海底泥火山形成机制——南海台西南盆地泥火山钻探建议     

万志峰  吴婷婷  张伟  苏丕波  钟思玲  张金锋  罗钧升 《地质学报》2022,96(8):2906-2916

泥火山是地下泥质流体喷发到地表或海底所形成的丘状构造，其形成与油气成藏、天然气水合物成矿有着直接联系，其喷发活动易引发工程事故，喷发的大量甲烷气体会加剧温室效应。国内外学者已在泥火山发育、地球化学、地球物理特征等方面开展了诸多研究。然而泥火山形成机制问题仍存在多种争议，其触发因素可能来自断层活动、地震、超压等。泥火山流体的传热传质及其对水合物形成与动态分布的控制作用还有待深入研究，同时海底泥火山碳排放亦是重要地质问题。因而我们建议选取南海北部台西南盆地典型泥火山开展钻探，获取海底泥火山发育的构造环境、沉积背景、温压场等系列参数，揭示泥火山成因机制，建立海底泥火山油气渗漏模式，探讨泥火山流体传热过程对水合物形成与分布的影响。研究成果对于超压沉积盆地油气勘探与开发、海底渗漏型水合物研究与勘探、新构造活动与地质灾害分析等都具有重要指导意义。  相似文献   

水泥土挡墙整体稳定的敏感性分析     

李二兵  谭跃虎  刘向东  段建立 《岩土力学》2006,27(Z1):1137-1140

水泥土挡墙广泛应用于软土地区基坑支护。针对目前对于水泥土挡墙的整体稳定性与其影响因素之间相关性认识不足,引入正交设计方法分析水泥土挡墙整体稳定影响因素墙体厚度、嵌固深度、土体粘聚力、土体内摩擦角、土层重度、地下水位、地面超载的重要性和敏感性规律。分析结果表明,土的抗剪强度指标是影响水泥土挡墙的最重要因素,其变化对整体稳定有高度显著影响;而墙体厚度和嵌固深度对水泥土挡墙整体稳定无显著影响。  相似文献   

西沙群岛精细植被分布的遥感制图及动态变化     

孙晓慧  史建康  李新武  吴文瑾  梁雷  宫晨 《遥感学报》2021,25(7):1473-1488

西沙群岛是南海群岛中岛屿最多、面积最大的群岛,自然环境独特、植物区系特殊、岛上植被一直都是植物学家及地理学家重点关注的问题。本文基于光谱分类,于决策层融合支持向量机与光谱信息散度两类分类器进行西沙群岛典型岛屿植被类型识别,形成典型植被分布图。建立西沙群岛典型植被光谱库,分析西沙群岛典型植被实测光谱与其一阶导数的特性,并基于典型岛屿不同时期的植被分布图进行变化分析。结果表明：（1）采用光谱分类的生产精度及用户精度在西沙群岛主要岛屿的平均值为83.49%、85.54%,Kappa系数为0.8728。（2）2002年—2018年,各典型岛屿主要受到人类活动影响,整体上植被种类及植被面积增加,草海桐形成单优植被群落。（3）经相关性分析,各典型岛屿植被种类数量与本岛面积基本成正相关关系,且面积越大,植被种类随时间增加速度越快;相邻岛屿之间的距离与两岛植被相似性呈正相关,两岛距离越近,植被种类相似性越高。  相似文献   

Resazurin as an indicator of reducing capacity for analyzing the physiologic status of deep-sea bacterium Photobacterium phosphoreum ANT-2200     

Dai  Jie  Tang  Hongzhi  Li  Xuegong  Santini  Claire-Lise  Cui  Wenpeng  Liu  Na  Qi  Xiaoqing  Cui  Xuehua  Grossi  Alain  Notareschi  Philippe  Zhang  Wei-Jia  Wu  Long-Fei 《中国海洋湖沼学报》2021,39(1):297-305

Journal of Oceanology and Limnology - Resazurin (RZ) is a weakly fluorescent blue dye and can be reduced irreversibly to highly fluorescent pink resorufin (RF) that is reduced reversibly to...  相似文献   

三亚造礁石珊瑚虫黄藻光合作用效率的日周期及其调控因素          下载免费PDF全文

周洁  施祺  余克服 《热带海洋学报》2014,33(1):81-89

珊瑚与虫黄藻的共生是珊瑚礁生态系统最基本的生态特征,虫黄藻光合作用效率直接决定着珊瑚的健康状况。本研究对海南三亚鹿回头珊瑚礁礁坪上5种典型珊瑚(澄黄滨珊瑚Porites lutea、丛生盔形珊瑚Galaxea fascicularis、标准蜂巢珊瑚Favia speciosa、多弯角蜂巢珊瑚Goniastrea favulus和伞房鹿角珊瑚Acropora corymbosa)共生藻的实际光量子产量ΦPSⅡ进行了连续5日的现场监测,并同时监测了该海域的7种环境参数(温度、盐度、溶解氧、pH、海水中二氧化碳分压pCO2、辐射和潮位),旨在探索鹿回头海域珊瑚共生虫黄藻光合作用的日变化规律及其调控因素。结果表明,珊瑚共生虫黄藻光合作用效率和各环境参数都存在明显的日变化,但共生藻光合作用效率主要受光合有效辐射强度(photosynthetic active radiation,PAR)所调控,其次是温度和潮位变化。澄黄滨珊瑚的共生藻光合作用最易受到环境因素的影响。  相似文献   

The basins of Sundaland (SE Asia): Evolution and boundary conditions     

《Marine and Petroleum Geology》2014

Most of the basins developed in the continental core of SE Asia (Sundaland) evolved since the Late Cretaceous in a manner that may be correlated to the conditions of the subduction in the Sunda Trench. By the end of Mesozoic times Sundaland was an elevated area composed of granite and metamorphic basement on the rims; which suffered collapse and incipient extension, whereas the central part was stable. This promontory was surrounded by a large subduction zone, except in the north and was a free boundary in the Early Cenozoic. Starting from the Palaeogene and following fractures initiated during the India Eurasia collision, rifting began along large faults (mostly N–S and NNW–SSE strike-slip), which crosscut the whole region. The basins remained in a continental fluvio-lacustrine or shallow marine environment for a long time and some are marked by extremely stretched crust (Phu Khanh, Natuna, N. Makassar) or even reached the ocean floor spreading stage (Celebes, Flores). Western Sundaland was a combination of basin opening and strike-slip transpressional deformation. The configuration suggests a free boundary particularly to the east (trench pull associated with the Proto-South China Sea subduction; Java–Sulawesi trench subduction rollback). In the Early Miocene, Australian blocks reached the Sunda subduction zone and imposed local shortening in the south and southeast, whereas the western part was free from compression after the Indian continent had moved away to the north. This suggests an important coupling of the Sunda Plate with the Indo-Australian Plate both to SE and NW, possibly further west rollback had ceased in the Java–Sumatra subduction zone, and compressional stress was being transferred northwards across the plate boundary. The internal compression is expressed to the south by shortening which is transmitted as far as the Malay basin. In the Late Miocene, most of the Sunda Plate was under compression, except the tectonically isolated Andaman Sea and the Damar basins. In the Pliocene, collision north of Australia propagated toward the north and west causing subduction reversal and compression in the short-lived Damar Basin. Docking of the Philippine Plate confined the eastern side of Sundaland and created local compression and uplift such as in NW Borneo, Palawan and Taiwan. Transpressional deformation created extensive folding, strike-slip faulting and uplift of the Central Basin and Arakan Yoma in Myanmar. Minor inversion affected many Thailand rift basins. All the other basins record subsidence. The uplift is responsible for gravity tectonics where thick sediments were accumulated (Sarawak, NE Luconia, Bangladesh wedge).  相似文献   

Solar dynamo and geomagnetic activity     

Katya Georgieva  Boian Kirov 《Journal of Atmospheric and Solar》2011,73(2-3):207-222

The correlation between geomagnetic activity and the sunspot number in the 11-year solar cycle exhibits long-term variations due to the varying time lag between the sunspot-related and non-sunspot related geomagnetic activity, and the varying relative amplitude of the respective geomagnetic activity peaks. As the sunspot-related and non-sunspot related geomagnetic activity peaks are caused by different solar agents, related to the solar toroidal and poloidal fields, respectively, we use their variations to derive the parameters of the solar dynamo transforming the poloidal field into toroidal field and back. We find that in the last 12 cycles the solar surface meridional circulation varied between 5 and 20 m/s (averaged over latitude and over the sunspot cycle), the deep circulation varied between 2.5 and 5.5 m/s, and the diffusivity in the whole of the convection zone was ～10⁸ m²/s. In the last 12 cycles solar dynamo has been operating in moderately diffusion dominated regime in the bulk of the convection zone. This means that a part of the poloidal field generated at the surface is advected by the meridional circulation all the way to the poles, down to the tachocline and equatorward to sunspot latitudes, while another part is diffused directly to the tachocline at midlatitudes, “short-circuiting” the meridional circulation. The sunspot maximum is the superposition of the two surges of toroidal field generated by these two parts of the poloidal field, which is the explanation of the double peaks and the Gnevyshev gap in sunspot maximum. Near the tachocline, dynamo has been operating in diffusion dominated regime in which diffusion is more important than advection, so with increasing speed of the deep circulation the time for diffusive decay of the poloidal field decreases, and more toroidal field is generated leading to a higher sunspot maximum. During the Maunder minimum the dynamo was operating in advection dominated regime near the tachocline, with the transition from diffusion dominated to advection dominated regime caused by a sharp drop in the surface meridional circulation which is in general the most important factor modulating the amplitude of the sunspot cycle.  相似文献   

An overview of the earth crust under China     

Zhongjie Zhang  Liqiang Yang  Jiwen Teng  José Badal 《Earth》2011,104(1-3):143-166

We assess the results of a number of deep seismic soundings performed in China over the last few decades, and study the variations in crustal structure in 18 tectonic units comprised of three platforms and 15 fold systems. Thickness data on 344 Mesozoic–Cenozoic sedimentary basins, as well as data on Moho depth are collected in order to discuss the relationship between the thickness of the basins and the average thickness of the consolidated crust in each tectonic unit. The degree of mirror-image symmetry between Mesozoic–Cenozoic sedimentary basins and the uplifting topmost parts of the mantle is herein analyzed using deep geophysical data on sedimentary basins. By applying standard methods of least-squares analysis to both datasets, we have obtained both the average thickness of the consolidated crust and the mirror-image symmetry factor for every platform and tectonic fold system, thereby allowing us to explore the correlation between the depths of the bottom of the sedimentary basins and the top of the uplifting mantle. The thickness of the consolidated crust in China is found to be between 20 and 63 km, following a pattern of gradual thickening from east to west. Expressed in terms of spatial seismicity and the concentration of seismic energy, and according to the sharing-out of earthquake hypocenters in the top 80 km of the earth, the rheology of the area does not appear to suit the widely accepted “jelly–sandwich” model for the continents, which does not seem to be entirely valid in China. The findings on the mirror-image symmetry factor show that this parameter varies mainly in the range ? 0.5 to ? 1.8 compared with each other tectonic unit. Most of the tectonic systems in China appear to be isostatically compensated. Tibet is an exception, in that the symmetry factor is positive for the Gangdise–Nyainqentanglha (1.0) and Himalayan (0.1) fold systems, implying that these tectonic zones are far from being in the isostatic equilibrium of the other regions. We have also analyzed the zoning characteristics through the logarithmic relationship ln R = ln (h/|a|), using the average thickness of the consolidated crust and the absolute value of the symmetry factor. The key finding is that regardless of geographical location, all the values of R = h/|a| for those sedimentary basins in which oil/gas reservoirs have to date been found, fall into the narrow range of values between 19.38 and 37.40. There is some appeal in a possible relationship involving the ratio of crustal thickness to symmetry factor, more so when the results obtained appear to suggest a prognostic tool for exploratory practice in relation to oil/gas reservoirs.  相似文献   

凡纳滨对虾α-淀粉酶基因PCR-RFLP多态性与生长性状的相关分析   总被引：2，自引：1，他引：1  

辛静静  刘小林  李喜莲  王宪宗  黄皓  相建海 《海洋学报》2011,33(3):124-130

采用PCR-RFLP法对379尾凡纳滨对虾α-淀粉酶基因(AMY)多态性进行检测,并分析AMY基因多态性与生长性状的相关性.结果表明:引物AMY-5与AMY-6扩增片段均具多态性,引物AMY-5扩增产物有CC,CT和TT 3种基因型,AMY-6扩增产物有AA,AB和BB 3种基因型.AMY基因AMY-5引物位点TT基因...  相似文献   

A new presentation of the Indian Ocean shallow overturning circulation from a vertical perspective          下载免费PDF全文

Tiecheng Zhang  Weiqiang Wang  Qiang Xie  Kexiu Liu  Dongxiao Wang  Xinrong Wu  Xiaoshuang Zhang  Kang Xu  Wenya Yuan 《大气和海洋科学快报》2021,14(5):56-61

由于印尼贯穿流干扰了南印度洋经向翻转环流的计算,本文应用垂向翻转流函数来诊断印度洋浅层经向翻转环流.基于海洋环流模拟产品(OFES),本文探讨了垂向流函数相比经向翻转流函数的改进.研究结果表明垂向翻转流函数能平滑连接南北印度洋的翻转环流,包括完整的副热带翻转环流和跨赤道翻转环流.经向翻转流函数低估了印度洋浅层翻转环流;而垂向翻转流函数表示的印度洋浅层翻转环流受印尼贯穿流影响更小,其评估的印度洋浅层翻转环流强度约13 Sv,其中副热带翻转环流强度约8 Sv(1 Sv ≡ 106 m3 s-1).此外,垂向翻转流函数在印度洋南开边界(30°S～34°S)上600 m层表现为顺时针翻转结构,其强度约-5 Sv,可能对应风驱的副热带流系.因此,垂向翻转流函数提供了一种新方法来评估印度洋浅层翻转环流.  相似文献