Texture and tectonic attribute of Cenozoic basin basement in the northern South China Sea

Based on the drilling data,the geological characteristics of the coast in South China,and the interpretation of the long seismic profiles covering the Pearl River Mouth Basin and southeastern Hainan Basin,the basin basement in the northern South China Sea is divided into four structural layers,namely,Pre-Sinian crystalline basement,Sinian-lower Paleozoic,upper Paleozoic,and Mesozoic structural layers.This paper discusses the distribution range and law and reveals the tectonic attribute of each structural layer.The Pre-Sinian crystalline basement is distributed in the northern South China Sea,which is linked to the Pre-Sinian crystalline basement of the Cathaysian Block and together they constitute a larger-scale continental block—the Cathaysian-northern South China Sea continental block.The Sinian-lower Paleozoic structural layer is distributed in the northern South China Sea,which is the natural extension of the Caledonian fold belt in South China to the sea area.The sediments are derived from southern East China Sea-Taiwan,Zhongsha-Xisha islands and Yunkai ancient uplifts,and some small basement uplifts.The Caledonian fold belt in the northern South China Sea is linked with that in South China and they constitute the wider fold belt.The upper Paleozoic structural layer is unevenly distributed in the northern South China.In the basement of Beibu Gulf Basin and southwestern Taiwan Basin,the structural layer is composed of the stable epicontinental sea deposit.The distribution areas in the Pearl River Mouth Basin and the southeastern Hainan Basin belong to ancient uplifts in the late Paleozoic,lacking the upper Paleozoic structural layers.The stratigraphic distribution and sedimentary environment in Middle-Late Jurassic to Cretaceous are characteristic of differentiation in the east and the west.The marine,paralic deposit is well developed in the basin basement of southwestern Taiwan but the volcanic activity is not obvious.The marine and paralic facies deposit is distributed in the eastern Pearl River Mouth Basin basement and the volcanic activity is stronger.The continental facies volcano-sediment in the Early Cretaceous is distributed in the basement of the western Pearl River Mouth Basin and Southeastern Hainan Basin.The Upper Cretaceous red continental facies clastic rocks are distributed in the Beibu Gulf Basin and Yinggehai Basin.The NE direction granitic volcanic-intrusive complex,volcano-sedimentary basin,fold and fault in Mesozoic basement have the similar temporal and spatial distribution,geological feature,and tectonic attribute with the coastal land in South China,and they belong to the same magma-deposition-tectonic system,which demonstrates that the late Mesozoic structural layer was formed in the background of active continental margin.Based on the analysis of basement structure and the study on tectonic attribute,the paleogeographic map of the basin basement in different periods in the northern South China Sea is compiled.     

鄂尔多斯盆地深部热结构特征及其对华北克拉通破坏的启示

基于二维稳态热传导方程,利用有限元数值模拟方法,选取东西向横穿鄂尔多斯盆地地质与地球物理解释大剖面进行了深部温度场数值模拟研究,得到了华北克拉通西部的鄂尔多斯盆地下伏岩石圈热结构特征.地幔热流变化范围:21.2~24.5mW·m-2,体现为东高西低特征.壳幔热流比(Qc/Qm)介于1.51~1.84之间,为"热壳冷幔".与华北东部地幔热流对比表明,西部的鄂尔多斯盆地相对处于稳定的深部动力学环境.在岩石圈热结构研究基础上,对克拉通地震岩石圈与热岩石圈厚度差异进行了对比,研究表明:鄂尔多斯盆地西部地震岩石圈与热岩石圈厚度差异约达140km,而东部的汾渭地堑,渤海湾盆地二者差异逐渐减小.华北克拉通自西向东,地震岩石圈厚度与热岩石圈厚度差异不断减小,意味着华北克拉通岩石圈下部的软流圈地幔黏性系数自西向东逐渐降低,本文从地热学角度可能印证了太平洋俯冲脱水作用对华北克拉通的影响.     

Evolution and petroleum systems of the Ying-Qiong Basin

The Ying-Qiong Basin, a newly-discovered large gas province in China, lies to the west and south of the Hainan Island. Although the Yinggehai Basin and the Qiongdongnan Basin are different in genesis, the rapid subsidence and the fast deposition since 5 Ma made both of them share the same environments of overtemperature and overpressure, which resulted in different petroleum systems from others in China. Part of tht study results of the State Eighth Five-Year-Plan Key Science and Technology Prolects     

向错-位错组合模型模拟渭河盆地地壳水平变形特征

基于向错-位错组合模型模拟渭河盆地内主要断层的滑动与转动运动变形,通过数值计算获得断层滑动及转动变形引起的地表水平位移,并与盆地内实测GPS水平位移进行了对比。结果表明:采用向错-位错组合模型能够完整地描述断层实际的滑动与转动运动变形状态,组合模型模拟断层滑动与转动引起的地表水平位移与实测GPS水平位移,无论在量级或是运动趋势上均具有较好的一致性特征。     

黄河中下游活动断层分布及其对古河道变迁的影响

黄河流域是我国遭受地震灾害最为严重的流域,近年来探测工作对黄河中下游的活动断层有较多新认识,如构成北华北盆地与南华北盆地新构造分界的新乡-商丘断裂,新发现存在多个晚更新世活动段,具备发生中强级以上地震的可能,对识别沿黄河中下游的地震危险源、提高地震危险性认识有重要影响。本文通过总结近年来活动断层探测的最新进展,分析了沿黄河中下游地区的活动断层分布特征及其可能产生的灾害影响,并提出后续工作规划建议。     

南海前新生代残留盆地分布综合地球物理研究

为了对南海海域的前新生代残留盆地分布有个整体而全面的认识,本文开展了南海残留盆地宏观分布的综合地球物理研究.通过岩石物性分析,综合重、磁、震等地球物理方法,利用正演与反演方法,分区计算并求取了南海的重力基底和磁性基底埋深,得到了中生界及前中生界残余厚度,给出了整个南海前新生代残留盆地的宏观格架与残余厚度分布特征并讨论了...     

南海北部盆地基底岩性地震-重磁响应特征与识别

针对性选取东南沿海露头剖面18条,采集245件南海盆地基底可能出现的岩性样品,测定其密度和磁化率,建立各种岩性的密度-磁化率交会图版,以此约束过井地震剖面和重磁异常的地质解释,总结出南海北部盆地基底火山岩、侵入岩、变质岩和沉积岩4大类11亚类岩性的地震-重磁响应特征.应用重磁震-岩性解释模型逐一对南海盆地北部主干剖面进行地质-地球物理综合解释,从而实现了盆地基底岩性的平面填图.这种从盆缘剖面到盆地内部、从岩石物性测量到地质-地球物理综合解释的方法,在资料获取难度大、地质条件复杂的南海盆地基底地质研究中,业已证明是行之有效的,相信在其他盆地研究中也会有借鉴意义.     

华北盆地强震孕育的动力学机制研究

强震活跃区通常出现在地壳变形剧烈的地区.但是,华北盆地地壳变形速率小,而破坏性强震却十分频繁.文中利用有限元方法对华北盆地发震断层下方可能存在的速度异常体进行了力学分析,计算结果显示：无论这个异常区是低速异常还是高速异常,在水平构造力的作用下（无论是挤压还是引张力作用）,应力及应变能密度都在空间某些区域积聚.根据本文的工作及前人的研究结果,认为华北盆地强震孕育的物理机制如下：华北克拉通在减薄、破坏过程中,浸入的岩浆或上涌的地幔物质经过漫长的地质时期演化,成为低速异常体.当断裂带下面存在这种低速异常体时,水平向构造力的作用,会使异常体上方应力集中、应变能积聚.当异常体上方的应力水平达到某种限度,介质发生破坏.在破坏过程中,异常体释放的能量,使断裂带上的应变能集聚速度加快;另一方面,异常体的破坏使断层的闭锁面积减小.随着外部构造应力的持续加载,当发震断层上的应力及能量积累达到一定极限,断层产生错动,发生强震.同时,文中结果还显示,断层在从闭锁、积累能量到解锁、发生强震的过程中,其下方的低速异常体起着重要的推进作用.     

Hyperextended crustal structure of the Qiongdongnan Basin and subsequent magmatic influence from the Hainan mantle plume

Science China Earth Sciences - The Qiongdongnan Basin (QDNB) is a rift basin located in the extension direction of the oceanic ridge of the Northwest Subbasin of the South China Sea. This basin is...     

A Cretaceous to Paleocene-Eocene South China sea basin origin for the Zambales Ophiolite Complex,Luzon, Philippines?

Abstract The Eocene Zambales Ophiolite Complex that exhibits transitional mid-ocean ridge basalt-island arc tholeiite (MORB-IAT) characteristics was formed in a subduction-related marginal basin. The different surrounding marginal basins of the Philippines, namely, the South China Sea, Sulu Sea Basin, Celebes Basin and the West Philippine Basin have all been modeled to be of probable provenance of this ophiolite complex. Certain information (e.g. age, rock geochemistry, paleomagnetic rotations) and limitations, nevertheless, are inconsistent with the ophiolite complex being generated in these regions. Recent geophysical evidence suggests that the southwest sub-basin of the South China Sea Basin is probably Cretaceous to Paleocene-Eocene in age. This makes it possible to speculate that the Zambales Ophiolite Complex could have come from this sub-basin. The present day rifting of the southern Izu-Mariana arc can be taken as a modern day analog of this type of ophiolite generation.     

Detrital zircon U-Pb dating in the southern Hefei Basin: Evidence for exhumation of HP-UHP rocks of the Dabie Orogen

The Hefei Basin of eastern China developed in response to uplift of the Dabie Orogen, and zircon dating can be used to assess the exhumation history of the orogen. Zircons were collected from samples of the Lower Jurassic Fanghushan Formation and Middle Jurassic Sanjianpu Formation in the southern Hefei Basin, and mica-quartz schist and biotite granite gneiss from the Susong Complex of the Dabie Orogen. The zircon U-Pb dating was undertaken using laser ablation-inductively coupled plasma-mass spectrometry. The detrital zircons from conglomerates of the Fanghushan Formation and from clasts within the conglomerates have age-frequency distributions with the main clusters between 2.0 and 1.8 Ga, similar to age data of the Susong Complex. On the other hand, the zircons of the Fanghushan Formation do not show the age cluster at 1000–900 Ma that characterizes zircons in the underlying metasediments of the lower Paleozoic Foziling Group. A cluster of Triassic zircon ages also appears in the arkosic sandstones of the Fanghushan Formation. These data indicate that the provenance of the Fanghushan Formation was a mixture of high-pressure(HP) and ultrahigh-pressure(UHP) Triassic metamorphic rocks, Paleozoic magmatic rocks, and the Susong Complex, but not the lower Paleozoic Foziling Group even though it directly underlies the sediments of the Hefei Basin. Two samples from the Sanjianpu Formation show zircon age clusters at 797 and 791 Ma(middle Neoproterozoic)and 226 Ma(Triassic), and again, these are markedly different from the age clusters that characterize the Foziling Group. It seems, therefore, that despite the Foziling Group being at the surface in the underwater depositional area of the Hefei Basin, it was not exposed in the source area of the Hefei basinal sediments during the Jurassic, and there are two possible reasons for this.First, the exhumation of the Dabie Orogen was directed partly towards the north, in the process of which some of the Foziling Group was covered. Second, the Susong Complex rocks became involved in the development of an accretionary wedge, thus covering some of the Foziling Group during the process of subduction.     

A comparative study of the atmospheric circulations associated with rainy-season floods between the Yangtze and Huaihe River Basins

Here we present the results from the composite analyses of the atmospheric circulations and physical quantity fields associated with rainy-season for the selected floods cases over the Yangtze and Huaihe River basins for the 21 years(1990–2010),using the daily rain gauge measurements taken in the 756 stations throughout China and the NCEP/reanalysis data for the rainyseasons(June–July)from 1990 to 2010.The major differences in the atmospheric circulations and physical quantity fields between the Yangtze and Huaihe River basins are as follows:for flooding years of the Yangtze River Basin,the South Asia high center is located further east than normal,the blocking high over the Urals and the Sea of Okhotsk maintains,and the Meiyu front is situated near 30°N whereas for flooding years of the Huaihe River Basin,the South Asia high center is further west than normal,the atmospheric circulations over the mid and high latitudes in the Northern Hemisphere are of meridional distribution,and the Meiyu front is situated near 33°N.In addition,there are distinct differences in water vapor sources and associated transports between the Yangtze and Huaihe River basins.The water vapor is transported by southwesterly flows from the Bay of Bengal and monsoon flows over the South China Sea for flooding years of the Yangtze River Basin whereas by southeast monsoons from the eastern and southern seas off China and monsoon flows over the South China Sea for flooding years of the Huaihe River Basin.     

内蒙古通辽5.3级地震序列特征及发震背景分析

2013年4月22日在赤峰—开原断裂中段发生了内蒙古通辽5.3级地震,对我国华北和东北地区的地震形势产生双重影响。基于K值、G-R关系、能量释放比例RE和M-T等指标判定通辽5.3级地震为主震-余震型。根据1900年以来东北地区中强地震时空演化规律分析认为,大兴安岭和松辽盆地5级以上地震具有基于时间相依的空间对跳现象,通辽5.3地震是继2008年6月10日阿荣旗与鄂伦春交界5.2级地震之后,对跳发生于松辽盆地东南边缘的一次中强地震;对比东北地区以往震例分析认为,通辽5.3级地震既具有符合历史统计规律的普遍性,又具有不同于历史统计规律的特殊性。根据2011年3月11日日本东海岸9.0级强震前后东北地区中等以上地震的时空演化特征分析认为,海拉尔盆地及大兴安岭过渡带、环渤海地区至开鲁盆地的"菱形"区域是日本9.0级地震之后我国东部地区响应最为强烈的地区。由于同时受到日本9.0级地震和鄂霍次克海8.2级深震前所未有的双重影响,2013年东北地区的松辽盆地史无前例的发生了8次5级以上中强地震,未来东北地区很可能将重启新的地震活动格局。     

汶川地震前后太原盆地应力场变化特征研究

利用小震震源机制解、地震视应力、GPS测量结果等资料,对汶川地震前后太原盆地应力场变化特征进行了研究。结果表明,汶川地震对太原盆地构造应力场的影响较为显著,不仅改变了应力场的方向,也改变了应力值的大小;应力场特征由震前NNE-SSW向拉张应力的局部小区域应力场为主,转为震后NEE-SWW向挤压应力为主且接近华北地区应力场。该变化态势有利于局部应变能积累,因而可能是太原盆地中小地震活跃的诱发因素。     

山西断陷带地壳结构的接收函数研究

利用2006年8月到2008年3月北京大学在山西断陷带南部架设的两条东西向流动观测地震台阵记录的远震资料,提取各台站接收函数,然后进行倾斜叠加(Slant stack)和台阵偏移成像,获得了沿台阵横穿山西断陷带的地壳和上地幔的精细结构变化.研究结果显示,山西断陷带下面莫霍面存在明显不连续,莫霍面上隆约4~6 km,纵横波速比从两侧的1.75上升为山西断陷带内部2.0左右,且中、下地壳可能存在一个低速层.山西断陷带的构造模式沿相距140 km的两条剖面表现出明显差异:南端的临汾盆地为拉张作用下的纯剪切模式,向北转化为太原盆地的简单剪切模式.     

Subdivision and age of the Yanchang Formation and the Middle/Upper Triassic boundary in Ordos Basin,North China

The Yanchang Formation is extensively developed in the Ordos Basin and its surrounding regions. As one of the best terrestrial Triassic sequences in China and the major oil-gas bearing formations in the Ordos Basin, its age determination and stratigraphic assignment are important in geological survey and oil-gas exploration. It had been attributed to the Late Triassic and regarded as the typical representative of the Upper Triassic in northern China for a long time, although some scholars had already proposed that the lower part of this formation should be of the Middle Triassic age in the mid-late 20th century. In this paper, we suggest that the lower and middle parts of the Yanchang Formation should be of the Ladinian and the bottom possibly belongs to the late Anisian of the Middle Triassic, mainly based on new fossils found in it and high resolution radiometric dating results. The main source rocks, namely the oil shales and mudstones of the Chang-7, are of the Ladinian Age. The upper part of the Yanchang Formation, namely the Chang-6 and the above parts, belongs to the Late Triassic. The uppermost of the Triassic is missed in most parts of the Ordos Basin. The Middle-Upper Triassic Series boundary lies in the Yanchang Formation, equivalent to the boundary between Chang-7 and Chang-6. The Ladinian is an important palaeoenvironmental turning point in the Ordos Basin. Palaeoenvironmental changes in the basin are coincidence with that of the Sichuan Basin and the main tectonic movement of the Qinling Mountains. It indicates that tectonic activities of the Qinling Mountains are related to the big palaeoenvironmental changes in both the Ordos and Sichuan Basins, which are caused by the same structural dynamic system during the Ladinian.     

Natural gas origins of large and medium-scale gas fields in China sedimentary basins

China sedimentary basins present abundant natural gas resource thanks to its unique geological settings.Marine highly-matured hydrocarbon source rocks,widespread coal-measure strata and low temperature Quaternary saline strata,etc.,indicate the wide foreground of China natural gas resources. Up to now,most of the petroliferous basins have been discovered to have wholesale natural gas accumulation from Precambrian,Paleozoic,Mesozoic to Cenozoic in the east,the central,the west and the coast of China.These large and medium-scale gas reservoirs are mainly composed of hydrocarbon gas with big dry coefficient,tiny non-hydrocarbon,wide carbon isotope distribution and varying origin types,the hydrocarbon gas includes coal-formed gas,oil-formed gas,biogenic gas and inorganic gas, etc.Coal-formed gas is the main type of China natural gas resources,in particular several explored large-scale gas fields(>100 billion cubic meter)of Kela 2,Sulige and Daniudi,etc.,they all belong to coal-formed gas fields or the gas fields consisting mostly of coal-formed gas.Oil-formed gas is also abundant in China marine basins,for example marine natural gas of Sichuan Basin generated from crude oil cracking gas.Primary and secondary biogenic gas fields were discovered respectively in the Qaidam Basin and Western Slope of Songliao Basin.In addition,inorganic gases are mainly distributed in the eastern China,in particular the Songliao Basin with abundant carbon dioxide accumulation,indicating that the eastern China present large exploration potential of inorganic gas.     

利用随机噪声研究华南地区瑞利波相速度特征

基于2009~2010年国家、区域测震台网的387个宽频带台站数据,通过互相关方法提取到可靠的瑞利波经验格林函数,利用相位匹配滤波时频分析技术测量瑞利波相速度频散曲线,最后采用噪声层析成像方法获得了华南地区不同周期的瑞利波相速度分布图。结果显示,华南地区速度结构横向变化幅度较小,反映了华南地区作为一个整体较为稳定,与华南地区自晚中生代以来未发生过强烈构造活动的特征基本一致;虽然华南地区整个岩石圈速度结构较为均匀,但扬子块体西部、四川盆地与扬子块体东部、华夏块体间存在明显的速度差异,体现在周期为8~10s时华夏块体相速度大于扬子块体西部、川滇块体以及四川盆地,由于沉积层较厚四川盆地速度最低;周期为10~30s时华夏块体面波相速度大于扬子块体西部和四川盆地,而川滇块体速度最低;周期为35s时扬子块体、华夏块体、四川盆地的速度基本一致,且高于川滇块体,这与华南地区地壳厚度明显小于川滇块体的特征相符。     

南海北部深水区盆地热历史及烃源岩热演化研究

南海北部深水区是中国重要的油气潜力区.本文在前人对其现今地温场和正演热史研究的基础上,利用磷灰石(U-Th)/He和镜质体反射率(R_o)数据对根据拉张盆地模型正演获得的热历史进行了进一步约束,并在此基础上对南海北部深水区的烃源岩热演化进行了研究.研究结果表明基于盆地构造演化模型的正演热历史可以作为烃源岩热演化计算的热史基础,而盆地内主力烃源岩热演化计算结果显示:南海北部深水区存在4个生烃中心,即珠江口盆地的白云凹陷和琼东南盆地的乐东凹陷、陵水凹陷和松南凹陷,生烃中心烃源岩有机质现今处于过成熟状态,以生气为主;受盆地基底热流显著升高的影响,32~23.3 Ma时段为南海北部深水区烃源岩快速成熟阶段,琼东南盆地烃源岩有机质现今(2.48 Ma后)还存在一期加速成熟过程,而珠江口盆地则不存在此期快速成熟过程.     

西峡盆地含恐龙蛋化石剖面磁性地层学结果及其构造地质意义

通过对河南南阳西峡盆地含恐龙蛋化石的阳域-丹水剖面的岩石磁学与古地磁学研究表明,该陆相沉积地层的特征剩磁载体以赤铁矿与磁铁矿为主,特征剩磁通过了倒转检验,表明其很可能为岩石形成时期获得的原生剩磁.结合该剖面古生物资料,磁性地层学结果表明,剖面上部2973~3023 m处年代为83~79 Ma;该剖面蛋化石所在最高层位年龄不晚于83 Ma,暗示该地区大型爬行动物的绝灭可能与西峡地区当时的气候、环境变化有关.此外,自晚白垩世以来,该剖面所处位置相对华北和华南地块发生了约18°的顺时针旋转,可能由该地区的局部构造活动引起.