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排序方式: 共有3525条查询结果,搜索用时 15 毫秒
71.
大别山超高压变质岩的退变质赤微构造:折返过程的启示   总被引:13,自引:5,他引:13  
游振东  张泽明 《地质学报》2000,74(3):224-233
大别山超高压变质岩中发现了一系列退变质显微构造,其主要类型有:①由于出溶而产生的定一包裹物;②由于多型转变而产生的假像替代;③固→固反应产生的冠状体;④涉及流体的退变质反应产生的冠状体或后成合晶。借助显微构造关系,可以建立超高压变质岩的退变质演化阶段,从而构筑其PT演化趋势、识别出碰撞造山和超高压变质峰期之后的两阶段隆升历史;早期为“挤出”作用诱发的近等温减压退变质;晚期则是地壳伸展体制下的退变质  相似文献   
72.
This paper discusses the Cretaceous-Tertiary magnetic polarity sequence of the the Hengyang Basin on the basis of magnetostratigraphic study. The age of each stratigraphic unit has been determined with the magnetic polarity time scale combined with 39Ar/40Ar dating, thus providing evidence for determining the geological ages of different formations. The authors assign the age of the Dongjing Formation of the Hengyang Basin to Early Cretaceous, the Shenhuangshan Formation to Early-Late Cretaceous, the Daijiaping Formation to Late Cretaceous, and the Dongtang and Xialiushi formations to Palaeocene.  相似文献   
73.
74.
应用航放资料寻找非放射性金属矿产效果探讨   总被引:1,自引:0,他引:1  
陈中华 《铀矿地质》2003,19(2):106-113
本通过对粤北地区已知的52个非放射性金属矿床(点)的地质、物化探特征的统计资料综合分析,建立了评价非放射性金属矿产成矿远景的航空能谱参数模型,结合重磁测量、重砂测量及金属量测量成果,预测了4片非放射性金属矿产成矿远景区。  相似文献   
75.
粒度和元素证据指示的居延海1.5kaBP来环境演化   总被引:6,自引:1,他引:6  
靳鹤龄  肖洪浪  张洪  孙忠 《冰川冻土》2005,27(2):233-240
居延海是黑河的终端湖, 在最近3 000 a来已由原来面积 800 km2逐渐萎缩而最终干涸, 同时其周边环境也发生了巨大的变化.东居延海(索果诺尔)湖相沉积的粒度和元素资料研究结果表明: 明清以前湖泊的变化主要受气候变化的影响, 温暖时期, 气候偏湿, 入湖水量增多, 湖泊面积扩大, 流域化学风化作用增强; 寒冷时期, 气候偏干, 入湖水量减小, 湖泊萎缩, 流域化学风化作用减弱.明清之后特别是近40 a来, 由于黑河上中游地区大规模的土地开发及水资源利用, 入湖水量不断减小, 甚至河流断流, 最终导致了目前居延海的干涸.  相似文献   
76.
综合物探方法在松辽盆地北部基底结构研究中的应用   总被引:3,自引:0,他引:3  
根据综合地球物理方法,查明松辽盆地北部基底的断裂26条,其中岩石圈断裂6条,壳断裂5条,基底断裂15条;盆地基底岩性由五种类型所组成一前寒武系变质岩、糜棱岩、下古生界变质岩、二叠系浅变质岩及花岗岩。为盆地演化及含油气性提供重要信息。  相似文献   
77.
碳同位素与早元古代地层对比   总被引:2,自引:0,他引:2  
本文首次较详细地研究了早元古代碳酸盐地层的碳同位素组成,样品采自华北早元古代标准地层单元──山西五台地区滹沱群,结果表明碳同位素组成随地质时代有明显的变化,并与地层层位有很好的对应关系。作者认为,碳同位素对于早元古代碳酸盐地层的对比是很有用的。  相似文献   
78.
土体固结弹塑性分析的参数二次规划理论及有限元解   总被引:1,自引:0,他引:1  
基于广义Biot理论对土体弹塑性固结过程进行求解,建立了问题对应的参变量变分理论,并给出了数学证明,对此基础上推导了有限元分析列式,问题的求解最终化为参数二次规划问题,本文提出的方法适用于固结弹塑性分析的关联与非关流流动问题,也可处理各类软化问题。  相似文献   
79.
To mitigate the impact of natural or man-made hazards on the services of an infrastructure facility, it is important to quantitatively assess its available capacity. For example, in a post-disaster scenario, critical infrastructure is likely to experience (i) excessive demand for the service of an infrastructure and/or (ii) compromised capacity because of damage to the infrastructure and the failure of infrastructure interdependencies. As the demand grows and nears the capacity limit of an infrastructure facility, a shortage of services required for the community’s recovery will occur. The development of mitigation strategies and an assessment of their effectiveness require a systematic approach. In this paper, a functional stress–strain principle for infrastructure facilities is proposed to quantitatively assess their serviceability in post-disaster scenarios. Functional stress in infrastructure management represents a service-related demand on an infrastructure facility, while strain indicates its coping capacity. The dynamic nature of infrastructure services will be considered depending on the relationship between demand and available capacity. The allowable range of functional stress is then defined, considering plastic and elastic patterns of responses of a facility during recovery to explore strain capacity variations. The proposed principle facilitates a systematic understanding of how infrastructure facilities can adapt themselves to growing stress and the maximum level of stress they can handle. The application of the proposed functional stress–strain principle is demonstrated through case studies of two infrastructure facilities in a post-earthquake scenario: a medical facility and a power facility.  相似文献   
80.
Sand-rich tight sandstone reservoirs are potential areas for oil and gas exploration. However, the high ratio of sandstone thickness to that of the strata in the formation poses many challenges and uncertainties to traditional lithofacies paleogeography mapping. Therefore, the prediction of reservoir sweet spots has remained problematic in the field of petroleum exploration. This study provides new insight into resolving this problem, based on the analyses of depositional characteristics of a typical modern sand-rich formation in a shallow braided river delta of the central Sichuan Basin, China. The varieties of sand-rich strata in the braided river delta environment include primary braided channels, secondary distributary channels and the distribution of sediments is controlled by the successive superposed strata deposited in paleogeomorphic valleys. The primary distributary channels have stronger hydrodynamic forces with higher proportions of coarse sand deposits than the secondary distributary channels. Therefore, lithofacies paleogeography mapping is controlled by the geomorphology, valley locations, and the migration of channels. We reconstructed the paleogeomorphology and valley systems that existed prior to the deposition of the Xujiahe Formation. Following this, rock-electro identification model for coarse skeletal sand bodies was constructed based on coring data. The results suggest that skeletal sand bodies in primary distributary channels occur mainly in the valleys and low-lying areas, whereas secondary distributary channels and fine deposits generally occur in the highland areas. The thickness distribution of skeletal sand bodies and lithofacies paleogeography map indicate a positive correlation in primary distributary channels and reservoir thickness. A significant correlation exists between different sedimentary facies and petrophysical properties. In addition, the degree of reservoir development in different sedimentary facies indicates that the mapping method reliably predicts the distribution of sweet spots. The application and understanding of the mapping method provide a reference for exploring tight sandstone reservoirs on a regional basis.  相似文献   
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