澜沧江某电站右坝肩复杂岩体质量分类

笔者通过对澜沧江某电站右岸坝肩复杂岩体的成因进行分析,采用岩体质量指数Z并结合水利水电工程围岩分级和RMR分级等岩体分类方法对电站右岸坝肩的复杂岩体进行了综合分类。     

贵州乌江渡水电站至楠木渡磷迁移转化机制分析

通过2009年3月～4月对排入乌江的废水水质监测结果进行分析,可以看出废水总磷浓度高、强度大且相当稳定,严重污染了乌江的水质.乌江总磷的主要来源是流域内磷化工企业排放的废水废渣且废水中大颗粒总磷含量高.本文通过乌江总磷的分布特征,总磷的存在形态,分析总磷在乌江的迁移转化机制.乌江总磷在迁移转化过程中主要是在水动力条件下...     

黄河中游汛期水沙联合分布模型及其应用

为在宏观上对黄河中游水沙运动的变化规律从随机过程的角度予以揭示,以黄河中游潼关水文站1952-1998年期间流量超过6 000m3/s的次洪过程中的洪峰流量和相应的沙峰含沙量系列为基础,运用Copula函数方法构建了黄河中游汛期水沙联合分布模型并对其应用进行了探讨.结果表明:在水沙丰枯同步频率中,同丰的频率略大于同枯的...     

21世纪黄河下游防洪减灾对策

黄河是受人类活动强烈影响的河流,随着人类活动对流域环境的影响日趋增强,进入黄河下游的水沙条件发生了重大改变,防洪出现了许多新情况、新问题。黄河水资源进一步开发利用,下游牵断流及小水时间逐年延长,黄河将无有效输沙水量,如果来沙不能控制,现行河道的行洪能力和寿命将始终是中国的忧患。小浪底水库２００１年投入运用后,对黄河下游又将强烈堆积。２１世纪社会经济发展对黄河下游防洪减灾提出了更高要求,根据多年对黄     

武当山地块基性岩墙群地球化学研究及其大地构造意义

武当山地块基性岩墙群的地球化学特征表明,它们为具大陆拉斑玄武央珠大陆板内岸 浆侵入的产物,是古陆块裂并保存在造山带内基底岩块的重要证据,这表明南秦岭和扬子板块曾存在晋宁期固结的统一古陆块,该古陆块在新元古代早期发生了一次重要的裂解作用。     

Elemental mobility in subduction metamorphism: insight from metamorphic rocks of the Franciscan Complex and the Feather River ultramafic belt,California

The degree of element mobility in subduction metamorphism has generated much debate; some workers advocate considerable mobility during metamorphism, whereas others postulate minimal mobility. We assess this issue by examination of major and trace element concentrations and Pb-, Nd-isotopic data for 39 mafic metavolcanic rocks from the Franciscan subduction complex, related units of coastal California, and the Feather River ultramafic belt of the northern Sierra Nevada, California; these samples span a wide range of metamorphic grade. We conclude that these rocks, despite their metamorphism up to eclogite facies, preserve protolith major and trace elemental compositions and isotopic ratios, with the exception of some mobile large ion lithophile elements such as Ba, Pb, and to a smaller extent La, U, and Sr. Thus subduction metamorphism of these metabasalts occurred in a largely closed system. Lack of light rare earth element enrichment in the rocks demonstrates lack of chemical exchange with subducted metasediments. Relatively low SiO₂ content (<48 wt.%) of many of the metamorphic rocks and the lack of correspondence between silica depletion and metamorphic grade suggests that the silica depletion resulted from seafloor hydrothermal alteration before subduction. In spite of demonstrated mobility of Pb, and possible mobility of Nd, isotopic ratios of Pb and Nd were not modified during subduction metamorphism. In contrast to our results from metabasaltic rocks, our analysis of actinolite-rich rinds from high-grade Franciscan mélange blocks suggests some chemical exchange between metachert and the overlying mantle. The increasing enrichment in Ba and Pb with increasing metamorphic grade suggests that Ba- and Pb-rich fluids interacted more intensely with metabasalt at the higher grades of metamorphism. Comparison of these results with studies of the active Mariana forearc suggests that fluids interacting with the mantle wedge up-dip of the region of magma genesis are derived from subducting sediments overlying the down-going plate.     

Interplay between river discharge and topography of the basin floor in a hyperpycnal lacustrine delta

Basin‐floor topography influences the flow path of hyperpycnal plumes and delta morphology during progradation of the Red River delta in Lake Texoma, USA. The Red River discharge is typically a hyperpycnal plume due to elevated total dissolved solids. Because the river plume is a bottom‐hugging hyperpycnal flow, lake bathymetry and topography strongly influence deposition and subsequent delta morphology. In addition to elevated total dissolved solid concentrations compared with Lake Texoma water, the density contrast of the Red River outflow is increased by high suspended‐sediment concentrations during high‐discharge events. Steep lateral slopes in the Lake Texoma basin deflect hyperpycnal river plumes and, subsequently, change the delta progradation direction before the delta reaches the opposite bank of the lake. Analysis of multi‐temporal aerial and satellite images indicates that the hyperpycnal delta follows the steepest lake‐bottom gradients, corresponding to the pre‐impoundment river thalweg (i.e. bypassing shallow parts of the lake). An analytical model for the hyperpycnal‐plume trajectory indicates plume deflection during low‐discharge or high‐discharge events, towards the deepest part of the basin. The magnitude of plume deflection is a function of river discharge and basin‐margin gradients. Plume deflection can vary between 10° and 80° from the channel axis towards the old river thalweg. The high deflection appears in the case of maximum basin side gradients of 12·8° and in conditions of low river discharge. During low‐discharge periods, the Red River delta builds a lobate shape with multiple terminal distributary channels whereas, during high‐discharge periods the Red River delta builds an elongate shape with a single large distributary channel. The elongate morphology of the delta is formed through the development of a single distributary channel and abandonment of the other distributaries. Therefore, the lobate shaped delta is expected to be preserved in the rock record.     

大陆造山带基底岩块中的基性岩墙群研究——以南秦岭武当地块为例

基性岩墙群是大陆和大陆造山带内发育的特殊地质体,包含丰富的地球动力学信息。造山带内基底岩块是造山作用过程卷入造山带的外来或原地地块（陆块）,基底岩块中基性岩墙群的发育及其变形、变质特征,既为造山带内存在古老陆块和古陆块的裂离提供了证据,也为造山过程的构造动力学研究提供了重要信息。加强造山带基底岩块中基性岩墙群的多学科综合研究,对于探讨大陆造山带的形成、演化及其动力学过程具重要意义。     

黄河内蒙古段上覆水、悬浮物和底泥重金属特征及生态风险研究

系统地采集黄河内蒙古段上覆水、悬浮物和底泥样品,分析其中重金属元素的含量。采用地质累积指数法和潜在生态危害系数法,研究了黄河干流内蒙古段的上覆水、悬浮物和底泥的重金属沿程分布特征、污染程度和生态风险。分析结果显示:除了As元素,悬浮物中重金属元素含量总体上高于底泥中的含量。地质累积指数法评价结果表明:悬浮物和底泥属于无污染—中度污染,悬浮物总体上比底泥污染严重;潜在生态危害系数法评价结果表明:底泥和悬浮物中重金属的生态危害总体上属轻微状态;因此,生态风险指数法和地质累积指数评价结果基本一致。