【作者】 张鹏飞；

【导师】 陈世悦；

【作者基本信息】 中国石油大学 ， 矿物学、岩石学、矿床学， 2009， 博士

【摘要】 本论文定位于中国南方海相油气勘探的基础性地质研究。在对前人相关研究成果充分调研的前提下,以野外露头剖面为主要基础资料,以沉积学、构造地质学为理论指导,通过野外地质调查、镜下薄片鉴定、地球化学分析测试和岩相古地理编图等技术手段,对中扬子地区古生代地层进行了系统的沉积学、构造古地理学研究,明确了中扬子地区古生代的构造古地理格局及其演化历程,针对研究区争议较大的加里东期华南盆地属性和雪峰造山带属性两大问题,由相关证据入手阐明了本论文自己的观点。中扬子地区古生代地层中发育3大相组、15种沉积相类型。分别为陆相组的风化残积相、冲积扇相和河流相;海陆过渡相组的三角洲相和河口湾相;海相组的碎屑岩潮坪相、碎屑岩无障壁海岸相、缓坡型碳酸盐岩台地相、镶边型碳酸盐岩台地相、碳酸盐岩台盆相、碎屑岩-碳酸盐岩混积台地相、碎屑岩-碳酸盐岩混积陆棚相、浅海局限盆地相、欠补偿型盆地相和补偿型浊积岩盆地相。中扬子地区古生代构造古地理演化可以划分为3大阶段,分别为早寒武世-早奥陶世扬子陆内海盆稳定沉降阶段、中奥陶世-志留纪的挤压隆升阶段和晚古生代加里东运动后海浸盆地阶段。早寒武世-早奥陶世研究区总体古地理格局为西北高、东南低,该时期中上扬子大型镶边碳酸盐岩台地沉积体系占据了主导地位。中奥陶世-志留纪研究区古地理格局发生重大变革,黔中隆起、江南-雪峰隆起、华夏隆起相继隆升,晚奥陶世五峰期黑色页岩为代表的浅海局限盆地沉积和志留系碎屑岩潮坪沉积为该时期的典型沉积相类型,中晚志留世中扬子全区都隆升为陆。泥盆纪-二叠纪为加里东运动后的新型海浸盆地演化阶段,海浸是沉积相展布的重要控制机制,形成了陆源区周缘高能碎屑岩滨海、低能碎屑岩潮坪与碳酸盐岩台地、台盆在横向上过渡的沉积古地理格局。针对加里东期华南盆地的属性问题,本论文最终研究成果表明加里东期扬子地块与华夏地块已经拼贴为一体,该时期华南盆地为一个陆内坳陷海盆,加里东期不存在分隔扬子与华夏两大地块的华南洋盆。得出该结论的证据主要有两方面:①湘桂赣地区加里东期花岗岩体呈面状展布,且地球化学测试结果表明为壳源S型花岗岩,这些特征与洋壳消亡形成的花岗岩体无论在分布特征还是在地球化学特征上都有显著的差别;②湘桂赣地区加里东期地层的沉积古地理特征研究表明在目前多数人公认的扬子与华夏的缝合带,即江绍断裂带两侧的加里东期沉积物不存在两大古地理体系的截然跳相现象,而是表现为两侧沉积相带的指状交叉、过渡或呈现为完全相同、统一的岩相古地理单元。针对“雪峰古陆”的属性问题,通过对雪峰地区加里东期、印支期和燕山期不整合面属性分布规律的研究表明,雪峰造山运动的强度由南东向北西逐渐减弱,影响的范围从加里东期到燕山期逐渐向北西扩展。雪峰及其周缘地区的地层沉积特征则表明,震旦纪-白垩纪雪峰地区经历了复杂的隆凹变迁历程,可概括为五大阶段,分别为早震旦世-中奥陶世的碳酸盐斜坡-陆棚-盆地阶段、晚奥陶世-晚石炭世的隆起剥蚀阶段、二叠纪的碳酸盐岩台地阶段、早三叠世的碳酸盐陆棚阶段和中三叠世-白垩纪的隆起-陆相山间盆地阶段。结合上述加里东期华南不存在洋陆碰撞事件的结论,可以看出以元古界出露区为标志的“雪峰古陆”事实上并非古陆,而是一个经历了多期陆内造山事件的复合叠加陆内造山带。更多还原

【Abstract】 This paper is devoted to the basic geologic research on the marine oil and gas exploration in south China.In this paper, on the basis of the summary of previous research, using lots of outcrop section as the foundation data, based on the theory of sedimentology and tectonics, combining field geologic survey, microscope section analysis, geochemical detection, and lithofacies palaeogeographic map, pattern and evolution of tectono-palaeogeography is studied systematically. Besides, the two questions tectonic attribute of South China Basin in the Caledonian period and Xuefeng Orogen are discussed on basis of dependent evidence.3 facies groups and 15 kinds of sedimentary facies are recognized in the Palaeozoic strata in Middle Yangtze Region, including weathering residual facies, alluvial fan facies and fluvial facies in continental facies group; delta facies and estuarine facies in transitional facies group; clastic tidal flat facies, clastic non-barrier shore facies, ramp carbonate platform facies, rimmed carbonate platform facies, carbonate platform-basin facies, mixed platform facies, mixed continental shelf facies, offshore closed basin facies, undercompensation basin facies, turbidite basin facies in marine facies group. Evolution of Paleozoic tectono-palaeogeography is divided into three stages, including stable subsidence of intracontinental sea basin in Early Cambrian-Early Ordovician, compressional uplifting in Middle Ordovician-Silurian, transgressive basin after Caledonian orogeny in Neopaleozolc. The palaeotopography declined gradually form northwest to southeast in Early Cambrian-Early Ordovician, large scale rimmed carbonate platform sedimentary system hold leading position. The paleogeograhpical framework experienced great transformation in Middle Ordovician-Silurian. Qianzhong Uplift, Jiangnan-Xuefeng Uplift and Cathaysia uplifted successively. Blackshale of offshore closed basin facies of Wufeng formation in late Ordovician and clastic tidal flat deposition are typical facies during this stage, the Middle and Upper Yangtze Region uplifted in Middle-late Silurian. Transgression is major controlling mechanism of distribution of facies in Devonian-Permian, clastic offshore facies, clastic tidal flat facies changed each other with carbonate platform and carbonate shelf.In view of tectonic attribution of South China Basin in Caledonian stage, dependent evidence suggested that Yangtze Block and Cathaysia Block had matched in Caledonian stage; South China Basin is not ocean basin which segregated two blocks, but intracontinental sea basin. This evidence chiefly include two sides, firtly Caledonian granites in Hunan, Guangxi and Jiangxi assume planar distribution, and their element of geochemical detection suggested that they are compatible with the characteristics of crustal derived S-type granites, they are significantly different compared with granites forming in collision zone of oceancrust to continental crust. Secondly the sedimentary characteristics of Caledonian strata in Hunan, Guangxi, Jiangxi suggested that there is not discontinuity of facies on both sides of Jiangshan-Shaoxing Fault Zone, which is considered to be Caledonian suture zone of Yangtze Block and Cathaysia Block, but the interdigitation, continuity of facies or assuming the united paleogeographic unit.In view of tectonic attribution of Xuefeng ancient land, distribution of Caledonian, Indo-China and Yanshanian uncomformable surface suggested that intensity of orogenesis in Xuefeng area descended gradually form southeast to northwest, influence region spread gradually towards northwest from Caledonian to Indo-Chinese epoch. The sedimentary characteristics in Xuefeng area suggested that Xuefeng experienced complex vicissitudes of uplift-depression from Sinian to Cretaceous, it can be divided into five stages, including carbonate slope-shelf basin in Early Sinian-Middle Ordovician, uplifting and denuding in Late Ordovician-Late Carboniferous, carbonate platform in Permian, carbonate shelf in Early Triassic, uplift and intermountain basin in Middle Triassic-Cretaceous. Combining the above conclusion that there was not collision event of oceancrust to continental crust in Caledonian, we can draw a conclusion that Xuefeng ancient land which is marked by outcropped land of Proterozoic group is not an ancient land as a matter of fact, but a multipled, superimposed intracontinental orogen which experienced multiphasic intracontinental orogenic event.更多还原