南海北部陆缘黏土矿物组合特征与地质意义

采用沉积矿物分析方法对南海北部九口探井渐新世—中新世沉积物进行系统的黏土矿物分析.结果表明:南海北部沉积物黏土矿物组成随时间及空间呈现规律性变化,黏土矿物伊/蒙转化深度具有自北向南逐步变浅的规律,与地温梯度升高变化趋势基本一致,这种黏土矿物伊/蒙转化的变化规律反映了南海北部洋陆过渡地壳减薄,莫霍面抬升,热流值升高的趋势.通过黏土矿物组合演变特征与热流变化趋势的相关关系,可以预测区域性温度场变化规律,加深对南海北部洋陆过渡地壳厚度变化的认识.     

南海海底特征、资源区位与疆界断续线

根据南海海底的成因与地形特征 ,并通过建立和分析南海海底数字地形模型 ,将南海的海底分为中央的深海盆地、两侧的阶梯状大陆坡、以及周边亚洲大陆延伸的大陆架 3个地貌单元 .再据 194 7年“南海诸岛位置图”精确计算出二战后依据波茨坦公告为国际认可的断续线疆界的经纬度坐标 ,阐述了中国对南海主权的历史延续性 .最后 ,论述了南海区位与资源的优势 ,论证了其海域具体位置与巨大的经济政治战略意义 .     

中亚与中国西部侏罗纪沉积盆地的成因分析

通过对中亚与中国西部侏罗纪大地构造格局和侏罗系沉积特征的对比分析表明：早-中侏罗世本地区总体处于伸展构造背景之下,地壳向西南方向减薄,海水从西南向东北方向逐渐浸漫;在此背景下形成了两类侏罗纪沉积盆地,一类是被动大陆边缘近海开阔盆地,存在良好的侏罗系油气生储盖组合,另一类是山前先断后拗的陆相盆地,虽然也存在侏罗系烃源岩和储层,但往往缺乏好的盖层。     

沉积边缘与跌积边缘—碳酸盐大陆斜坡古代实例及特征

大陆斜坡是联系浅水台地与深水盆地的枢纽地带,以包括巨大岩块在内的巨厚斜坡边缘型沉积为特征。黔南地区在中三叠世时,具有活跃的碳酸盐大陆斜坡沉积,按其性质,该期斜坡环境可分为沉积边缘型与跌积边缘型。它们主要受强烈而不均匀的断裂作用控制。在不同类型斜坡上,各种沉积作用标志也有较明显的差异。     

南海准被动陆缘深水油气与水合物共生意义

南海北部准被动陆缘深水区处在欧亚、印-澳和太平洋-菲律宾三大板块相互作用之特殊大地构造位置,具有被动大陆边缘拉张裂陷的基本属性和典型断拗双层或三层盆地结构及沉积充填特征,与相邻的北部陆架浅水区一样具备基本油气成藏地质条件。南海北部准被动陆缘深水盆地油气运聚成藏地质条件与世界典型被动陆缘盆地深水油气富集区基本类似,但亦存在一定的差异和特殊性。南海北部深水油气运聚成藏及其空间分布与天然气水合物具有纵向上的共生组合关系及烃源供给上的成因联系,其油气地质意义在于其浅层油气及海底水合物显示可以指示深部油气藏的存在或作为深部油气藏勘探的指向和示踪,而这种空间上的共生叠置关系,亦拓宽了资源勘探领域,扩大了其资源规模及潜力。     

南海玄武岩：扩张洋脊与海山

 南海存在两种火山岩：洋中脊玄武岩（MORB）和洋岛玄武岩（OIB）。国际大洋发现计划（IODP）第349、367、368、368X航次在南海海盆的成功钻取,获得了南海初始扩张（~34 Ma）和停止扩张（~15-16 Ma）前的洋壳样品。南海东部、西南次海盆及北缘洋-陆过渡带代表海盆发展的不同阶段,具有不同的地幔潜能温度、物质组成和洋脊扩张速度,因此产生的洋中脊玄武岩成分差异显著。南海地区在扩张晚期及停止扩张之后存在大规模地幔上涌,与其周缘地区的持续俯冲有关,产出的海山OIB不同于地幔柱活动产生的火山链。南海虽小,但蕴含的信息异常丰富,是窥探地球深部难得的天然窗口。     

闽西南晚古生代-早三叠世沉积特征及其大地构造意义

闽西南晚古生代-早三叠世具有典型的被动大陆边缘沉积建造特征,被动大陆边缘大陆坡向南倾斜,大田、漳平一线相当于当时陆坡下部的位置,沉积盆地中心位于大田-龙岩-永定一带,具有北、南两个方向的物质来源.闽西南晚古生代古生物有特提斯域亲缘分子,早三叠世溪口组是被动大陆边缘最后的海相沉积,其构造演化历史与古特提斯洋的演化在时间和地质特征等方面非常相似.晚古生代-早三叠世早期,闽西南海域可能是古特提斯海域的一个分支,它的构造演化从一个侧面反映了东古特提斯的演化.     

南海北部大陆边缘深水环境的沉积物波

利用南海北部数万公里的多道地震剖面、3.5kHz单道地震剖面、重力活塞柱状样以及精细地形地貌,发现南海北部大陆边缘的深水环境发育有浊流、等深流(底流)、沉积变形等三种单一成因的沉积物波波域,以及复合成因的沉积物波波域,且勾勒了各沉积物波波域的空间分布.并发现,不同类型或同一类型但不同位置的波域其规模差异悬殊、波形特征也千差万别.这种差异背后隐藏着各自独特的成因机制和地理背景,也蕴涵了南海封闭性较强的这一特点所致的等深流循环的、不同于开阔大洋环境的独特性.     

海南岛早二叠世冰海相沉积的确定及其板块构造意义

海南岛西南部东方县境内,分布着一套石炭、二叠纪地层,其中含有特殊沉积——杂砾岩(diamictite)。笔者从地层的剖面组合、沉积组构、砾石特征和岩石薄片等方面对杂砾岩进行了研究。研究表明,运是一种属干冰海相的沉积建造,它在剖面组合、岩性特征和地质时代等方面与西藏北部、云南西部以及东南亚地区分布的冰海相沉积相同或相似,与冈瓦纳大陆冰碛岩亦属同时代产物。本区冰海沉积的存在表明,海南岛在古生代后期与冈瓦纳大陆有密切联系,属于冈瓦纳大陆北缘构造区,是冈瓦纳大陆分裂出来的一个地体。     

塔里木盆地周缘洋盆开合在盆地内部的构造沉积响应

依据塔里木盆地周缘蛇绿岩年龄及盆内钻井岩性、古生物、地球物理等资料,以古天山洋和古昆仑洋的开合演化为线索,将盆地构造沉积响应划分为五个期次。南华纪-震旦纪早世Rodinia泛大陆开始裂解,塔里木陆块北部发育南天山海槽、南部发育库地小洋盆,同期塔里木盆地只有中北部地区沉积碎屑物,塘古孜巴斯至古城墟地区为古隆起无沉积;震旦纪晚世-奥陶纪中世南天山洋和北昆仑洋(原库地小洋盆)进入成年期,塔里木陆块西部高地发育快速生长的碳酸盐岩台地,东部低地(满加尔)发育饥饿盆地,塔里木陆块形成了西台东盆的沉积格局;奥陶纪晚世-泥盆纪北昆仑洋和南天山洋分别向中昆仑和中天山微陆块俯冲(最终与塔里木陆块拼贴),塔里木陆块边缘逐渐出现不同规模的陆源剥蚀区,陆块内碳酸盐台地逐渐消亡;石炭纪-二叠纪中世北天山洋和南昆仑洋-阿尼玛卿洋关闭造山,塔里木陆块内部实际处于广义的弧后扩张状态,期间接受了海陆交互相碎屑岩沉积及海相碳酸盐岩沉积;二叠纪晚世至今金沙江洋、澜沧江洋、班公-怒江洋和雅鲁藏布江洋等先后关闭,受此影响天山、昆仑造山带强烈抬升,塔里木盆地发育库车和塔西南2个前陆盆地。     

Identification of the thick-layer greigite in sediments of the South Yellow Sea and its geological significances

Magnetic minerals in sediments of the continental shelf are sensitive to environmental changes. Therefore, to determine the exact phases of magnetic minerals is the prerequisite to investigate the paleoenvironmental significances. In this study, a comprehensive rock magnetic investigation, coupled with mineralogical studies, was carried out on the long core NHH01 （with a length of 125.64 m） from the central continental shelf of the South Yellow Sea. Single-domain greigite was identified as the dominant magnetic carrier in sediments between 44.90 and 51.80 m, and terrigenous magnetite is the major magnetic phase in the adjacent layers. The existence of greigite unambiguously indicates an anoxic environment. We tentatively interpreted that such an environment could be formed by the fast sea level changes, longexisting of the cold eddies during warm stages, or in a lake which might be related to locally tectonic uplifting. Therefore, the occurrence of the thicklayer greigite could supply a new perspective to paleoenvironmental or even tectonic studies.     

Magnetic recording of the Cenozoic oceanic crustal accretion and evolution of the South China Sea basin

We review and discuss some of the recent scientific findings made on magnetic data in the South China Sea (SCS). Magnetic anomalies bear extremely rich information on Mesozoic and Cenozoic tectonic evolution. 3D analytical signal amplitudes computed from magnetic anomalies reveal very precisely relict distributions of Mesozoic sedimentary sequences on the two conjugate continental margins, and they are also found very effective in depicting later-stage magmatism and tectonic transitions and zonation within the SCS oceanic crust. Through integrated analyses of magnetic, gravity and reflection seismic data, we define the continent-ocean boundary (COB) around the South China Sea continental margin, and find that the COB coincides very well with a transition zone from mostly positive to negative free-air gravity anomalies. This accurate outlining of the COB is critical for better tracing magnetic anomalies induced by the oceanic crust. The geometrically complex COB and inner magnetic zonation require the introduction of an episodic opening model, as well as a transform fault (here coined as Zhongnan Fault) between the East and Southwest Sub-basins, while within the East and Southwest Sub-basins, magnetic anomalies are rather continuous later-ally, indicating nonexistence of large transform faults within these sub-basins. We enhance magnetic anomalies caused by the shallow basaltic layer via a band-pass filter, and recognize that the likely oldest magnetic anomaly near the northern continental margin is C12 according to the magnetic time scale CK95. Near the southern continental margin, magnetic anomalies are less recognizable and the anomaly C12 appears to be missing. These differences show an asymmetrical opening style with respect to the relict spreading center, and the northern part appears to have slightly faster spreading rates than to the south. The magnetic anomalies C8 (M1 and M2, ~26 Ma) represent important magnetic boundaries within the oceanic basin, and are possibly related to changes in spreading rates and magmatic intensities. The magnetic evidence for a previously proposed ridge jump after the anomaly C7 is not clear. The age of the Southwest Sub-basin has yet to be further examined, most favorably with deep-tow magnetic surveys and ocean drilling. Our magnetic spectral study shows that the shallowest Curie points are located around the eastern part of the Southwestern Sub-basin, whereas within the East Sub-basin Curie depths are smaller to the north of the relict spreading center than to the south. This pattern of Curie depths is consistent to regional heat flow measurements and later-stage volcanic seamount distributions, and we therefore reason that Curie-depth variations are closely associated with later-stage magmatism, rather than with crustal ages. Although magnetic anomalies located around the northern continent-ocean transition zone (COT) are relatively quiet, this area is not a typical magnetic quiet zone since conceptually it differs markedly from an oceanic magnetic quiet zone. The relatively quiet magnetic anomalies are seemingly associated with a shallowing in Curie isotherm and thinning in magnetic layer, but our comprehensive observations suggest that the well-preserved thick Mesozoic sedimentary rocks are major causes for the magnetically quiet zone. The high similarities between various low-pass filtered marine and air-borne magnetic anomalies and satellite magnetic anomalies clearly confirm that deeper magnetic sources (in the lower crust and the uppermost mantle) have contributions to long-wavelength surface magnetic anomalies in the area, as already inferred from magnetically inversed Curie depths. The offshore south China magnetic anomaly (SCMA) becomes more prominent on low-pass filtered marine and air-borne magnetic anomalies and satellite magnetic anomalies, indicating very deeply-buried magnetic sources beneath it.     

The propagation of seafloor spreading in the southwestern subbasin, South China Sea

On the basis of the summary of basic characteristics of propagation, the dynamic model of the tectonic evolution in the South-western Subbasin (SWSB), South China Sea (SCS), has been established through high resolution multi-beam swatch bathymetry and multi-channel seismic profiles, combined with magnetic anomaly analysis. Spreading propagates from NE to SW and shows a transition from steady seafloor spreading, to initial seafloor spreading, and to continental rifting in the southwest end. The spreading in SWSB (SCS) is tectonic dominated, with a series of phenomena of inhomogeneous tectonics and sedimentation.     

Whole-rock Ar-Ar dating for low-grade metavolcanics within the Dabie orogen and its geological significance

Greenschist-facies metasedimentary and metaigne- ous rocks are frequently found to occur continuously along convergent plate margins where high pressure (HP) or ultrahigh pressure (UHP) metamorphic rocks also crop out[1-7]. Geological investigations of co…     

贵州地壳发展及其演化特征

贵州地处特殊构造部位和地史时期经历了多次构造活动和多种地质事件,使贵州由活动陆缘一被动陆缘一陆块内部转化;由准大洋型地壳（红海型）一过渡型地壳一大陆型地壳转化;地壳由活动一稳定转化;地壳厚度由薄一厚转化,地壳结构可划分为三层,地壳发展与演化划分为四阶段。因此,贵州地壳具有多层性、地壳发展与演化具有多期多阶段的特点,大地...     

祁连-阿拉善地区石炭纪构造特征

在沉积建造及区域大地构造背景分析的基础上 ,对研究区石炭纪构造单元进行划分 .重点解剖了柴达木 华北板块 ,其二级构造单元自北而南可划分为北部活动大陆边缘带、中部祁连 阿拉善类克拉通及南部宗务隆裂陷槽 .北部活动大陆边缘带的三级构造单元有沙拉扎山 宗乃山火山岛弧、查干础鲁 霍尔森弧后盆地及图克木大陆边缘块断区 .祁连 阿拉善类克拉通进一步划分为阿拉善隆起区、祁连 走廊 贺兰坳陷区及中南祁连隆起区等三个三级构造单元 .在详细论述各单元沉积及构造特征的基础上 ,指出石炭系油气勘探有利区块 .     

阿中地块南缘晚元古代火山岩地质特征及构造环境分析

阿中地块南缘晚元古代索尔库里群基性火山岩与滨浅海相细粒陆源碎屑岩、成熟度较高的石英砾岩和碳酸盐岩共生,这套火山-沉积岩发生浅变质强变形作用改造,其形成于大陆裂谷构造环境,基性火山岩为大陆裂谷拉斑玄武岩,火山岩-火山碎屑岩上覆岩系--碳酸盐岩中含大量小型叠层石,通过区域对比证明该套地层时代为晚元古代青白口纪,其沉积建造、岩相古地理环境与塔里木北缘库鲁克塔格地区同时代地层特征相似,说明青白口纪时南、北塔里木就有了统一的盖层.     

粤东地区中生代岩浆作用的大地构造背景及构造－岩浆演化

粤东地区中生代岩浆活动十分强烈．形成了遍及全区的火山－侵入杂岩。作者根据区域火山－侵入杂岩的地质地球化学的系统研究．结合区域地质、地球物理和西太平洋板块构造格局的研究成果，认为粤东地区中生代岩浆作用的大地构造背景不同于安第斯型活动大陆边缘．具有大陆板内向活动大陆边缘过渡的特征，构造变动和相应的岩浆活动是在中生代全球构造运动背景之下．亚洲大陆板块与南半球洋中脊体系和库拉－太平洋板块三者之间共同作用的结果．     

Continental subduction channel processes: Plate interface interaction during continental collision

The study of subduction-zone processes is a key to development of the plate tectonic theory. Plate interface interaction is a basic mechanism for the mass and energy exchange between Earth＇s surface and interior. By developing the subduction channel model into continental collision orogens, insights are provided into tectonic processes during continental subduction and its products. The continental crust, composed of felsic to mafic rocks, is detached at different depths from subducting continental lithosphere and then migrates into continental subduction channel. Part of the subcontinental lithospheric mantle wedge, composed of perido- tile, is offscrapped from its bottom. The crustal and mantle fragments of different sizes are transported downwards and upwards inside subduction channels by the corner flow, resulting in varying extents of metamorphism, with heterogeneous deformation and local anatexis. All these metamorphic rocks can be viewed as tectonic melanges due to mechanical mixing of crust- and man- lie-derived rocks in the subduction channels, resulting in different types of metamorphic rocks now exposed in the same orogens. The crust-mantle interaction in the continental subduction channel is realized by reaction of the overlying ancient subcontinental lithospheric mantle wedge peridotite with aqueous fluid and hydrous melt derived from partial melting of subducted continental basement granite and cover sediment. The nature of premetamorphic protoliths dictates the type of collisional orogens, the size of ultrahigh-pressure metamorphic terranes and the duration of ultrahigh-pressure metamorphism.