Geochemical characteristics and sedimentary environment of the Middle Devonian organic-rich shales in the Northwest of Guizhong Depression,Southwest China     

《China Geology》2020,3(4):567-574

In order to figure out the redox conditions and paleo-sedimentary environment of the Middle Devonian shales in the northwest of Guizhong Depression, the trace element analysis was conducted on the Middle Devonian cores (320.35–938.50 m) of the typical shale gas investigation well (GY-1) at a 1.50 m sampling interval through X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). According to the test result, the average values of V/(V+Ni), V/Cr and Ni/Co in Nabiao formation (Fm.) are larger than 0.67, 4.65 and 7.71 respectively, and Nabiao Fm. is rich in biological assemblages such as tabasheer, ammonite, etc. These evidences indicate the rising sea level rose relatively in the sedimentation period of Nabiao Fm. and a deepwater shelf environment, which was favorable for the preservation of organic matters. The V/(V+Ni), V/Cr and Ni/Co in Luofu Fm. and Tangting Fm. are 0.38–0.65, 0.73–4.10 and 3.70–6.72 respectively, indicating that the sea level dropped relatively in their sedimentation period, during which the water bodies became shallow, and the sedimentary environment was a weak oxidizing shallow water shelf environment. In addition, the variation of TOC has a high correlation with the enrichment degree of Ba element, indicating the favorable conditions for the enrichment and preservation of organic matters under an oxygen-deficient environment. Moreover, according to the identification of trace element indexes, the northwest of Guizhong Depression experienced the sedimentary cycle of relative rise to relative fall of sea level from bottom to top in the Middle Devonian sedimentation period. The relative sea level rose to the highest in the sedimentation period of Nabiao Fm., in which the organic-rich shales with stable thickness and high organic content were deposited. Hence, the Nabiao Fm. could be regarded as the favorable exploration target interval in this area.  相似文献   

The paleobiogeographical significance of the Silurian and Devonian trilobites of Japan     

Christopher P. Stocker  Derek J. Siveter  Philip D. Lane  Mark Williams  Tatsuo Oji  Simon R. Wallis  Gengo Tanaka  Toshifumi Komatsu  David J. Siveter  Thijs R. A. Vandenbroucke 《Island Arc》2019,28(2)

Six major groups of trilobites from the Silurian and Devonian of Japan are evaluated for their paleobiogeographical signature. Silurian illaenids and scutelluids show four generic‐level and at least two species‐level links with the Australian segment of the Gondwana paleocontinent; encrinurids also indicate two generic‐level links with Australia and also the South China paleocontinent; whilst Devonian phacopids, and possibly proetids, suggest at least two generic‐level links with the North China paleocontinent. These different patterns may reflect the fragmentary biostratigraphical record of Japanese trilobites, but they also appear to reflect paleoenvironmental parameters associated with lithofacies, and paleoecology. Thus, Japanese assemblages of proetids and phacopids occurring in deep‐water clastic lithofacies have counterparts in similar settings in North China, and Japanese scutelluids and illaenids are strongly associated with shallow marine carbonate lithofacies that are similar to those of their occurrences in Australia. Japanese encrinurids occur in carbonate rocks indicative of shallow marine settings in the Kurosegawa Terrane, and they demonstrate a consistent paleobiogeographical affinity with Australia and South China. Larval ecology cannot be directly assessed for Japanese trilobite groups. However, proetids have consistently been shown to have planktonic protaspides, whereas illaenids, scutelluids, and encrinurids have benthic protaspides. Planktonic protaspides would have a greater propensity for distribution in ocean currents than benthic ones, and therefore may be of more limited paleobiogeographical utility. The combined data from the six different groups indicates that the complex paleobiogeographical patterns of the Japanese trilobite assemblages need to be interpreted with caution, and similarity of taxa does not necessarily denote paleogeographical proximity to other regions.  相似文献   

南海西南次海盆岩石圈结构及其地质意义          下载免费PDF全文

胡立天  张培震  郝天珧  徐亚 《地球物理学报》2019,62(9):3464-3481

南海地区岩石圈资料稀少，阻碍了其形成演化过程的研究.为此，本次研究结合大地热流、空间重力异常、高程、大地水准面和地震数据，在南海西南次海盆反演了两条2.5维岩石圈剖面.本次计算基于三种假设：岩石圈地幔的密度取决于岩石温度；研究区岩石圈处于热稳定状态；研究区处于重力均衡状态.在剖面A-E中，岩石圈底界面从珠江口盆地的105 km迅速抬升到西沙海槽处的50 km，在西沙海槽、西沙-中沙群岛和西南次海盆变化不大，为50~60 km.在剖面F-I中，岩石圈底界面从西沙群岛-中建地块处的88 km向海盆逐渐抬升，在西南次海盆处为46~50 km，到郑和隆起再逐渐变深至64 km.我们比较了西南次海盆岩石圈的冷却模型和热稳定模型，根据冷却模型由水深和热流数据所推断的西南次海盆年龄比实际年龄差很多，说明冷却模型不适用于西南次海盆.通过对比剖面A-E和剖面F-I，说明了剖面A-E经历了更长时间的拉伸，证明南海西南次海盆在形成演化过程中是从北东向南西逐步打开的渐进式扩张.最后，我们综合分析西南次海盆及其大陆边缘的岩石圈结构、减薄陆壳区范围、碳酸盐台地的分布、下地壳韧性流动、流变结构和沉积层特征等多方面资料，认为西南次海盆在形成演化过程中岩石圈地幔首先破裂而地壳后破裂，属于type Ⅱ型非火山型大陆边缘.  相似文献   

基于多源遥感数据的日本海内波特征研究   总被引：2，自引：1，他引：1  

孙丽娜  张杰  孟俊敏  王晶  张旭东 《海洋学报》2018,40(3):102-111

日本海特殊的地理位置和复杂的地形使得该海域内波表征极为复杂，遥感是大范围观测内波的有效手段，已被广泛应用于内波的探测研究。本文利用MODIS、GF-1和ENVISAT ASAR遥感影像，开展了日本海内波特征研究。通过提取内波波峰线，生成了日本海内波空间分布图；获取了内波的波峰线长度和传播速度，并基于非线性薛定谔方程反演了内波振幅。研究结果表明，日本海内波分布范围宽广，不仅大陆架沿海区内波分布密集，深海盆地也探测到了大量内波；日本海北部45°N附近海域有少量内波出现，利用高分影像探测到朝鲜陆架浅海区有大量小尺度内波，大和海盆、大和隆起的西南部海域没有发现内波。日本海内波波峰线长达100多千米，深海区的传播速度大于1 m/s；浅海区内波振幅约10 m左右，深海区可达60 m以上。  相似文献   

超慢速扩张环境下超镁铁质岩系统的热液硫化物成矿机理以及启示     

曹红  孙治雷  刘昌岭  姜学钧  何拥军  黄威  尚鲁宁  王利波  张喜林  耿威  施美娟  李东义 《海洋学报》2018,40(4):61-75

西南印度洋63.5°E热液区是在超慢速扩张洋脊发现的首个超镁铁质岩热液系统。对取自该区的热液硫化物样品进行了系统的矿物学和地球化学分析，矿物学分析结果表明:该热液区硫化物为富Fe型高温硫化物，且经历了较深程度的氧化蚀变，大量中间态的Fe氧化物充填在硫化物矿物间的孔隙及内部解理中；这些硫化物相以白铁矿为主，其次是等轴古巴矿和少量铜蓝，缺乏黄铁矿、闪锌矿。据推断，该区的热液成矿作用分为4个阶段:低温白铁矿阶段→高温等轴古巴矿阶段→自形白铁矿阶段→后期海底风化阶段（少量铜蓝以及大量的Fe的羟氧化物）。与之相对应，地球化学分析结果表明这些硫化物的Fe含量较高（31.57%~44.59%），Cu含量次之（0.16%~7.24%），而Zn含量普遍较低（0.01%~0.11%）；微量元素较为富集Co（328×10-6~2 400×10-6）和Mn（48.5×10-6~1 730×10-6）。该区硫化物中较高含量的Fe、Co与超镁铁质岩热液系统相似，明显高于镁铁质岩热液系统。独特的热液硫化物矿物学特征和元素组成可能与该区普遍出露的地幔岩、橄榄岩蛇纹石化作用以及拆离断层的广泛发育的环境有关。  相似文献   

利用基于环境因子的动态产量模型评估西南大西洋阿根廷滑柔鱼     

汪金涛  陈新军  Kevin W. Staples  陈勇 《海洋学报(英文版)》2018,37(2):94-101

西南大西洋阿根廷滑柔鱼，Illex argentinus，巴塔哥尼亚南部群体是重要的经济种类。海洋环境因子在柔鱼资源分布中起着重要的作用。本研究利用基于环境因子的动态产量模型评估2000-2010年的滑柔鱼的资源量。假设海洋环境因子（滑柔鱼产卵场最适宜海表温度占比）影响动态产量模型的参数K，DIC值表明在正态分布和均匀分布下均是基于环境因子的评估模型优于基本的动态产量模型。阿根廷滑柔鱼的最大可持续产量（MSY）在351600吨到685 100吨之间，资源生物量在1322400吨到1 803 000吨之间，其捕捞死亡系数均小于F_0.1和F_MSY，资源处在良好状态，没有遭受过度捕捞。本研究为应用环境因子在柔鱼类的资源评估与管理提中供了科学的参考方法。  相似文献   

Newly discovered hydrothermal fields along the ultraslow-spreading Southwest Indian Ridge around 63°E     

陈杰  陶春辉  梁锦  廖时理  董传万  李怀明  李伟  王媛  岳羲和  何拥华 《海洋学报(英文版)》2018,37(11):61-67

The ultraslow-spreading Southwest Indian Ridge(SWIR) to the east of the Melville fracture zone is characterized by very low melt supply and intensive tectonic activity. Due to its weak thermal budget and extremely slow spreading rate, the easternmost SWIR was considered to be devoid of hydrothermal activity until the discovery of the inactive Mt. Jourdanne hydrothermal field(27°51′S, 63°56′E) in 1998. During the COMRA DY115-20 cruise in2009, two additional hydrothermal fields(i.e., the Tiancheng(27°51′S, 63°55′E) and Tianzuo(27°57′S, 63°32′E)fields) were discovered. Further detailed investigations of these two hydrothermal sites were conducted by Chinese manned submersible Jiaolong in 2014–2015. The Tiancheng filed can be characterized as a lowtemperature(up to 13.2°C) diffuse flow hydrothermal field, and is hosted by fractured basalts with hydrothermal fauna widespread on the seafloor. The Tianzuo hydrothermal field is an inactive sulfide field, which is hosted by ultramafic rocks and controlled by detachment fault. The discovery of the three hydrothermal fields around Segment #11 which receives more melt than the regional average, provided evidence for local enhanced magmatism providing heat source to drive hydrothermal circulation. We further imply that hydrothermal activity and sulfide deposits may be rather promising along the easternmost SWIR.  相似文献   

Tectonostratigraphic framework and depositional history of the deepwater Ulleung Basin,East Sea/Sea of Japan     

Kyoung-Jin Kim  Dong-Geun Yoo  Nyeon-Keon Kang  Bo-Yeon Yi 《Basin Research》2020,32(4):613-635

The Ulleung Basin, East Sea/Japan Sea, is a Neogene back-arc basin and occupies a tectonically crucial zone under the influence of relative motions between Eurasian, Pacific and Philippine Sea plates. However, the link between tectonics and sedimentation remains poorly understood in the back-arc Ulleung Basin, as it does in many other back-arc basins as well, because of a paucity of seismic data and controversy over the tectonic history of the basin. This paper presents an integrated tectonostratigraphic and sedimentary evolution in the deepwater Ulleung Basin using 2D multichannel seismic reflection data. The sedimentary succession within the deepwater Ulleung Basin is divided into four second-order seismic megasequences (MS1 to MS4). Detailed seismic stratigraphy interpretation of the four megasequences suggests the depositional history of the deepwater Ulleung Basin occurred in four stages, controlled by tectonic movement, volcanism, and sea-level fluctuations. In Stage 1 (late Oligocene through early Miocene), syn-rift sediment supplied to the basin was restricted to the southern base-of-slope, whereas the northern distal part of the basin was dominated by volcanic sills and lava flows derived from initial rifting-related volcanism. In Stage 2 (late early Miocene through middle Miocene), volcanic extrusion occurred through post-rift, chain volcanism in the earliest time, followed by hemipelagic and turbidite sedimentation in a quiescent open marine setting. In Stage 3 (late middle Miocene through late Miocene), compressional activity was predominant throughout the Ulleung Basin, resulting in regional uplift and sub-aerial erosion/denudation of the southern shelf of the basin, which provided enormous volumes of sediment into the basin through mass transport processes. In Stage 4 (early Pliocene through present), although the degree of tectonic stress decreased significantly, mass movement was still generated by sea-level fluctuations as well as compressional tectonic movement, resulting in stacked mass transport deposits along the southern basin margin. We propose a new depositional history model for the deepwater Ulleung Basin and provide a window into understanding how tectonic, volcanic and eustatic interactions control sedimentation in back-arc basins.  相似文献   

A natural gas hydrate-oil-gas system in the Qilian Mountain permafrost area,northeast of Qinghai-Tibet Plateau     

《China Geology》2020,3(4):511-523

Natural gas hydrate, oil and gas were all found together in the Qilian Mountain permafrost area, northeast of Qinghai-Tibet Plateau, China. They are closely associated with each other in space, but whether they are in any genetic relations are unknown yet. In this paper, a hydrocarbon gas-generation series, gas-fluid migration series and hydrocarbon gas-accumulation series are analyzed to probe the spatial, temporal and genetic relationships among natural natural gas hydrate, oil and gas. The subsequent results show that natural gas hydrate, oil and gas actually form a natural gas hydrate-oil-gas system. Based on the Middle Jurassic and the Upper Triassic hydrocarbon gas-generation series, it is divided into four major sub-systems in the study area: (1) A conventional Upper Triassic gas-bearing sub-system with peak hydrocarbon gas-generation in the late Middle Jurassic; (2) a conventional Middle Jurassic oil-bearing sub-system with low to mature hydrocarbon gas-generation in the late Middle Jurassic; (3) a natural gas hydrate sub-system with main gas source from the Upper Triassic gas-bearing sub-system and minor gas source from the Middle Jurassic oil-bearing sub-system as well as little gas source from the Middle Jurassic coal-bed gas and the microbial gas; (4) a shallower gas sub-system with microbial alteration of the main gas source from the Upper Triassic gas-bearing sub-system. This natural gas hydrate-oil-gas system and its sub-systems are not only theoretical but also practical, and thus they will play an important role in the further exploration of natural gas hydrate, oil and gas, even other energy resources in the study area.  相似文献   

闽西南多金属成矿带地质地球物理特征综合研究——以永定大排多金属矿区为例          下载免费PDF全文

张兴东  孟小红  陈召曦  王俊  修春晓 《地球物理学报》2018,61(4):1588-1595

闽西南地区位于福建武夷山成矿带西南部，自远古宙以来经历了多期次的构造演化.该区地处东南沿海构造-岩浆-成矿带上，为环太平洋大陆边缘多金属成矿带与南岭多金属成矿带复合部位，是我国重要的多金属矿产地.永定大排多金属矿区作为近年来武夷山成矿带新发现的大型多金属矿，区内叠加作用和控矿作用相对复杂，现有的地质地球物理工作程度不足以满足对该区域成矿规律的深入认识，一些基础地质问题亟待解决.因此，本文在深入收集永定大排矿区地质地球物理资料基础上，综合分析区域成矿背景与成矿构造，在重点区域布设综合地球物理勘探工作，包括1：1万高精度磁测、可控源音频大地电磁剖面及反射地震剖面.基于上述工作：1）开展了研究区航磁数据三维磁化率反演与分布特征分析与大地电磁二维电阻率反演与分布特征分析，开展了地震资料真地表深度偏移成像，获得了更加准确的地震剖面成像结果.2）结合推覆体控矿特征，地震剖面和电阻率剖面、航磁反演结果相互验证和约束，勾画了地下构造形态.地表地质剖面延伸和标定了构造形态的地质内涵，获得了从地表到3000 m深度的构造解释结果.解释结果清晰地显示了与推覆相关的构造、控矿层位以及岩体信息，为三位一体的找矿思路提供了地球物理依据.  相似文献