之上。在盆地演化的前三个阶段,沉积中心均分布在延安附近及其以东;而堆积中心则位于邻近物源的盆地西部,且不同阶段位置有别;直到早白垩世,盆地的沉积中心和堆积中心的分布位置才大体一致,主要位于盆地西部的中南段。早白垩世末,鄂尔多斯盆地整体抬升,大型盆地消亡;盆地开始进入后期改造时期。在晚白垩世以来的盆地后期改造时期,鄂尔多斯盆地主要发生了以下重要地质事件:1盆地主体持续幕式、差异性整体抬升和强烈而不均匀的剥蚀,东部黄河附近被剥蚀的中生界厚度最大可达2000m;2盆地本部长期幕式整体的差异抬升和剥蚀,形成3期区域侵蚀-夷平面(E32—E12,E23和N21);3地块边部裂陷,周缘断陷盆地相继形成,接受巨厚沉积;4持续达2亿多年的东隆西降运动于中新世晚期(8MaBP)反转易位;东部开始沉降,广泛接受红黏土沉积;六盘山、地块西缘和西部相继隆升;标志着中国西部区域构造运动对该区的影响更为重要;5分别在8MaBP和2.5MaBP,风成红黏土、黄土开始广泛堆积,先后形成红土准高原和黄土高原及黄土高原面;6黄河水系的发育、外流和侵蚀地貌的形成。根据各主要地质事件的发生和动力学环境的演变,将该区晚白垩世以来划分为5个演化阶段(K2—E1;E2-3;N1-21;N31—N2;Q)。这些地质事件的发生和构造变动,与周邻各构造域,特别是中国东、西部(含青藏高原)重大构造运动的复合、叠加及其与时彼此消长变化密切相关;其活动和改造,使中生代盆地的原始面貌大为改观。鄂尔多斯盆地多种能源矿产成生—成藏(矿)和定位的主要期次,与盆地中新生代演化和改造的阶段有明显的响应联系和密切的耦合关系。盆地演化末(晚)期及之后的整体差异隆升和区域剥蚀,对鄂尔多斯盆地多种能源矿产的成藏(矿)和分布及其相互作用的影响最为重要。
Ordos basin has developed during middle--late Triassic and early Cretaceous and has been reformed since late Cretaceous. It mainly possesses the characters of intra-craton and is a residual basin with multi-stage and different reformation. Ordos basin also belongs to multi-superimposed basin which overlapped on the early and late Paleozoic basins. Therefore, Multi-energy mineral deposits are abundant and petroleum, coal and uranium are beared in the same basin.
According to the the main geological structure features and geological events in Ordos baisn and peripheral areas, together with the comprehensional research of the fission track ages in various district of the basin, the paper concludes that there exists four evident stages of structural fluctuation at least during basin development and also four stages of evolution and sedimentation in the basin, middle--late Triassic and early--middle Jurassic Fuxian and Yan＇an stage is the two most prosperous stages during which the lake is broad and basin deposits extensively with an area over two times of that in present, the main oil and coal bearing strata develop. The two stages are divided by the regional early Jurassic uplift fluctuation, which causes interruption in deposition and development of the roughness of relief on the upper part of the Yanehang formation by reason of forceful and uneven cutting erosion. The uplift fluctuation is weak and the depositional interruption and erosion continuous time is short in the late Yan＇an stage. Then basin subsides and enters the third evolution stage of middle Jurassic Zhiluo--Anding stage in which sedimentary range is still broad and the lake area is minish in the basin. There happens strongly structural movement and develops the thrust-nappe belt in western margin of the basin in late Jurassic during which the different depth of conglomerate deposit in the foredeep part in the east side of the western margin, erosion reform occurs in the middle and east of the basin. The structural movement causes the form of structure framework of regional east uplift and west subside in the west area of Yellow river. Broad sediments unconformablely overlap on the west margin thrust belt and sideral uplift of the basin north and south at the early Cretaceous stage. Ordos basin uplifts wholely to disappear and enters the late reformation period. In the first three stages, the depocenters lie near or to the east of Yan＇an city, while deposit center in the west of the basin near provenance. The two centers differs in space in different stage. Until early Cretaeious, the location of sedimentary depocenters and accumulation center is nearly the same which is on the middle-south part of the west of the basin. There happen six major geological events in Ordos basin m late reformation perioa since late cretaceous. （1） The main part of the basin uplifts continuously, episodically and differently, which causes the strong and uneven erosion, for example, the max erosion depth in Mesozoic can be two thousand meters near Yellow river on the east. （2） This uplift forms two or three stages of regional erosion-planation surfaces with ages of E1^3-E2^1 E3^2 and N1^2. （3） The side of Ordos block subsides and the peripheral faulted basins form successively to deposit with heavy depth. （4） The regional east uplift and west subside movement continuing two bill years has been reversed which means the east subsides to widely deposit red clay and Liupianhshan, western margin of Ordos block and west part of basin uplift successively. The reverse event embodies the important influence of the regional structural movement of the west of China. （5） Aeolian red clay and loess begin to sediment broadly in 8Ma BPand 2. 5Ma BP, respectively. Also the red mud semi-plateau, loess plateau and loess plateau surface develop successively. （6） Drainage system of Yellow river grows and fluid outside to erode the side rock. According to the above major geological events and the evolution of dynamics environment, five evolution stages is divided since late Cretaceous in Ordos basin which are late Cretaceous to Paleocene, Eocene to Oligocene, Early--Middle Miocene, late Miocene to Plioeene and Quaternary. The happening of these geological events and structural fluctuation are closely related with the compound, superimpose, change with time and strongweak of major structural movement of peripheral structural domain especially that of the east and west of China. These activity and reformation change the Mesozoic prototype basin topography greatly. The main times and stages ot the occurrence and formation and reset of mlluple energy resources nave evident recall and decoupling relations with those of the Mesozoic and Cenozoic evolution and reformation in Ordos basin. The whole different uplift and regional erosion in and after the late of basin evolution own the important influence to the formation and distribution of the milti-mineral deposits and the eoaetion among them in Ordos basin.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2006年第5期617-638,共22页
Acta Geologica Sinica
基金
国家重点基础研究发展规划"973"项目(编号2003CB214600)
国家自然科学基金项目(编号40372096)
长江学者和创新团队发展计划(编号IRT0559)资助的成果。
关键词
鄂尔多斯盆地
盆地演化
原盆面貌
后期改造
裂陷盆地
隆降反转
沉积中心
堆积中心
侵蚀-夷平面
风尘红黏土-黄土
成藏(矿)响应
Ordos basin
basin evolution
prototype basin topography
late reformation
faulted basin
reverse of uplift and subside
depoeenter
accumulation center
erosion-planation surfaces
Aeolian red clay and loess
response to the formation of mineralization
