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Ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers. Due to differential settlement, the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure. Here, we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks, which increasingly affect some middle- and large-sized cities in the world. For that purpose, the ground loss theory is applied to sediments overlying a sinusoidal-shaped graben. This analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear. It also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues. Finally, when a crack has completely developed, the tensile zone shifts towards the center of the graben, creating a new area for potential cracking and faulting. 相似文献
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L. A. Morgan W. C. Shanks III D. A. Lovalvo S. Y. Johnson W. J. Stephenson K. L. Pierce S. S. Harlan C. A. Finn G. Lee M. Webring B. Schulze J. Dühn R. Sweeney L. Balistrieri 《Journal of Volcanology and Geothermal Research》2003,122(3-4):221-242
‘No portion of the American continent is perhaps so rich in wonders as the Yellow Stone’ (F.V. Hayden, September 2, 1874)Discoveries from multi-beam sonar mapping and seismic reflection surveys of the northern, central, and West Thumb basins of Yellowstone Lake provide new insight into the extent of post-collapse volcanism and active hydrothermal processes occurring in a large lake environment above a large magma chamber. Yellowstone Lake has an irregular bottom covered with dozens of features directly related to hydrothermal, tectonic, volcanic, and sedimentary processes. Detailed bathymetric, seismic reflection, and magnetic evidence reveals that rhyolitic lava flows underlie much of Yellowstone Lake and exert fundamental control on lake bathymetry and localization of hydrothermal activity. Many previously unknown features have been identified and include over 250 hydrothermal vents, several very large (>500 m diameter) hydrothermal explosion craters, many small hydrothermal vent craters (1–200 m diameter), domed lacustrine sediments related to hydrothermal activity, elongate fissures cutting post-glacial sediments, siliceous hydrothermal spire structures, sublacustrine landslide deposits, submerged former shorelines, and a recently active graben. Sampling and observations with a submersible remotely operated vehicle confirm and extend our understanding of the identified features. Faults, fissures, hydrothermally inflated domal structures, hydrothermal explosion craters, and sublacustrine landslides constitute potentially significant geologic hazards. Toxic elements derived from hydrothermal processes also may significantly affect the Yellowstone ecosystem. 相似文献
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氡射气测量在西安地裂缝勘察中的应用研究 总被引:2,自引:0,他引:2
为了避免大量开挖揭露工作量, 加快地裂缝的勘察速度, 研究出一种简便易行的探测方法是目前西安地裂缝勘察中迫切需要解决的问题。本文研究了氡射气测量在西安地裂缝勘察应用的地质基础, 结合近十几年工程勘察实践, 讨论了氡射气异常的特征, 分析了氡射气的探测效果, 结果认为:氡射气测量在西安地裂缝探测中的有效率为:80%左右。 相似文献
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HAN Ke YANG Xingke CHAO Huixi HE Hujun RUAN Shiqi GAO Yunfeng ZHANG Weisheng ZHU Wei JIN Gang 《《地质学报》英文版》2021,95(2):500-516
A W-Mo mineralized region is located along the northern margin of the South Qinling tectonic belt of China. WMo mineralization occurs mainly in Cambrian–Ordovician clastic and carbonate rocks, and the ore bodies are structurally controlled by NW–SE-and NNE–SSW-striking faults. Evidence for magmatism in the area is widespread and is dominated by intermediate–felsic intrusives or apophyses, such as the Dongjiangkou, Yanzhiba, Lanbandeng, and Sihaiping granitic bodies. Quartz-vein-type mineralization and fault-controlled skarn-type mineralization dominate the ore systems, with additional enrichment in residual deposits. At present, there are few or insufficient studies on(1) the age of mineralization,(2) the relationship between intermediate–felsic granite and W-Mo mineralization,(3) the source of ore-forming materials,and(4) the metallogenic and tectonic setting of the mineralized area. In this paper, we present geochronology results for numerous intrusive granitic bodies in the South Qinling tectonic belt. U-Pb zircon geochronology of the Lanbandeng monzogranite and Wangjiaping biotite monzogranite yields ages of 222.7 ± 2.3 and 201.9 ± 1.8 Ma, respectively. In contrast to the Late Triassic age of the Lanbandeng monzogranite, the age of the newly discovered Wangjiaping biotite monzogranite places it at the Triassic–Jurassic boundary. Re-Os molybdenite geochronology on the Qipangou W-Mo deposit yielded a model age of 199.7 ± 3.9 Ma, indicating the deposit formed in the early Yanshanian period of the Early Jurassic. Granitoid intrusions in the mineralized area are characterized by composite granite bodies that crystallized at ca.240–190 Ma. While there were multiple stages of intrusion, most occurred at 210–220 Ma, with waning magmatic activity at 200–190 Ma. The Re-Os age of molybdenite in the region is ca. 200–190 Ma, which may represent a newly discovered period of W-Mo metallogenesis that occurred during the final stages of magmatism. The heat associated with this magmatism drove ore formation and might have provided additional ore-forming components for metallogenesis(represented by the Wangjiaping biotite monzogranite). Ore materials in the mineralized area were derived from mixed crustal and mantle sources. Enrichment of the region occurred during intracontinental orogenesis in the late Indosinian–Yanshanian, subsequent to the main Indosinian collision. At this time, the tectonic environment was dominated by extension and strike-slip motion. 相似文献
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南秦岭中段中、上志留统金矿化特征及控制因素分析 总被引:2,自引:0,他引:2
区域地球化学测量和金矿勘查工作显示,中、上志留统是南秦岭中段继泥盆系之后的又一套赋金地层,这套地层的分布区存在一条近EW向展布的金矿化带,宏观上,金矿化带的展布受青泥河-留坝复背斜和大河店-长坪-留坝区域性断裂带的控制.金矿(化)点和金矿(化)体的产出受层位、岩性、煌斑岩脉、火山活动、褶皱、层间构造破碎蚀变带、标高及氧化作用等因素的联合控制.矿体呈似层状产出,由多个呈串珠状展布的透镜体组成,金矿石类型以微细浸染型为主,属金-毒砂-黄铁矿建造.通过对已有矿(化)点和区域水系沉积物异常区进一步工作,有望找到中-大型金矿产地1~2处. 相似文献