Deep tectonic subdivision of Kazakhstan,from geophysical data

Interpretative analysis of geological-geophysical data, with a comprehensive characterization of the principal tectonic blocks of Kazakhstan (fig. 3) and the map of abyssal fractures, from the “M” surface up, each with its own orientation, dip, and the accompanying specific complex of intrusive rocks (fig. 4), lead to the map of tectonic regions of the country (fig. 5) – an intricate configuration of discrete and/or presumptive structures of different origin, age, position, stage and other characteristics controlled essentially by some particular zone of abyssal fractures. – IGR Staff.     

Recognition of the regional lineaments of Iran: Using geospatial data and their implications for exploration of metallic ore deposits

The relationship between major structural lineaments and locations of ore deposits in Iran has been investigated using geospatial data. In the course of lineament extraction, satellite images, aeromagnetic data, digital elevation model (DEM) and structural maps were processed and the lineaments and large-scale faults were identified. The extracted lineaments, based on subjective assessment, from each dataset were imported into GIS software and the “lineament map of Iran” was prepared by data integration. The analysis for selecting significant lineament was mainly based on fault correlated lineament and lineament with field map fractures, which was sets as benchmarks for compiling a final output map. Four major regional lineament trends of N–S, E–W, NW–SE and NE–SW were identified in the data of all images, which are corresponded to the structural zones and the major fault systems of Iran. The mineral deposits (active and abandoned) and mineral indications database compiled are based on the published maps, papers, reports and the ore deposits data files of Geological Survey of Iran. Integrating the output of these two datasets by GIS software resulted in the “Combined Map of Lineaments and Gold, Copper, Lead, Zinc and Iron Deposits of Iran”. The number and distance of ore deposits toward the lineaments were processed by the counting and cumulative methods in the GIS software's. Approximately, over 90% of the ore deposits of Iran are located in the central part of the lineaments (15 km on each side) which are concordant with a definition of large lineament. About 50% of these mineral deposits are closer than 5 km to the lineaments. There are significant correlations between lineament density and intersections with ore deposits occurrences. The observed associations at this scale are informative in establishing exploration strategy and decreasing exploration risks for detailed work on ore deposit scale.     

Interpretation of airborne geophysical data of Nsukka area,southeastern Nigeria

Airborne geophysical (aeromagnetic and gravity) data of Nsukka area was interpreted qualitatively and quantitatively with the aim of determining the susceptibilities of rock types, depth/mass of the anomalous bodies, possible cause of the anomalies and type of mineralization prevalent in the area. The estimated depths from forward and inverse modeling of aeromagnetic data for profiles 1, 2, 3, 4 and 5 were 1200m, 1644m, 1972m, 2193m and 2285m respectively. The respective susceptibility values were 0.0031, 0.0073, 1.4493, 0.0069 and 0.0016. These indicate dominance of iron rich minerals like limonite, hematite, pyrrhotite, and pyrite and forms lateritic caps on sandstones. SPI depth result ranges from 151.6m minimum (shallow magnetic bodies) to 3082.7 m maximum (deep lying magnetic bodies). Euler depths for the four different structural index (SI = 0.5, 1, 2, 3) ranges from 7.99 to 128.93m which are depths of shallow magnetic sources resulting from lateritic bodies in the outcrops in the study area. From the gravity data interpretation, Euler depth estimation reveals that depth to anomalous bodies ranges from 89.13 to 2296.92m. Density of the causative body obtained from modeling results for profile 1 was 1498kg/m³, which is in the range of clay material and the depth was about 923m. From models 2, 4 and 5, the densities of the causative bodies were 3523, 4127 and 3707kg/m³, while depths to the surface were about 604, 815 and 1893m respectively. These density ranges correspond to that of ironstone. From model three, the density of causative body obtained was 2508kg/m³, located at a depth of about 268m below the surface. This work has shown that Nsukka area is underlain by thick strata of shales, sandstones and ironstones, which together are suitable for ceramic production, and sufficiently thick sediments suitable for hydrocarbon accumulation.     

航空地球物理勘探在南极调查中的应用

航空地球物理勘探是认识极地区域构造的重要技术手段.在回顾和分析南极航空地球物理勘探发展历史与现状的基础上,总结归纳了航空地球物理勘探在南极地区取得的主要成果.归纳出南极地壳结构研究、南极古大陆重建与恢复、南极火山与岩浆作用调查和南极冰架与地质相互作用研究等4方面典型实例,航空地球物理勘探为南极地区域地质构造研究提供了有...     

月海盆地线性构造展布及其成因分析

综合多源遥感数据识别提取月球正面南北纬50°之间的线性构造,重点分析月岭和月溪的影像特征、分布规律和时空关系,结合月海沉降模型分析两者的成因机制,结合地形和重力场数据预测影响月岭类型的因素。研究表明,在质量瘤盆地,月岭和月溪存在明显的时空关系和构造成因联系,两者主要由月海沉降产生的局部应力引起,前月海时期盆地的均衡状态和月海充填的几何形状可能影响了月岭的分布类型。     

月海盆地线性构造展布及其成因分析

综合多源遥感数据识别提取月球正面南北纬50°之间的线性构造,重点分析月岭和月溪的影像特征、分布规律和时空关系,结合月海沉降模型分析两者的成因机制,结合地形和重力场数据预测影响月岭类型的因素。研究表明,在质量瘤盆地,月岭和月溪存在明显的时空关系和构造成因联系,两者主要由月海沉降产生的局部应力引起,前月海时期盆地的均衡状态和月海充填的几何形状可能影响了月岭的分布类型。     

Correlation of lineaments and groundwater quality in Dasht-e-Arjan Fars,SW of Iran

The NE-oriented Dasht-e-Arjan graben is located 65 km west of Shiraz and has resulted from the active Kare-e-Bas fault segmentations. This extensional graben bounded by two fault system east-Arjan and west-Arjan to the Shahneshin and Salamati anticline. In these study using Landsat 7 ETM images with resolution 2.5 m and directional filtering in the four azimuths and semi-automatic technique for linear structure in the study area. Using the obtained data from extracted lineaments, the rose diagrams of the main strike lineaments are well confirm with field measurements of faults with N56° ± 4°E direction. The structural lineaments of the study area show that the Dasht-e-Arjan area is underlain by the limestone, sandstone, and marl. LANDSAT imagery of the area has been analyzed and interpreted in order to determine the lineament and groundwater quality across the area. The fracture is structurally controlled and mostly influences both the groundwater and surface water pollution and flow directions in the Dasht-e-Arjan. Using visual interpretation, determining the lineaments on the satellite image is very difficult and subjective, and it requires an experienced interpreter. In this study, the lineament analysis is undertaken to examine the orientation of the lineament, the relationship between lineaments and tectonic features and groundwater quality. Lineament density maps show that the lineament density is high around areas. Areas having high lineament density represent areas with relatively high groundwater pollution. Field observations agreed with the results from the analysis of the imagery.     

东昆仑成矿带东段井中物探找矿中的几个实例

在“东昆仑成矿带东段资源评价井中立体物探方法技术示范”项目中,在典型地区选择多种井中物探方法进行试验,取得了较好的应用效果,为在高寒山区物探找矿起到较好的示范作用.     

航空地球物理勘查科技创新与应用

简要回顾了中国航空物探技术的发展历程，重点阐述了21世纪以来、尤其是"十一五"以来国内航空物探的主要技术创新与应用成果，并对今后发展趋势进行了分析与预测。为满足国家与社会需求，"十一五"以来，中国的航空物探技术，尤其是航磁多参量、矢量测量、航空重力测量和时间域航空电磁测量技术得到快速发展；在航空物探技术创新过程中，航空物探资料的综合研究和应用得到了加强，在基础地质、固体矿产勘查与评价、能源勘查与评价等方面取得了重要成果，在地下水资源调查、工程地质勘查、环境地质调查等方面显示出了良好的应用前景。为满足国家资源勘查和环境评价对航空探测技术的需求，未来中国航空物探测量系统的分辨率、稳定性和实用性将进一步提高，航空物探在加强基础地质、固体矿产勘查、能源勘查等传统领域应用的基础上，将拓展及加强在深地探测、深海探测、深部地热调查、水资源调查、地质灾害调查、军事及测绘等领域的应用。      

Sedimentary basins of the east antarctic craton from geophysical evidence

Ninety-five percent of Antarctica is buried under an ice sheet up to 4.7 km thick. Within interior East Antarctica (~10.2 · 10⁶ km²) recent airborne geophysical observations, principally radio echo sounding, have enabled widespread investigation of ice covered bedrock. Limited seismic refraction profiling, magnetic and gravity investigations combined with the radar studies have provided a generalized picture of sedimentary basins in Antarctica between 180° and 60° E.Two major basinal structures have been detected within East Antarctica—the Wilkes Basin and Aurora Basin complex. The former lies sub-parallel to the Transantarctic Mountains, while the Aurora Basin forms a branching system of basins in central East Antarctica trending northwest towards the Wilkes Land coast.Analyses of macro-scale terrain roughness and bedrock reflection coefficients from radio echo sounding indicate significant differences between basins and their surrounding regions. Small-scale surface irregularities and slowly changing, high reflectivities from radar measurements are interpreted as suggesting the presence of a smoothing cover of sediments. Residual magnetic anomalies (from airborne operations), when combined with topographic data, exhibit low gradients over basins, but steep, fluctuating characteristics over adjacent basement highs. Source-depth calculations from oversnow magnetic determinations across the Wilkes Basin indicate an average thickness for the sedimentary layer of <3 km. This is corroborated by reinterpretation of gravity anomalies, which average ~—30 mGal, over the basin. Sediments appear absent or extremely thin on the flanks of the Wilkes Basin where seismic refraction shooting has detected the near-surface presence of granitic crust. Furthermore an increase in roughness of terrain combined with sudden breaks in slope argue that these basin margins may be fault-controlled and deeply eroded.The distribution and configuration of the depressions is therefore thought to be governed by intra-cratonic fracture patterns possibly related to ancient orogenic sutures. Juxtaposition of basins and flanking basement highs of probable Precambrian and Early Palaeozoic age are reminiscent of basin and swell structures of the African and Australian cratons, with which East Antarctica has had a common geologic history throughout most of the Phanerozoic. Any sediments must pre-date growth of the ice sheet and are hence older than Miocene.     

A lithological assessment of the resistivity data acquired during the airborne geophysical survey of Anglesey,North Wales

A recent airborne geophysical survey has provided high resolution estimates of the electrical resistivity of the near-surface and deeper (bedrock) formations found across Anglesey and a portion of the coastal area of North Wales. This single small survey provides new geophysical information on both the complex configuration of the Neoproterozoic and Cambrian bedrock units and the shallow near-surface geology and glacial features.     

Genetic classification of tectonic platform structures and paleotectonic reconstructions,from geophysical data on basement block structure

Geophysical expressions of the relatively mobile Cambrian-Sinian blocky layer of the platform, underlain by the relatively stable Precambrian base and overlain by sediments containing structures created by transfers of tensions from the blocky layer, are particularly well suitedfor structural regionalizations in Latvian Lithuanian territories and possibly elsewhere in the platform. Further testing and applications of the method are recommended. — V. P. Sokoloff.     

A radiometric airborne geophysical survey of the Isle of Wight

A high resolution airborne geophysical survey across the Isle of Wight and Lymington area conducted in 2008 provided the first modern radiometric survey across the geological formations that characterise much of southern England. The basic radiometric data are presented and it is evident that bedrock geology exerts a controlling influence on the broad response characteristics of the naturally occurring radioelements. A GIS-based geological classification of the data provides a quantitative assessment and reveals that a relatively high percentage of the variability of the data is explained by the Cretaceous bedrock geology but this is much reduced in the Palaeogene. The three traditional Chalk units (Lower, Middle and Upper Chalk depicted on the currently available Geological Map) provide the lowest and most distinct behaviour within the Cretaceous sequence. Mineral content within the Chalk appears to increase with increasing age. A new method of representing the baseline radiometric information from the survey in terms of the mean values of the geological classification is presented. The variation of radioelement geochemistry within individual formations is examined in two case studies from the Cretaceous Lower Greensand Group and the Palaeogene Hamstead Member (Bouldnor Formation). The Cretaceous sequences provide the higher levels of discrimination of localised variations in radioelement distributions. A more detailed case study examines the potential influences from the degree of water saturation in the soil and superficial deposits.     

The role of geophysical and seismological data in evaluating the subsurface structures and tectonic trends of Nile Delta, Egypt

In the present study, the Bouguer, aeromagnetic, and seismological data analysis for Nile Delta including the Greater Cairo region and its surroundings was used to examine and trace the tectonic framework for some deep-seated faults (mostly normal faults with a small strike–slip component) and their orientation, on which most earthquakes have occurred. The new tilt derivative (TDR) geophysical map and Euler deconvolution presented here can be used to trace the structural relationships and their depth investigations across the entire region. Generally, most of the Euler deconvolution results especially from the gravity map were well coincided with the location of contacts derived by TDR particularly NNW to NS, EW, and NE trended structures. The depths to the gravity or magnetic sources, and the locations of the contacts of density contrast were estimated. Results of the Euler deconvolution method suggested that, in the southeastern part of the area, the basement could be observed to be shallow and has become deeper beneath the northern part. Furthermore, the resulting structural map of this study is well correlated with previous geological and seismological data analyses. At least two sets of predominant faults are suspected, faults with a NNW strike (Clysmic trend) which are particularly felt in the southern portion of the Delta, and some of them give it the shape of a “graben like structure.” Another parallel set of faults, having NE–SW strike (Pelusium trend), was also obvious in the southern part between Cairo and Suez cities (at Abu Zabal area). The evaluated trending faults (NNW–SSE or NE–SW) are intersecting with predominant major WNW–ESE to E–W (Tethys trend) striking faults. These intersections may generate more additional seismic pulses and consequently increase the seismic activity for these structures. However, minor NW (Najd Fault System) is obvious in the TDR magnetic map, whereas less attendance NS (East African trend) structural trends are evident in the TDR gravity map. Moreover, it could be said that the southeastern portion of the Nile Delta (especially the eastern portion of Greater Cairo) is affected by highly tectonic fault systems. Finally, a new tectonic map was also evaluated from the resulting structural map, which helps to quantify different structural patterns (faults and/or contacts), and their relations with the regional tectonic trends are discussed.     

高精度航空物探在幕阜山地区地质构造研究中的应用

根据湘赣鄂交界区最新开展的高精度航空物探资料,从宏观地球物理的角度对幕阜山及邻区的地质构造及岩浆岩进行了研究.首先详细介绍了区内航空物探(包括航磁、航空伽玛能谱)的基本特征,重点分析了幕阜山特殊的航磁及伽玛能谱综合特征,并结合重力等相关资料,推断了主要的断裂构造和隐伏岩体,分析了区内的岩浆热液活动特征,进一步总结了花岗岩侵入体与主要断裂构造之间的关系,其成果能够为该地区进一步的地质研究工作提供一些参考.