Formation Conditions and Sedimentary Model of Over-Flooding Lake Deltas within Continental Lake Basins: An Example from the Paleogene in the Jiyang Subbasin, Bohai Bay Basin

A large quantity of drilling core, paleontology, geochemistry and geophysics data revealed several features of the Jiyang subbasin during the deposition of the Ekl-ES4x members： （1） the paleotopography of the gentle slope belt had an extremely low gradient; （2） the paleoclimate frequently alternated between dry and wet periods in a generally arid setting; （3） there was strong weathering around the periphery of the basin; （4） the lake was very shallow; （5） the lake level frequently rose and fell; and （6） the sedimentary environment of the gentle slope belt was an over- flooding lake. All of these factors provided favorable geological conditions for the development of an over-flooding lake delta. The lithologies of the continental over-flooding lake delta deposits are complex and diverse. The compositional maturity is moderate to low, and the grain size distribution curves and sedimentary structures indicate the presence of both gravity and traction currents. The sedimentary microfacies associations consist of a combination of ordered superposition of flood channels, distributary channels and sheet sands. The delta exhibits a weak foreset seismic reflection. The over-flooding lake delta deposits are laterally extensive. The sandstone content is high, and the individual sandstone beds are thin. The flood channel and distributary channel deposits exhibit evidence of bifurcation and lateral migration. The distribution of the sandbodies and the oxidation color of the mudstones provide evidence of cyclic deposition. The paleoclimate was the dominant factor controlling the development of the over-flooding lake delta. Due to the frequently alternating wet and dry paleoclimates, the over-flooding lake delta is characterized by the development of a broad upper plain and a lower delta plain. The upper delta plain is characterized by flood channel deposits, whereas the lower delta plain is represented by distributary channel deposits. The transition zone is characterized by the interaction of flood channels and distributary channels. Due to fault activity, the sandbodies of the over-flooding lake delta were juxtaposed against hydrocarbon source rocks, which was favorable for the development of lithologic reservoirs or structural-lithologic reservoirs. The lower delta plain deposits comprise the most favorable reservoirs.

Sequence associations of sedimentary facies in continental basins and their applications to palaeogeographic mapping

According to the characteristics of sedimentary facies and their vertical associations, sequence association of sedimentary facies can be divided into 2 types and 28 subtypes. The first type(type A)is a sedimentary sequence without volcanic rocks, including 18 subtypes. The second type(type B)is a volcanogenic succession including 10 subtypes. Each subtype may reflect certain filling condition under certain sedimentary environment. Time and space distribution of different types of sequence associations can reflect tectonics that controlled the basin evolution, sedimentary environments and palaeogeography.

Methods for seismic sedimentology research on continental basins

In contrast to marine deposits, continental deposits in China are characterized by diverse sedimentary types, rapid changes in sedimentary facies, complex lithology, and thin, small sand bodies. In seismic sedimentology studies on continental lacustrine basins, new thinking and more detailed and effective technical means are needed to generate lithological data cubes and conduct seismic geo- morphologic analyses. Based on a series of tests and studies, this paper presents the concepts of time-equivalent seismic attributes and seismic sedimentary bodies and a ＂four-step approach＂ for the seismic sedimentologic study of conti- nental basins： Step 1, build a time-equivalent stratigraphic framework based on vertical analysis and horizontal corre- lation of lithofacies, electrofacies, seismic facies, and pale- ontological combinations; Step 2, further build a sedimentary facies model based on the analysis of single- well facies with outcrop, coring, and lab test data; Step 3, convert the seismic data into a lithological data cube reflecting different lithologies by means of seismic tech- niques; and Step 4, perform a time-equivalent attribute analysis and convert the planar attribute into a sedimentary facies map under the guidance of the sedimentary facies model. The whole process, highlighting the verification and calibration of geological data, is an iteration and feedback procedure of geoseismic data. The key technologies include the following： （1） a seismic data-lithology conversion technique applicable to complex lithology, which can convert the seismic reflection from interface types to rock layers; and （2） time-equivalent seismic unit analysis and a time- equivalent seismic attribute extraction technique. Finally, this paper demonstrates the validity of the approach with an example from the Qikou Sag in the Bohai Bay Basin and subsequent drilling results.

Structural Characteristics and Formation Dynamics: A Review of the Main Sedimentary Basins in the Continent of China

The formation and evolution of basins in the China continent are closely related to the collages of many blocks and orogenic belts. Based on a large amount of the geological, geophysical, petroleum exploration data and a large number of published research results, the basement constitutions and evolutions of tectonic-sedimentary of sedimentary basins, the main border fault belts and the orogenesis of their peripheries of the basins are analyzed. Especially, the main typical basins in the eight divisions in the continent of China are analyzed in detail, including the Tarim, Ordos, Sichuan, Songliao, Bohai Bay, Junggar, Qiadam and Qiangtang basins. The main five stages of superimposed evolutions processes of basins revealed, which accompanied with the tectonic processes of the Paleo-Asian Ocean, Tethyan and Western Pacific domains. They contained the formations of main Cratons （1850-800 Ma）, developments of marine basins （800-386 Ma）, developments of Marine- continental transition basins and super mantle plumes （386-252 Ma）, amalgamation of China Continent and developments of continental basins （252-205 Ma） and development of the foreland basins in the western and extensional faulted basin in the eastern of China （205~0 Ma）. Therefore, large scale marine sedimentary basins existed in the relatively stable continental blocks of the Proterozoic, developed during the Neoproterozoic to Paleozoic, with the property of the intracontinental cratons and peripheral foreland basins, the multistage superimposing and late reformations of basins. The continental basins developed on the weak or preexisting divisional basements, or the remnant and reformed marine basins in the Meso-Cenozoic, are mainly the continental margins, back-arc basins, retroarc foreland basins, intracontinental rifts and pull-apart basins. The styles and intensity deformation containing the faults, folds and the structural architecture of regional unconformities of the basins, responded to the openings, subductions, closures of oceans, the continent-continent collisions and reactivation of orogenies near the basins in different periods. The evolutions of the Tianshan-Mongol-Hinggan, Kunlun-Qilian-Qinling-Dabie-Sulu, Jiangshao-Shiwandashan, Helanshan-Longmengshan, Taihang-Wuling orogenic belts, the Tibet Plateau and the Altun and Tan- Lu Fault belts have importantly influenced on the tectonic-sedimentary developments, mineralization and hydrocarbon reservoir conditions of their adjacent basins in different times. The evolutions of basins also rely on the deep structures of lithosphere and the rheological properties of the mantle. The mosaic and mirroring geological structures of the deep lithosphere reflect the pre-existed divisions and hot mantle upwelling, constrain to the origins and transforms dynamics of the basins. The leading edges of the basin tectonic dynamics will focus on the basin and mountain coupling, reconstruction of the paleotectonic-paleogeography, establishing relationship between the structural deformations of shallow surface to the deep lithosphere or asthenosphere, as well as the restoring proto-basin and depicting residual basin of the Paleozoic basin, the effects of multiple stages of volcanism and paleo- earthquake events in China.

Multi-source genesis of continental carbonate-rich fine-grained sedimentary rocks and hydrocarbon sweet spots

This paper systematically discusses the multiple source characteristics and formation mechanisms of carbonate-rich fine-grained sedimentary rocks through the analysis of material source and rock formation.The hydrocarbon accumulation characteristics of carbonate-rich fine-grained sedimentary rocks are also summarized.The results show that the main reason for the enrichment of fine-grained carbonate materials in rift lake basins was the supply of multiple material sources,including terrestrial material input,formation of intrabasinal authigenic carbonate,volcanic-hydrothermal material feeding and mixed source.The development of carbonate bedrock in the provenance area controlled the filling scale of carbonate materials in rift lake basins.The volcanic-hydrothermal activity might provide an alkaline fluid to the lake basins to strengthen the material supply for the formation of carbonate crystals.Authigenic carbonate crystals induced by biological processes were the main source of long-term accumulation of fine-grained carbonate materials in the lake basins.Carbonate-rich fine-grained sedimentary rocks with multiple features were formed through the interaction of physical,biochemical and chemical processes during the deposition and post-deposition stages.The source and sedimentary origin of the fine-grained carbonate rock controlled the hydrocarbon accumulation in it.In the multi-source system,the types of"sweet spots"of continental shale oil and gas include endogenous type,terrigenous type,volcanic-hydrothermal type and mixed source type.

Basic Types and Structural Characteristics of Uplifts:An Overview of Sedimentary Basins in China

The uplift is a positive structural unit of the crust. It is an important window for continental dynamics owing to its abundant structural phenomena, such as fault, fold, unconformity and denudation of strata. Meanwhile, it is the very place to store important minerals like oil, natural gas, coal and uranium. Giant and large-scale oil and gas fields in China, such as the Daqing Oilfield, Lunnan-Tahe Oilfield, Penglai 19-3 Oilfield, Puguang Gas Field and Jingbian Gas Field, are developed mainly on uplifts. Therefore, it is the main target both for oil and gas exploration and for geological study. The uplift can be either a basement uplift, or one developed only in the sedimentary cover. Extension, compression and wrench or their combined forces may give rise to uplifts. The development process of uplifting, such as formation, development, dwindling and destruction, can be taken as the uplifting cycle. The uplifts on the giant Precambrian cratons are large in scale with less extensive structural deformation. The uplifts on the medium- and small-sized cratons or neo-cratons are formed in various shapes with strong structural deformation and complicated geological structure. Owing to changes in the geodynamic environment, uplift experiences a multi-stage or multi-cycle development process. Its geological structure is characterized in superposition of multi-structural layers. Based on the basement properties, mechanical stratigraphy and development sequence, uplifts can be divided into three basic types-the succession, superposition and destruction ones. The succession type is subdivided into the maintaining type and the lasting type. The superposition type can be subdivided into the composite anticlinal type, the buried-hill draped type, the faulted uplift type and the migration type according to the different scales and superimposed styles of uplifts in different cycles. The destruction type is subdivided into the tilting type and the negative inverted type. The development history of uplifts and their controlling effects on sedimentation and fluids are quite different from one another, although the uplifts with different structural types store important minerals. Uplifts and their slopes are the main areas for oil and gas accumulation. They usually become the composite oil and gas accumulation zones （belts） with multiple productive formations and various types of oil and gas reservoirs.

Structure Styles of Mesozoic-Cenozoic U-bearing Rock Series in Northern China

In Northern China, sandstone-type uranium （U） deposits are mostly developed in Mesozoic-Cenozoic basins. These U deposits are usually hosted in unvarying horizons within the basins and exhibit typical U-forming sedimentary associations, which is referred to as U-bearing rock series. This study describes the structural features of U-bearing rock series within the main Mesozoic-Cenozoic U-producing continental basins in Kazakhstan, Uzbekistan, and Russia in the western segment of the Central Asian Metallogenic Belt （CAMB）, and Northern China in the eastern segment of the CAMB. We analyze the basic structural conditions and sedimentary environments of U-bearing rock series in Northern China and classify their structural styles in typical basins into river valley, basin margin, and intrabasin uplift margin types. The intrabasin uplift margin structural style proposed in this study can be used to indicate directions for the exploration of sandstone-type U deposits hosted in the center of a basin. At the same time, the study of structural style provides a new idea for exploring sandstone-type U deposits in Mesozoic-Cenozoic basins and it is of great significance to prospecting of sandstone-type uranium deposits.

Cenozoic tectono-sedimentary characteristics and extension model of the Northwest Sub-basin,South China Sea

Based on the interpretations of three seismic profiles and one wide-angle seismic profile across the Northwest Sub-basin,South China Sea.stratigraphic sequences,deformation characteristics and an extension model for this sub-basin have been worked out.Three tectonic-stratigraphic units are determined.Detailed analyses of extension show that the event occurred mainly during the Paleogene and resulted in the formation of half-grabens or grabens distributed symmetrically around the spreading center.Sediments are characterized by chaotic and discontinuous reflectors,indicating clastic sediments. Farther to the southwest,the sub-basin features mainly continental rifting instead of sea-floor spreading. The rifting would have been controlled by the shape of the massif and developed just along the northern edge of the Zhongsha-Xisha Block,rather than joined the Xisha Trough.After 25 Ma.a southward ridge jump triggered the opening of the Southwest Sub-basin.The NW-directed stress caused by the sea-floor spreading of the Northwest Sub-basin may have prevented the continuous opening of the sub-basin.After that the Northwest Sub-basin experienced thermal cooling and exhibited broad subsidence.The deep crustal structure shown by the velocity model from a wide-angle seismic profile is also symmetrical around the spreading center,which indicates that the Northwest Sub-basin might have opened in a pure shear model.

Fractional Crystallization and Crustal Contamination of Doleritic and Trachytic Dykes Crosscutting the Cretaceous Sedimentary Basins from Figuil (North Cameroon) and Léré(South-Western Chad): Geodynamic Implications

Magmatism in the Cretaceous sedimentary basins of the Figuil and Léré regions constitutes one of the fundamental parameters in the reconstruction of the history of the Cretaceous sedimentary basins. The main objective of this paper is to constrain the petrogenetic processes of hypovolcanic rocks and to determine their geodynamic context of emplacement. The petrographic study of mafic hypovolcanic and trachytic rocks was carried out under a polarizing microscope on thin sections. For the geochemical study, the major oxides and some trace elements were analyzed by ICP-AES. Trace and rare earth elements were analyzed by ICP-MS. The dolerites of the Cretaceous sedimentary basins are composed of dykes of amphibole bearing dolerites, biotite and pyroxene bearing dolerite, pyroxene bearing dolerites and trachytes. The dykes are in the order of 20 to 100 m wide by several kilometers long and oriented from N23°E to N90°E. The textures of these rocks are sub-ophitic to intergranular for dolerites and trachytic for evolved rocks (trachytes). The geochemical study shows that the dolerites are basaltic in composition with alkaline to subalkaline character. The sampled dykes have an evolution dominated by fractional with the minor impact of the crustal assimilation characterized by low Rb/Y ratios for dolerites (0.36 - 0.97) and high values of Rb/Y for the Pan-African granitoids’ samples (1.95 - 4.01). The nature of doleritic and trachytic magma sources is supported by their (Tb/Yb)N > 1.9 (1.91 - 3.79) and Dy/Yb > 2 (2.32 - 3.50) ratios of most samples, which suggests melting in a garnet-bearing mantle. Concerning the geodynamic context of the studied rocks, doleritic samples are classified as within-plate tholeiite and volcanic arc basalt, and within-plate alkali basalts.

Tectono-Sedimentary History of Southeastern Coast Region,China:a Synthesis

According to the ideas and concepts of systems dynamic of continent structure, using previous information related to the study area, combining analyses on orogenic belt, basin and magmatic rock, the present paper synthesizes the tectono - sedimentary development of southeastern coast region, China, with special emphasis on the mountain making, basining and magmatic activity. The tectonic evolution after Late Caledonian orogeny was dominated by alternating rifting and converging, subsiding and uplifting, mountain making and basining in central and southern parts of southeastern China and the adjacent regions to the east and west. Seventeen geologic events , nine events of plate or terrain convergence , and continental crust accretion , as well as eight events of intracontinental rifting and basin faulting , are closely related to the tectonic and sedimentary evolution of the study area . The accompanied intense and frequent sedimentation , folding , faulting , magmatism and ore- forming process allowed huge coal , multimetal and potential petroleum source rocks to form in local depressions throughout the Caledonian to Himalavan time .

特提斯域演化对四川超级盆地油气系统形成的影响

基于“单向裂解—聚合”地球动力学模型,研究特提斯域演化对四川超级盆地油气系统形成的影响,探讨天然气富集规律。结果表明:①四川盆地及周缘新元古代—三叠纪历经了原特提斯洋和古特提斯洋叠加影响的两次单向裂解—聚合旋回,侏罗纪—新生代并入新特提斯构造域及环青藏高原盆山体系,板块内部各幕次构造运动控制沉积充填形式。②特提斯域演化、古气候环境和重大地质事件控制了盆地内部优质烃源岩形成与分布;裂谷、克拉通内裂陷、被动大陆边缘斜坡和克拉通内凹陷是烃源岩发育的有利地质构造单元。③特提斯域演化、超级大陆旋回、全球海平面变化以及构造-气候事件控制了碳酸盐台地及储盖组合的分布;克拉通台地边缘、台地内部水下地貌高带是寻找碳酸盐岩高能相带的重点区,同沉积古隆起及围斜区、区域性不整合面和后期改造断裂带是规模碳酸盐岩储层分布区;区域性蒸发岩或者泥页岩盖层有利于盆地油气大规模保存。④早期构造-沉积演化格局和后期构造改造程度共同影响的成藏要素时空匹配关系是油气富集的关键,未来油气勘探要重点关注南华纪裂谷期潜在含气系统,四川盆地东部—南部地区寒武系盐下含气系统以及二叠系、三叠系全油气系统等领域。

中国典型陆相盆地细粒沉积环境和岩相特征

细粒沉积环境和岩相时-空分布规律是控制页岩油富集高产的主要因素。在前人细粒沉积环境和岩相研究的基础上,分析研究了松辽、渤海湾、鄂尔多斯和准噶尔等中国典型陆相盆地的细粒沉积环境及主要特征。研究认为:①淡水-微咸水湖盆发育粉砂质纹层、黏土质纹层、有机质纹层的黏土岩、粉砂岩以及二者之间过渡岩性,咸水湖和盐湖多发育具方解石(白云石)纹层及黏土级灰泥纹层的细粒碳酸盐岩和细粒混积岩。②陆相湖盆不同演化阶段发育不同细粒岩相组合。裂陷期细粒沉积岩以富碳酸盐矿物的岩相组合发育为特征,拗陷期形成的富有机质页岩层系则以长英质+黏土质沉积岩相组合为主。③湖盆泥页岩沉积机制主要为悬浮沉降、风成输入、浊流、异重流和泥质碎屑流。④中国陆相页岩油类型多样且资源丰富,松辽、鄂尔多斯、准噶尔、渤海湾等中生代—新生代陆相盆地是中国页岩油勘探开发的重要领域。⑤未来细粒沉积环境和岩相研究重点发展方向:开展天文旋回研究,建立系统有效的沉积古环境判识参数及标准;建立陆相湖盆页岩型、夹层型和混合型细粒沉积岩岩相分类和沉积模式,有效地预测细粒沉积岩岩相时空分布;开展细粒沉积成因过程物理和数值模拟,研究细粒沉积物物理、化学和生物沉积耦合过程和形成发育机理;关注数据集成与深度挖掘、人工智能大数据与计算机辅助技术,研究细粒沉积物分布规律。

渤海湾盆地临清坳陷西部山西组—太原组海陆过渡相泥页岩沉积环境及有机质富集

海陆过渡相页岩气勘探开发处于初级阶段,而渤海湾盆地临清坳陷西部石炭—二叠系山西组—太原组泥页岩具有良好的生烃潜力,也是中国海陆过渡相页岩气开发的重要层位。为研究山西组—太原组泥页岩沉积环境与有机质富集关系,以XJ1井为研究对象,系统开展了岩石矿物、有机地球化学、元素地球化学以及数值分析等工作。研究表明:研究区山西组—太原组泥页岩脆性矿物含量低、黏土矿物含量高,压裂难度大,TOC含量平均值为4.03%,属于优质烃源岩,具备页岩气勘探开发潜力;太原组泥页岩沉积时期处于温暖湿润的气候条件,具有频繁变化的陆源碎屑输入、较低的沉积速率以及低—中等古生产力水平,沉积水体为海水沉积,处于缺氧还原和中等滞留环境;山西组泥页岩沉积时期,古气候条件复杂多变,具有稳定且较高的陆源碎屑输入、中等的沉积速率以及中—高等古生产力水平,沉积水体为微咸水—海水沉积,处于缺氧还原和中等—强滞留环境。根据古环境条件与TOC含量的线性相关性、灰色关联度以及稳健回归分析,认为太原组泥页岩有机质富集主要受控于古气候、古氧化还原以及古水体盐度条件,而山西组泥页岩有机质富集主要受控于古气候以及陆源碎屑输入条件。

陆相细粒沉积岩岩相组合类型划分研究现状及其油气地质意义

细粒沉积岩是陆相页岩油气重要的烃源岩和储集层。然而该类岩石具有岩相类型多样、垂向叠置复杂的特征,已知大部分获得高产油气井对应的甜点层通常为多种岩相类型的组合。当前,细粒沉积岩岩相分类方案仍存在分歧,岩相组合相关研究尚处于初步阶段。通过对比近年来国内学者关于陆相细粒沉积岩岩相类型划分方案的差异性,梳理了岩相组合的划分依据,探寻岩相组合划分新方法及其研究的油气地质意义。认为在岩相类型识别基础上,开展天文旋回理论指导下的岩相组合类型划分、展布特征刻画,对于陆相页岩油甜点精细预测具有重要意义;分析不同岩相组合源-储耦合特征、油气分布特征,注重微运移的相关研究有助于提升对页岩油气差异性富集的认识。

滇西河西锶矿床的陆相热水沉积成因——天青石矿物化学和Sr-S同位素证据

滇西河西大型锶矿床产于青藏高原东南缘兰坪中-新生代盆地北部,矿体主要赋存于上三叠统三合洞组碳酸盐岩中,且中新统金顶群含石膏砂泥质岩石中也多有产出,受成矿期近S-N向逆断层和近E-W向走滑断层控制。本文通过天青石岩相学观察和矿物化学分析,将热液期天青石分为Cls1、Cls2和Cls3三个世代,Cls1主要为他形粒状结构,Cls2和Cls3为自形柱状或板条状结构。其中,Cls2以发育Sr-Ba固溶体震荡环带为特点,指示矿石沉淀经历了快速到缓慢的结晶转换过程。Sr-S同位素示踪结果显示,天青石具有较均一的^(87)Sr/^(86)Sr值(0.707695~0.707792,均值为0.707740),与区域三合洞组灰岩及晚三叠世海水的Sr同位素组成一致;天青石的δ^(34)S值(17.26‰~17.49‰,均值为17.36‰)略高于金顶群石膏岩的δ^(34)S值(12.5‰~15.0‰)。分析认为,富Sr流体的形成可能与三合洞组灰岩受重力压实及深部热源导致的高压脱水作用有关,这些含矿热液早期聚集在三合洞组有利的构造圈闭空间内。在印度-欧亚大陆碰撞导致的构造应力变化和深部热源驱动下,含矿热液沿深切盆地基底的近S-N向逆冲构造上升运移,最后在浅表部与金顶群沉积期的氧化性湖相盆地卤水发生混合,导致三合洞组热液充填交代和金顶群热水沉积成矿作用近于同步发生。因此,河西锶矿床是一类兼具陆相热水沉积成矿特点的后生热液充填型矿床。

鄂尔多斯盆地山西组沉积环境讨论及其地质启示

鄂尔多斯盆地晚古生代经历了巨大的海陆变迁,并发生多次海侵。其中,关于本溪组-太原组的陆表海沉积环境经长期研究已达成广泛共识,而对处于海陆转换关键时期的山西组沉积环境问题至今存在较大争议。鉴此,本文在前人研究基础上,根据地层与古生物、沉积构造、岩性特征、成岩作用等地质依据,结合硼元素法所计算的古盐度、Sr/Ba比值以及硼、镓、铷三元素含量关系等不同地球化学测试分析结果,对早二叠世山西期沉积环境进行了较为深入的研究。认为山西期为陆表海背景下的海陆过渡沉积演化阶段,发育大面积分布的海陆过渡三角洲体系,到下石盒子期才完全进入陆相湖盆的沉积演化阶段。通过盆地山西组东西向与南北向地球化学基干剖面的建立,呈现古盐度和Sr/Ba比值由南向北、自西向东、层位自下而上总体减小的变化趋势,于山1晚期这种差异性基本消失,表明鄂尔多斯盆地山西期由南向北、层位自下而上受海水影响的规模与范围愈来愈弱。在此基础之上,将晚古生代鄂尔多斯盆地划分为3大沉积演化阶段,并建立了该时期盆地的基准面旋回层序地层格架。该成果认识对扩展和深入鄂尔多斯盆地油气勘探具有重要指导意义。

沉积盆地类型划分及其相关问题讨论

沉积盆地类型划分是盆地及其相关领域研究的重要基础。已有的盆地分类方案较多,各有侧重和所长,但对陆内盆地的划分和研究较为薄弱。沉积盆地是一个典型的复杂巨系统,对其分类是一个复杂的系统工程。盆地分类的原则和结果应体现此系统的整体性、层次性、关联性、典型性(代表性)和可对比性(预测性)。盆地类型划分的依据主要包括盆地发育鼎盛时期所处的大地构造位置、地壳-岩石圈类型、沉降机制和动力环境、盆地结构构造特征与基底性质、沉积环境及充填特征等。导致盆地沉降的动力主要源自地球深部,可分为热力、应力、重力及其复合4种。小行星等天体撞击地球所形成的盆地属特殊类型,将其划归重力成因盆地大类。还有一种值得注意的地貌成因盆地,其形成与内动力地质作用联系不密切,主要由地表负向地形存在而导致沉积物充填和水体汇聚。这类盆地在不同大地构造环境中均有发育,但其地球动力学意义和沉积矿产赋存条件等均与内动力成因的盆地差别颇大。故将其作为新的盆地和成因类型单独列出。根据上述沉积盆地分类的原则和基础,以全球板块构造动力环境、大陆内部动力活动的独立性、主动性和盆地沉降成因的主动力为主线,综合和归纳前人分类方案和盆地研究成果,将盆地发育的区域构造动力环境分为6大类(大洋和大陆板块内部,离散型、消减型、碰撞型、转换型大陆(板块)边缘),增加了天体撞击的特殊型和后期改造的复合型2大类与之并列;将前6大类构造动力环境中发育的沉积盆地分为44(亚)类,按构造动力环境、盆地主要构造力学性质(即应力)两大系统,分别进行了划分和归类。对本盆地分类方案中新的类型、或内涵有变、或需说明的部分盆地及术语,进行了进一步讨论或说明。这些盆地如后陆盆地、侧陆盆地、转换-补偿盆地、拉裂盆地、地貌成因盆地、(天体)撞击盆地、中间地块盆地、陆内前陆盆地、改造(型)盆地等。本盆地分类方案是对不同地区相同或相近构造环境所发育盆地类型的理性归纳和综合,相对较为系统全面。但在地史上和现世界中,因地质条件的差异或发展进程的不同,其中某类盆地可能在具相同构造环境的某地并未出现,或发育特征并不典型。任一个全球沉积盆地分类方案,从问世之日起就处于检验、争议和修补之中,周而复始,日臻完善。

南黄海盆地基底及海相中、古生界地层分布特征

南黄海盆地是大型海相中、古生界和陆相中、新生界两期叠合型盆地,本文根据最新地震资料结合钻井资料及与海陆地质资料的对比研究对盆地内地震层序进行了划分,得到了陆相中、新生界盆地基底即中、古生界海相盆地的顶界埋深、三叠系和上二叠统的残留厚度,推断了陆相层基底地层分布,并根据磁力异常资料推测了海相中、古生界盆地结晶基底埋深,推断了海相中、古生界整体残留情况.下三叠统青龙组和上二叠大隆及龙潭组在南黄海盆地南部坳陷及勿南沙隆起广泛存在,而在北部坳陷的分布则狭窄,中部隆起则由于隆起和剥蚀作用导致这两套地层几乎没有残余.对中-古生界海相盆地和中-新生界陆相盆地的基底特征进行了比较,认为海相中、古生界在南黄海地区区域性存在,海相层厚度分布特征受基底起伏控制,同时受到印支板块运动的影响,中部隆起区是海相中、古生界比较稳定的地区.下古生界可能在南黄海盆地广泛分布,但受资料限制,还难以获知其残余地层的特征.

三塘湖盆地二叠系陆相热水沉积方沸石岩特征及成因分析

在新疆三塘湖盆地野外露头及钻井中二叠统芦草沟组(P2l)厚层黑色泥岩中发现多层白色纹层状方沸石岩。根据主要造岩矿物特征,将其大致分为两类,第一类为方沸钾长白云岩,主要造岩矿物包括细粒方沸石、泥晶钾长石(透长石、正长石)、泥晶白云石、泥晶铁白云石等,碳酸盐矿物以高的Fe、Mn含量为特征;第二类为方沸硅质岩与硅质方沸石岩,以细粒方沸石及泥晶石英为主,含少量碳酸盐。扫描电镜观察方沸石以自形的四角三八面体少见,多为它形块状或无定形胶体状。样品主量元素以富SiO2、Al2O3、Na2O、贫TiO2为特征,微量元素Th、Nb、Ti强烈亏损,Sr/Nd比值为44.73～831.78,Nb*介于0.02～0.17之间。∑REE总量偏低7.33～20.619μg/g,LREE/HREE为4.77～11.20,δEu 0.60～0.99略具负异常,δCe 0.96～1.04,基本无亏损,稀土配分曲线为较平缓的右倾。方沸石岩微量元素、稀土元素配分曲线与研究区早、中二叠世玄武岩、粗面岩及上地壳有较大差异。87Sr/86Sr介于0.705 118～0.706438之间,低于同时期全球海水及中上二叠统海相碳酸盐的87Sr/86Sr比值,143PNd/144Nd介于0.512 454～0.512 713之间,εNd介于-0.81～3.84之间,表明造岩热液可能含有幔源组分。通过详细的岩石学、地球化学及Sr、Nd同位素研究,认为这是一类与陆相裂谷盆地湖底热泉喷流作用有关的热水沉积岩组合,热液组分除了有壳源物质及大气水等的混入外,可能还有深部物质的参与。

论陆相含油气沉积盆地地下水动力场与油气运移、聚集

含油气沉积盆地地下水动力场的形成、演化是沉积盆地演化在孔隙流体中的综合反映,它直接受盆地地貌、水文网、沉积环境、构造性质及其演化史的控制。地下水动力场的形成、演化与油气的运移、聚集和分布规律具有十分密切的关系。含油气沉积盆地通常经历了多期水文地质旋回,从而决定了在一个独立的水动力体系中油气阶段性运移和阶梯式—环带状分布的特点。油气的阶梯式—环带状分布以沉积凹陷控制的包括部分相邻三级构造单元的具有相对独立的水动力体系为基本单元。因此,作为一个具有多个沉积凹陷的盆地来说,油气的分布通常由多个环带复合而成。