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31.
Pyrite in LT–HP eclogites from the western Tianshan orogenic belt yields a Re‐Os age of 378.1 ± 8.9 Ma, which is 30–70 Ma older than ages previously obtained for the same rocks using the Rb–Sr, Sm–Nd, Ar–Ar, U–Pb, and Lu–Hf isotope systems. The Tianshan LT–HP eclogite experienced temperatures of up to ~570 °C combined with pressures of up to 2.1 GPa during metamorphism. These conditions are below the transition of pyrite to pyrrhotite, which defines both pyrite stability and possibly its closure temperature for Re‐Os. Pyrite can preserve Re‐Os signatures through eclogite facies peak metamorphic conditions, and thus allow determination of the formation age of pyrite in the protolith. 相似文献
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Suspended sediment and total dissolved solid yield patterns at the headwaters of Urumqi River,northwestern China: a comparison between glacial and non‐glacial catchments 下载免费PDF全文
In order to understand the differences in the suspended sediment and total dissolved solid (TDS) yield patterns between the glacial and non‐glacial catchments at the headwaters of Urumqi River, northwestern China, water samples were collected from a glacier catchment and an empty cirque catchment within the region, during three melting seasons from 2006 to 2008. These samples were analyzed to estimate suspended sediment and TDS concentrations, fluxes and erosion rates in the two adjoining catchments. There were remarked differences in suspended sediment and TDS yield patterns between the two catchments. Suspended sediment concentrations were controlled mainly by the sediment source, whereas TDS concentrations were primarily related to the hydrologic interaction with soil minerals. Generally, the glacial catchment had much higher suspended sediment and TDS yields, together with higher denudation rates, than the non‐glacial catchment. Overall, glacial catchment was mainly dominated by physical denudation process, whereas the non‐glacial catchment was jointly influenced by physical and chemical denudation processes. The observed differences in material delivery patterns were mainly controlled by the runoff source and the glacial processes. The melting periods of glacier and snow were typically the most important time for the suspended sediment and TDS yields. Meanwhile, episodic precipitation events could generate disproportionately large yields. Subglacial hydrology dynamics, glaciers pluck and grind processes could affect erodibility, and the large quantities of dust stored on the glacier surface provided additional sources for suspended sediment transport in the glacial catchment. These mechanisms imply that, in response to climate change, the catchment behaviour will be modified significantly in this region, in terms of material flux. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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The drainage evolution and valley development of the Jinsha River is an important issue constantly concerned by researchers in geology and geomorphology. Despite hundreds of years of research, there is a big dispute on the formation time and the evolution process of the fluvial valley. Fluvial terraces are very important geomorphic markers for studying the formation and evolution of the fluvial valley. Through field investigation combined with Electron Spin Resonance (ESR) dating, we confirmed that 5 fluvial terraces were formed, and then preserved, along the course of the Jinsha River near the Longjie, which are all strath terraces. Among them, T5 developed on the base rock, with an age of (78±12) ka; all T4~T1 developed on the lacustrine sediments, named Longjie Group by Chinese, with an age of (29±1.4) ka, (26±2.4) ka, (23±1.4) ka, (18±1.7) ka, respectively. Compared with the global and regional climate change history, the terraces are all the result of the river responding to the climate change. T5 formed at MIS 5/4, and T4~T1 formed at the period of regional climate fluctuation. The relationship of terraces and the Longjie Formation, combined with sedimentary characteristics analysis demonstrate that the Longjie Formation is landslide dammed lake sediment. The landslide and blocking events.seriously influenced the valley evolution, inhibiting the river incising, and making the valley evolution defer to the mode of “cut-landside-damming-fill-cut” in the period of Late Pleistocene. Synthesized studies of the terraces and the correlative sediments indicate that the formation of the Jinsha River valley may have begun in the late Early Pleistocene. 相似文献
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分别构建广州主建成区垂直比例尺为1﹕2 000、1﹕1 000和1﹕500的3个建筑物模型,利用大型边界层风洞,在西北和东南两风向下,基于中性流模拟分析了复杂城市地形下湍流度随高度的变化及其对宏观地形的依赖。结果表明:风廓线指数α与不同高度的湍流度之间的关系密切,利用现有模型,根据4类粗糙度边界层和不同垂直比例尺,可确定相应的湍流度随高度变化模型的主要系数,预测精度高。城市地形下最大湍流度面发育在0~0.2 h之间狭窄的范围内。用湍流度形态指数β来表征湍流度随高度的变化,无论城市屋脊还是平坦地形,随着风程区的延伸,廓线的指数α升高,湍流度形态指数β降低。表明同一高度湍流度值具有由迎风区、丘顶区向背风区增高,沿风程逐渐增大的规律,对地形部位和风程的依赖性强,与来流翻越简单地形时的特征一致。 相似文献
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电镀园区废水处理过程中,由于园区企业难以做到彻底的分质分流,导致废水处理出现破络不彻底,次亚磷酸盐、氰化物等出现再络合与难降解等问题,同时,深度处理后,浓水需要进行深度处理,重金属离子浓度、总磷、总氮处理都存在难以达标的情况。本文根据企业电镀废水的典型水质和水量特征,研究设计了改进的CAFE处理工艺,详细论证了各工艺的处理过程、主要设备及相关设计参数,并将该工艺在南通某电镀园区电镀废水处理中进行了实际应用。运行的实践表明,该套设计方案污水处理运行稳定,最终出水的CODCr(化学需氧量)、NH4-N、总铬、六价铬、总镍指标的平均质量浓度分别为34.00、5.41、0.29、0.03、0.05 mg/L,均远远小于电镀废水的排放标准,达到了电镀废水的深度处理要求。 相似文献
38.
近断层速度脉冲与震源机制的关系浅析 总被引:1,自引:1,他引:0
本文初步分析了近断层速度脉冲的成因和特点,主要包括方向性效应与滑冲效应,并通过中国台湾集集地震的脉冲记录,分析了断层破裂方向和位移大小等震源参数对脉冲强度的影响。此外,基于有限移动源理论,说明了断层辐射与速度脉冲分布的关系,并探讨了利用运动学震源模型研究近断层地震动对速度脉冲影响的技术路线;评述了7种典型的等效速度脉冲模型,建议进一步研究等效速度脉冲函数与震源机制之间的关系。最后,简述了不同类型的断层引起速度脉冲的差异,并推测了产生脉冲型地震动的下限条件,同时展望该研究在地震预警方面的可能性。 相似文献
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Global research progress on coastal flooding was studied using a bibliometric evaluation of publications listed in the Web of Science extended scientific citation index. There was substantial growth in coastal flooding research output, with increasing publications, a higher collaboration index, and more references during the 1995–2016 period. The USA has taken a dominant position in coastal flooding research, with the US Geological Survey leading the publications ranking. Research collaborations at institutional scales have become more important than those at global scales. International collaborative publications consistently drew more citations than those from a single country. Furthermore, coastal flooding research included combinations of multi-disciplinary categories, including ‘Geology' and ‘Environmental Sciences Ecology'. The most important coastal flooding research sites were wetlands and estuaries. While numerical modeling and 3 S(Remote sensing, RS; Geography information systems, GIS; Global positioning systems, GPS) technology were the most commonly used methods for studying coastal flooding, Lidar gained in popularity. The vulnerability and adaptation of coastal environments, their resilience after flooding, and ecosystem services function showed increases in interest. 相似文献
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