Coastal processes and cliff recession between Gabicce and Pesaro (northern Adriatic Sea): a case history     

P. Colantoni  D. Mencucci  O. Nesci   《Geomorphology》2004,62(3-4):257-268

Cliff recession on the high rocky coast between Gabicce and Pesaro Adriatic sea causes a wide range of mass movement processes on the whole slope, affecting both the bedrock and the overburden. The outcropping late Miocene rock formations are represented by marls, marly limestones, dark laminated mudstones and bedded sandstones and marls. Mass movements are common because of stratification and discontinuities in the rocks that, together with the presence of groundwater and weathering processes, reduce the overall strength of the slopes. A model for the evolution of this coastal area is proposed, which involves cyclic basal erosion, followed by mass movement that favours debris accumulation at the base of the cliff. The longshore currents have to then remove the material before a new cycle can begin.  相似文献   

利用微波等离子体炬四极杆质谱在线测定稀土矿样中的多种稀土元素     

初晨  张瑛  王尚贤  周润芝  蒋涛  朱志强  卢爱民 《岩矿测试》2016,35(5):468-474

随着稀土的应用越来越广泛,开发稀土元素的快速在线检测技术已日趋成为行业发展的需求。本文以微波等离子体炬(MPT)为离子源,以四极杆质谱仪(QMS)作为质量分析器建立了一种快速、直接检测水样中稀土元素的质谱检测方法,并将其应用于分析稀土矿样中的多种稀土元素。研究表明,应用MPT-QMS测定水样中的钇、镧、铈、钕、铕五种稀土元素,检出限(LOD)可达11.0~60.5μg/L,测定范围为50~1000μg/L。当分析固体稀土矿样时,样品经酸溶处理后通过气动雾化形成气溶胶,再进行冷却干燥,气溶胶由MPT的中心管道进入等离子体中,产生稀土元素复合离子,再引入QMS中进行分析,即可以定量地测定矿样中稀土元素的含量。同一样品用电感耦合等离子体质谱(ICP-MS)进行对比实验,两者的检测结果在数量级上接近,证明了MPTQMS方法在半定量的意义下是准确、可靠的,因而这种快速的检测方法可发展成为水体中金属元素的现场分析方法,应用于环境水、生活水质量在线监测等领域。  相似文献   

青岛冷水团的消亡机理研究   总被引：1，自引：0，他引：1  

张启龙  刘志亮  齐继峰  杨德周  郑冬梅 《海洋学报》2016,38(5):27-33

本文基于多年月平均水温资料,分析了青岛冷水团的长消过程,并利用气候态月平均大气数据和数值模拟结果,探讨了青岛冷水团的消亡机理。结果表明,青岛冷水团3月出现,4月成型,5月最盛,6月减弱,7月消失;南黄海6-7月间偏南风的增强和温跃层以下反气旋涡的减弱是青岛冷水团消亡的动力机制,而海面净热通量的下传和水平热量的输入则是青岛冷水团消亡的热力机制。  相似文献   

Three dimensional seismic studies of deep-water hazard-related features on the northern slope of South China Sea     

《Marine and Petroleum Geology》2016

Mass transport deposits and geological features related to fluid flow such as gas chimneys, mud diapirs and volcanos, pockmarks and gas hydrates are pervasive on the canyon dominated northern slope of the Pearl River Mouth basin of the South China Sea. These deposits and structures are linked to serious geohazards and are considered risk factors for seabed installations. Based on high resolution three dimensional seismic surveys, seismic characteristics, distributions and origins of these features are analyzed. A distribution map is presented and geometrical parameters and spatial distribution patterns are summarized. Results show that various groups of the mapped features are closely tied to local or regional tectonism and sedimentary processes. Mass transport complexes are classified as slides near the shelf break, initially deformed slumps on the flanks of canyons and highly deformed slumps on the lower slope downslope of the mouth of canyons. We propose them to be preconditioned by pore pressure changes related to sea level fluctuations, steep topography, and fluid and fault activities. Gas chimneys are mainly located in the vicinity of gas reservoirs, while bottom-simulating reflectors are observed within the gas chimney regions, suggesting gas chimneys serve as conduits for thermogenic gas. Mud diapirs/volcanos and pockmarks are observed in small numbers and the formation of pockmarks is related to underlying gas chimneys and faults. This study aims at reducing risks for deep-water engineering on the northern slope of South China Sea.  相似文献   

元素分析仪-同位素比值质谱测量碳氮同位素比值最佳反应温度和进样量的确定   总被引：2，自引：2，他引：0  

徐丽  邢蓝田  王鑫  李中平  毛俊丽 《岩矿测试》2018,37(1):15-20

沉积有机质的碳氮稳定同位素值是进行古气候、古环境及生态系统研究不可或缺的主要研究手段,目前碳氮同位素主要利用元素分析仪-同位素比值质谱(EA-IRMS)系统来测定。EA-IRMS测定过程中的反应温度及样品进样量直接影响反应物在测试中的燃烧程度,从而影响测试数据的精度。本文利用EA-IRMS技术,以标准样品为参考,在不同转化温度下测试碳氮同位素值,研究保证测试精度的最佳反应温度条件;同时,通过分析不同含氮量样品的检测限,明确了样品含氮量与最低检测限之间的关系,确定了精确测定氮同位素值的最低进样量。结果表明:反应温度对测试精度有显著影响,在碳同位素测定时,将反应温度设定为900℃或以上时测试精度均能达到±0.2‰;氮同位素测定时,反应温度须设定为950℃时测试精度才能达到±0.3‰。实验得出样品含氮量与检测限之间的线性相关性为R2=0.873,开展氮同位素测定时可根据此关系来判断和控制进样量。  相似文献   

全球海平面变化研究新进展   总被引：9，自引：1，他引：8  

吴涛  康建成  王芳  郑琰明 《地球科学进展》2006,21(7):730-737

综述了近10年来海平面变化研究的主要成果,分析了影响海平面变化的主要因素,探讨了海平面变化研究中存在的一些问题。结果表明：①近10年全球平均海平面上升幅度大约为2.5~3.84 mm/a,热膨胀是引起海平面上升的主因;②海平面变化具有时空分布差异——西太平洋和东印度洋地区上升最快,其值高出全球平均值的10倍以上;大西洋与太平洋30~40°N地区季节变化最明显;③将海平面季节高值时段与北半球热带气旋出现时间进行对比,发现每年8~10月份,在20~50°N的西北太平洋与北大西洋沿岸地区出现海平面最高值与热带气旋相叠加的全球危险海岸带,该地带包括中国大陆东部、日本沿海地区、美国东部海岸带、墨西哥湾地区和加勒比海地区。  相似文献   

冕洞阻碍太阳高能粒子事件形成的典型事例分析          下载免费PDF全文

申成龙  汪毓明  叶品中  王水 《地球物理学报》2006,49(3):629-635

通过对比两次快速晕状日冕物质抛射(CME)事件,分析相应的日面和行星际的观测资料,发现源区距离冕洞较远的CME引起了极强的太阳高能粒子(Solar Energetic Particle,SEP)事件,而源区非常靠近冕洞的CME则没有引起大的SEP事件.该结果表明,冕洞可能对CME形成SEP事件有阻碍作用.继而分析1997～2003年所有爆发在冕洞边缘的快速晕状CME,发现源区离冕洞距离小于02Rs(太阳半径)的CME均没有引起大的SEP事件.从而进一步证实了冕洞可能对邻近CME形成大SEP事件有影响,它阻碍SEP事件的形成.最后讨论了冕洞阻碍CME形成大SEP事件的可能原因.  相似文献   

Hydrothermal alteration processes in the giant Dahutang tungsten deposit,South China: Implications from litho-geochemistry and mass balance calculation     

Hai-Bo Zhao  Yong Zhang  Lei Liu 《China Geology》2021,4(2):230-244

The giant Dahutang tungsten (W) deposit has a total reserve of more than 1.31 Mt WO₃. Veinlet-disseminated scheelite and vein type wolframite mineralization are developed in this deposit, which are related to Late Mesozoic biotite granite. Four major types of alterations, which include albitization, potassic-alteration, and greisenization, and overprinted silicification developed in contact zone. The mass balance calculate of the four alteration types were used to further understanding of the mineralization process. The fresh porphyritic biotite granite has high Nb, Ta, and W, but low Ca and Sr while the Jiuling granodiorite has high Ca and Sr, but low Nb, Ta, and W concentrations. The altered porphyritic biotite granite indicated that the Nb, Ta, and W were leached out from the fresh porphyritic biotite granite, especially by sodic alteration. The low Ca and Sr contents of the altered Neoproterozoic Jiuling granodiorite indicate that Ca and Sr had been leached out from the fresh granodiorite by the fluid from Mesozoic porphyritic biotite granites. The metal W of the Dahutang deposit was mainly derived from the fluid exsolution from the melt and alteration of W-bearing granites. This study of alteration presents a new hydrothermal circulation model to understand tungsten mineralization in the Dahutang deposit.  相似文献   

Impacts of confining pressure and safety thickness on water and mud inrush in weathered granite     

Jinquan Liu  Weizhong Chen  Zhiping Deng  Taogen Liu 《Marine Georesources & Geotechnology》2020,38(2):144-153

Abstract

Due to the strong disintegration and water erosion of completely weathered granite, water and mud inrush disasters are apt to take place in this zone during underwater tunnel construction. The pore, compactness, seepage path length, fracture geometries and their interconnections for water and mud transfer are strongly influenced by confining pressure and waterproof-resistant slab safety thickness. In order to inspect the influence, a series of experiments based on a self-designed testing system and non-Darcy testing method were performed. The results indicated that the water and mud inrush evolution increased with the increase of confining pressure and decreased with the increase of safety thickness. In particular, the confining pressure mainly influences the initial evolution stage, and a critical safety thickness to prevent water and mud inrush is obtained. Besides, the non-Darcy testing method results shows that the water and mud inrush evolution affects the influence of non-Darcy flow. For example, while the safety thickness was smaller than the critical value, the evolution was large and unstable and its behavior transferred into nonlinear. In this case, the flow changed to non-Darcy flow.  相似文献   

南黄海物理-生物地球化学过程的时空异质性及内在关联和机制   总被引：2，自引：0，他引：2  

韦钦胜  王保栋  傅明珠  孙俊川  姚庆祯  辛明  于志刚 《海洋学报(英文版)》2020,39(10):11-26

研究多重物理过程控制下陆架边缘海生物地球化学过程的时空异质性及其生态响应,对于深入认识海洋生态系统具有重要的意义。基于相关历史观测资料和卫星遥感海表温度,本文综合分析了南黄海物理-生物地球化学过程的时空变化和空间异质性特征,探讨了该海域内部典型地理单元之间的内在关联和机制。结果显示,冷季沿岸流南向输送和暖季锋面上升流垂向输运的季节性交替是影响石岛外海与海州湾外侧海域生物地球化学和初级生产的重要物理过程。夏季苏北沿岸水的东北向扩展可形成浒苔离岸/跨区域输送的动力驱动。暖季水体层化显著影响着南黄海中部冷水团海域的生物地球化学过程,春至秋季冷水团海域底层水体中的营养盐逐渐累积,形成了营养盐的重要贮库;层化季节黄海冷水团边界锋区上升流系统的存在使得南黄海叶绿素a和初级生产力高值区位置同海表低温涌升流区总体相一致。冷季南黄海西部南下的冷水与中部北向入侵的暖水共同导致了“S”型锋面的形成;暖季黄海冷水团边界锋区的上升流系统是连接层化海域和近岸区的纽带,可实现对冷水团内部营养盐的提取,从而将冷水团内部和边界区的生物地球化学过程形成有机连接,并在成山角-石岛外海、海州湾外侧、苏北浅滩东部形成三个典型的物理-生物地球化学相互作用区。本研究细化和整合了南黄海区域海洋学研究,揭示了该海域物理-生物地球化学过程的空间异质性特征和不同地理单元之间的关联性及机制,获得了对南黄海水文-生物地球化学-生态过程的综合、系统认知。  相似文献