粤东盆地下中生界物源分析及其构造背景意义

发布时间：2018-03-25 09:33

本文选题：华南　切入点：晚三叠世-早侏罗世　出处：《南京大学》2017年硕士论文

【摘要】：目前,华南早中生代构造背景还存在很大争议。粤东盆地位于华南东南缘,其盆地特征、地球化学数据、岩浆活动、砂岩碎屑组分、古地理演化等方面记录了这一时期重要的地质信息。本文以粤东盆地晚三叠世-早侏罗世碎屑沉积岩为研究对象,采用碎屑颗粒统计法、碎屑锆石U-Pb年代学分析法、古地理分析法和地球化学分析法,并结合盆地演化、古水流数据和区域岩浆活动,探讨华南晚三叠世-早侏罗世盆地物源及其构造背景意义。在Q-F-L和Qm-F-L三角图解上,晚三叠世-早侏罗世样品基本投于陆块物源区,表明存在稳定克拉通为其提供物源。测年结果显示晚三叠世样品存在七个峰值:231Ma、436 Ma、305 Ma、815Ma、1853 Ma、2067 Ma 和 2487 Ma,年龄跨度在206 Ma至2544 Ma之间;早侏罗世样品存在八个峰值:196 Ma、247 Ma、320Ma、432 Ma、770Ma、1060Ma、1820Ma 和 2430 Ma,年龄跨度在 194Ma至3284 Ma之间。物源分析表明晚三叠世-早侏罗世粤东盆地物源主要来自盆地北侧和东北侧两个方向,与东北侧的永安盆地和北侧的东坑盆地物源类似,与晚三叠世-早侏罗世古水流方向吻合。晚三叠世-早侏罗世华南东南部发生了两次规模较大的海侵,在华南东部形成一系列海陆过渡相含煤盆地。古地理分析结果显示晚三叠世-早侏罗世粤东盆地为N-E向展布。由闽西至粤东地区和由湘东南至粤东地区,碎屑粒度在空间上展示出由粗变细的特征,表明物源来自盆地东北部和北部地区,与碎屑锆石U-Pb年代学分析结果一致。在La-Th-Sc和Th-Sc-Zr/10构造背景判别图上,晚三叠世-早侏罗世样品大都落于大陆岛弧或活动型大陆边缘区域,表明晚三叠世-早侏罗世华南已经受到了古太平洋板块俯冲的影响。岩相特征、盆地物源、古地理演化和地球化学数据综合分析显示晚三叠世-早侏罗世华南东南部盆地尽管还是以稳定的克拉通边缘盆地为特征,但是古太平洋板块向华南更东侧俯冲已经开始为其提供物源,表明晚三叠世-早侏罗世华南隶属于太平洋构造域。
[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.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P534.5;P548

【参考文献】