The paper focuses on the formation of Nanzhangzhuang ground fissure through emphatically analysing factors including the intersection fault dislocation,the deep ground-water over-exploitation together with the landfor...The paper focuses on the formation of Nanzhangzhuang ground fissure through emphatically analysing factors including the intersection fault dislocation,the deep ground-water over-exploitation together with the landform and lithology features.Features of the ground fissure are explained in detail after describing the geological setting in the study area.The paper also provides dynamic mode of the ground fissure formation via force analysis of the soil body unit at ground fissures.Conclusions can be drawn that the stress state of soil bodies changed with the activities of two intersection faults,namely Hengshui fault and Hubei fault.In addition,the stress fields control the development of ground fissure.The deep groundwater in Hengshui area dropped considerably in recent years,to be precise,the water elevation of deep groundwater dropped from -26 m to -94 m by 2010 at the centre of groundwater funnel.The over-exploitation of deep groundwater in Hengshui area enlarged the ground fissures.The data concerning shallow borehole show that the vertical lithology mainly consists of silt,silty clay and silty sandy soil,which all belong to the middle-compressed soil.The lateral extension of the soil bodies occur with pumping and tectonic creep,and the clay layers on both sides of the cracks can stay upright.Thus the ground fissure came visible.展开更多
The gold orefield studied is located on the south border of the underthrust-collision zone of the Qinling microplate and the North China microplate in the Indosinian epoch. The main ore deposits localized in the area ...The gold orefield studied is located on the south border of the underthrust-collision zone of the Qinling microplate and the North China microplate in the Indosinian epoch. The main ore deposits localized in the area where the WNW-trending compression-shear type fault of the Indosinian epoch intersected the NE-trending tenso-shear type fault of the Yanshanian epoch. The orebody appeared in a chambered or wedged form. The mineral composition is relatively complex. On the southeastern border of the orefield there have developed intermediate-acid anatectic magmatites of the Mesozoic Era. Three-phase inclusions (Lco2, Vco2 and LNaCl-H2O) comprise over 50%, associated with vapor phase consisting of H2O, CO2, CO, CH4, N2 and H2. The ore-forming fluids can be divided into 2 stages (the early and the late). The samples are projected in the area of mixture of initial magmatic and meteoric water on the δD-δ18O diagram, suggesting two types of mineralization, i.e. the re-equilibrated magmatic-hydrothermal type and the circulating geothermal water type of a meteoric water source. The mineralization occurring in this orefield might be a superimposition of 2 tectono-magmatic activities (the Indosinian and Yanshanian movements). Therefore, it is considered a superimposed B-S type gold orefield.展开更多
基金Hebei Province Natural Science Foundation of China(D2017403020)the Joint foundation of Key Laboratory of Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences(KF201602)
文摘The paper focuses on the formation of Nanzhangzhuang ground fissure through emphatically analysing factors including the intersection fault dislocation,the deep ground-water over-exploitation together with the landform and lithology features.Features of the ground fissure are explained in detail after describing the geological setting in the study area.The paper also provides dynamic mode of the ground fissure formation via force analysis of the soil body unit at ground fissures.Conclusions can be drawn that the stress state of soil bodies changed with the activities of two intersection faults,namely Hengshui fault and Hubei fault.In addition,the stress fields control the development of ground fissure.The deep groundwater in Hengshui area dropped considerably in recent years,to be precise,the water elevation of deep groundwater dropped from -26 m to -94 m by 2010 at the centre of groundwater funnel.The over-exploitation of deep groundwater in Hengshui area enlarged the ground fissures.The data concerning shallow borehole show that the vertical lithology mainly consists of silt,silty clay and silty sandy soil,which all belong to the middle-compressed soil.The lateral extension of the soil bodies occur with pumping and tectonic creep,and the clay layers on both sides of the cracks can stay upright.Thus the ground fissure came visible.
文摘The gold orefield studied is located on the south border of the underthrust-collision zone of the Qinling microplate and the North China microplate in the Indosinian epoch. The main ore deposits localized in the area where the WNW-trending compression-shear type fault of the Indosinian epoch intersected the NE-trending tenso-shear type fault of the Yanshanian epoch. The orebody appeared in a chambered or wedged form. The mineral composition is relatively complex. On the southeastern border of the orefield there have developed intermediate-acid anatectic magmatites of the Mesozoic Era. Three-phase inclusions (Lco2, Vco2 and LNaCl-H2O) comprise over 50%, associated with vapor phase consisting of H2O, CO2, CO, CH4, N2 and H2. The ore-forming fluids can be divided into 2 stages (the early and the late). The samples are projected in the area of mixture of initial magmatic and meteoric water on the δD-δ18O diagram, suggesting two types of mineralization, i.e. the re-equilibrated magmatic-hydrothermal type and the circulating geothermal water type of a meteoric water source. The mineralization occurring in this orefield might be a superimposition of 2 tectono-magmatic activities (the Indosinian and Yanshanian movements). Therefore, it is considered a superimposed B-S type gold orefield.
