哀牢山-红河左旋走滑剪切带中新世抬升的时间序列

在哀牢山-红河剪切带的元阳到者龙的6个不同地点,对18个变质岩样品进行系统分析钾长石的~(40)Ar-~(39)Ar年龄。发现用MDD模式得到的18条冷却曲线(温度范围在400-150℃之间)均存在一次(或两次)快速冷却过程(冷却速度>100°C/Ma),这种快速冷却(抬升)过程不仅反映了该剪切带在大约25-17Ma时,韧性走滑作用结束和正断作用的开始,而且它的起始时间还有自东南向西北逐渐变新的趋势。利用6个不同地点快速冷却(抬升)的起始时间与相对距离作图时,得到了较好的线性函数关系(斜率为34mm/a)     

Geohydrological models and earthquake effects at Yucca Mountain, Nevada

 Yucca Mountain, the proposed site for the high-level nuclear waste repository, is located just south of where the present water table begins a sharp rise in elevation. This large hydraulic gradient is a regional feature that extends for over 100 km. Yucca Mountain and its vicinity are underlain by faulted and fractured tuffs with hydraulic conductivities controlled by flow through the fractures. Close to and parallel with the region of large hydraulic gradient, and surrounding the core of the Timber Mountain Caldera, there is a 10- to 20-km-wide zone containing few faults and thus, most likely, few open fractures. Consequently, this zone should have a relatively low hydraulic conductivity, and this inference is supported by the available conductivity measurements in wells near the large hydraulic gradient. Also, slug injection tests indicate significantly higher pressures for fracture opening in wells located near the large hydraulic gradient compared to the opening pressures in wells further to the south, hence implying that lower extensional stresses prevail to the north with consequently fewer open fractures there. Analytical and numerical modeling shows that such a boundary between media of high and low conductivity can produce the observed, large hydraulic gradient, with the high conductivity medium having a lower elevation than the water table. Further, as fractures can close due to tectonic activity, the conductivity of the Yucca Mountain tuffs can be reduced to a value near that for the hydraulic barrier due to strain release by a moderate earthquake. Under these conditions, simulations show that the elevation of the steady-state water table could rise between 150 and 250 m at the repository site. This elevation rise is due to the projected shift in the location of the large hydraulic gradient to the south in response to a moderate earthquake, near magnitude 6, along one of the major normal faults adjacent to Yucca Mountain. As the proposed repository would only be 200–400 m above the present water table, this predicted rise in the water table indicates a potential hazard involving water intrusion. Received: 7 June 1996 / Accepted: 19 November 1996     

GRADIENT DISTRIBUTION OF ACID RAIN IN THE SCENIC RESORT OF THE BAIYUN MOUNTAIN IN GUANGZHOU

1 INTRODUCTION Sitting in the central part of the Pearl River Delta, Guangzhou is one of the cities in China that are most polluted by acid rain. Broad attention has been brought to the problem. Since the early 1980s, a series of observation and studies h…     

新疆及边邻地区7级以上地震前后北天山地下流体动态的异常变化

重点分析了新疆及边邻地区1980年以来6次7级以上地震前后北天山地下流体动态异常资料，其中3次地震前地下水有短期前兆异常变化，震时同震地震波效应普遍存在，震后异常十分突出且幅度大；以水位为主的水动力学效应反映了大区域应力调整过程具有不可逆特征。水文地球化学参数的变化不敏感。讨论了地下水远程效应与井震距离的关系以及阶跃异常的幅度等问题。     

金沙江下游白鹤滩水电站岩体结构的建造特征

拟建的白鹤滩水电站的坝基为峨眉山玄武岩。峨眉山玄武岩由火山熔岩类、火山碎屑熔岩类、火山碎屑岩类和沉积火山碎屑岩类所组成。火山熔岩又可划分为斜斑玄武岩、块状玄武岩和杏仁状玄武岩;火山碎屑岩包括集块岩、火山角砾岩以及凝灰岩;而沉积火山碎屑岩类则由沉火山角砾岩和沉凝灰岩所组成。不同类型岩石的结构构造、矿物成分和形成环境不同,导致它们的岩石力学性质和工程性能也不相同。块状玄武岩、斜斑玄武岩和沉积火山碎屑熔岩的抗压强度和抗风化能力都比较大,因而具有很好的工程地质稳定性;杏仁状玄武岩、火山碎屑熔岩的抗压强度稍低,但抗风化能力很好,因此也具有较好的工程地质稳定性;而火山碎屑岩包括火山角砾岩、凝灰岩的抗压强度和抗风化能力都很低,往往形成岩体中的软弱夹层,工程地质稳定性较差。     

大坂山隧道地下水动态分析及对隧道作用评估

Base on the groundwater yield, water temperature and hydrochemistry change of the groundwater, we can analyze that the summer water content is obviously greater than winter water content where the in and-out wall rock of the Daban Mountain tunnel. The groundwater supply has the extensity and the seasonality. The groundwater content of the middle tunnel wall rock changes relatively steady, mainly supply through horizontal direction. And the total groundwater content is relatively little and steady in winter. The water pressure of the wall rock cranny is little. It has the fluent drainage system to dredge groundwater, which cannot constitute a threat to the tunnel lining. And the cold-proof sluice hole can normally work to drain water.     

新疆博格达山分段及深浅构造转换关系

研究表明 ,天山及邻区自中生代以来一直处于热衰减状态 ,博格达山新生代再造山具有“冷隆升”性 ,盆山边界断裂多限于上地壳内 ,而非直通中地壳低速体甚至上地幔的“深大断裂”。造山带内的韧性剪切带是在古生代形成的 ,而不是再造山期的断裂 ,它对造山带隆升及盆山耦合无贡献 ,博格达山的隆升为复式背斜构造所支持。博格达山与准东的关系为背斜北翼与盆地平缓基底构成的挠曲构造 ,而不是被深大断裂分隔的断块。博格达山具有独特鲜明的分段性 ,造山带的两个弧形构造与新生代再生前陆盆地构成独特的“斜方对称”分布样式。以板条观点为指导 ,从盆山单元的平面配置关系和深浅构造转换关系入手 ,探讨了博格达山板内造山阶段的几何学和运动学分段性的成因 ,构建了盆山耦合模式     

内蒙古"宝音图隆起"的归属讨论

对比研究表明，内蒙古“宝音图隆起”和狼山地区的古元古代宝音图岩群与新太古代色尔腾山岩群都是由中低级变质的各种片岩、大理岩组成，一致的岩石组合和变质相暗示二者可能是等同物而不是两个岩群。以物探资料为据的构造研究也证实，“宝音图隆起”与狼山地区之间并无槽一台级的大型断裂构造分开，二者实为统一的构造整体而不是分属槽台，只因两侧被两条近于平行的NE向断裂围限，使其总构造线方向呈NE或NNE向而与色尔腾山的构造线不同。结论认为，“宝音图隆起”仍是华北陆块的一部分，不属于内蒙古一大兴安蛉地槽褶皱系。     

贡嘎山东坡亚高山不同林地土壤水分特性与生态环境效应

森林土壤水分特性，包括水分的渗透与蒸发、保持与贮存等对森林生态环境都有重要意义。本文研究了长江上游贡嘎山亚高山不同森林类型土壤的水分特征及其生态环境作用，结果表明：成熟林、过熟林土壤在储水、渗透、容水、蒸发和持水特性等多数方面利于保持和改善生态环境，次生或林分单一森林类型次之，林木皆伐后最差。研究区以成熟林和过熟林为主，生态环境保护较好。尽管该区与长江上游其它地区一样同具自然地理条件差、生态环境脆弱的特征，但由于该区森林植被和环境得到了有效保护，土壤水分特性好，促进了森林生态系统的良性循环，生态环境问题得到进一步改善。