【作者】 孙连浦；

【导师】 周祖翼；

【作者基本信息】 同济大学 ， 海洋地质， 2005， 博士

【摘要】 系统观引入地球科学研究的一个重要方面就是造山带与相邻沉积盆地的耦合研究。将盆山之间物质转移作为切入点进行盆山之间耦合关系的研究，成为近些年来大陆动力学研究的热点。物源分析除了告诉我们盆地沉积充填历史以外，还能告诉我们源区的一系列构造演化信息，因此成为盆山耦合研究中非常重要的手段。大别造山带以其独特而罕见的高压—超高压变质相带的连续分布而成为国内外地学界关注的焦点。大别造山带与相邻的合肥盆地研究的一个新的课题就是如何将大别造山带的演化进程与合肥盆地形成机制以及盆地充填特征有机的联系起来。本文在上述学术背景指导下，结合研究区工作现状，开展了多角度的研究工作，取得的主要认识如下：1．大别山造山带的构造单元划分及物质组成大别造山带从北向南可分为北淮阳弧后复理石带、北大别弧杂岩带、南大别碰撞杂岩带(高压变质带)、宿松变质杂岩带。分划这4个构造单元的是信阳—舒城断裂、磨子潭—晓天断裂、水吼—英山断裂(剪切带)、太湖—马庙断裂(剪切带)及襄樊—广济断裂。从东到西，商麻断裂将大别造山带分为大别地块和红安地块。2．合肥盆地前中生代基底特征、断裂特征及中生代构造单元划分合肥盆地基底纵向上具双层结构，分为晚太古代—早元古代深变质岩系和晚元古代—晚古生代浅变质至未变质海相构造层。平面上以肥中断裂和六安断裂为界分为三种类型即华北地台型、大陆边缘过渡型和北淮阳型。盆地由四条控盆边界断裂控制，中生代以来可以划分出四个二级构造单元、11个三级构造单元。盆地独特的构造位置赋予了它丰富的构造样式，包括拉张构造样式，挤压构造样式和走滑构造样式。3．中生代合肥盆地沉积相组合、地层展布和沉积旋回演化规律合肥盆地大致以六安断裂为界，北带主要沉积中生界侏罗—白垩系地层，其中防虎山组属早侏罗世晚期到中侏罗世早期沉积，圆洞山组属中侏罗世晚期到晚侏罗世沉积，周公山组为早白垩世沉积；南带主要沉积中生界侏罗—白垩系碎屑岩夹火山岩和火山碎屑岩建造，其中三尖铺组属于中侏罗世晚期到晚侏罗世沉积，凤凰台组／毛坦厂组属早白垩世早期沉积／火山喷发旋回，黑石渡组为早白垩世晚期沉积。南北带地层可以对比。合肥盆地中生带发育的沉积相主要有冲积扇相、河流相及湖泊相并沉积相及沉积旋回随时间的演化规律具有盆地北带和盆地南带同步性和相带的连续性。4．合肥盆地中生代古环境演变特征合肥盆地早侏罗世晚期到中侏罗世早期沉积时古水流优势方向表明自西向东方向甚至自北向南方向的纵向水系为主要特征；中侏罗世晚期到晚侏罗世古水流的优势方向表明水流方向基本垂直大别造山带；早白垩世早期总体的水流方向为大致垂直大别造山带的横向水流；早白垩世晚期古水流方向发散。中生界砂岩粒度特征主要反映的是河流相的特征。早侏罗世晚期到中侏罗世早期的河流具有近源特征；中侏罗世晚期到晚侏罗世河流自南向北(山到盆)具有近源河流—远源河流的明显变化；早白垩世反映了自大别造山带向盆地内部从山间急流形成的冲刷沟道和断陷盆地河流—远源河流的特征。5．合肥盆地中生代沉积物源的演化合肥盆地南带和北带中生界露头中砾石成分具有一定规律可循。盆地北带侏罗系砾石成分表现了其来源的复杂性，除了北淮阳带提供大量物质、北大别带提供少量物质以外，尚有其他的物质来源，推测可能为盆地华北地台型基底提供物质，甚至物源来自华北板块；盆地南带早侏罗世沉积缺失，中、晚侏罗世砾石来源主要为盆地北淮阳型基底和北淮阳带的物质、大别杂岩带物源贡献不大。白垩纪，南北大别带除了对盆地南带提供了大量的物质以外(凤凰台组和火山岩盆地中充填的黑石渡组)，尚远波及到盆地北带周公山组的沉积。合肥盆地北带早、中侏罗世砂岩重矿物组合所恢复的源岩组合为沉积岩和低级变质岩，表明早、中侏罗世盆地主要接受来自华北板块(克拉通)的沉积物，中、晚侏罗世砂岩重矿物组合指示的母岩物质组合为基性岩浆岩和中酸性岩浆岩，白垩世主要母岩组合为基性和中酸性岩浆岩。合肥盆地南带中生代重矿物组合所反映的母岩组合在剖面上的演化趋势为中、晚侏罗世物源的岩性配置与北淮阳带岩石组合相一致，随时间推移来自大别杂岩带的变质岩岩石的贡献逐渐增大；早白垩世主要母岩物质表现为早期以中酸性岩浆岩和中高级变质岩为主，越晚以中酸性岩浆岩为主。6．合肥盆地中生代沉积源区的构造背景演变早侏罗世砂岩骨架组分源区构造环境以岩浆弧物源区，兼出现造山带物源区和大陆地块物源区为特征，表明该时期合肥盆地物源的复杂性；中、晚侏罗世非常明显的源区环境表现为大陆地块和板块碰撞造山带，但混合源区表现比较明显。一进入早白垩世早期，明显的源区指示为再旋回造山带及碰撞造山带，大别造山带来源的物质单一并主要影响着合肥盆地的充填。早白垩世晚期的岩浆弧物源区和岛弧造山带物源区形成，是此时期区域拉张构造背景的极好反映。沉积地球化学源区环境判别的结果进一步证实了合肥盆地北南带源区性质的差异性。盆地北带侏罗系的沉积充填可能受华北地块的影响更大，而盆地南带侏罗系物质受到大别造山带的影响似乎更大。白垩系盆地整体反映了造山带的物质特征，反映的主动大陆边缘环境更为明显。盆地南北带均有岛弧源区背景显示，这与北淮阳带的构造属性非常一致。7．大别造山带构造演化与再造大别造山带构造演化复杂，单纯从造山带本身很难恢复起演化信息，但合肥盆地充填的一系列特征对恢复大别造山带的构造演化和结构再造具有很重要的作用。根据合肥盆地沉积充填特征、古地理演变、物源分析以及物源区构造背景判别，可以大致重塑大别造山带的演化历史以及再造其构造单元。大别造山带早侏罗世晚期到中侏罗世早期碰撞造山规模有限，其主碰撞造山期主要发生在中侏罗世晚期到晚侏罗世，大规模造山发生在早白垩世，并表现为伸展背景下的热隆造山。更多还原

【Abstract】 The introduction of system theory into earth science resulted in research of basin-range coupling. To be a bridge connecting orogenic belt and peripheral basins, mass transfer was employed as a key in the research between orogen tectonic evolution and basin sedimentary filling. This, therefore, became a focus in the study of earth dynamics. Provenance analysis can depict the history of basin filling, furthermore it can provide a series of clues for the understanding of evolution in source areas. For these reasons, it has become an important approach in basin-range coupling.Dabieshan Orogen has become a hotspot in geological research both in China and abroad for its large scale outcrop of HP/UHP metamorphic rocks. A new challenge in this region lies in the integration of tectonic evolution of Dabieshan Orogen with sedimentary filling of Hefei Basin.In this paper, integrated sedimentological, geochemical, petrological and mineralogical studies are carried out on Mesozoic sedimentary rocks of Hefei basin. Major conclusions are as follows:1. Tectonic units of Dabieshan Orogen and their rock compositionsFrom north to south, Dabieshan Orogen can be divided into four belts, namely, North Huaiyang retroarc flysch belt, North Dabie arc complex belt, South Dabie collision complex belt and Susong metamorphic complex belt. The faults dividing these units are Xinyang-Shucheng Fault, Mozitan-Xiaotian Fault, Shuihou-Yingshan Falut (shear zone), Mamiao-Taihu Fault (shear zone) and Xiangfan-Guangji Fault respectively. Located in the middle of Dabieshan Orogen, the N-S trending Shangma Fault divides the orogen into two parts, with Dabie Block (include North Dabie arc complex belt and South Dabie collision complex belt) in east and Hongan Block in west. Each unit has its characteristic rocks.2. Basement characteristics, fault features and tectonic units of Hefei BasinVertically, the basement of Hefei Basin is recognized to have double-layer structure, and is divided into Archaean-Paleoproterozoic high-grade metamorphic rocks and Neoproterozoic-Late Palaeozoic low grade metomorhpic/original marine structure layer。Horizontally, Feizhong Fault and Liuan Fault act as boundaries and divide the basement of Hefei Basin into three parts, i.e., North China platform basement, continental margin transitional basement and North Huaiyang basement. Hefei Basin is controlled by four boundary faults and can be divided into four secondary tectonic units since Mesozoic, and each unit has its own subunits. Unique tectonic setting endow abundant structure styles to Hefei Basin, such as extensional structure, compressive structure and strike-slip structure.3. Mesozoic sedimentary facies assemblages, strata distribution and sedimentary cyclicityLiuan Fault divides Hefei Basin into two deposition systems. The north system (i. e., main body of basin) is composed of Jurassic-Cretaceous deposition. Fanghushan Formation, Yuandongshan Formation and Zhougongshan Formation belong to late Lower Jurassic-early Middle Jurassic deposition, late Middle Jurassic-Upper Jurassic deposition and early Lower Cretaceous deposition, respectively. The south system is mainly composed of Jurassic-Cretaceous clastic rocks interbeded by volcanic rocks and pyroclastic rocks, including Sanjianpu Formation, Fenghuangtai Formation/Maotanchang Formation, and Heishidu Formation. Sanjianpu Formation span late Middle Jurassic-Lower Jurassic; Fenghuangtai Formation/Maotanchang Formation is the result of earlist Cretaceous deposition-volcanic eruption cyclicity, while Heishidu Formation formed in late Early Cretaceous. The strata between different systems can be well correlated. The dominant facies in Hefei Basin in Mesozoic include alluvial fan, fluvial and lacustrine facies. The evolution of facies and sedimentary cyclicity with time shows synchrony and continuity between the north and the south system.4. Mesozoic paleoenvironment variance in Hefei BasinIn late Early Jurassic-early Middle Jurassic, the preponderant paleocurrent directions indicate the feature of longitudinal drainage system from west to east in Hefei Basin. Surprisingly, paleocurrent directions from north to south also exist in this region. In late Middle Jurassic-Late Jurassic, the paleocurrent is attributed to lateral drainage system and crossed Dabieshan Orogen. The paleocurrent of earlist Cretaceous shared the same features as Late Jurassic. In late Early Cretaceous, the paleocurrent of Hefei Basin was emanative.The sandstone particle distribution of Hefei basin in Mesozoic reflects fluvial features. Particle analysis indicates that the fluvial was proximal from late Early Jurassic to early Middle Jurassic; Between late Middle Jurassic and Upper Jurassic, the fluvial in this region transferred from proximal to distal fluvial. The onflow from Dabieshan Orogen to Hefei Basin and distal fluvial in fault basins were formed in Early Cretaceous.5. Mesozoic provenance evolution of Hefei BasinThe trend of gravel components distribution was tracked both in the north and south deposition system of Hefei Basin. In the north system, gravel components show a complex origin in Jurassic. North Huaiyang belt mainly contributed sediments to the basin. Dabie complex provided less sediment to the main body of Hefei Basin. An unknown source area existed in this period and is presumed to be North China platform basement, or North China Plate. There is no deposition in Lower Jurassic, the gravel deposition of Middle to Upper Jurassic mainly derived from North Huaiyang belt and North Huaiyang type basement. Dabie complex provided a small proportion of sediments to the south system. In Cretaceous, Dabie complex provided most of the sediments to the south system. Furthermore, complex rocks spread to the north system.Source rock compositions determined by heavy mineral assembles in the north system of Hefei Basin include sedimentary rock and low-grade metamorphic rock. This indicates that North China Plate was the main source area. Middle to Upper Jurassic heavy mineral assembles has the characteristics of basic magmatic rocks and acid-medium magmatic rocks. The source rocks in Cretaceous are acid-medium magmatites。The evolution trend of source rocks in vertical geological section reflected by Mesozoic heavy mineral assembles in the south system shows that the source rocks are consistent with those in North Huaiyang belt in Jurassic. The contribution of Dabie complex became more and more significant from base to top of the section. In Cretaceous, almost all of sediments were derived from Dabie complex.6. Tectonic evolution of source areas of Hefei Basin in MesozoicThe Lower Jurassic sandstone detrital mode of Hefei Basin indicates that, while its provenance mainly belongs to magmatic arc setting, orogen and continental block setting also appear to be possible settings. This reflects the complexity of source areas. Middle to Late Jurassic tectonic settings of source areas are continental block and collision orogen, exhibiting a clear mixed sources. It is evident that the source areas are recycled orogen and collision orogen in Cretaceous, the simplex clast derived from Dabieshan Orogen affected the filling of Hefei Basin in this period. The presence of magametic provenance and island provenance reflects the extensional setting. The provenance determination from geochemical data confirms the source areas’ difference between the north and the south system in Jurassic. The north system is mainly affected by North China plate. In contrast, the south system is mainly affected by Dabieshan Orogen. In Cretaceous, active margin setting is distinguishable. Arc provenance appeared both in the north and south system, which is in accordance with the setting of North Huaiyang belt.7. Tectonic evolution and reconstruction of Dabieshan OrogenTectonic evolution of Dabieshan Orogen is complicated. It is difficult to rebuild the tectonic evolution merely based on Orogen itself. While a series of clues from the sedimentary filling of Hefei Basin are very useful for a better understanding of the tectonic evolution and structure reconstruction of Dabieshan Orogen. According to the filling features, paleocurrent variance, provenance analysis and tectonic setting determination of source areas, the tectonic evolution history and tectonic units can be reconstructed. Though orogency occurred in Late Triassic, the collision orogency in Dabieshan region was less active from Early Jurassic to early Middle Jurassic. Main collision orogency lasted from late Middle Jurassic to Late Jurassic. While large scale orogency occurred in Cretaceous, and belong to thermal doming orogency under regional extensional background.更多还原