Geological Structure Conditions Research Articles

The hydrogeology of high-mountain carbonate areas: an example of some Alpine systems in southern Piedmont (Italy)

The hydrogeological characteristics of some springs supplied by high-mountain carbonate rock aquifers, located in the south of Piedmont, in Italy, are presented in this work. The aquifers have different geological-structural conditions, including both deep and superficial karstification. Their catchment areas are located in a typical Alpine context at a high altitude of about 2000 m. These aquifers are ideal representations of the different hydrogeological situations that can be encountered in the high-altitude carbonate aquifers of the Mediterranean basin. It is first shown how the high-altitude zones present typical situations, in particular related to the climate, which control the infiltration processes to a great extent. Snowfall accumulates on the ground from November to April, often reaching remarkable thicknesses. The snow usually begins to melt in spring and continues to feed the aquifer for several months. This type of recharge is characterized by continuous daily variations caused by the typical thermal excursions. The hourly values are somewhat modest, but snowmelt lasts for a long time, beginning in the lower sectors and ending, after various months, in the higher areas. Abundant rainfall also occurs in the same period, and this contributes further to the aquifer supply. In the summer period, there is very little rainfall, but frequent storms. In autumn, abundant rainfall occurs and there are therefore short but relevant recharge events. It has been shown how the trend of the yearly flow of the high mountain springs is influenced to a great extent by the snowmelt processes and autumn rainfall. It has also been shown, by means of the annual hydrographs of the flow and the electric conductivity of the spring water, how the different examined aquifers are characterized by very different measured value trends, according to the characteristics of the aquifer.

Numerical Simulation on Forming Dynamics Mechanism and Stress State of Qianning Basin

Two-dimensional finite element model of Qianning basin was built on the basis of depth study on geological structure conditions and of rock mechanical properties in Qianning basin, tectonic stress field characteristics of Qianning fault belt and Qianning basin formation mechanism were inversed. The results show that: (1)A remarkable low stress region is come into being in the central part of Qianning basin, the low stress environment in the strike-slip fault zone has a very important control function for the basin formation. (2)in the rock bridge area of secondary fault belt sinistral right order, high stress concentration zone are formed, rock body subject to extrusion, which often forms pushing structure, the surface morphology appears landforms phenomenon such as surface uplift, drum kits etc.

Numerical Simulation of Tectonic Stress Field in Longmenshan Tectonic Belts after Earthquake

Two-dimensional finite element model of Longmenshan area was built on the basis of depth study on geological structure conditions and of rock mechanical properties in Longmenshan area, tectonic stress field and variation process of Longmenshan fault belt were inversed after the earthquake. The results show that: (1)After the earthquake, the maximum principal stress appears in fault endpoint, partial inflection point, intersection of Longmenshan fault and Xianshuihe fault and intersection of Minjiang fault, Animaqing-lueyang fault and Longmenshan Fault. The maximum principal stress in area is overall NEE to SEE.(2)After earthquake, shear stress distribution is more uniform, and compared after earthquake to before earthquake, shearing stress of Longmenshan central fault and Qianshan fault reduces obviously, but shear stress of Houshan fault increases.

Reseach on Controlling of Rock Mass Structure on Water Inrush From Coal Seam Floor in Huaibei Mining Area

Abstract Huaibei Mining Area is located in the south of the North China Coal-bearing Region. Its hydrogeological condition has basic features of the North China Coalfield. The hydrogeological condition is complex. The mining in the coal seam of Shanxi Formation where water inrush from coal seam floor happened mang times is generally seriously threatened by the limestone water from floor. The paper systematically analyzes typical cases about water inrush from coal seam floor in the researched area, and uncovered the different features of water inrush caused by different geological structure condition and water-inrush passage, which is of typical meaning to study controlling of rock mass structure on water inrush from coal seam floor.

THE APPLICATION OF REMOTE SENSING TO ENGINEERING GEOLOGICAL SITE SELECTION

The prerequisites for engineering geological site selection,such as regional topographic and geomorphic conditions,geotechnical engineering conditions,geological structural conditions,geological hazard conditions and hydrogeological conditions have been summarized in this paper.Some problems that deserve further attention have also been analyzed in detail.

Geology and geochemistry of D–O–C isotope systematics of the Qolqoleh gold deposit, Northwestern Iran: Implications for ore genesis

The Qolqoleh gold deposit is located in northwestern part of the Sanandaj–Sirjan metamorphic belt, northwestern Iran. Igneous and sedimentary units exposed in the area have undergone greenschist metamorphism. The area was affected by a NE–SW trending shear zone and subsequent deformation. Two different types of mineralization are distinguished in the Qolqoleh gold deposit based on geological–structural conditions indicated by microtextural analysis: ductile and then brittle. Ore-forming processes are divided into three stages: Early (I), Middle (II) and Late (III), which include quartz–pyrite (I), sulfides and gold (II) and carbonate veinlets (III), respectively. The stage I fluids are characterized by δ 18O = 15.5‰ at 440 ºC, and are thought to be deep-sourced metamorphic waters; the stage III fluids, with δ 18O = 1.6‰, are shallow-sourced meteoric waters; whereas, the stage II fluids, with δ 18O = 13.1‰, are a mixture of deep-sourced metamorphic and shallow-sourced meteoric fluids. Based on comparisons of the D–O–C isotopic systematics, the ore-forming fluids with characteristic high δ 18O and δ 13C and low δD originated from metamorphic devolatilization of Cretaceous volcano-sedimentary (felsic to mafic metavolcanic rocks–shale–carbonate–carbonaceous chert) sequences, locally rich in organic matter. During late Cretaceous continental collision of the Afro-Arabian continent and the Iranian microcontinent, a crustal slab consisting of felsic to mafic metavolcanic rocks, carbonate, shale and carbonaceous chert was underthrust northwards beneath the central Iranian microcontinent along the Zagros fault. During further contraction, deformation was localized in reverse oblique-slip structures with vergence toward south; shear zones generally follow contacts between more competent and less competent rock units. Metamorphic devolatilization of this underthrust slab is the source of the ore-forming fluids that generated the Au ore belt, which includes the Qolqoleh gold deposit.

Crustal Structure and Its Features in Northwest Margin of Bohai Bay and Its Adjacent Areas

AbstractIn this paper wide‐angle reflection and refraction data is used along Tanggu‐Yutian profile and other five profiles intersecting with this profile, and the seismic sounding data was processed and interpreted comprehensively along Tanggu‐Yutian profile. The purpose is to find out the basic features of 2‐D velocity structure, spacial distribution of faults, geological structure condition of shallow and deep crust in the northwest margin of Bohai bay and its adjacent area. The result shows that obvious layered structure appears along the profile, the crustal thickness increases gradually from south to north, and the crustal velocity structures in different regions have obvious inhomogeneity in the lateral and vertical directions. The Moho is a slope between Tanggu and Ninghe near Bohai bay. The crustal depth deepens gradually towards north from 28 km in Tanggu to 31 km in Ninghe.

Chemical and isotopic ( δ18O‰, δ2H‰, δ13C‰, 222Rn) multi-tracing for groundwater conceptual model of carbonate aquifer (Gran Sasso INFN underground laboratory – central Italy)

Summary A hydrochemical and isotope study was conducted on the drainage waters of an underground laboratory, located inside the Gran Sasso massif (central Italy). The study was expected to improve the conceptual model of groundwater circulation at the base of an over 1000-thick unsaturated zone in the Gran Sasso partitioned karst aquifer. This lithostratigraphically and tectonically complex aquifer is typical of Africa–Europe thrust-and-fold collision belt in the Mediterranean area. In this case, investigations on water–rock interactions during recharge in complex aquifers, overlaid by a thick unsaturated zone, have been made thanks to the strategic location of the Gran Sasso underground laboratories, located in the core of a huge carbonate aquifer. Knowledge of the local basic hydrogeological setting was the starting point for a detailed hydrogeochemical and isotopic study, which was carried out at the aquifer scale and at the fine scale in the underground laboratories. The water–rock interaction processes were investigated both spatially and in temporal sequences, analysing recharge waters and groundwater in the underground laboratories by multitracing techniques, including major ions and δ18O‰, δ2H‰ and δ13C‰ stable isotopes. Use of 222Rn provides information on transit time in the aquifer. Processes proved to be typical of carbonate rocks, with clear influence of vertical movement of water on chemical–physical parameters through the unsaturated zone. Conversely, in the saturated zone, these processes proved to be dominantly affected by local geological–structural conditions. A conceptual model with dual flow velocity is proposed, directly related to the local geological-structural setting. 222Rn decay enables to calculate an effective velocity of around 10 m/day for the fracture network, through the sequence of less permeable dolomites and underlying limestone. Lag time between recharge and chemical changes in the saturated zone testifies to an effective velocity of about 35 m/day for fast flow through recent and active extensional faults.

2‐D Crustal Structures Along Wuqing‐Beijing‐Chicheng Deep Seismic Sounding Profile

AbstractIn this paper wide angle reflection and refraction data is used to obtain the 2‐D velocity structure, spatial distribution of faults, and geological structure condition along Wuqing‐Beijing‐Chicheng profile. The results reveal strong vertical and lateral heterogeneities in the crust. The crust has layered features and its thickness gradually increases from 31.0 km in Wuqing to 40.0 km in Yanqing. The strong variation of topography of the crustal interfaces appears around the Beijing area, and the Moho deepens rapidly in the northwest of Beijing area. Five shallow faults in the crust are inferred along this profile, based on the crustal velocity structures and the variations of the crustal interfaces

Predicting the technological properties of uranium ores in natural deposits on the basis of a regression model

The technological properties of ores are characterized by spatial variability, the level of which depends on the geological-struc tural and mineralogical-ge ochemical conditions of localization of the deposit. For most deposits of nonferrous, rare, trace, and radioactive elements, the variability of these properties is relatively high. The discovery and description of variability in the technological properties of ores (without which optimization of the processes of mtning, refining, and hydrometallurgic al treatment is impossible) requires a closely meshed screen of technological tests, which, because of the complexities and difficulties of obtaining and studying bulk samples, has not been attained by the stages of detailed and commercial prospecting as a rule. Therefore, in practice, the activities of mining concerns raise the problem of quantitatively predicting and mapping the technological properties of ores in natural deposits, without significantly increasing the volume of bulk, technological testing, on the basis of a complex of indirect geological-struc tural and mineralogical-geochemical factors. A description of these factors may be obtained in the course of performing the geological documentation and testing of the mine workings or well center. It should be possible to obtain extensive quantitative (or semiquantitative ) estimates of the technological properties of ores in natural deposits by constructing and investigating mathematical models relating the technological properties of the ores with their chemical and mineralogical composition, the geological-struc tural conditions of localization of the deposit, and the form of the changes in the area surrounding the ore, and then predicting, on this basis, the properties of the ore in the natural deposit according to the data of the primary geological documentation, testing, and mineralogical-te chnological mapping. Examples of various approaches to the solution of this problem are described in [1-9].

Experimental investigation for determining the stability of the Nizhne-Kama hydroelectric station building

1. The investigations showed that the strength characteristics of soil specimens differ substantially from the strength characteristics of the foundation as a whole. This is due both to the different mechanism of soil deformation in the shear tests, and model and block shear, and the presence in the foundation of weakened zones and fissuring, affecting the shear resistance at the base of plates and hydroelectric station buildings. Under conditions of geological structure of the Nizhne-Kama hydroelectric station building foundation, evaluation of stability in shear must be based on the results of field tests in accordance with shearing on model stamps and blocks of soil. 2. On the basis of analysis of the results of stamp and block shear tests, taking into account the engineering geologic situation, it can be recommended that the design strength characteristics of the soil in the foundation of the Nizhne-Kama hydroelectric station building be taken as tan \gp=0.5, C=0 (safety factor), instead of tan \gp=0.42 and C=0 as assumed in the design. 3. The data from investigations for clarifying the nature of soil deformation in the foundation of the hydroelectric station building point to the possibility of destruction of stability of the installation, based on the geological structure of the foundation soil or due to plane shear along the weakened contact between soil strata or the foundation reaching the limit state, accompanied by fissuring. Under conditions where two types of failure are possible, an important result of the investigations is that experimental points for both forms of limit state of the foundation are approximated by a single linear equation {ie227-1. Hence, the stability calculation for the lower Kama hydroelectric station building should be carried out in accordance with the plane shear diagram, taking into account the possibility of the shear surface occurring within the limits of weaker clay-soil differences. 4. Beyond the scope of this article, regarding the results of investigations of long-term strength of the soils in the foundation of the Nizhne-Kama building, it is observed that, since under these conditions, destruction of the strength of the soil is accompanied by fissuring processes independent of the time of application of the load, the degree of stability to shear of the Nizhne-Kama building may be determined in accordance with the above systems of calculation, using the theoretical (mean minimum) tan \gp and C values provided in the article.

Genesis of alkalic rocks in Ural

As a rule, infiltrational metasomatism in axial parts of geosynclines terminates in the formation of a eutectic granitic magmatic solution. However, in case such solutions fail to develop while the accessions of the alkalic solutions continue, a miaskitic magmatic solution may arise, the parent of miaskites. Thus the crystallization of miaskites is contingent upon a progressive local metamorphism, in geologically rare and special environments in which the substratum acquires gradually a eutectoid, i.e. the miaskitic. The widely different series of intrusive alkalic rocks, from nephelinolites and alkalic gabbroids to plagioclase and corundum syenites, are the result of their reactions with their hosts, the mechanisms and the types of which depend upon the geological-structural conditions and other variables. – V. P. Sokoloff.