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  本文關(guān)鍵詞： 賀蘭山 晚三疊世 物源分析 古構(gòu)造背景 物源時空演化　出處：《西北大學》2015年碩士論文　論文類型：學位論文

【摘要】：賀蘭山地區(qū)晚三疊世的物源來源以及時空演化規(guī)律,是恢復鄂爾多斯盆地西部北段原盆邊界,分析盆地內(nèi)沉積地層時空展布特征和沉積相演變規(guī)律的重要環(huán)節(jié),是客觀評價改造盆地油氣資源分布特征以及科學預測盆地有利勘探區(qū)塊的重要前提和基礎(chǔ)。賀蘭山地區(qū)處于多構(gòu)造單元的結(jié)合部位,經(jīng)歷了復雜的沉積構(gòu)造演化歷史,研究賀蘭山晚三疊世物源屬性必須要考慮這些因素的影響。通過對賀蘭山周邊構(gòu)造單元演化過程的系統(tǒng)分析,論文重點考慮了古亞洲洋閉合過程與勉略洋閉合過程對賀蘭山地區(qū)晚三疊世沉積演化的影響,并認為當時賀蘭山地區(qū)可能為被動拉張背景下的裂谷環(huán)境。此外,還重點考慮了晚侏羅世大地構(gòu)造運動以及新生代銀川地塹、河套盆地形成過程中對研究區(qū)晚三疊世地層的后期改造特征。結(jié)合賀蘭山地區(qū)的區(qū)域構(gòu)造背景和后期改造程度,運用地層變形恢復的方法,對研究區(qū)主要斷層的斷距以及小塊體的相對位置進行了恢復和復原,合理推斷了賀蘭山地區(qū)晚三疊世的沉積邊界范圍。論文主要運用古水流分析、礫石成分分析、地球化學、薄片鑒定、陰極發(fā)光以及重礦物組合分析等方法對研究區(qū)物源進行了綜合研究。認為賀蘭山晚三疊世的物源具有多源、混源以及上下層段時空演化差異性明顯的特點。晚三疊世的物源主要有西北部、西部和東部物源,并在汝箕溝-香棒子溝一帶發(fā)生混源。西北部物源主要為阿拉善地塊之上的前寒武紀變質(zhì)巖、古生代巖漿巖及沉積地層,西部南段地區(qū)可能與西部北段的物源巖性有較明顯不同；東部地區(qū)物源可能為鄂爾多斯地塊之上的古生代沉積地層。通過對延長組五個層段物源特征的對比研究,認為不同時期物源方向具有一定的差異。延長組一段、二段、三段主要物源來自西北部和西南部,這時賀蘭山盆地和鄂爾多斯盆地之間是連通,而且連通范圍較廣,到了延長組四段、五段時,在荒草灘及其以東地區(qū)開始明顯出現(xiàn)東部物源,此時賀蘭山盆地和鄂爾多斯盆地之間仍然是連通的,由于汝箕溝溝口東部地區(qū)已經(jīng)隆起,連通的范圍開始縮小,這幾個方向的物源在汝箕溝-香棒子溝一帶發(fā)生混源,之后沿著大水溝一帶流入鄂爾多斯盆地。結(jié)合區(qū)域構(gòu)造環(huán)境和鄰區(qū)的構(gòu)造特征,指出賀蘭山地區(qū)晚三疊世延長期的物源性質(zhì)在研究區(qū)的不同部位存在明顯差異,并嘗試性地建立了物源的時空演化模式。
[Abstract]:The provenance and spatiotemporal evolution of the late Triassic in Helanshan area is an important link in restoring the basin boundary in the northern part of the western Ordos basin and analyzing the temporal and spatial distribution characteristics of sedimentary strata and the evolution law of sedimentary facies in the basin. It is an important premise and foundation for objectively evaluating the distribution characteristics of oil and gas resources in the reformed basin and scientifically predicting favorable exploration blocks in the basin. The Helanshan area is located in the combination of multiple structural units. After a complicated history of sedimentary tectonic evolution, the influence of these factors must be considered in studying the provenance of late Triassic in Helan Mountain. The evolution process of tectonic units around Helan Mountain is systematically analyzed. The paper focuses on the influence of paleo-Asian ocean closure process and Mianluo ocean closure process on the sedimentary evolution of the late Triassic in Helanshan area, and considers that the Helanshan area at that time may be a rift environment in the passive extensional background. The late Jurassic geotectonic movement and the Cenozoic Yinchuan graben are also considered. In the process of formation of Hetao Basin, the late Triassic strata were reformed in the study area. Combined with the regional tectonic background and the degree of late transformation in Helanshan area, the method of formation deformation restoration was used. The fault spacing of the main faults and the relative position of the small blocks in the study area are restored and restored, and the sedimentary boundary range of the late Triassic in Helanshan area is reasonably inferred. The paleocurrent analysis is mainly used in this paper. Gravel composition analysis, geochemistry, sheet identification, cathodoluminescence and heavy mineral assemblage analysis were used to study the provenance of the studied area. It is considered that the late Triassic provenance of Helan Mountain has multiple sources. The main provenances of late Triassic are northwest, west and east. The main provenances in the northwest are Precambrian metamorphic rocks, Paleozoic magmatic rocks and sedimentary strata. The source lithology of the southern part of the west may be obviously different from that of the northern part of the west. The material source in the eastern area may be Paleozoic sedimentary strata above the Ordos block. Through the comparative study of the characteristics of the five layers of Yanchang formation, it is considered that there are some differences in the direction of provenance in different periods and one section in Yanchang formation. The main provenance of the third member is from the northwest and southwest. At this time, it is connected between the Helanshan basin and the Ordos basin, and has a wide range of connectivity, when the fourth and fifth member of the Yanchang formation. The eastern provenance began to appear in the wasteland and its east area, and the connection between Helanshan basin and Ordos basin was still connected at this time, because the eastern area of Rujigou gully mouth had been uplifted, the connected area began to shrink. These material sources are mixed in Rujigou and Xiangliangzigou, and then flow into Ordos basin along Dashuigou, combining with the regional tectonic environment and the structural characteristics of the adjacent area. It is pointed out that the provenance properties of the extension period of the late Triassic in Helanshan area are obviously different in different parts of the study area, and the spatio-temporal evolution model of the provenance has been established.
【學位授予單位】：西北大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P618.13

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