【摘要】：伊犁盆地位于西天山造山帶西南緣,侏羅系發(fā)育一套巨厚的陸源碎屑沉積巖,它記錄了西天山的造山作用與伊犁盆地的沉積充填演化歷史。對(duì)該套碎屑巖物源的系統(tǒng)研究可以清楚揭示西天山與伊犁盆地的盆山關(guān)系,為深入研究中生代中亞造山帶西段的成盆-成山作用提供借鑒。同時(shí),伊犁盆地是我國(guó)重要的砂巖型鈾礦富集盆地,侏羅系是其主要賦礦層位。針對(duì)砂巖型鈾礦的勘探,明確賦鈾砂體成因,查明碎屑物來(lái)源,進(jìn)而準(zhǔn)確評(píng)估蝕源區(qū)巖石供鈾能力具有極其重要的生產(chǎn)實(shí)踐意義。基于此,本論文依托對(duì)伊犁盆地南緣露頭的調(diào)查和典型剖面的精細(xì)測(cè)量,結(jié)合收集到的盆地內(nèi)鉆井巖心和測(cè)井資料,以沉積學(xué)、高分辨層序地層學(xué)、構(gòu)造地質(zhì)學(xué)、沉積地球化學(xué)等理論為指導(dǎo),通過(guò)大量的巖石薄片的鑒定、巖屑和穩(wěn)定輕礦物的統(tǒng)計(jì),并結(jié)合野外古流向的測(cè)量和室內(nèi)全巖元素地球化學(xué)、碎屑鋯石年代學(xué)及微量元素地球化學(xué)、陰極發(fā)光等多種測(cè)試手段,對(duì)伊犁盆地侏羅系碎屑巖巖石學(xué)特征、高分辨層序格架內(nèi)的古地理展布、碎屑物質(zhì)來(lái)源、碎屑巖物源區(qū)母巖成分及形成時(shí)大地構(gòu)造背景、盆地充填沉積特征與周緣造山帶耦合關(guān)系進(jìn)行了系統(tǒng)而深入的研究。伊犁盆地南緣侏羅系主要為中粗粒硅質(zhì)巖屑砂巖、中粗粒巖屑石英砂巖及雜砂巖,分選中等-較差,大多數(shù)顆粒磨圓度呈次圓狀-次菱角狀,顆粒間主要為雜基充填,部分砂巖為鈣質(zhì)膠結(jié),顆粒支撐,孔隙式膠結(jié)。碎屑顆粒中巖屑含量約占23-65%,石英約為32-74%,長(zhǎng)石含量約為2-10%。砂巖成分和結(jié)構(gòu)成熟度均較低,顯示其近物源堆積的特征。伊犁盆地南緣侏羅系砂巖中巖屑主要為硅質(zhì)巖巖屑、粉砂巖巖屑、泥巖巖屑,流紋巖、花崗巖等中酸性火成巖巖屑次之,另含少量石英巖巖屑;碎屑石英顆粒主要為單晶石英,大多數(shù)呈非波狀消光特征,多晶石英顆粒邊界呈平直線狀接觸,陰極發(fā)光顯示藍(lán)色或藍(lán)紫光;長(zhǎng)石含量少,且以來(lái)源于中酸性火山巖區(qū)的微斜長(zhǎng)石等鉀長(zhǎng)石為主,少見(jiàn)中基性斜長(zhǎng)石。碎屑顆粒組分特征表明物源區(qū)母巖來(lái)源于火山巖源區(qū),砂巖碎屑組分Dickinson圖解投點(diǎn)則顯示該套碎屑巖形成于再旋回造山帶環(huán)境,元素地球化學(xué)特征顯示其母巖為大陸島弧背景下長(zhǎng)英質(zhì)巖石,碎屑鋯石年代學(xué)特征表明八道灣組碎屑巖來(lái)源于早中二疊世和石炭紀(jì)的巖石,三工河組和西山窯組主要來(lái)自石炭紀(jì)巖石,且隨著時(shí)代越新,來(lái)自泥盆紀(jì)和志留紀(jì)物源貢獻(xiàn)越大,表明侏羅紀(jì)時(shí)期物源區(qū)剝蝕具有揭頂特征。據(jù)此可知,伊犁盆地侏羅紀(jì)碎屑來(lái)源于再旋回造山帶環(huán)境,物源區(qū)母巖主要形成于石炭紀(jì)大陸島弧環(huán)境下中酸性火山-沉積巖系。伊犁盆地南緣侏羅紀(jì)時(shí)期主要發(fā)育扇三角洲-湖泊-辮狀河三角洲-河流相沉積體系,其中八道灣組主要為扇三角洲沉積,三工河組主要為淺湖-半深湖沉積,西山窯組主要為辮狀河三角洲沉積,頭屯河組主要為河流相沉積。古植物葉片化石主要呈寬大平直特征,泥巖表現(xiàn)較強(qiáng)的Na、Ca和Sr虧損,且泥巖化學(xué)風(fēng)化指數(shù)值(CIA)高達(dá)85~91,表明侏羅紀(jì)碎屑巖沉積時(shí)期為溫暖、潮濕古氣候環(huán)境。自晚泥盆世末期到晚石炭世,受古南天山洋向北俯沖作用的影響,在伊犁-中天山地塊南緣發(fā)育大量大陸島弧環(huán)境火山巖。晚石炭世末期,伊犁-中天山地塊與塔里木地塊碰撞,南天山造山帶進(jìn)入后碰撞演化階段,并形成大量火山-碎屑巖。在早侏羅世早期,受盆地南緣快速隆升的影響,石炭紀(jì)-二疊紀(jì)火山-沉積巖地層被再次抬升遭受剝蝕,此時(shí)山體與盆地落差較大,坡度陡,粗粒碎屑物快速充填盆地,形成了八道灣組扇三角洲沉積;早侏羅世末期,湖盆迅速擴(kuò)張,湖平面上升,沉積物供給量不足,形成了三工河組湖泊相沉積;中侏羅世后,受前期山體不斷被剝蝕和盆地不斷被充填的雙重影響,山體與盆地相對(duì)高程差不斷減少,湖平面不斷萎縮,直至消失,形成了西山窯組辮狀河三角洲沉積和頭屯河組河流相沉積�？傊�,伊犁盆地南緣在侏羅紀(jì)沉積時(shí)期表現(xiàn)為明顯的填平補(bǔ)齊的準(zhǔn)平原化特征。
[Abstract]:The Yili basin is located in the southwestern margin of the western Tianshan orogenic belt. A set of thick terrigenous clastic sedimentary rocks developed in the Jurassic system, which records the orogeny of the western Tianshan Mountains and the history of sedimentary filling and evolution of the Yili basin. Meanwhile, Yili Basin is an important sandstone-type uranium enrichment basin in China, and Jurassic is its main ore-bearing horizon. It is very important to clarify the genesis of uranium-bearing sand bodies, ascertain the source of clastic materials and accurately evaluate the uranium-supplying capacity of rocks in the source area for sandstone-type uranium exploration. Based on the investigation of outcrop in the southern margin of Yili Basin and the fine measurement of typical section, the paper combines the collected drilling core and logging data in the basin, guided by the theories of sedimentology, high-resolution sequence stratigraphy, structural geology and sedimentary geochemistry, and identifies a large number of thin sections of rocks and rocks. Based on the statistics of clastic and stable light minerals, combined with field paleocurrent measurements and indoor whole-rock element geochemistry, detrital zircon chronology and trace element geochemistry, and cathodoluminescence measurements, the petrological characteristics of the Jurassic clastic rocks in the Yili Basin, paleogeographic distribution within the framework of high-resolution sequence, source of clastic materials, and clastic materials were studied. The compositions of parent rocks and the tectonic setting at the time of their formation, the coupling relationship between basin filling and sedimentary characteristics and the surrounding orogenic belts have been studied systematically and deeply. The clastic grains contain about 23-65% lithic debris, 32-74% quartz and 2-10% feldspar. The compositions and structures of the sandstones are low maturity, showing the characteristics of near provenance accumulation. The Jurassic sandstones in the southern margin of Yili Basin are sandstones. The intermediate debris is mainly siliceous, siltstone, mudstone, rhyolite, granite and other intermediate-acidic igneous rock debris, followed by a small amount of quartz rock debris; the detrital quartz particles are mainly monocrystalline quartz, most of them are non-wavy extinction characteristics, the boundary of polycrystalline quartz particles is flat linear contact, cathodoluminescence shows blue or blue violet. Light and feldspar content is low, and micro-plagioclase and other K-feldspar from intermediate-acidic volcanic rocks are dominant, but medium-basic plagioclase is rare. Characteristic of clastic grain composition indicates that source rocks originate from volcanic source area, while the Dickinson plot of sandstone clastic component shows that the clastic rocks were formed in the environment of recycle orogenic belt and the elements are geochemical. The clastic zircon chronology indicates that the clastic rocks of the Badaowan Formation originated from the Early-Middle Permian and Carboniferous rocks, and the Sangonghe Formation and Xishanyao Formation mainly originated from the Carboniferous rocks. With the development of the age, the contribution of the Devonian and Silurian provenances increased, indicating the Jurassic. It can be concluded that the Jurassic clastic rocks in Yili Basin originated from the environment of the recycling orogenic belt, and the parent rocks in the provenance area were mainly formed in the intermediate-acid volcanic-sedimentary rocks under the Carboniferous continental island arc environment. The fan delta-lake-braided River delta-fluvial facies were mainly developed in the southern margin of Yili Basin during the Jurassic. The Badaowan Formation is mainly fan-delta deposit, the Sangonghe Formation is mainly shallow-semi-deep Lake deposit, the Xishanyao Formation is mainly Braided River Delta deposit, and the Toutunhe Formation is mainly fluvial deposit. The values (CIA) are as high as 85-91, indicating that the Jurassic clastic rocks were deposited in a warm, humid paleoclimate. From the late Devonian to the Late Carboniferous, a large number of continental island-arc volcanic rocks were developed in the southern margin of the Ili-Zhongtianshan block due to the northward subduction of the Paleo-South Tianshan Ocean. In the early Early Jurassic, the Carboniferous-Permian volcanic-sedimentary strata were uplifted and eroded again under the influence of rapid uplift in the southern margin of the basin. At this time, the difference between the mountain and the basin was large, the slope was steep, and coarse-grained clastic materials filled the basin rapidly. The fan delta deposits of Badaowan Formation were formed; in the late Early Jurassic, the lake basin expanded rapidly, the lake level rose, and the sediment supply was insufficient, forming the lacustrine deposits of Sangonghe Formation; after the Middle Jurassic, the relative elevation difference between the mountain and the basin decreased and the lake level did not change because of the double effects of the erosion of the mountain body and the filling of the basin. The braided river delta deposits of Xishanyao Formation and fluvial deposits of Toutunhe Formation were formed by faulting and shrinking until disappearance.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：P619.14

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