本文選題：華南　切入點(diǎn)：晚三疊世-早侏羅世　出處：《南京大學(xué)》2017年碩士論文

【摘要】：目前,華南早中生代構(gòu)造背景還存在很大爭議。粵東盆地位于華南東南緣,其盆地特征、地球化學(xué)數(shù)據(jù)、巖漿活動、砂巖碎屑組分、古地理演化等方面記錄了這一時期重要的地質(zhì)信息。本文以粵東盆地晚三疊世-早侏羅世碎屑沉積巖為研究對象,采用碎屑顆粒統(tǒng)計(jì)法、碎屑鋯石U-Pb年代學(xué)分析法、古地理分析法和地球化學(xué)分析法,并結(jié)合盆地演化、古水流數(shù)據(jù)和區(qū)域巖漿活動,探討華南晚三疊世-早侏羅世盆地物源及其構(gòu)造背景意義。在Q-F-L和Qm-F-L三角圖解上,晚三疊世-早侏羅世樣品基本投于陸塊物源區(qū),表明存在穩(wěn)定克拉通為其提供物源。測年結(jié)果顯示晚三疊世樣品存在七個峰值:231Ma、436 Ma、305 Ma、815Ma、1853 Ma、2067 Ma 和 2487 Ma,年齡跨度在206 Ma至2544 Ma之間;早侏羅世樣品存在八個峰值:196 Ma、247 Ma、320Ma、432 Ma、770Ma、1060Ma、1820Ma 和 2430 Ma,年齡跨度在 194Ma至3284 Ma之間。物源分析表明晚三疊世-早侏羅世粵東盆地物源主要來自盆地北側(cè)和東北側(cè)兩個方向,與東北側(cè)的永安盆地和北側(cè)的東坑盆地物源類似,與晚三疊世-早侏羅世古水流方向吻合。晚三疊世-早侏羅世華南東南部發(fā)生了兩次規(guī)模較大的海侵,在華南東部形成一系列海陸過渡相含煤盆地。古地理分析結(jié)果顯示晚三疊世-早侏羅世粵東盆地為N-E向展布。由閩西至粵東地區(qū)和由湘東南至粵東地區(qū),碎屑粒度在空間上展示出由粗變細(xì)的特征,表明物源來自盆地東北部和北部地區(qū),與碎屑鋯石U-Pb年代學(xué)分析結(jié)果一致。在La-Th-Sc和Th-Sc-Zr/10構(gòu)造背景判別圖上,晚三疊世-早侏羅世樣品大都落于大陸島弧或活動型大陸邊緣區(qū)域,表明晚三疊世-早侏羅世華南已經(jīng)受到了古太平洋板塊俯沖的影響。巖相特征、盆地物源、古地理演化和地球化學(xué)數(shù)據(jù)綜合分析顯示晚三疊世-早侏羅世華南東南部盆地盡管還是以穩(wěn)定的克拉通邊緣盆地為特征,但是古太平洋板塊向華南更東側(cè)俯沖已經(jīng)開始為其提供物源,表明晚三疊世-早侏羅世華南隸屬于太平洋構(gòu)造域。
[Abstract]:At present, the early Mesozoic tectonic background in South China is still very controversial. The eastern Guangdong basin is located in the southeastern margin of South China. Its basin features, geochemical data, magmatic activity, sandstone clastic components, etc. The important geological information of this period was recorded in paleogeographic evolution. The late Triassic-early Jurassic clastic sedimentary rocks in the eastern Guangdong Basin were studied in this paper. The clastic grain statistics method and the U-Pb chronological analysis of detrital zircon were used in this paper. Paleogeographic analysis and geochemical analysis, combined with basin evolution, paleocurrent data and regional magma activity, discuss the provenance and tectonic background of the late Triassic-early Jurassic basin in South China. The late Triassic-early Jurassic samples were basically deposited in the source area of the continental block, indicating the existence of stable cratons as the source of their provenances. The dating results show that the samples of the late Triassic have seven peaks: 231 Ma-436 Ma-305 Ma-815Ma-1853 Ma-2067 Ma and 2487 Ma, with ages ranging from 206Ma to 2544 Ma. The early Jurassic samples have eight peaks: 196Ma-247Ma-247Ma-320Ma-432 Ma-770Ma-1060Ma-1820Ma and 2430 Ma-ages ranging from 194Ma to 3284 Ma. The provenance analysis shows that the provenance of the East Guangdong Basin in the late Triassic and early Jurassic mainly came from the north and northeast sides of the basin. It is similar to the Yongan basin on the northeast side and the Dongkeng basin on the north side, and coincides with the paleocurrent direction of the late Triassic to early Jurassic. Two large-scale transgressions occurred in the southeast of South China from the late Triassic to the early Jurassic. A series of transitional facies coal-bearing basins were formed in the eastern part of South China. Paleogeographic analysis showed that the late Triassic-Early Jurassic Guangdong Basin was N-E distributed, from the west of Fujian to the east of Guangdong, and from the southeast of Hunan to the eastern part of Guangdong. The grain size of the clastic grain shows the feature of coarse thinning in space, which indicates that the source came from the northeast and northern parts of the basin, which is consistent with the result of U-Pb chronological analysis of the detrital zircon. On the discriminant diagram of La-Th-Sc and Th-Sc-Zr/10 tectonic background, The samples of late Triassic-early Jurassic are mostly located in the continental island arc or active continental margin, indicating that the late Triassic-early Jurassic South China has been affected by the subduction of the paleo-Pacific plate. The comprehensive analysis of paleogeographic evolution and geochemical data shows that the late Triassic to early Jurassic southeastern South China basins are still characterized by stable cratonic margin basins. However, the subduction of the paleo-Pacific plate to the east of South China has begun to provide its provenance, indicating that South China from late Triassic to early Jurassic belongs to the Pacific tectonic domain.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P534.5;P548

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