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31.
长白山及邻区地壳、上地幔顶部三维速度结构 总被引:2,自引:0,他引:2
根据沿长白山布设的宽频带流动地震台站及吉林省地震台网所记录的近震P波走时数据,利用层析成像方法对长白山及邻区(39°N-45°N、122°E-130°E)深至40 km的地壳和上地幔顶部三维速度结构进行了研究。结果表明:地震的发生和分布多集中于断裂等复杂地质构造。利用较高分辨率的地壳、上地幔顶部三维速度结构证实了长白山火山区岩浆囊存在,并推测岩浆囊的位置位于火山口的西南方向,深度为10~40 km。壳内岩浆囊分布对进一步解释、认识火山灾害提供了重要的深部信息。 相似文献
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沿海地区深基坑设计施工都十分重视其抗浮问题,在深基坑开挖前掌握抗拔桩对于基坑隆起和围护结构变形及受力规律十分重要,其研究成果对于节约工程成本和保证基坑施工安全具有重要的指导意义。以港珠澳大桥侧接线拱北海关隧道明挖段为依托,首先建立抗拔桩与土体的硬接触模型,并验证该模型对于抗拔桩模拟的合理性,采用极差分析法研究底板不同桩长和桩径加固对基坑围护结构稳定性的影响规律。分析结果表明,增大桩长可更有效地减小地表沉降,增大桩径可更好地控制连续墙的变形,增大桩长和桩径都可以很好地控制坑底隆起。 相似文献
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The Au-SiO2 and Sn-SiO2 complexes have been experimentally calibrated at varying temperature,silica comcentration and pH: Au^ H2SiO4^-=AuH3SiO4 lgK=-1.65436 9611.21/T; Sn^4 4H3SiO4^-=Sn(H3SiO4)4 lgK200℃=42.73 Compared with Au-Cl,Au-HS and Sn-OH complexes,AuH3SiO4 and Sn(H3SiO4)4complexes can be recognized as the dominant transport forms in Si-bearing solurtions under pH and Eh conditions of general interest.The decrease of SiO2 concentration and oxygen fugacity would reverse the direction of dissolution-complexing reactions,resulting in the precipitation of gold and silica,as well as cassiterite and silica.This study illustrates the significance of SiO2-complexation in hydrothermal solutions for gold,tin and other metallizations. 相似文献
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Peixin Duan Cui Liu Xuanxue Mo Jinfu Deng Jinhua Qin Yu Zhang Shipan Tian 《地学前缘(英文版)》2018,9(5):1417-1431
The Chalukou porphyry Mo deposit, located in the Great Hinggan Range, is the largest Mo deposit in northeast China, although the age and genesis of the associated magmatic intrusions remain debated.Here we report zircon U-Pb ages and trace elements, whole rock geochemistry and Sre Nd isotope data with a view to understand the relationship between the magmatism and molybdenum mineralization.Zircon U-Pb analysis yield an age of 475 Ma for rhyolite in the older strata, 168 Ma for the premineralization monzogranite, and 154 Ma for the syn-mineralization granite porphyry. The granite porphyry and quartz porphyry are considered as the ore-forming intrusions. These rocks are peraluminous, alkali-calcic, and belong to high-K to shoshonitic series with a strong depletion of Eu. They also display characteristics of I-type granites. The rocks exhibit wide variations of(87 Sr/86 Sr)iin the range of 0.705426 -0.707363, and ε_(Nd)(t) of -3.7 to 0.93. Zircon REE distribution patterns show characteristics between crust and the mantle, implying magma genesis through crust-mantle interaction. The Fe_2O_3/FeO values(average 1) for the whole rock and EuN/Eu*Nvalues(average 0.45), Ce~(4+)/Ce~(3+) values(average 301)for zircon grains from the granite porphyry are higher than those from other lithologies. These features suggest that the ore-forming intrusions(syn-mineralization porphyry) had higher oxygen fugacity conditions than those of the pre-mineralization and post-mineralization rocks. The Chalukou Mo deposit formed in relation to the southward subduction of the Mongol-Okhotsk Ocean. Our study suggests that the subduction-related setting, crust-mantle interaction, and the large-scale magmatic intrusion were favorable factors to generate the super-large Mo deposits in this area. 相似文献
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瑞利波法检验客运专线湿陷性黄土地基处理效果 总被引:1,自引:0,他引:1
黄土地基具有明显的湿陷性,试验采用3种方法(柱锤冲扩桩、挤密桩、强夯)进行处理.测试得到地基在3种方案处理前后的瞬态瑞利波频散曲线,比较处理前后的瑞利波波速分布图,反演分析地基剪切波速度,得到黄土地基处理后的波速变化特性.结果表明,经3种方案处理后的黄土地基弹性波波速均得到了提高,波速增大幅度从大到小分别为柱锤冲扩桩、挤密桩和强夯,与静力触探法对比结果较为一致,表明瞬态瑞利波测试方法能大面积无损测试地基处理效果. 相似文献
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Guan Qing Yu Pan Bao Tian Li NaLi Qiong Zhang JundiGao Hongshan Liu Jia 《Comptes Rendus Geoscience》2010,342(3):189-196
Records of two loess sections located in mid-eastern and western margins of the East Asian Monsoon area captured 20 Dansgaard-Oescher events and six Heinrich events. All these suggested that the climate in the East Asian Monsoon area fluctuated rapidly on millennial to century timescales during the whole Last Glacial. We found that these loess-based events of rapid climate fluctuations were generally synchronous with those of GRIP records, but that there were differences between the Shagou loess section in the west and the Wangguan loess section in the east: the former was more sensitive to climate change than the latter. Compared with earlier studies on loess records covering the Last Glacial from neighboring areas, we discovered that the magnitude of Dansgaard-Oeschger cycles decreased gradually from west to east and we suggest that it resulted from the combined effect of the Westerlies and the East Asian Monsoon. 相似文献
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