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81.
藏南裂谷作为青藏高原最显著的伸展构造样式之一,是研究高原生长过程的重要窗口,但目前其深部成因机制仍存在较大争议。本文利用沿错那—沃卡裂谷中部的大地电磁数据,分析裂谷区域的大地电磁测深曲线特征和相位张量,并通过三维大地电磁反演获得邛多江地堑和沃卡地堑深部电性结构。三维大地电磁反演结果显示,沃卡地堑和邛多江地堑深部存在一条连续的显著高导异常,并呈现“俯冲”形态,且上覆高阻结构体,而在邛多江地堑两侧浅部则分布低阻异常。结合早期的研究结果,本文支持错那—沃卡裂谷深部的高导异常为地壳部分熔融,可能与南向地壳流相关,并研究认为在南北向持续挤压作用下,裂谷下方的弱地壳层,通过解耦上地壳和下部地壳,促进了藏南裂谷系的发育。 相似文献
82.
脆性作为岩石的重要的力学指标,对深部岩体性态评价以及灾害预防具有重要意义。岩石应力−应变曲线能够很好地表征岩石的脆性。考虑到现有基于应力−应变曲线的脆性指标大多都只对曲线的一部分进行分析,且少有指标能够准确地应用于岩石II类曲线中,对整体判断的缺乏可能会导致工程应用上适应性及可靠性不足的情况。针对现有脆性指标普遍存在的物理意义模糊、评估结果与岩石脆性的关系非连续等问题,综合考量岩石应力−应变曲线中峰前应力上升速率、峰后应力跌落速率以及峰值点应变值对岩石脆性的影响,提出了一种物理意义明确、计算结果与岩石脆性之间的关系是单调且连续的岩石脆性指数计算方法。选取国内外常用脆性指标对锦屏II级水电站大理岩和某铁路隧道花岗岩、变质砂岩以及片麻岩的单轴压缩试验数据进行脆性评价后进行比较,验证了指标的适用性。进一步将提出的指标应用于常规三轴试验条件下大理岩脆性分析,结果表明,该指标不仅能够量化和分类不同岩石的脆性特征,还能表征围压对岩石脆性的抑制作用。 相似文献
83.
湘西北地区铅锌矿床成矿地质特征及矿床成因研究 总被引:3,自引:1,他引:2
湘西北铅锌矿带属于中国16个重点成矿区带之湘西-鄂西成矿带的南西段,区内成矿地质条件优越,形成保靖、洛塔、花垣渔塘、凤凰4个矿田。文章在野外考察和室内研究的基础上,以洛塔矿田中的下光荣、江家垭等铅锌矿床、花垣渔塘矿田中的李梅铅锌矿床为例,从地层、岩性、构造等分析入手,采用同位素测试、包裹体分析等手段,对湘西北铅锌矿带的成矿地质特征及成矿机制进行了探讨,认为区内成矿物质主要来源于寒武纪地层,成矿作用过程中,油田卤水在构造作用下的大规模运移、循环,导致了成矿物质的富集和沉淀,主要成矿时代为加里东期。 相似文献
84.
85.
Huang Sijing Li Xiaoning Wu Wenhui Zhang Meng Hu Zuowei Liu Sibing Huang Keke Zhong Yijiang 《地球科学进展》2015,30(11):1185-1197
Carbon isotopic composition of marine carbonates is a record for various important geological events in the process of earth development and evolution. The carbonates of Carboniferous, Permian and Triassic, as the transition from Paleozoic to Mesozoic-Cenozoic have very high 13C value. Taking this as the main point, and combined with the oxygen, strontium isotopic composition in carbonates, distribution of carbonate basin area through geologic time, the correlation of carbon isotopic composition of marine carbonates to sea level change, organic carbon burial flux, exchange of CO2 content in atmosphere and ocean, and long cycle evolution of the earth ecosystems were approached. The results are shown as follows: ①The interval of 13C >3‰ during Phanerozoic was concentrated in Carboniferous, Permian and the beginning of Triassic, but the beginning of Triassic was characterized by higher frequency and larger fluctuations in 13C value during a short time, whereas the Carboniferous-Permian presented a continuously stable high 13C value, indicating a larger amount of organic carbon accumulation in this time interval. Relatively high 18O values during this time was also observed, showing a long time of glaciations and cold climate, which suggest a connection among rapid organic carbon burial, cold climate, as well as pCO2 and pO2 states of atmosphere. ②The over consumption of atmosphere CO2 by green plants during the time with high 13C of seawater forced CO2 being transferred from ocean to atmosphere for the balance, but the decrease in the seawater amount and water column pressure caused by the global cooling could weaken dissolution capacity of CO2 in seawater and carbon storage of marine carbonates, and also reduce the carbonate sedimentary rate and decrease the carbonate basin area globally from Devonian to Carboniferous and Permian. During the middle-late Permian carbonate was widely replaced by siliceous sediments even though in shallow carbonate platform, which resulted in the decrease of marine invertebrates, suggesting the Permian chert event should be global. ③The Phanerozoic 87Sr/86Sr trend of seawater showed a sharp fall in Permian and drop to a minimum at the end of the Permian, indicting input of strontium from the submarine hydrothermal systems (mantle flux). Such process should accompany with a supplement of CO2 from deep earth to atmosphere and ocean system, but the process associated with widespread volcanism and rises of earth’s surface temperature pricked up the mass extinction during the time of end Permian. ④Cold climate and increase of continental icecap volume, the amalgamation of northern Africa and Laurentia continentals were the main reasons responsible for the sea level drop, but the water consumption result from the significantly increased accumulation of organic carbon should also be one of the reasons for the sea level drop on the order of tens of meters. ⑤The mass extinction at the end Permian was an inevitable event in the process of earth system adjustment. It was difficult for marine invertebrates to survive because of the continuously rapid burial of organic carbon, and of the decrease of sea water amount and its dissolution ability to CO2. At last, at the end of Paleozoic, the supplement of CO2 to atmosphere and ocean by widely magma activities resulted in a high temperature of earth surface and intensified mass extinction. 相似文献
86.
87.
在利用遥感数据和地理信息系统(GIS)技术的矿产资源勘查与评价中,矿化蚀变信息提取和构造信息提取起着至关重要的作用。以缅甸铜金矿为例,利用ETM+遥感图像,采用比值法、阈值分割和主成分分析(PCA)提取羟基蚀变信息;利用数字高程模型和遥感数据提取与铜金矿化有关的线环构造,结合地质资料和上述信息,利用证据权和分形方法进行整合,确定该研究区的成矿远景区。结果发现,已知铜金矿均分布于成矿靶区中,综合信息可为下一步的矿产资源勘探工作提供决策依据。 相似文献
88.
研究城市地表覆盖与地表温度(LST)的关系对改善城市生态环境具有重要科学意义。在Landsat TM数据支持下,利用线性光谱混合分析模型提取不透水地表信息,结合LST和地表热通量,分析不透水地表覆盖度(ISA)和LST的时空变化特征及其相互关系,探讨不透水地表对LST的影响机理。结果表明:1984—2014年北京不透水地表面积迅速增长,中覆盖度比例下降,高覆盖度比例增加;LST从市中心向郊区递减,高温区向外扩张;LST和ISA呈显著正相关,但不是简单的线性关系;ISA处于0.6~0.9时LST上升速率最快,减少ISA在此范围内的不透水地表集中分布可缓解高温区集中的现象。 相似文献
89.
90.
京津唐城市群不透水地表增长对水环境的影响(英文) 总被引:5,自引:1,他引:4
匡文慧 《地理学报(英文版)》2012,22(3):535-547
The impervious surface area (ISA) at the regional scale is one of the important en-vironmental factors for examining the interaction and mechanism of Land Use/Cover Change (LUCC)-ecosystem processes-climate change under the interactions of urbanization and global environmental change. Timely and accurate extraction of ISA from remotely sensed data at the regional scale is challenging. This study explored the ISA extraction based on MODIS and DMSP-OLS data and the incorporation of China’s land use/cover data. ISA datasets in Beijing-Tianjin-Tangshan Metropolitan Area (BTTMA) in 2000 and 2008 at a spa-tial resolution of 250 m were developed, their spatiotemporal changes were analyzed, and their impacts on water quality were then evaluated. The results indicated that ISA in BTTMA increased rapidly along urban fringe, transportation corridors and coastal belt both in intensity and extents from 2000 to 2008. Three cities (Tangshan, Langfang and Qinhuangdao) in Hebei Province had higher ISA growth rates than Beijing due to the pressure of population-re?sour?ces-envi?ronments in the city resulting in increasingly transferring industries to the nearby areas. The dense ISA distribution in BTTMA has serious impacts on water quality in the Haihe River watershed. Meanwhile, the proportion of ISA in sub-watersheds has significantly linear relationships with the densities of river COD and NH3-N. 相似文献