Shallow water body data processing based on the seismic oceanography     

LIU Huaishan  HU Yi  YIN Yanxin  WANG Linfei  TONG Siyou  MA Hai 《中国海洋大学学报(英文版)》2013,12(3):319-326

Physical properties of sea water,such as salinity,temperature,density and acoustic velocity,could be demarcated through degradation of energy caused by water absorption,attenuation and other factors.To overcome the challenging difficulties in the quick monitoring of these physical properties,we have explored the high resolution marine seismic survey to instantly characterize them.Based on the unique wavefield propagating in the sea water,we have developed a new approach to suppress the noise caused by the shallow sea water disturbance and obtain useful information for estimating the sea water structure.This approach improves seismic data with high signal-to-noise ratio and resolution.The seismic reflection imaging can map the sea water structure acoustically.Combined with the knowledge of local water body structure profile over years,the instant model for predicting the sea water properties could be built using the seismic data acquired from the specially designed high precision marine seismic acquisition.This model can also be updated with instant observation and the complete data processing system.The present study has the potential value to many applications,such as 3D sea water monitoring,engineering evaluation,geological disaster assessment and environmental assessment.  相似文献   

基于SVM的海底声纳图像底质识别*     

熊明宽  吴自银  李守军  罗孝文  唐秋华 《海洋通报》2012,31(4):409-414

对海底底质声纳图像分割,提取单元特征向量进行主成份分析,选取均值、标准差、对比度、相关系数、能量及同质性作为训练特征向量,优化支持向量机(SVM)参数.利用多分类 SVM 对砂、礁石、泥进行训练,有效、快速地分离出了3种底质类型,测试精度高于80%,表明该方法可有效用于海底底质声纳图像的识别和分类.  相似文献   

Structural Geology and Tectonics in Marine Science：Perspectives in the Research of Deep Sea and Deep Interior     

LI Sanzhong  JIN Chong  SUO Yanhui  M. Santosh  DAI Liming  LIU Xin  MA Yun  WANG Xiaofei  ZHANG Bingkun  YU Shan 《青岛海洋大学学报(英文版)》2012,(3):257-266

  相似文献   

珠江口西部海域表层沉积物重金属元素多尺度空间变化特征     

赵建如  初凤友  金路  杨克红  葛倩 《吉林大学学报(地球科学版)》2015,45(6):1772-1780

笔者应用因子克里格分析方法,研究了珠江口西部海域388个表层沉积物中7种重金属元素Cd, Ni,Cu,Zn,Pb,Cr和As的空间结构特征,识别并分离了重金属元素不同尺度的空间主成分及其分布特征,探讨了不同空间尺度重金属的物源及控制因素。结果显示,研究区7种重金属元素在空间上存在块金尺度、局部尺度(变程为60 km的球状结构)和区域尺度(变程为160 km的球状结构)3种尺度的空间变化。以迭代算法模拟了研究区重金属元素线性协同区域化模型。根据不同尺度上区域化因子的主成分得分分布特征可知:局部尺度上,F₁因子(Zn,Cr,Ni,Cu)和F₂因子(As)的高值区表现为"牛眼"状局部特征,并分布在陆地沿海的河口或者港湾区,指示了可能受人为污染成分影响的重金属区域。其中,雷州半岛东部沿海是最可能的重金属污染区,其空间分布主要受控于局部的地形、海流等因素。F₂因子不同于F₁的空间分布,主要在于As不同于Zn,Cr,Ni,Cu等的地球化学行为。区域尺度上,F₁(Zn,Cr,Ni)和F₂(As)因子主要反映了不同陆源母岩物质的影响。Zn,Cr,Ni等主要源于华南大陆陆源母岩物质,而As主要受到海南岛陆源母岩物质的控制。F₁和F₂因子得分高值区整体上表现为NNE向自陆地向较深海域延伸的"片状"分布特征,推测其主要受到海平面变化及NNE向区域性海洋环流的控制。  相似文献   

Geochronology and geochemistry of porphyritic intrusions in the Duolong porphyry and epithermal Cu-Au district,central Tibet: Implications for the genesis and exploration of porphyry copper deposits     

《Ore Geology Reviews》2017

The Duolong district in central Tibet hosts a number of porphyry as well as high sulfidation epithermal copper–gold deposits and prospects, associated with voluminous calc-alkaline volcanism and plutonism. In this study, we present new geochronological, geochemical, isotopic and mineralogical data for both economically mineralized and barren porphyritic intrusions from the Duobuza and Naruo porphyry Cu–Au deposits. Zircon U–Pb analyses suggest the emplacement of economically mineralized granodiorite porphyry and barren granodiorite porphyry at Naruo deposit took place at 119.8 ± 1.4 Ma and 117.2 ± 0.5 Ma, respectively. Four molybdenite samples from the Naruo deposit yield an isochron Re–Os age of 119.5 ± 3.2 Ma, indicating mineralization occurred synchronously with the emplacement of the early granodiorite porphyry. At Duobuza deposit, the barren quartz diorite porphyry intruded at 119.5 ± 0.7 Ma, and two economically mineralized intrusions intruded at 118.5 ± 1.2 Ma (granodiorite porphyry) and 117.5 ± 1.2 Ma (quartz diorite porphyry), respectively. Petrographic investigations and geochemical data indicate that all of the porphyritic intrusions were oxidized, water rich, and subduction-related calc-alkaline magmas. Zircons from the porphyritic intrusions have a wide range in the ε_Hf (0–11.1) indicating that they were sourced from mixing of mantle-derived mafic, and crust-derived felsic melts. Moreover, the variation of trace element content of plagioclase phenocrysts indicates that the magma chambers were recharged by mafic magmas.Comparison of the composition of amphibole phenocrysts indicates the porphyry copper–gold mineralization at Duolong was generated in magma chambers at low crystallization temperatures and pressures (754° to 791 °C, 59 M to 73 MPa, n = 8), and under highly oxidizing conditions (ΔNNO 2.2 to 2.7, n = 8). In contrast, barren intrusions were sourced from the magma chambers with higher crystallization temperatures and pressures (816° to 892 °C, 111 to 232 MPa, n = 22) that were less oxidizing (ΔNNO 0.6 to 1.6, n = 22). The requirement for a thermal contrast is supported by the declining of Ti content in magnetite crystals in barren intrusions (12,550 to 34,200 ppm) versus those from economically mineralized intrusions (600 to 3400 ppm). Moreover, the V content in magnetite crystals from economically mineralized intrusions (990 to 2510 ppm) is lower than those recorded from barren intrusions (2610 to 3510 ppm), which might reflect the variation in oxidation state of the magma. The calculated water solubility of the magma forming the economically mineralized intrusions (3.2–3.7 wt%) is lower than that of magma forming the barren intrusions (4.6–6.4 wt%). Based on the chemical–physical characteristics of economically mineralized magma, our study suggests that the development of porphyry Cu–Au mineralization at Duolong was initiated by shallow-level emplacement of a magma that crystallized at lower temperatures and pressures. Experimental studies show that copper and water solubilities in silicate melts decrease with falling temperatures and pressures, indicating metals and ore-forming fluids are more likely to be released from a magma reservoir emplaced at shallow crustal levels. We propose the magnetite might be a convenient exploration tool in the search for porphyry copper mineralization because the variations in Ti and V content of mineral concentrates and rock samples are indicative of barren versus mineralized intrusions.  相似文献   

Sulfur and lead isotopic compositions of massive sulfides from deep-sea hydrothermal systems: Implications for ore genesis and fluid circulation     

《Ore Geology Reviews》2017

Studies of sulfur and lead isotopic compositions in hydrothermal deposits are an important tool to determine the source and processes of both sulfur and lead, and to understand the origin of hydrothermal ore deposits. Here, the sulfur and lead isotopic compositions of sulfide minerals have been studied for different hydrothermal fields in the East Pacific Rise (EPR), Mid-Atlantic Ridge (MAR), Central Indian Ridge (CIR), Southwest Indian Ridge (SWIR), and North Fiji Basin (NFB). The sulfur isotopic compositions of the studied sulfide samples are variable (δ³⁴S 0.0 to 9.6‰, avg. δ³⁴S 4.7‰; n = 60), being close to the associated igneous rocks (~ 0‰ for, e.g., basalt, serpentinized peridotite), which may reflect the S in the sulfide samples is derived mainly from the associated igneous rocks, and a relatively small proportion (< 36%) of seawater sulfur incorporated into these sulfides during mixing between seawater (δ³⁴S 21‰) and hydrothermal fluid. In contrast for a mixed origin for the source of S, the majority of the lead isotopic compositions (²⁰⁶Pb/²⁰⁴Pb 17.541 ± 0.004 to 19.268 ± 0.001, ²⁰⁷Pb/²⁰⁴Pb 15.451 ± 0.001 to 15.684 ± 0.001, ²⁰⁸Pb/²⁰⁴Pb 37.557 ± 0.008 to 38.988 ± 0.002, n = 21) of the sulfides possess a basaltic Pb isotopic composition, suggesting that the lead in the massive sulfide is mainly leached from local basaltic rocks that host the sub-seafloor hydrothermal systems in sediment-free mid-ocean ridges and mature back-arc basins. Furthermore, sulfide minerals in the super-fast and fast spreading mid-ocean ridges (MORs) exhibit less spread in their the δ³⁴S values compared to sulfides from super-slow, and slow spreading MORs, which is most easily explained as a lesser degree of fluid-rock interaction and hydrothermal fluid-seawater mixing during hydrothermal ore-forming process. Additionally, the S and Pb isotope compositions of sulfides are controlled by the fluid processes for forming seafloor massive sulfide deposits. We demonstrate that the variable sulfur and lead isotopic compositions exhibit a relationship with the sulfur and lead sources, fluid–rock interaction, and fluid–seawater mixing.  相似文献   

东亚原特提斯洋(Ⅳ):北界西段早古生代构造变形   总被引：2，自引：2，他引：0  

李三忠  李涛  赵淑娟  李玺瑶  刘鑫  郭玲莉  于胜尧  李少俊 《岩石学报》2017,33(6):1615-1632

北祁连造山带是原特提斯洋北支西段——古祁连洋闭合的地质记录,其经历了早古生代复杂的造山过程,但其俯冲极性、闭合时间、拼合方式还存在争议。通过详细的野外构造解析,并对变质年代学资料进行统计,在研究区识别出三幕早古生代褶皱变形。其中,第一幕变形发生在489~442Ma,形成于古祁连洋壳俯冲-碰撞阶段,主要表现为区域性的片理、片麻理或糜棱叶理;第二幕变形发生在422~406Ma,形成于俯冲板片的折返阶段,主要表现为轴面南倾的紧闭褶皱;第三幕变形则主要为轴面近于直立的宽缓褶皱。前两幕变形被第三幕变形叠加改造。祁连地区广泛分布着奥陶系-志留系与上覆泥盆系的角度不整合,不整合面上、下的地层对比指示西段不整合时间早于东段不整合时间,可能代表了古祁连洋西段拼合较早、东段拼合较晚的斜向"剪刀式"拼合。此外,多条穿过整个研究区的1∶20万地质剖面上的运动学解析,揭示了古祁连洋壳自北向南的俯冲极性。综合以上研究结果,认为古祁连洋壳最早的俯冲时间为544Ma,中祁连和阿拉善微陆块自462Ma开始碰撞拼合,古祁连洋于442Ma最终闭合。早古生代原特提斯洋北界西段俯冲方式为自南向北"后退式"俯冲,可能发生过俯冲带跃迁事件。  相似文献   

Combined adaptive multiple subtraction based on optimized event tracing and extended wiener filtering     

Jun Tan  Peng Song  Jinshan Li  Lei Wang  Mengxuan Zhong  Xiaobo Zhang 《中国海洋大学学报(英文版)》2017,16(3):411-421

The surface-related multiple elimination (SRME) method is based on feedback formulation and has become one of the most preferred multiple suppression methods used. However, some differences are apparent between the predicted multiples and those in the source seismic records, which may result in conventional adaptive multiple subtraction methods being barely able to effectively suppress multiples in actual production. This paper introduces a combined adaptive multiple attenuation method based on the optimized event tracing technique and extended Wiener filtering. The method firstly uses multiple records predicted by SRME to generate a multiple velocity spectrum, then separates the original record to an approximate primary record and an approximate multiple record by applying the optimized event tracing method and short-time window FK filtering method. After applying the extended Wiener filtering method, residual multiples in the approximate primary record can then be eliminated and the damaged primary can be restored from the approximate multiple record. This method combines the advantages of multiple elimination based on the optimized event tracing method and the extended Wiener filtering technique. It is an ideal method for suppressing typical hyperbolic and other types of multiples, with the advantage of minimizing damage of the primary. Synthetic and field data tests show that this method produces better multiple elimination results than the traditional multi-channel Wiener filter method and is more suitable for multiple elimination in complicated geological areas.  相似文献   

Evidence for low viscosity garnet-rich layers in the upper mantle     

Auke Barnhoorn  Martyn R. Drury  Herman L.M. van Roermund 《Earth and Planetary Science Letters》2010,289(1-2):54-67

The rheological properties of upper mantle rocks play an important role in controlling the dynamics of the lithosphere and mantle convection. Experimental studies and microstructures in naturally deformed mantle rocks usually imply that olivine controls the upper mantle rheology. Here we show for the first time evidence from the geometry of folded compositional layers in mantle rocks from Western Norway that garnet-rich rocks can have lower solid-state viscosities than olivine-rich rocks. Modeling of melt-free and dry rheology of garnet and olivine confirms that the reversed viscosity contrast between garnet-rich and olivine-rich layers for this folding event can be achieved over a relatively wide range of temperatures at low stress conditions when the fine-grained garnet deforms by diffusion creep while the coarse-grained olivine deforms by dislocation creep and/or diffusion creep.In general, modeling of the fold viscosity contrast shows that in the stable subcontinental lithospheric mantle or convecting mantle such a reversed viscosity contrast can be formed due to diffusion creep processes in fine-grained garnets in a dry mantle environment or at conditions where the garnet-pyroxene layer is partially molten, i.e. close to solidus–liquidus conditions in the upper mantle. Alternatively in cold plate tectonic settings, e.g. in subduction zones, some water-weakening is a feasible mechanism to create the reversed viscosity contrast between garnet and olivine.  相似文献   

南海北部陆缘的磁异常特征及居里面深度   总被引：4，自引：0，他引：4  

吴招才  高金耀  赵俐红  张涛  杨春国  王健 《地球科学》2010,35(6):1060-1068

为了研究南海北部张裂大陆边缘的地壳热结构,利用船载测量磁力数据,通过功率谱方法反演南海北部陆缘居里等温面,并结合深地震剖面、区域断裂及大地热流分布,讨论了深部热结构状态.结果显示研究区居里面深度在13~26 km之间,在上下陆坡转换带处与莫霍面相交,北东向断裂多位于居里面梯度带上,北西向断裂多具有分割、错断的特点,居里面深度和大地热流值具有相关性.结果揭示了陆架、上陆坡地区磁性体可能主要位于上地壳和下地壳上部,下陆坡及洋壳区地壳与地幔顶部有被磁化的迹象.磁静区位于居里面上隆区边缘,F3断裂和F4断裂之间可能是残留古洋壳.潮汕凹陷和台西南盆地中央隆起是发生底侵的主要区域,F2断裂为其北界.   相似文献