构造分析方法在伸展盆地中的综合运用

为了更有效地研究伸展盆地，论述了目前伸展盆地研究中几种常用软件的方法和原理，包括用于盆地反演研究的一维Airy均衡模型、二维挠曲回剥模型、平衡剖面技术以及用于盆地正演研究的挠曲悬臂梁模型和二维粘弹塑性热-力学数值模拟模型。综合分析了这些方法的原理、优势与不足，在此基础上进一步探讨了不同方法之间的综合运用。其中平衡剖面技术恢复得到的盆地剖面可以为裂谷期构造沉降展布范围提供约束，并与挠曲悬臂梁模型结合可以得到盆地演化过程中不同时期上地壳的伸展减薄情况。数值模拟方法则在以上盆地模拟方法得到的结果约束下，模拟伸展盆地的形成过程进而得到初始地质参数与演化过程。综合利用盆地分析的方法可以对盆地演化有更准确的认识并指导油气资源的勘探与开发。     

南海双峰盆地的形成演化及其对构造样式的约束

南海北部深水区已逐渐成为我国南海北部油气资源调查的热点区域,开展南海北部双峰盆地构造样式及成因分析研究对进一步认识南海北部沉积盆地的形成演化和评价油气资源潜力具有重要的借鉴意义。利用广州海洋地质调查局已有的二维地震资料,在对双峰盆地地震层序和构造精细解释的基础上,厘定了双峰盆地主要的构造样式;采用平衡剖面技术,重建了双峰盆地的构造演化史;结合南海北部区域构造背景,分析了双峰盆地的性质和成因。研究认为,双峰盆地为与洋壳热沉降有关的坳陷沉积盆地。从神狐运动开始,双峰盆地经历了大陆破裂-大陆裂解-海底扩张完整的构造演化旋回,在持续伸展构造应力场的作用下,形成了双峰盆地,主要发育伸展构造样式、转换-伸展构造样式、重力滑动构造样式和火成构造样式4类,其中伸展构造和火成构造较为发育。     

南海成因机制及北部岩石圈热-流变结构研究进展

南海是西太平洋地区最大的边缘海之一,其北部具有被动大陆边缘特征。南海的形成演化动力学过程对理解该区地质、资源、环境等科学问题有重要意义。综述了近年来在南海北部大陆边缘开展的岩石圈热状态、流变学及南海成因机制和国际上伸展盆地成因数值模拟等方面的研究进展。南海北部大陆边缘区的大地热流相对较高,平均为75 mW/m2,其中绝大部分为来自地幔热流的贡献。莫霍面温度亦较高,从陆架向海盆方向,深部地温越来越高。岩石圈具有温度高、强度低和强烈流变分层等特征,且下地壳表现为韧性流动变形。伸展盆地成因模拟研究已从运动学向动力学模拟过渡,并逐渐强调岩石圈流变学性质的影响。目前对南海成因机制的理解仍存在争议,大陆裂解过程中岩石圈热-流变结构随时间的变化是控制南海形成演化的关键因素,对南海形成中岩石圈的热-流变学结构随时间的演化过程需要进行深入研究。     

琼东南盆地岩石圈伸展模拟探讨——以测线1为例

在挠曲悬臂梁模型的基础上,利用二维正、反演相结合的方法,对琼东南盆地近垂直于盆地走向、过陆架、陆坡的测线1岩石圈不同圈层的伸展因子进行计算。其中,上地壳伸展因子是通过统计地震剖面上断层水平伸展量获得,介于1.678~2.238之间;全地壳伸展因子则采用拉伸前后地壳厚度之比的方法,分布在1.251~2.468之间;岩石圈伸展因子利用剖面二维反演回剥和正演伸展模拟得到的,分布在1.062~2.647之间。沿剖面方向不同圈层的伸展因子综合对比分析表明,琼东南盆地岩石圈发生了随深度变化的伸展,但并非简单的随深度增加,而可能与岩石圈不同层次的流变学特征及伸展前岩石圈流变性的不均匀性有关。     

东海陆架盆地南部中生代成盆过程的数值模拟

采用I2VIS有限差分方法,模拟了东海陆架盆地南部中生代的盆地演化过程。数值模型的构建主要基于研究区域内现有的地震剖面、测井、层析成像等资料获得的中生代地层结构特征。根据模拟结果,对比已知的岩浆侵入特征和断裂组合规律,定量分析了在不同边界条件下,各阶段盆地演化的岩浆断裂及沉积特征,并探讨了影响盆地构造特征的主要因素。得出以下认识:(1)通过改变模型的边界条件发现,层状含水地幔在拉伸环境下,会对地壳结构造成破坏,中生代东海陆架盆地区域性伸展不是盆地演化过程的唯一主控因素。(2)东海陆架盆地中生代的成盆过程及属性与中生代时期上地幔物质流动有着密切关系。(3)中生代的地幔物质流动导致的大规模岩浆事件很可能作用于闽江凹陷之下,由此导致了闽江凹陷的进一步抬升,形成现今的斜坡带,而基隆凹陷进一步沉降,形成凹陷的沉积中心。基于以上结论,认为区域性伸展和上地幔物质流动导致的岩浆上涌两大因素共同控制下,影响了东海陆架盆地南部中生代的演化。     

莺歌海盆地形成与演化的动力学机制

莺歌海盆地位于印支半岛与南海北部大陆边缘交接区,复杂的地质构造背景使其形成演化的动力学机制成为国内外的研究焦点。从区域动力学演化的角度,系统分析了影响莺歌海盆地发育的印支地块构造演化特征,认为莺歌海盆地构造演化主要受印支半岛早期的逃逸挤出构造和晚期的挤压-伸展构造系统影响(或控制),在此动力学驱动机制下,莺歌海盆地新生代以来的构造演化经历了3个阶段,即左旋走滑-伸展裂陷阶段、中下地壳韧性伸展-热沉降阶段和加速沉降阶段。     

南沙海区万安盆地构造演化与成因机制

本文基于地震、钻井和区域地质资料，运用回剥法和平衡剖面技术定量研究了万安盆地的构造沉降和伸展程度，重建盆地的构造演化史并探讨其成因机制。模拟结果表明，万安盆地构造沉降曲线为多段式，其南北部构造沉降差异明显，且沉降中心逐渐向南发展的趋势。晚始新世-渐新世（37.8~23.03 Ma BP）盆地中、北部快速沉降，存在两个沉降中心；早中新世（23.03~16.0 Ma BP）盆地南部也发生快速沉降，整个盆地存在3个沉降中心；中中新世（约16.0~11.63 Ma BP）沉降作用减弱，盆地进入裂后热沉降期。万安盆地的伸展和形成演化呈现北早南晚的特征，与南海海底扩张密切相关，同时受控于万安断裂带交替地右旋-左旋走滑作用，是伸展和走滑双重作用的结果。盆地的构造演化过程可细分为4个阶段:初始裂谷期、主要裂谷期、走滑改造期和裂后加速沉降期。     

南海北部莺歌海盆地成因机制:与渭河盆地构造对比分析的启示

南海北部莺歌海盆地为新生代沉积盆地,地处欧亚板块、太平洋板块和印度-澳大利亚板块交汇处,构造位置独特,复杂的地质构造现象使其形成演化的动力学机制成为国内外研究的热点。同一类型盆地具有相似的构造、沉降、沉积演化历史与成因机制。莺歌海盆地与渭河盆地均位于多板块交汇处,存在长期相对快速沉积、沉降及构造演化迁移等典型走滑型盆地特征。在明确渭河盆地成因机制的基础上,对比两盆地构造、沉降及沉积演化历史,结合莺歌海盆地特殊的构造位置及南海扩张的构造背景,分析得出:莺歌海盆地形成演化和印度-澳大利亚板块与青藏板块碰撞、印支板块逃逸及自身旋转、华南板块向东挤出及太平洋板块俯冲关系密切,受多板块构造活动影响较大,新生代以来先后依次经历左旋走滑、伸展—热沉降—右旋走滑、伸展三大成盆演化期。另外,与渭河盆地相比,莺歌海盆地发育有高温、高压及泥底辟等特殊地质现象,主要受控于热沉降阶段,与渐新世以来(33~15Ma)南海扩张事件具有重要关系。     

莺歌海盆地反转构造变形特征及其动力学演化

莺歌海盆地位于印支半岛与南海北部大陆边缘交接区,复杂的地质构造背景使其形成演化的动力学机制成为国内外研究的焦点。综合新的区域资料,对影响莺歌海盆地发育的区域构造演化特征进行了系统分析,认为新生代以来印度板块与欧亚板块的碰撞造成印支板块的逃逸构造,以及印支板块的顺时针旋转,红河断裂带新生代的变形机制,直接或间接地控制了莺歌海盆地的形成与演化。在此背景条件下,莺歌海盆地新生代以来的构造演化经历了3个阶段,即左旋走滑-伸展裂陷阶段、地壳韧性伸展-热沉降阶段和加速沉降阶段。     

南海中央海盆岩石圈纵向演化模拟

基于南海海盆的地质构造历史、地球物理和构造应力场资料建立准三维有限元模型,对南海中央海盆进行岩石圈纵向演化动力学模拟.本文采用弹塑性各向同性连续岩石介质模型,充分考虑拉伸速率、拉伸位移以及模型参数对模拟结果的影响,共建立了3个模型进行比较.从数值模拟结果可以看出中央海盆在被动拉张的地质构造背景下是单向生长的,动态模拟出南海中央海盆在形成过程中的陆缘裂离、海底扩张两个阶段的岩石圈纵向演化过程,并且分析了两个阶段岩石圈的动力学性质.提出水平的被动拉张力是南海岩石圈纵向演化前两个阶段形成的主要因素,并且在这两个阶段中,岩石圈的纵向演化时间主要集中在海底扩张阶段.     

Peat formation and accumulation mechanism in northern marginal basin of South China Sea

In the present study, the coal-rock organic facies of Oligocene Yacheng Formation of the marginal basin in the South China Sea were classified and divided. In addition, through the correlations of the large-scale coal-bearing basins between the epicontinental sea and the South China Sea, it was concluded that the coal forming activities in the South China Sea presented particularity and complexity. Furthermore, the coal forming mechanisms also presented distinctiveness. The marginal basins in the South China Sea consist of several large and complex rift or depression basins, which are distributed at different tectonic positions in the South China Sea. Therefore, the marginal basins in the South China Sea are not simple traditional units with onshore continental slopes extending toward the deep sea. The marginal basins are known to consist of multi-level structures and distinctive types of basins which differ from the continental regions to the sea. During the Oligocene, the existing luxuriant plants and beneficial conditions assisted in the development of peat. Therefore, the Oligocene was the significant period for the formation and aggregation of the peat. However, the peat did not form in unified sedimentary dynamic fields,but instead displayed multi-level geographical units, multiple provenance areas, instability, and nonevent characteristics. As a result, the marginal basins in the South China Sea are characterized by non-uniform peat aggregation stages. In another words, the majority of the peat had entered the marine system in a dispersive manner and acted as part of the marine deposits, rather than during one or several suitable coal-forming stages.These peat deposits then became the main material source for hydrocarbon generation in all of the marginal basins of the South China Sea. The study will be of much significance for the hydrocarbon exploration in the marginal basins of the South China Sea.     

南海北缘新生代盆地沉积与构造演化及地球动力学背景

南海北缘新生代沉积盆地是全面揭示南海北缘形成演化及与邻区大地构造单元相互作用的重要窗口。通过对盆地沉积-构造特征分析,南海北缘新生代裂陷过程显示出明显的多幕性和旋转性的特点。在从北向南逐渐迁移的趋势下,东、西段裂陷过程也具有一定的差异,西部裂陷活动及海侵时间明显早于东部,裂陷中心由西向东呈雁列式扩展。晚白垩世-早始新世裂陷活动应是东亚陆缘中生代构造-岩浆演化的延续,始新世中、晚期太平洋板块俯冲方向改变导致裂陷中心南移,印度欧亚板块碰撞效应是南海中央海盆扩张方向顺时针旋转的主要原因。     

The final rifting evolution in the South China Sea

Seismic reflection data imaging conjugate crustal sections at the South China Sea margins result in a conceptual model for rift-evolution at conjugate magma-poor margins in time and space.The wide Early Cenozoic South China Sea rift preserves the initial rift architecture at the distal margins. Most distinct are regular undulations in the crust–mantle boundary. Individual rift basins are bounded to crustal blocks by listric normal faults on either side. Moho uplifts are distinct beneath major rift basins, while the Moho is downbended beneath crustal blocks, with a wavelength of undulations in the crust–mantle boundary that approximately equals the thickness of the continental crust. Most of the basin-bounding faults sole out within the middle crust. At the distal margins, detachment faults are located at a mid-crustal level where a weak zone decouples crust and mantle lithosphere during rifting. The lower crust in contrast is interpreted as being strong. Only in the region within about 50 km from the Continent–Ocean Transition (COT) we suggest that normal faults reach the mantle, enabling potentially a coupling between the crust and the mantle. Here, at the proximal margins detachment fault dip either seaward or landward. This may indicate the presence of exhumed mantle bordering the continental margins.Post-rift shallow-water platform carbonates indicate a delay in subsidence during rifting in the South China Sea. We propose that this is an inherent process in highly extended continental margins and a common origin may be the influx of warm asthenospheric material into initially cool sub-lithospheric mantle.On a crustal-scale largely symmetric process predominate in the initial rifting stage. At the future COT either of the rift basin-bounding faults subsequently penetrates the entire crust, resulting in asymmetry at this location. However, asymmetric deformation which is controlled by large scale detachment faulting is confined to narrow areas and does not result in a margin-wide simple-shear model. Rather considerable along-margin variations are suggested resulting in alternating “upper and lower plate” margins.     

Study on the distribution characteristics of faults and their control over petroliferous basins in the China seas and its adjacent areas

As one of the main controlling factors of oil and gas accumulation, faults are closely related to the distribution of oil and gas reservoirs. Studying how faults control petroliferous basins is particularly important. In this work, we investigated the plane positions of major faults in the China seas and its adjacent areas using the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) of the Bouguer gravity anomaly, the fusion results of gravity and magnetic anomalies, and the residual Bouguer gravity anomaly. The apparent depths of major faults in the China seas and its adjacent areas were inverted using the Tilt-Euler method based on the Bouguer gravity anomaly. The results show that the strikes of the faults in the China seas and its adjacent areas are mainly NE and NW, followed by EW, and near-SN. Among them, the lengths of most ultra-crustal faults are in the range of 1 000–3 000 km, and their apparent depths lie between 10 km and 40 km. The lengths of crustal faults lie between 300 km and 1 000 km, and their apparent depths are between 0 km and 20 km. According to the plane positions and apparent depths of the faults, we put forward the concept of fault influence factor for the first time. Based on this factor, the key areas for oil and gas exploration were found as follows: the east of South North China Basin in the intracontinental rift basins; the southeast region of East China Sea Shelf Basin, the Taixinan and Qiongdongnan basins in the continental margin rift basins; Zhongjiannan Basin in the strike-slip pull-apart basins; the Liyue, Beikang, and the Nanweixi basins in the rifted continental basins. This work provides valuable insights into oil and gas exploration, mineral resource exploration, and deep geological structure research in the China seas and its adjacent areas.     

南海海盆海山古地磁及海盆的形成演化

根据海山磁性反演获取的古地磁成果发现,南海海盆东部和西南部的运动形式、生成时代存在很大差异,东部海盆和西南部海盆之间由一条北北西走向的岩石圈压性左旋转换(性)断层——"南海海盆中央断裂"分界.结合已有的地质地球物理成果分析和论证,确定了南海海盆在古南海和与之接壤的华南地块南部边缘形成.南海海盆的形成演化分四个阶段:第一阶段,始新世"古南海断裂"产生,古南海被一分为二;第二阶段,渐新世东部海盆开始发育——扩裂;第三阶段,中中新世西南部海盆开始发育——张裂;第四阶段,南海海盆整体旋转,古南海圈闭.     

南黄海盆地构造特征及油气地质意义

南黄海盆地发育于前南华纪变质基底之上,是一个大型叠合盆地,经历了多期成盆和多期构造改造,形成了海相盆地和中新生代断陷盆地叠合改造型残留盆地。盆地演化历经南华纪—早、中三叠世海相地层发育期、晚白垩世—古近纪箕状断陷发育期和新近纪—第四纪坳陷发育期,为一典型地台—断陷—坳陷多层结构的复合型盆地。通过对地震资料解释、区域地质构造特征分析,综合烃源条件和后期保存条件,探讨了南黄海盆地油气远景。     

南海深水盆地油气地质特征及勘探方向

在深入调研南海深水盆地油气地质条件的基础上,系统分析了油气分布规律和成藏主控因素,明确了油气资源潜力和有利勘探方向,旨在为南海深水油气勘探决策提供科学依据。研究结果表明:南海深水盆地发育在非典型边缘海大陆边缘,其石油地质条件具有特殊性,油气分布特征存在显著的南北差异。其中,南海北部深水的珠江口盆地和琼东南盆地,以构造圈闭型油气藏为主;南海中南部深水的曾母盆地南部和文莱-沙巴盆地,主要为构造圈闭型油气藏,曾母盆地北部以岩性油气藏(生物礁滩型油气藏)为主,万安盆地主要为构造圈闭型和基岩潜山型油气藏。南海北部深水盆地和中南部深水盆地的烃源岩、储盖和圈闭等油气地质特征表明,南海深水盆地具有巨大的油气勘探潜力。南海深水的有利勘探方向为:①琼东南盆地乐东-陵水凹陷的中央峡谷、陵南斜坡带,松南-宝岛凹陷的反转构造带,宝岛凹陷北坡海底扇,长昌凹陷的环A洼圈闭带(海底扇);珠江口盆地白云凹陷的主洼深水扇、主洼两翼、西南断阶带,荔湾凹陷的深水扇。②南海中南部深水盆地的文莱-沙巴、曾母和万安盆地。     

重力模型探寻南海北部陆坡特提斯痕迹

The South China Sea is the largest marginal sea of west Paicfic Ocean.Its valuable to the continental margin.The evolution of Tethyan structure is a very important part of the evolution of the South China Sea.Its formation is due to a sequence opening and closing of Tethys Ocean loke a horn,and made violent influence to the evolution history of the global geologic strcture.When Gondwana continent separated from Euro-Asian continent in the norh,there produced a series of small oceanic basins. The fromation of new oceanic basin was in company with the extinction of the older ones. This recyeling of new oceanic basin was in company with the extinction of the older ones. This reaycling function made the formation of a huge strucfor successive continental margin and oil-gas exploring. Furthermore, it is impirtant for discovering the relationship brtween Tethyan realm and Pacfic realm. In this paper,the authors have done 3 gravtational models basing on deep crustal research,and they want to discuss the reace of Tethyan structure in the northern slope of the South China Sea.     

南海的岩石圈结构与均衡模型

本文用四种方法计算了南海的岩石圈厚度,并建立了南海海盆的岩石圈均衡模型。在此基础上,分析了南海海盆的岩石圈结构特征:即从海盆中部向南、北两侧,层3厚度、地壳厚度和岩石圈厚度逐渐增大,与地壳年龄呈正向关系。这表明,南海海盆有如大洋(大西洋)一样的形成演化机制—由正常的裂谷和扩张过程发育而成。     

Rifted margin architecture and crustal rheology: Reviewing Iberia-Newfoundland,Central South Atlantic,and South China Sea

Crustal rheology controls the style of rifting and ultimately the architecture of rifted margins. Here we review the formation of three magma-poor margin pairs, Iberia-Newfoundland, the central segment of the South Atlantic Rift, and the South China Sea by integrating observational data into a numerical forward modelling framework. We utilise a 2D version of the finite element code SLIM3D, which includes nonlinear temperature- and stress-dependent elasto-visco-plastic rheology and is able to reproduce a wide range of rift-related deformation processes such as flexure, lower crustal flow, and faulting.Extension in cold, strong, or thin crust is accommodated by brittle faults and ductile shear zones that facilitate narrow rifts with asymmetric fault geometries. Hot, weak, or thick continental crust is dominated by ductile deformation and often extends symmetrically into a wide rift system. This simple recipe provides the standard framework to understand initial rift geometry, however, it is insufficient to account for the dynamics of intermediate and late rift stages that shape the final margin architecture.Asymmetric conjugate margins where one side is wide and the other narrow can be formed via both wide and narrow rift styles, which we reproduce with weak and strong crustal rheologies, respectively. Exemplified by the Iberia-Newfoundland conjugates and the Central South Atlantic, we define three characteristic rift phases: an initial phase of simultaneous faulting, an intermediate phase of rift migration that involves sequential fault activity, and finally, the breakup phase. Crustal rheology plays an overarching role in governing the dynamics of these asymmetric margins: we illustrate that weak rheologies generally prolong the phase of simultaneous faulting, while rift migration is enabled by initial fault asymmetry as well as relatively weak crust.Formation of the predominantly symmetric and wide margins of the South China Sea was controlled by extraordinarily weak crust that extended the phase of simultaneous faulting until breakup. The weak crustal rheology of this region relates to the South China Sea's pre-rift history where plate convergence lead to crustal thickening and magmatic additions in a back-arc regime shortly before the onset of rifting.