扬马延微陆块构造特征及火山型被动陆缘远端带构造演化模式

随着全球油气勘探的不断深入,北大西洋极地逐渐成为油气勘探研究的前沿领域,而扬马延矿区勘探程度极低。基于中海油冰岛矿区新采集的地震及重磁资料,结合其他有关扬马延微陆块最新的研究资料,开展了扬马延微陆块的地层和构造特征分析,以及与共轭盆地的对比,建立了扬马延火山型被动陆缘远端带的构造演化模式。研究表明:位于北大西洋格陵兰与挪威之间海域的扬马延微陆块,与北大西洋两侧陆架盆地古生代-中生代地层具有共轭特征;构造呈NE-SE向展布,发育拆离断裂体系,与挪威西部陆架盆地中生界拆离断裂体系具有相似性;构造内部受岩浆侵入及喷出等强烈影响,发育向海倾斜反射层(SDR)及岩浆溢流相沉积。在上述研究基础上,探讨了扬马延微陆块与格陵兰古陆和波罗的海古陆拉断分离的构造演化过程,认为扬马延在古生代-中生代与格陵兰古陆和波罗的海古陆为一体,在经历了古生代-中生代陆内碰撞、弱伸展到陆内裂谷和陆内热沉降后,受北大西洋拉开影响,经历了古近纪和新近纪火山型被动陆缘远端带的形成演化过程,在55 Ma第一次洋中脊扩张期,与波罗的海古陆挪威陆缘盆地分离,在25 Ma第二次洋脊跃迁时期,新生洋脊扩张导致扬马延微陆块与格陵兰古陆分离,在沉积与构造上开始与北大西洋火山型被动陆缘盆地产生分异,最终扬马延微陆块成为孤立在洋壳上的一个"弃子"。本次关于扬马延微陆块的研究揭示了火山型被动陆缘远端带在岩浆活动、拆离断裂作用下,减薄-破裂的残余陆壳及内部新生洋壳的构造面貌及板块构造背景下的演化过程。      

Moho Structure of the Southwest Sub-Basin,South China Sea,from a Multichannel Seismic Reflection Profile NH973-1

Moho structure provides important clues for understanding crustal structure, isostatic state and magmatic flux from mantle to surface. Across-basin Moho structure of the South China Sea(SCS) is important for understanding crustal evolution mechanisms of both continental break-up and seafloor spreading processes. Southwest Sub-basin(SWSB) opened up the latest and has the closest continental margins, making it the best to study the across-basin structure. Multichannel seismic(MCS) reflection data of line NH973-1 that crosses SWSB in NW-SE direction were reprocessed in order to image Moho structure. In MCS data, Moho reflectors are observed in places, which were not revealed in prior researches. The Moho generally shows symmetric structure on both sides of the central rift valley(CRV) and with variations in crustal thickness. Around CRV, the Moho is 2 seconds depth in two-way travel time(TWTT) beneath the igneous basement, which corresponds to 7 km depth, indicating normal oceanic crustal accretion during the ending of seafloor spreading. Close to the continent-ocean boundary(COB), the Moho becomes shallow to 1 second depth in TWTT(3.5 km), implying strong crustal thinning towards the continent, probably because of poor magma supply at the beginning of seafloor spreading. At south COB, the Moho depth under the crust almost reaches zero, which could be explained as a result of exhumed mantle. In addition, two low-angle, deep-penetrating normal faults are observed at south COB. The faults cut across the Moho into the upper mantle, which may be attributed to lithospheric hyper-stretching at COB during continental break-up.     

南海西南次海盆V型尖端地壳岩石圈最终裂解的特征及过程

为了明确南海西南次海盆V型尖端地壳岩石圈发生最终裂解的特征及其演化过程,通过精细的构造解释、断层活动性定量分析、不同构造演化阶段盆地原型分析、沉降速率分析、沉降史模拟等方法综合分析表明,南海西南次海盆V型尖端临界破裂区为远端带和洋陆转换带构成的地壳岩石圈强烈伸展区,依据地壳岩石圈几何形态,该区域可进一步划分为箱型域和楔型域。楔型域内盆地原型可划分为断陷盆地（Tb-SD）、拆离盆地（SD-PD）和拗陷盆地（PD-Bi）;箱型域在古新世-渐新世（Tb-SD）盆地原型为断陷盆地,之后该区域进入被动沉降期。新生代以来,南海西南次海盆V型尖端在构造演化过程中,盆地沉降中心由陆向洋方向逐渐迁移,岩浆作用在断拗转换幕发育最强烈,致使岩石圈地壳最终发生裂解。区域资料对比分析表明,南海西南次海盆V型尖端在不同构造带内,盆地构造-地层格架具有差异性,且南海西南次海盆V型尖端经历"双拆离作用"后地壳发生破裂,岩浆侵入,形成原洋洋壳。该认识对南海西南部深水盆地内油气勘探具有重大指示意义。      

ON TECTONIC PROBLEMS OF THE OKINAWA TROUGH

The Okinawa Trough is a very active tectonic zone at the margin of the Northwest Pacific and is typical of back-arc rifting at the young stage of tectonic evolution. Many scientists from Japan,China, Germany, France, the U. S.A. and Russia have done a lot of geologic and geophysical investigations there. It is well known that the Okinawa Trough is an active back-arc rift with extremely high heat flow, very strong hydrothermal circulation, strong volcanic and magmatic activity, frequent earthquakes,rapid subsidence and rifting, well-developed fault and central graben. But up to now, there are still some important tectonic problems about the Okinawa Trough that require clarification on some aspects such as the type of its crust, its forming time, its tectonic evolution, the distribution of its central grabens, the relationship between its high heat flow and tectonic activity. Based on the data obtained from seismic sur-vey, geomagnetic and gravity measurements, submarine sampling and heat flow measurements in the last 15 years, the author discusses the following tectonic problems about the Okinawa Trough: (1) If the Okinawa Trough develops oceanic crust or not. (2) Is the South Okinawa Trough tectonically more active than the North Okinawa Trough with shallower water and few investigation data on it. (3) The formation time of the Okinawa Trough and its tectonic evolution. The Okinawa Trough has a very thin continental crust. Up to now, there is no evidence of oceanic crust in the Okinawa Trough. The North, Middle and South Okinawa Trough are all very strongly active areas. From 6 Ma B.P. , the Okinawa Trough began to form. Since 2 Ma, the Okinawa Trough has been very active.     

利用高分辨率地球影像研究全球洋壳活断层分布

利用谷歌三维地图勾绘出全球海底现今主要断层构造带的分布图,为观察海洋地壳运动与演化过程提供新的方法和视角,对海底活断层的分布和演化机理、海底扩张、地幔对流等方面的深入研究和探索具有重要意义。     

大陆岩石圈的增厚及对流剥离对青藏高原隆升的影响

伴随着印度板块对欧亚板块南缘的碰撞、挤压,青藏高原地壳及下伏地幔岩石圈的厚度增加了１倍。增厚岩石圈热结构的变化可导致高原海拨下降约１５００ｍ。其对流剥离并被较热的软流圈物质替代可用以解释青藏高原自８百万年或３百万年前开始的快速隆升。大陆岩石圈的增厚及热结构变化和对流剥离可能是青藏高原自９百万年前开始的夷平—快速隆升过程的主导控制因素。     

南海南部陆缘盆地裂陷-漂移-前陆期构造演化及沉积响应:以礼乐盆地为例

通过礼乐盆地构造-地层-沉积分析，查明了其构造演化及沉积充填特征，揭示了其与南海扩张事件的成因联系，为南海边缘海演化研究提供了参考。研究结果表明:礼乐盆地新生代构造-沉积演化经历了3个差异显著的阶段，即古新世-早渐新世陆缘裂陷-滨浅海碎屑岩沉积阶段、晚渐新世-早中新世裂离漂移-浅海碳酸盐岩沉积阶段、中中新世以来周缘前陆挠曲沉降-区域差异沉积阶段。古新世-早渐新世，古南海向东南俯冲，华南古陆陆缘因水平引张力作用发生被动裂陷，形成礼乐盆地；此时以滨浅海环境为主，受碎屑物源供给控制，在盆地西北部发育一系列规模相对较大的辫状河三角洲，礼乐盆地东部、南部邻近古南海，仅在孤立隆起边缘发育规模较小的扇三角洲。晚渐新世-早中新世，古南海持续俯冲，新南海扩张，礼乐-巴拉望地块裂离华南古陆，向南漂移，盆地沉降缓慢，断层活动弱；此时以浅海-半深海环境为主，碎屑物源匮乏，盆地北部发育大型碳酸盐岩台地和生物礁，南部总体为半深海环境。中中新世以来，新南海扩张停止，礼乐-巴拉望地块向菲律宾岛弧俯冲碰撞，礼乐盆地进入周缘前陆期，以非对称挠曲沉降为特点，水深增大，断层活动增强；此时以半深海-浅海为主，盆地北部总体以碳酸盐岩台地和生物礁为特色，盆地南部局部发育深水重力流沉积。礼乐盆地构造-沉积演化与古南海俯冲-消亡、新南海扩张-关闭过程密切相关。      

鲁西地区石门山—凤仙山岩体的锆石SHRIMP U-Pb定年及形成时代

鲁西地区石门山岩体主要岩性为片麻状花岗闪长岩,原划为新太古代早期侵入岩。根据新测锆石SHRIMPU-Pb年龄为(2530±8)Ma,其形成时代确定为新太古代晚期。凤仙山岩体为中粒二长花岗岩,锆石SHRIMP U-Pb年龄为(2513±12)Ma,并侵入片麻状花岗闪长岩。石门山岩体属峄山岩套,为TTG质花岗岩,是地幔岩浆侵入混入地壳物质形成的。凤仙山岩体属傲徕山岩套二长花岗岩,为上地壳物质重熔(深熔)作用形成的。峄山岩套TTG类岩石是2560~2530 Ma壳幔岩浆活动的产物,岩体普遍具有片麻状构造,表明经历变质变形作用。未受区域变质作用的傲徕山岩套大规模壳源花岗岩是2530~2500 Ma地壳物质部分熔融形成的,与华北克拉通新太古代末超大陆拼合有关,2530 Ma是鲁西地区重要的构造热事件发生时期。     

四川盆地北缘大巴山前陆构造中—新生代构造隆升史

大巴山前陆构造的抬升剥蚀与保存条件对其矿床和油气藏勘探潜力评价极为重要。应用磷灰石裂变径迹热年代学方法,通过研究大巴山前陆构造热演化史,恢复构造隆升过程,确定其中—新生代构造抬升剥蚀量,探讨大巴山前陆晚期构造隆升对矿床和油气资源的影响。结果表明:大巴山前陆构造在152Ma以前快速沉降,沉降速率平均高达150m·Ma-1,此后便长期处于隆升过程;136~152Ma时期为快速隆升阶段,隆升速率平均为56.3m·Ma-1,隆升量约为900m,是燕山运动导致秦岭造山期后的一次陆内挤压;70~136Ma时期为较缓慢隆升阶段,隆升速率平均为39.4m·Ma-1,隆升量约为2 600m,是秦岭造山晚期挤压的结果;0~70Ma时期的隆升速率为42.8m·Ma-1,持续时间较长,隆升幅度约3 000m,是喜马拉雅构造运动的结果。中生代构造隆升对本区低温热液矿体和油气保存极为不利;上新统以来(8Ma或5Ma),青藏高原快速隆升向东扩展的远程效应对大巴山前陆构造的影响不明显。     

天山博罗霍洛地区构造与演化

天山博罗霍洛地区构造是以中—上元古界为主体组成的赛里木地块为核部,以古生界为两翼的复式背斜构造为骨架,以两翼的扇形逆冲断裂推覆构造十分发育为特征。总结其演化历史,可归纳为:早元古代古陆壳的形成;中—晚元古代稳定型大陆边缘的发育;早古生代大陆裂谷作用;晚古生代活动大陆边缘的形成与造山;中—新生代断块升降、滑脱推覆构造叠加、改造、而形成极其复杂的构造形态。     

Late Cenozoic Tectonic Deformation in the Dongsha Islands and Adjacent Sea Area

Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post-fault sequences (Ⅴ, Ⅵ, Ⅶ). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement(4.4 - 5.2 Ma) and Liuhua movement (1.4 - 1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato-tectonic events correlated to the main collision phases between the East China and Taiwan 5 - 3 and 3 - 0 Ma ago.     

海南岛北部晚中-新生代剥露过程的低温年代学约束

【目的】研究海南岛大地构造在中-新生代的隆升剥露过程与热演化史,为华南地块的构造演化提供有力证据。【方法】利用磷灰石裂变径迹(AFT)、磷灰石及锆石(U-Th)/He等构造热年代学研究方法,重建海南岛北部岩体的构造-热演化历史,分析侵入岩体在不同构造热演化阶段的冷却剥蚀速率,并进一步探讨岩体隆升过程的动力学过程。【结果】AFT年龄介于(33.3±2.5)~(45.0±3.5)Ma之间,磷灰石平均长度为(12.68±0.28)~(13.04±0.9)μm;磷灰石(U-Th)/He(AHe)单颗粒年龄(36.3±2.2)~(60.2±3.7)Ma,锆石(U-Th)/He(ZHe)单颗粒年龄为(79.5±4.9)~(98.4±6.1)Ma及(37.1±2.3)~(59.6±3.7)Ma。联合反演热史揭示,研究区岩体自晚白垩世(约100 Ma)以来的冷却过程有明显的差异性,可分为4个阶段:1)约100~45 Ma相对缓慢冷却阶段;2)约45~35 Ma快速冷却剥蚀阶段;3)约30~35 Ma至10 Ma缓慢冷却过程;4)约10 Ma以来再次快速冷却剥露。【结论】海南岛北部花岗岩体阶段性抬升冷却与(古)太平洋板块的俯冲后撤、西南部印度-欧亚大陆碰撞和中新世晚期菲律宾海板块向西俯冲挤压有关。海南岛北部在Ⅰ、Ⅱ期(始新世晚期)剥蚀阶段基本造成总剥蚀量的2/3。     

Formation and syn-rifting process of the Wan’an Basin, South China Sea

Based on seismic and drilling data, we calculated tectonic subsidence amounts and rates of the Wan’an Basin by backstripping. The genetic mechanism and syn-rifting process of the basin were analyzed in combination with the regional geological setting. The results reveal that the basin syn-rifted in the Eocene and early Miocene under the control of the dextral strike-slip Wan’an Fault Zone. The transtensional/extentional stresses along this fault zone may be attributed to seafloor spreading of the South China Sea (SCS) in multiple episodes. Extensive basal faults and some small initial rifts in the early Paleogene can be related to southeastward extrusion and clockwise rotation of the Indochina Block. During the Oligocene, the nearly N-S directed spreading of the SCS derived the transtensional stresses in a roughly NW-SE orientation. The basin subsided rapidly in the middle and north to form two major subsidence centers. In the early Miocene, the SCS spread again in a nearly NW-SE direction, resulting in rapid subsidence in the southern basin continuous extending until the period ～16.3 Ma.     

Thermo-Rheological Structure and Passive Continental Margin Rifting in the Qiongdongnan Basin,South China Sea,China

To investigate the thermo-rheological structure and passive continental margin rifting in the Qiongdongnan Basin(QDNB),thermo-rheological models of two profiles across the western and eastern QDNB are presented.The continental shelf of western QDNB,having the lowest crustal extension factor,is recognized as the initial non-uniform extension crust model.This regime is referred to as the jelly sandwich-1(JS-1)regime,having a lower crustal ductile layer.The oceanward part of the western QDNB changes from the relatively strong JS-1 to the weak crème br?lée-1(CB-1)regime with a significantly thinned lower crust.However,the crustal extension in the eastern QDNB is significantly higher than that in the western QDNB,with conjugate faults extending deep into the lower crust.The central depression zone of the eastern QDNB is defined as the much stronger JS-2 regime,having a brittle deformation across the entire crust and upper mantle and characteristics of a cold and rigid oceanic crust.Unlike the widespread lower crustal high-velocity layers(HVLs)in the northern margin of the South China Sea,the HVLs are confined to the lower crustal base of the central depression zone of the QDNB.The HVLs of QDNB are the results of non-uniform extension with mantle underplating during the lower crustal-necking stage,which is facilitated by the lower crustal ductile layer and derived by mantle lat-eral flowing.The gigantic mantle low-velocity zone related to the Red River Fault should be a necessary factor for the east-west differential margin rifting process of QDNB,which may drive the lateral flowing in the mantle.     

陕西关中盆地地热资源及壳幔温度结构的地球物理分析

陕西关中盆地地下热水资源丰富,是中国典型的隐伏型中、低温地热资源分布区.为研究关中盆地中、低温地热系统形成机理,认识深部热源条件,利用地球物理方法分析了该区壳幔温度结构.结果表明:计算得到的居里面平均深度为25.0 km,莫霍面平均深度为36.6 km,地壳平均地温梯度为22.60℃·km-1,咸礼断阶、西安凹陷、固市...     

Tectonic Characteristics and Evolution of Bohai Bay Basin, China

Synthetical analyzing the deep geophysical data within Bohai bay basin the authors detect the deep crustal structure presenting high geothermal flux, thinned crust and arched Moho discontinuity, and the basin basement belongs to rigid continental crust. The development of the basin was controlled by two - dimensional faults in NNE and NWW directions. The tectonic units of the basin can be subdivided into three structural divisions: the east, middle and west division. The basin is considered as a continental rift. The tectonic background and regional right - lateral stress field during the late Cretaceous and Paleogene were a compound result of the Kula Plate W - directional subducting under Eurasia Continental Plate in 80 ～ 74Ma and the Philippine sea Plate W -directional subducting under the Eurasia Continental Plate since 60Ma, the long-rang effect of the India Continental Plate wedging into the Eurasia Continental Plate and of the Siberia Plate SE - directional relatively moving.     

大地构造和海陆起源的内波假说（Ⅰ）──关于板块学说的若干问题及其思考

随着资料的积累，不断发现与板块假说相矛盾的事实：地震层析没有发现地幔对流的证据，却发现大陆克拉通具有４００ｋｍ深的“壳根”；海洋地质调查发现了一系列否定板块假说的重要证据，尤其是大西洋中多处发现古岩石，使海底扩张模型受到严重挑战；跨越扩张脊的一系列测量结果实际上否定了扩张假说。此外，作为学说重要支柱的地磁资料的可靠性受到怀疑，板块消减过程中洋底沉积层堆积被否定，大陆碰撞模式与陆上地质资料的不符，动力机制不明，板块模式不适于解释复杂的大陆地质而难以登陆等事实，已令板块构造理论陷入了深刻的危机之中。根据煤和蒸发岩的地史分布等资料，说明一个海陆相对固定的大地构造模型更符合实际。通过对大地构造假说发展史的分析和研究，并借鉴天文学中太阳系的发现史，认为新假说的建立必须从确凿的地质现象，而非多解性的资料和推断出发。由此提出大地构造和海陆起源的内波假说。     

辽东滑移构造宏观特征

展布于辽宁东部鞍山—本溪间的寒岭—偏岭断裂走向为北东东,延长大于200km,运动方向为左行走滑,形成于中生代晚期,与之同期的本溪思山岭—塔子岭—三家子—大卫村屯断裂走向北东,延长140km,运动方向为右行走滑,两者同属于区域性地壳-岩石圈型断裂。研究证明,两者夹持的楔形断块体西起鞍山、海城、营口一线,东至本溪市,是一个陆内滑移造山带,最大滑移距离达37km。本溪市上卧龙—兴隆山断裂走向北西—南东,延长10km,则是其前缘挤压带。这一构造的形成与东亚大陆在中生代以来呈断块状向太平洋扩张有关,与壳内花岗岩质层的水平变异有关,与下辽河断陷内基底层次的侧向伸展力有关。滑移主体以斜切凤城凸起和太子河凹陷,改造着区域构造格架,在其影响区域内形成一个滑移构造体系。对此滑移构造体系的识别与建立,对研究上述地区晚中生代以来地质构造演化、找矿、找水及评价地壳稳定性都有重要意义。     

鲁苏碱性岩套特征及其形成的构造背景

鲁苏碱性岩套是指分布于胶莱盆地内的富钾火山岩系和鲁苏混杂岩带中的富钠侵入岩系 ,它们形成于中生代晚期至新生代早期大陆碰撞造山作用之后的伸展构造背景 ,是拉张作用下上地幔部分熔融与陆壳隆升作用的产物     

湘东北冷家溪群沉积岩地球化学特征及其构造意义

冷家溪群是江南造山带湖南段的最早物质纪录，其沉积构造背景及相关的钦杭结合带位置尚存争议。在野外地质调查基础上，对湘东北金井地区冷家溪群早期-中期相对新鲜砂岩采样进行系统的主量元素和微量元素含量分析，进而按时代先后对砂岩分组并进行地球化学研究，以此探讨沉积期盆地性质及大地构造格局。金井地区冷家溪群砂岩的主量元素组成变化较大，SiO₂质量分数总体较低、Al₂O₃质量分数和Al₂O₃/SiO₂比值较高、K₂O/Na₂O比值高且变化大。轻稀土富集、重稀土平坦、铕负异常明显等特征暨球粒陨石标准化曲线形态与典型的后太古宙页岩和上陆壳相似。主量元素地球化学特征反映沉积环境为弧后盆地，且早期易家桥组和潘家冲组的成熟度较高，主要来源于北邻构造相对稳定的扬子陆块南缘；中期雷神庙组-黄浒洞组的成熟度较低，可能更多来源于南邻构造相对活动的大陆岛弧。各组地层构造环境微量元素判别图解均显示为大陆岛弧环境，但从微量元素特征对母岩的继承性分析，仍反映出弧后盆地环境；有关微量元素参数的相对大小指示早期沉积环境为活动陆缘、中期沉积环境为大陆岛弧，与主量元素特征反映的信息一致。根据上述地球化学证据，提出冷家溪期构造格局与演化过程:早期受古华南洋板块向北西高角度俯冲影响，弧后软流圈上涌导致岩石圈伸展而形成宽阔的弧后盆地，金井地区处于盆地北部而主要接受北邻扬子陆块来源沉积；中期古华南洋板块俯冲角度变缓并推动大陆岛弧向北西运移，弧后盆地收缩，金井地区因构造迁移而主要接受南邻大陆岛弧来源沉积。结合区域资料，认为弧后盆地南邻大陆岛弧大体在安仁-双牌一线。