共查询到20条相似文献，搜索用时 31 毫秒
1.
Evidence for Triassic salt domes in the Tunisian Atlas from gravity and geological data 总被引：3，自引：1，他引：3
Chokri Jallouli Mongi Chikhaoui Ahmed Braham Mohamed Moncef Turki Kevin Mickus Ramdhane Benassi 《Tectonophysics》2005,396(3-4):209-225
Detailed gravity data were analyzed to constrain two controversial geological models of evaporitic structures within the Triassic diapiric zone (Triassic massifs of Jebel Debadib and Ben Gasseur) of the northern Tunisian Atlas. Based on surface observations, two geological models have been used to explain the origin of the Triassic evaporitic bodies: (1) salt dome/diapiric structure or (2) a “salt glacier”. The gravity analysis included the construction of a complete Bouguer gravity anomaly map, horizontal gravity gradient (HGG) map and two and a half-dimensional (2.5D) forward models. The complete Bouguer gravity anomaly map shows a prominent negative anomaly over the Triassic evaporite outcrops. The HGG map showed the location of the lateral density changes along northeast structural trends caused by Triassic/Cretaceous lithological differences. The modeling of the complete Bouguer gravity anomaly data favored the diapiric structure as the origin of the evaporitic bodies. The final gravity model constructed over Jebel Debadib indicates that the Triassic evaporitic bodies are thick and deeply rooted involving a dome/diapiric structure and that the Triassic material has pulled upward the younger sediment cover by halokinesis. Taking in account kinematic models and the regional tectonic events affecting the northern margin of Africa, the above diapirs formed during the reactive to active to passive stages of continental margin evolution with development of sinks. Otherwise, this study shows that modeling of detailed gravity data adds useful constraints on the evolution of salt structures that may have an important impact on petroleum exploration models. 相似文献
2.
The map expression of "abrupt" changes in lateral stratigraphic level of a thrust fault has been traditionally interpreted to be a result of the presence of(1) a lateral(or oblique) thrust-ramp,or(2) a frontal ramp with displacement gradient、and/or(3) a combination of these geometries.These geometries have been used to interpret the structures near transverse /ones in fold-thrust belts(FTB).This contribution outlines an alternative explanation that can result in the same map pattern by lateral variations in stratigraphy along the strike of a low angle thrust fault.We describe the natural example of the Leamington transverse zone.which marks the southern margin of the Pennsy lvanian—Permian Oquirrh basin with genetically related lateral stratigraphic variations in the North American Sevier(TB.Thus.the observed map pattern at this zone is closely related to lateral stratigraphic variations along the strike of a horizontal fault.Even though the present-day erosional level shows the map pattern that could be interpreted as a lateral ramp.the observed structures along the Leamington zone most likely share the effects of the presence of a lateral(or oblique) ramp,lateral stratigraphic variations along the fault trace.and the displacement gradient. 相似文献
3.
Priyom Roy A. Sai Krishnaveni K. Vinod Kumar 《Journal of the Geological Society of India》2017,90(1):51-61
New generation high resolution gravity models derived from space-borne gravity data, integrated with land based surveys, have enabled understanding of regional gravity field over regions, which are till date considered to be inaccessible for land surveys, especially in mountainous terrains. In this study, we evaluate two high resolution gravity models EIGEN-6C4 and GO_CONS_GCF_2_TIM_R5 in order to understand its usability in identification of meso-scale regional geological features and lithological boundaries around the Karakoram shear zone, in Leh, India. The EIGEN-6C4 is a “hybrid” model integrating data from space-borne sensors and terrestrial data, whereas GO_CONS_GCF_2_TIM_R5 is a model derived from the latest space-borne GOCE sensor. Bouguer gravity anomaly has been derived for both the models and compared. It is seen that, the GOCE derived model pertains to the regional gravity field of the region and compares well with the regional derivative of the EIGEN-6C4 model. Further, the EIGEN-6C4 has been analyzed using horizontal derivatives (dx, dy), analytical signal (ANS) and tilt derivative (TDR) techniques. These, derived maps are then overlain on published geological map of the area to understand the correlation between sub-surface geology vis a vis gravitational signal. The major and distinct geological signatures as derived from the various derivative maps correlate well with the existing geological map. The source boundaries derived from the TDR map agrees reasonably well with the lithological boundaries. Further, the anomaly and derivative maps from EIGEN-6C4 indicates towards a possible continuation of the Shyok suture zone in the region. Therefore, for the given spatial extent of the area under consideration, the GOCE derived model represents the regional field, whereas the EIGEN-6C4 data and derivatives are of sufficient resolution for understanding the geological variability in and around the Karakoram shear zone. 相似文献
4.
This study deals with the evaluation of the structural setup of the Ras Banas area on the northwestern part of the Red Sea by using magnetic data. Different analyzing techniques were applied to achieve this goal including regional-residual separation, trend analysis, depth estimation, Euler deconvolution, horizontal gradient, analytic signal, and magnetic modeling. The results of these techniques were used to construct a deep-seated structural feature map.Lineament analysis indicates that the area was mainly affected by the NW, WNW, and NE tectonic trends. The magnetic modeling was performed along four profiles supported by Euler deconvolution, horizontal gradient, and analytic signal profiles. The modeled profiles show that the basement rocks composed of uplifted and down-faulted blocks at different depths as well as step-like structure. The basement rocks seem to be acidic in nature intruded by basic/ultrabasic dikes. Generally, the magnetic susceptibility ranges from 0.0003 to 0.04 cgs indicating acidic to basic/ultrabasic rock composition. The basement relief map shows an irregular basement surface, which varies greatly in depth from 1 to 5.6 km below sea level. The deep-seated structure map shows that the basement was highly affected by two main fault trends in the NW and NNE directions. The NW trending structures were intersected by younger left lateral NNE transform faults. These cross-faults dissect the area into a number of alternated and elongated blocks. 相似文献
5.
为验证低飞航磁技术在推断断裂带和预测成矿远景区中的应用效果,以江西朱溪矿区以往的地质构造、物化探工作为背景,对朱溪测区的低飞航磁数据进行向上延拓和梯度处理,即总梯度模、斜导数和垂向一阶导数计算。将计算后的多幅异常等值线图与测区的区域地质构造及江西矿区成矿特点相结合,在该地区共推断出地质断裂8条,构造走向为NE向、近EW向及NW向。其中,NE向断裂为该区域主要的深大断裂,形成于下扬子板块和上华夏板块之间由于推覆构造所产生的压挤作用,主要位于塔前—赋春断裂带和双田—石劈山断裂带附近;近EW向和NW向断裂为次生断裂,近EW向断裂可能由九江—德兴断裂带产生。同时,通过分析朱溪矿区矽卡岩矿床所具有的特殊磁梯度异常现象,共推断成矿远景区4个,主要位于断裂带附近。 相似文献
6.
Ibrahim Mohamed Gaafar 《Arabian Journal of Geosciences》2012,5(6):1185-1197
The application of various geophysical tools with different responses succeeded in fixing U-mineralization in Wadi Eishimbai area. The area was studied using detailed ground spectrometric, magnetic, and filtered very low-frequency electromagnetic (VLF-EM) surveys. The interpretation of the obtained spectrometric maps clearly reflects the sharp increase of equivalent uranium (eU) content. Meanwhile, K and Th contents show sharp decreases. The eU/equivalent thorium (eTh) ratio correlates positively with eU concentrations and negatively with eTh concentrations, indicating an increase in U potentiality than the surrounding granite. The N?CS shear zone displays an eU content ranging from 20 to 140?ppm. The ENE-trending lamprophyre is characterized by elongated uranium anomalies trending in the E?CW direction, with values >90?ppm. Equivalent uranium content of the brecciated granite attains values up to 700?ppm. The ground magnetic and VLF-EM surveys played important roles in providing structural information which are proven useful in geological mapping and mineral exploration for the discovery of uranium mineralization in the study area. This study follows the expected subsurface extension of the Sela shear zone under Wadi sediments. The ground total magnetic intensity map shows a relatively narrow and an elongated shape for the lamprophyre anomaly extending for about 600?m in the Wadi toward the western direction. VLF-EM contour maps of the two used frequencies (17.1 and 28.5?kHz) show excellent agreement, indicating that the shear zone is distinguished with slightly strong conductivity westwards as an extension of the main shear zone. It is elongated in an ENE?CWSW trend and extends in the western direction, referring to the existence of conductive materials. Most of the NW/SE-trending faults cause sudden changes in the magnetic and VLF-EM contour spacing over an appreciable distance, which suggests a discontinuity in depth due to their left-lateral strike-slip displacements. The interpreted faults, with an ENE?CWSW trend representing the main trend of Sela shear zone through which hydrothermal solutions flowed, cause high alteration and uranium mineralization. 相似文献
7.
《Russian Geology and Geophysics》2015,56(12):1791-1800
In 2012, the renewable energy organization of Iran (SUNA) performed a gravity survey around hot springs of the Mahallat geothermal field in the Markazi Province of Central Iran, as part of the explorations and developments of geothermal energy investigation program in the region. The Mahallat region has the greatest geothermal field in Iran. This work presents interpretation results of various gravity maps and a calculated 3D inversion model. The residual gravity map shows three negative gravity anomaly zones (A1, A2, and A3) associated with the geothermal reservoirs in the region. The horizontal gradient maps reveal a complex fault system. In order to attain more information about the Khorhe geothermal reservoir, a 3D density contrast model was calculated using the Li-Oldenburg method. The attained 3D model provides an in-depth image of the evolution, showing the density contrast and the A1 zone having a high potential for the geothermal reservoir in the region. The results also show that the rocks which exist between 1000 and 3000 meters under the Earth’s surface in the A1 zone are the most suitable aquifers for utilization of geothermal energy. 相似文献
8.
Radia El Gout Driss Khattach Mohammed-Rachid Houari Touria Chennouf 《Arabian Journal of Geosciences》2011,4(1-2):299-308
From a geologist's perspective, magnetic data are most useful in mapping contacts and providing insight into the 3D geometry of the geology. Since the early 1970s, automatic methods based on the horizontal and vertical derivatives are applied to potential field data in order to map geological lineaments. In this paper, three methods for locating magnetic contacts are applied to magnetic anomaly data of the study area. The local maxima of horizontal gradient determined on the magnetic map and its upward continued maps to several heights delineate the contacts and indicate their dips. The amplitude of the 3D analytic signal of magnetic data provides information on the location of the edge of the sources in both the horizontal and vertical dimensions. The Euler deconvolution is also used to estimate the source depth at the contact location. These results allow the production of a structural map showing the magnetic lineaments for the survey area. This map is consistent with many faults already recognised or supposed by the traditional structural studies and highlights new ones by specifying their layout and dips. 相似文献
9.
The most recent seismic profiles in southern Italy show the existence of a sudden thinning of the crust at the boundary between the chain and the Tyrrhenian margin. The abrupt change in thickness can be followed along a zone which has the same geometry in plan as the Calabrian arc. By considering these data and the gravimetric anomalies, it is possible to associate this crustal anomaly with a deep-seated shear zone which determines a crustal shortening of about 40–60 km which can only be a consequence of post-Tortonian tectonics. The surface equivalents of the deep-seated shear zone can be recognized, from north to south, in the alignment of the intra-Apenninic basins (Vallo di Diano, San Arcangelo, Potenza), in the Crati-Mesima graben and in the Mount Kumeta-Alcantara fault zone.The distribution of the seismicity and its connection with the surface structures shows that the largest earthquakes occur along the deep shear-zone. In particular, shocks with the highest magnitude and the longest recurrence intervals are located in those areas where the deep shear zone is at an angle of about 90° with the direction of maximum shortening (Crati-Mesima graben). The fault zones nearly parallel to the regional compression axis (e.g., Mount Kumeta-Alcantara fault zone) are characterized by earthquakes of lower magnitude. Taking into account the neotectonic evolution of the regional structures, as well as the orientation of the stress field and its connection with the deep-seated shear zone, it is possible to distinguish the following seismotectonic zones: Upper Crati-Mesima graben, transverse throughs, Mount Pollino-Mount Raparo fault zone, external Ionian area, San Arcangelo basin-zone of the external flysch, Sicani Mountains, Mount Kumeta-Alcantara fault zone, Caltanissetta basin, and Iblean plateau-Bradanic trough-Murge ridge. The definition of the geometry of the shear zone at depth is one of the most important, but still unresolved problems. 相似文献
10.
The driving force for the basin subsiding against isostatic balance in and around Lake Biwa in the Kinki district, Japan is discussed. The lake region is characterized by strong negative Bouguer anomalies, especially by a steep horizontal gradient zone of gravity anomaly running along the western margin of the lake. The large negative anomaly (>50 mgal) cannot be explained by low-density sediments beneath it. A down-warping structure extending to the Moho depth should be taken into account. This conjecture has been strongly supported by a short-period receiver function imaging, which shows a clear offset of about 8 km for the Moho discontinuity under the steep gravity gradient zone.A question arises as to what is the driving force to create such a large down-warping structure. We consider that the subduction of the shallow-dipping slab under the region (Philippine Sea Slab) may cause crustal deformation by dragging the viscous mantle downward. In order to verify this model, we simulated the induced mantle flow due to the subduction of the Philippine Sea Slab and the pressure distribution on the crust–mantle boundary. This numerical experiment showed that the induced flow makes a strong negative pressure zone under the lake region if the slab has a vertical offset along the direction of subduction. This offset of the slab is consistent with plate models deduced from hypocentral distributions and Sp phases of the deep-focus earthquakes. 相似文献
11.
湘东南茶陵地区邓阜仙、锡田等岩体及其围岩、盖层等地质体内存在着复杂的断层构造,岩体及白垩系内部元素组合地球化学异常也显示出复杂样式。主要通过野外调查验证、断层分级、异常对比等方法,探讨了这些地质体内异常与复杂断层的关系模型,获得钨锡元素分布规律。结果显示：(1)老山坳一级断层附近的岩体中发育北东向延伸的二级断层,它们形成于统一构造体制下;二级断层之间也发育有三级剪裂隙,两者组成了里德尔剪切系。(2)岩体内部,北东向二级断层和三级断层交叉部位常发育显著钨锡异常。(3)白垩系内部,钨锡异常总体受到北东向二级断层和第四系控制作用。(4)围岩异常区受到接触带控制。化探异常与断层的关系模型,常能揭示出花岗岩地区的成矿穹隆,可用作一种深部找矿的依据。 相似文献
12.
庐枞火山岩盆地北部马鞭山铁矿床磁异常特征及找矿预测 总被引：2，自引：0，他引：2
马鞭山铁矿处于庐枞火山岩盆地北部边缘,其赋矿层位为东马鞍山(T2d)含铁质、钙质泥质粉砂岩。航磁为梯度带上叠加局部异常、局部异常形态规则,其走向与梯度带大致平行;地磁与航磁对应较好,异常未分解;地磁异常剖面曲线连续完整且正负伴生、具低缓特征。小波变换较好地分离出了矿致异常。盆地西侧和北侧二条航磁梯度带上局部低缓磁异常系寻找该类铁矿的重要指示信息。 相似文献
13.
位于炎陵－蓝山重力梯度带中的耒阳－临武SN向构造带与茶陵－永兴坳陷带复合部位的王仙岭地区，断裂构造发育，岩浆活动强烈，其中NE向断裂为主要控岩控矿构造。王仙岭花岗岩体W，Sn,Mo,Bi,Be,Nb等成矿元素半度值高，已发现锡多金属等矿床（点）39处。区内W,Sn,Pb,Zn,Au,Ag,As化探异常规律大，强度高，具水平分带现象。根据区域成矿地质条件，成矿规律，物化探,异常，结合以往找矿成果及最新的民采资料，圈定了野鸡窝，大壁口、龙潭和水源山4个锡多金属矿远景预测区，并提出了找矿工作部署建议。 相似文献
14.
高精度重力资料在胜利油区油气藏探测中的应用 总被引：2，自引：0，他引：2
摘要：应用改进的重力归一化总梯度法（ＧＨ法）对胜利油田ＤＢ区的高精度重力测量资料进行了处理。计算了ＧＨ值在地下的三维分布。某一深度ＧＨ平面等值线图中的闭合极小值（ＧＨ低）反映了低密度体的存在及其水平位置,而不同深度等值线图中ＧＨ低的数目的变化可以近似表示低密度体集中的深度范围。ＧＨ平面等值线图还可以为选择ＧＨ铅垂断面图的方向提供依据。ＧＨ铅垂断面等值线图中的闭合极小值更清楚地显示出低密度体的形态及其近似深度。计算出的ＧＨ值的三维分布与钻井资料的比较表明,ＧＨ的闭合极小值与已知油气藏在位置上有较明显的相关关系。 相似文献
15.
研究表明,康滇地轴及其东部地区属均衡补偿平衡区,西部属强烈上升的异常区。上升的原动力为板块碰撞的构造力与均衡调整力的综合。 相似文献
16.
17.
18.
Abdessamad Najine Mohammed Jaffal Kamal El Khammari Tahar Aïfa Driss Khattach Mahjoub Himi Albert Casas Said Badrane Hicham Aqil 《Comptes Rendus Geoscience》2006,338(10):676-682
This study is based on the analysis and the interpretation of the gravity data of the Tadla basin. Its purpose is to increase the knowledge of this basin structure. A residual anomaly map was first calculated from the Bouguer anomaly data witch are strongly affected by a regional gradient. The computed map provides information on the ground density variation but it does not bring enough of new elements. Data filtering allows us to emphasize the structures affecting the basin. We chose the horizontal gradient coupled to the upward continuation techniques that permit to highlight news structures and to give information on their dip. The elaborated structural map of the study area constitutes a useful document for rationalizing the future groundwater exploration in the Tadla basin. To cite this article: A. Najine et al., C. R. Geoscience 338 (2006). 相似文献
19.
中国视密度图与大地构造单元 总被引：6，自引：0，他引：6
提出根据区域重力异常计算地壳表层视密度分布的方法。依据原观测平面异常与延拓到某一高度平面异常的差值场所具有的突出浅源异常、压制深源异常的特点 ,按维纳滤波原理 ,应用多层格林等效层模型精确模拟该差值重力场的径向对数功率谱 ,设计重力场在频率域进行异常分离的具有自适应性的优选延拓算子 ,实现垂向异常分离。利用重力场可看成由许多等效直立棱柱体叠加的原理 ,在频率域内 ,通过换算重力场的一次导数 ,计算出视密度的分布。用上述方法处理中国布格重力异常图 ,获得了中国地壳表层 0 10km剩余重力异常 ,并成功编制视密度图。比较表明 ,视密度的分布特征与大地构造单元及分区有较好的对应关系。地壳表层的岩石密度分布的获得 ,为中国的基础地质与构造研究提供了重要依据。 相似文献
20.
The western part of the North Anatolian Shear Zone at the southern boundary of the Central Pontides in Turkey, was investigated in the Kurşunlu-Araç area by means of a geological-structural field study. In this area the North Anatolian Shear Zone results in a transpressional deformation zone that extends between two master faults striking parallel to the main shear direction. The main systems of structures identified in the deformation zone appear to be oriented parallel to the directions predicted by Riedel theoretical model. Nevertheless, the strain partitioning is more complicated than predicted by theory. The structural analysis suggests a polyphase deformation characterized by a steady component of transcurrence associated with alternance of compression and extension. Along each of theoretical directions the combination of double verging structures can be observed, with folds and thrust surfaces root into high-angle shear zones, according to flower-type geometries. The discrepancies of directions, kinematics and geometries from theoretical models are due to transpressive and/or transtensive nature of the deformation. According to the observed outcropping structures, we propose a conceptual model for the North Anatolian Shear Zone, interpreting it as a crustal-scale positive flower structure. 相似文献