【作者】 徐佑德；

【导师】 朱光；

【作者基本信息】 合肥工业大学 ， 矿物学、岩石学、矿床学， 2009， 博士

【摘要】 郯庐断裂带是中国东部呈NNE走向的巨型走滑断裂带,在中国境内延伸长度达2400km,该断裂带也是中国东部重要的地质分界线。经过50多年的研究表明,郯庐断裂带中生代以来经历了多期、复杂的演化历史,是一个兼具走滑、伸展、挤压性质的复杂地质体,其活动时期、活动方式一方面到受深部构造活动及区域构造背景的控制,另一方面又明显改造或控制了其周缘构造的演化,特别是对相邻中、新生代盆地的构造沉降、沉积充填及油气地质条件具有重要影响或控制作用。郯庐断裂带相邻地区发育了一系列中、新生代盆地,既包括渤海湾、苏北等富油气盆地,也包括目前尚未有油气发现的胶莱、南华北盆地等。因此,将郯庐断裂带与在时间、空间上彼此分割的相邻沉积盆地置于同一构造体系下来研究它们之间的构造演化关系,可以从宏观上把握郯庐断裂带对沉积盆地形成、演化乃至对油气生成、运聚成藏的影响,明确不同盆地地质条件的差异及油气富集规律,这对我国东部老油区寻找新层系、优选有利勘探区块具有重要意义。通过野外地质和室内实验分析,系统分析了郯庐晚期左旋剪切带的构造特征、形成的温压环境及形成时间。糜棱岩显微构造及野外露头尺度S-C构造、旋转残斑等均指示郯庐晚期剪切带为左旋走滑活动的产物;糜棱岩中新生矿物组合、变形行为及白云母电子探针测试结果表明,郯庐晚期剪切带形成温度为400-500℃,形成压力为低压环境;通过2个白云母、6个黑云母的40Ar/39Ar年龄测试,获得了一个代表郯庐断裂带晚期剪切带活动的冷却年龄(149.8±0.9 Ma),即郯庐断裂带晚期左旋走滑活动发生于150Ma之前的晚侏罗世。本论文通过对华北克拉通东部早白垩世岩浆活动时期分析表明,最早为蒙阴盆地青山组135Ma及郯庐断裂带上的黄石坝组133Ma,其峰期喷发时间为120-110Ma,这期岩浆活动在大部分断陷盆地均有发育,这指示郯庐断裂带与华北克拉通东部一起处于拉伸背景,在早白垩世发生了强烈的伸展断陷活动;同时,华北东部早白垩世断陷盆地在以青山组等为代表的火山喷发之前,普遍发育了一套陆相沉积,即莱阳群、蒙阴组、朱巷组,并且合肥盆地、胶莱盆地等早白垩世均表现为由郯庐断裂带控制的半地堑或地堑结构,地层时代指示郯庐断裂带伸展活动的时间持续至古近纪;另外,华北克拉通东部普遍发育的变质核杂岩形成时间集中在早白垩世初145Ma至早白垩世中晚期的116Ma,指示了伸展活动开始于早白垩世早期。因此,综合华北克拉通东部岩浆活动、断陷盆地发育及变质核杂岩形成时间等多种证据,认为郯庐断裂带伸展活动始于早白垩世初,并持续至古近纪。在综合前人研究成果的基础上,本研究应用断层滑动面上擦痕资料对郯庐断裂带及邻区区域应场进行了分析,获得了研究区晚侏罗世以来各时期的区域应力场演化状况,本次重点分析了晚侏罗世挤压作用、早白垩世区域拉张与裂谷作用、晚白垩世-古近纪区域拉张与郯庐断裂走滑伸展等3期构造应力场的转变与盆地演化的关系。通过对盆地沉积充填特征、区域构造及应力场的分析,明确了郯庐断裂带晚侏罗世以来与周缘盆地的关系:(1)晚侏罗世时期,由于太平洋区大洋板块的高速斜向运动,使中国大陆东部呈现左旋压扭性活动,中国东部普遍缺失晚侏罗世沉积,该时期郯庐断裂带发生晚期左旋平移;(2)在白垩纪期间郯庐断裂带转变为伸展断陷活动,成为中国东部的巨型断陷活动带,对带内及相邻陆相盆地发育与沉积具有明显的控制作用,其中下白垩统沉积时沉降中心明显向郯庐断裂带附近迁移,上白垩统沉积中心向郯庐断裂带旁侧的东西向断陷区迁移;(3)古近纪断陷活动最强处为渤海湾盆地,其次为苏北盆地。渤海湾盆地的强烈断陷活动是在近南北向的拉伸作用下,古近纪从早至晚沉积中心呈现自南向北、自西向东的有规律迁移,也使沉积中心最终向着郯庐断裂带所在的海域内迁移;(4)研究区至新近纪结束断陷活动,断陷盆地发生反转,一部分抬升消亡,另一部分转变为拗陷式盆地(渤海湾盆地、苏北盆地),接受披盖式沉积,拗陷最强处出现郯庐断裂带的海域内。以渤海湾盆地为重点,对郯庐断裂带周缘盆地古近纪伸展活动、构造沉降进行了对比分析。结果表明,渤海湾地区不同凹陷新生代主要伸展方向为南北向,伸展作用主要发生在孔店组—沙三段沉积时期,盆地最大伸展量、伸展率、伸展速率等从早到晚具有自南北两端向渤海中部迁移的特征;同时,郯庐断裂带内及其附近坳陷(昌潍、济阳、渤中、辽东等坳陷)古近纪构造沉降量较大,而远离郯庐断裂带坳陷(临清、冀中等坳陷)构造沉降量较小,指示郯庐断裂带是断陷活动中的强活动带,控制着强断陷带的发育。结合深部构造研究成果,分析了华北克拉通东部郯庐断裂带周缘盆地早白垩世以来构造沉降规律及与深部构造活动的关系。盆地的主要构造沉降中心早白垩世集中于华北克拉通南部和北部,而古近纪则迁移至华北克拉通内部渤海湾盆地区,构造沉降中心的迁移从早到晚具有由克拉通边缘向内部变化的规律;盆地构造沉降中心的迁移主要受岩石圈结构及岩石圈温度与强度演化的控制,而岩石圈热状态与强度、岩石圈结构、区域拉伸应力方向的控制及动力学机制等四个因素共同控制了郯庐断裂带周缘早白垩世以来断陷盆地的发育特征。本研究系统分析了郯庐断裂带周缘盆地古近系烃源岩有机地化、空间分布特征。研究区古近系主要发育孔店期、沙四期、沙三期、沙一期及东营期等五套烃源岩,其中孔店期、沙三期烃源岩是区内主要烃源岩,烃源岩发育层位自南而北时代逐渐变新;构造沉降中心的迁移控制了主要烃源岩发育层位和厚度大小的迁移变化,而沉积相带明显控制了烃源岩的有机丰度和类型,因而郯庐断裂带的伸展活动及盆地沉降中心的迁移控制了烃源岩品质。郯庐断裂带白垩纪期间的伸展活动造成盆地沉积与沉降中心向着郯庐断裂带附近迁移,深湖—半深湖相沉积环境主要出现在郯庐断裂带附近,烃源岩较为发育,品质较好,因此,济阳坳陷惠民、沾化凹陷、胶莱盆地莱阳凹陷中部是胜利探区下步中生界勘探的有利方向;孔店—沙四期渤海湾盆地南部潍北凹陷、东营凹陷和惠民凹陷烃源岩发育,是胜利探区古近系深层勘探的有利方向。更多还原

【Abstract】 The Tan-Lu fault zone is a large-scale strike-slip fault zone and important geological boundary striking NNE in East China, which extends about 2400 km. More than fifty years studies on the large fault zone suggest that it has experienced polyphase and complicated evolution history since Mesozoic , and is a complex geological body which has strike-slip, extensional and compressive behaviors on different segments during different geological stages. On the one hand the active stage and regime of the fault zone was controlled by the activities of deep structure and the regional tectonic setting, but on the other hand the active stage and regime significantly has modified or affected the evolution of its adjacent structures, and has important effects on the tectonic subsidence, sedimentary filling and petroleum geological conditions in the adjacent Meso-Cenozoic basins. There are many Meso-Cenozoic basins adjacent to the Tan-Lu fault zone, including basins rich in hydrocarbon, such as the Bohai Bay Basin and the Subei Basin, also including basins without oil and gas, such as the Jiaolai Basin and the Southern North China Basin. Therefore, putting the Tan-Lu fault zone and its adjacent basins, which is independent in time, space on each other, under the same tectonic system to research their evolution relationship in the macro level, we can understand the effects of the Tan-Lu fault zone on the formation, evolution as well as petroleum generation, migration and accumulation of its adjacent sedimentary basins, and grasp the law of geological conditions and the petroleum enrichment, which is meaningful for targeting new strata, optimizing favorable exploration blocks in the eastern old oilfields.On the basis of the field geology research and laboratory analysis, the dissertation systematically studied the structural features, the formation temperature and pressure environment, and the formation time of the late sinistral shear belt along the Tan-Lu fault zone. The structure characteristics, such as the microstructures of mylonite, the outcrop-scale S-C structures, the rotation porphyroblasts, indicates the late shear belt formed due to the sinistral activities of the Tan-Lu fault zone. The newformed mineral assemblage, deformation behaviors in mylonite, and muscovite electron probe test results show that the formation temperatures of the late shear belt is 400-500℃, and the formation pressure is low pressure environment; Through two muscovite, 6 biotite ⁴⁰Ar/³⁹Ar dating, this study obtained a representative age （149.8±0.9 Ma） which was the cooling age of the late shear belt due to the sinistral activity of the Tan-Lu fault zone, that is, the second sinistral activity of the Tan-Lu fault zone occurred at the Late Jurassic and before 150Ma. Timing of magmatic activities in North China in the Early Cretaceous shows that the earliest age of magmatic activities is 135Ma （found in the Qingshan Formaition in the Mengyi basin） and 133Ma （found in the Huangshiba Formation along the Tan-Lu fault zone）, and the peak time of magmatic eruption is 120-110Ma, which was widely distributed in most rift basins. The above magmatic activities indicate that both the Tan-Lu fault zone and the eastern North China Craton were involved into intensively extensional faulted events in the Early Cretaceous due to a tensile tectonic setting. According to the stratigraphic sequence of Cretaceous in the eastern North China craton, before the large-scale volcanic eruption represented by the Qingshan Formation, the rift basins were filled with a set of continental sediments including the Laiyang Group, the Mengyin Formation and the Zhuxiang Formation, etc. Some rift basins, such as the Hefei and Jiaolai basins, showed the half-graben or graben structures controlled by the Tan-Lu fault zone, and the stratigraphic thickness increases markedly near the boundary normal faults, thus the stratigraphic age of the faulted basins indicates the extensional activities of the Tan-Lu fault zone continued to Paleogene; In addition, the formation time of metamorphic core complex distributed generally in the eastern North China Craton, concentrates in the earliest（145 Ma） to middle （116 Ma） Early Cretaceous, and indicates the extensional activities of the Tan-Lu fault zone occurred at the beginning of the Early Cretaceous. Therefore, the evidence, including magmatic activities in the eastern North China Craton, faulted basin development and the formation of metamorphic core complexes and so on, demonstrates that the extensional activities of the Tan-Lu fault zone started at the beginning of the Early Cretaceous and continued to Paleogene.Combined with previous results and based on the fault slip data from field work along the Tan-Lu fault zone and adjacent areas, we analyzed the regional stress fields, and summarize stress field evolution since Late Jurassic. This study divides the stress field evolution into 6 stages, and focused on 3 stages of tectonic stress field evolution and their relationship with the evolution of the basins. Three stages are the compression in Late Jurassic, the regional extension and rifting in Early Cretaceous, and regional extension with a strike-slip component along the Tan-Lu fault zone during Late Cretaceous to Paleogene.The study established the relationship between activities of the Tan-Lu fault zone and its adjacent basin development since Late Jurassic, through analyzing sedimentary filling, regional tectonics and stress fields. The relation of activities between the fault zone and its adjacent tectonics can be divided into 4 stages: （1） During the Late Jurassic period, the high-speed, oblique subduction of the Pacific ocean plate occurred underneath the eastern Eurasia plate amrgin, which caused the eastern China in a sinistral transpression stress field and hiatus of Late Jurassic deposition. Sinistral motion took place along the Tan-Lu fault zone in the Late Jurassic; （2） During the Early Cretaceous, the activities of the Tan-Lu fault zone changed into extension, leading to devilment of rift basins along the Tan-Lu fault zone and its adjacent areas in eastern China. According to the isopach maps of the residual strata, normal faulting along the Tan-Lu fault zone resulted in the sedimentary centers obviously around the Tan-Lu fault zone when the Lower Cretaceous strata were deposited while the sedimentary centers of the Upper Cretaceous strata migrated to the east-west trending, normal faults flanking the Tan-Lu fault zone; （3） Bohai Bay Basin was the intense rifted area in Paleogene, followed by the Subei Basin. The near north-south extension event, combined with the right-lateral slip pull-apart between the Tan-Lu fault zone and the frontal fault of the Taihang Mountains, induced the intensive extension of the Bohai Bay Basin. Under the control by both the near norh-south extension and the right strike-slip pull-apart, the sedimentary centers in the Bohai Bay Basin in Paleogene, migrated from south to north and from west to east regularly. In the end of Paleogene, the sedimentary center migrated to the central part of the Bohai sea where the Tan-Lu fault zone passed through; （4） The extensional activities ended in the study area in the Early Neogene due to the change of regional stress field from extension to compression. As a response to the change of stress field, the inversion widely happened in the faulted basins with termination for most of the rift basins due to uplifting and survival for other basins into depression-type basins （such as the Bohai Bay Basin, Subei Basin） and filled with draping sediments. According to the isopach maps of the Neogene, the Bohai sea segment of the Tan-Lu fault zone was the center of the depression deposition.Focusing on the structural analysis in the Bohai Bay Basin in Cenozoic, this study analyzed Paleogene extensional activities, and compared tectonic subsidence in different basins or sags adjacent to the Tan-Lu fault zone. The results show that the main extension direction is north-south in different sags of the Bohai Bay region during Cenozoic, and extensional activities occurred mainly in the deposition period from the Kongdian Formation to Member 3 of the Shahejie Formation. From the Early Paleogene to the Late Paleogene, the largest extensional quantity, extensional rate, and extensional velocity migrate from both north and south ends in the study area to the Central Bohai. Moreover, the farther from the Tan-Lu fault zone, the smaller subsidence quantity of the depression is, that is, the depressions （such as the Changwei, Jiyang, Bozhong, Liaodong depression） within and near the Tan-Lu fault zone have a larger subsidence quantity, and the depressions far away from the Tan - Lu fault zone （the Linqing, Jizhong depression, etc.） have a smaller subsidence quantity. The above phenomenon shows that the Tan-Lu fault zone is a strong rifting zone during the extensional activities, and controls the development of the strong rifting region.On the basis of researches on the tectonic activities in the eastern North China Craton since Early Cretaceous, combined with the results from previous studies on deep structure, the tectonic subsidence characteristics of the basins adjacent to the Tan-Lu fault zone and its relationship with deep structures were discussed in this study. The main tectonic subsidence centers of the basins in the study area focused on the southern and northern areas of the eastern North China Craton in Early Cretaceous, and in Paleogene the subsidence centers moved to the Bohai Bay basin area within the eastern North China Craton, thus the subsidence centers migrated from the margin to the internal of the eastern North China Craton with the changes in geological ages since Early Cretaceous. The research results shows that tectonic subsidence centers of the basins were mainly controlled by the structures and temperatures of lithosphere while the development characteristics of the rift basins adjacent to the Tan-Lu fault zone since Early Cretaceous were controlled by the four geological factors, namely, thermal state and strength of lithosphere, lithosphere structure, regional extension stress direction and dynamic mechanism.The study systematically analyzed the organic geochemical characteristics and the spatial distribution characteristics of Paleogene source rocks in the basins adjacent to the Tan-Lu fault zone. There are five hydrocarbon source rocks for Eogene, including the Kongdian Formation, Member1, 3 and Member 4 of the Shahejie Formation, and the Dongying Formation, Of which source rocks for the Kongdian Formation and Member 3 of the Shahejie Formation are the major source rocks in the study area, and the geologic ages of the source rocks progressively become younger from south to north. The migration of tectonic subsidence centers controls the source rock development and thicknesses, and the sedimentary fades in the basins obviously controlled organic abundance and type of the source rocks, thus the extending of the Tan-Lu fault zone and tectonic subsidence center migration of the adjacent basins have great effect on quality of source rocks. The extensional activities along the Tan-Lu fault zone in Cretaceous make sedimentary centers in the adjacent basins migrated to the nearby of the Tan-Lu fault zone., such as deep lake -semi-deep lacustrine sedimentary environment mainly appearing near the Tan-Lu fault zone where is suitable for high-quality source rock development. Therefore, the Huming and zhanhua sags in the Jiyang Depression, and the center of the Laiyang sag in the Jiaolai Basin are the favorable exploration areas of Mesozoic exploration. The Weibei, Dongying and Huimin sags in the south of the Bohai bay basin are the favorable exploration areas for the Kongdian Formation and Member 4 of the Shahejie Formation.更多还原