جستجوی مقالات مرتبط با کلیدواژه "anomaly" در نشریات گروه "زمین شناسی"

In order to reduce errors and save money and energy, this research has dealt anomaly separation. The importance of detecting anomaly values from the background is not hidden from anyone. For this purpose, several methods have been invented, among which we can mention Mahalanobis distance separation method, which is an effective and multi-variable method for separating anomalous values from the background. In the present study, the performance of the combination of the above separation method with three data mining methods; K-Nearest Neighbor, Simple Bayes Classifier and Convolutional Neural Network is investigated. In this way, after separating the anomalous values of copper and molybdenum in the case of 177 samples obtained from the surface sampling operation in the area of Zafarghand with the Mahalanobis distance method, in order to predict these values for each random sample, The above three data mining methods were used. The results show that K-Nearest Neighbor method is much stronger, because in the network designed by this method, no sample has been wrongly identified, which shows the high accuracy of the designed network. It should be noted that the number of wrongly predicted samples for convolutional neural network and Bayes methods are reported as 2 and 3, respectively. Considering the far more acceptable error rate for the network designed by the combination of K-Nearest Neighbor method and Mahalanobis intervals, the said combination has been introduced to the decision makers of this industry as a reliable and useful method to reach the most accurate predictions.

The study area is located in the south of Qushadagh mountain range, in the north of Asbkhan village, Heris township. In terms of structural geology of Iran, this area is located in the main zone of Central Iran and Alborz-Azerbaijan sub-zone. The geological units of the region are including Eocene igneous and pyroclastic rocks with combination of andesitic, trachyandesitic, basaltic, tuffic and ignembritic. The semi-deep intrusive mass with Oligocene age, with the combination of quartz diorite, diorite and quartz monzonite in the form of stock and dyke is exposed in the area. Under the influence of hydrothermal processes originating from this intrusive mass and infiltration of fluids through the sedimentary-volcanic units of the Middle Eocene, extensive alterations (sericitic, medium argillic, propylitic and siliceous) have been taken place in the region. Preliminary results of geochemical studies of stream in the region led to the identification of several areas with grade 1, 2 and 3 anomalies of heavy minerals. The most important heavy minerals identified, include hematite, goethite, magnetite, pyrite-oxide, pyrite and zircon, These minerals and have closely relation to the alteration zones and veins mineralization. The conformity of the geochemical halos map with the geostructure and alteration map of the region shows a very high correlation between these regions and possibly the important role of faults and joints in the occurrence of alteration zones and abnormal regions. Anomaly maps and geostatistical analyzes performed on the findings in stream sediments and heavy minerals show that the enrichment of Ag, Au, Mo, Cu, As, Pb, Sb and Zn elements is higher than the background and the Au, Ag, Cu, As and Pb elements can be used as trace elements for epithermal gold reserves.

Magnetic anomalies before an earthquake occurrence have long been discussed as precursors to seismic activity. In this study, by repeatedly over-plotting magnetic data related to each day (24 hours) in the same frame, for different components (Z, Y, X) or (Z, D, H) of three geomagnetic stations in Japan (MMB, KAK, KNY) over a period of one year, the characteristic curve of the geomagnetic stations are extracted. The purpose of this method is to try to reduce the effect of diurnal variations in the magnetic field from geomagnetic records and its use led to a more significant differentiation of the anomalies observed before the earthquake compared to the original data. Although previous studies have shown that geomagnetic data can be used as a precursor of earthquakes, the presence of magnetic storms in the study period led to the conclusion that commenting on the relationship between the observed anomalies and the earthquake requires more data and investigations.

The magnetic data collected from airborne surveys need to be interpreted after processing. The most important information gathered from the interpretation stage, is the depth and horizontal position of anomalies. Various methods are developed for gathering these data. One of these methods is Euler deconvolution that is based on Euler’s homogenous equation. Euler's method is one of the fastest semi-automatic methods for determining the depth of buried magnetic and gravity anomalies. Its results are highly dependent on the structural index, Euler window size, and depth calculation error. This method identifies the depth and trend of changes in the depth of anomalies very well. The geological information of the study area is important for the application of this method. In this method, the potential field and its first-order derivatives are used in different directions to determine the position and depth of the potential field source. In this paper, by using this method, the depth, and boundaries of anomalies in the Lake Blatchford area of Canada are investigated. The obtained results indicate that most anomalies in this region have shallow to medium depth.

Haftsandoq prospect index is located in 25 km northwest of Takestan city, within Tarom-Sofla Tertiary metallogenic belt. Intrusion of granodiorite to monzonite igneous bodies into the Eocene volcanic/ pyroclastic complexes caused widespread hydrothermal alteration associated with the copper, lead and silver ore mineralization. During supergene alteration the secondary minerals such as oxide/hydroxides (hematite, goethite), sulfides (coverlet), sulfates (anglesite) and carbonates (malachite and azurite) were developed within oxidized zone. The purpose of this study is identifying the possible anomalies of Cu, Ag, Pb, As, Cd, Au in this prospect area. Accordingly, 99 lithic samples taken from a systematic litho-geochemical network were analyzed with ICP-MS method. These results were used to specifying of high mineralization potential districts based on non-structural (correlation, cluster analysis, factor analysis) and structural (fractal charts cutie - area) analyses methods. Consequently, the results of structural (multi-fractal) analyses in comparison of non-structural methods lead to identify three elemental anomalies of copper, silver and lead. The copper with 4 stages enrichment shows grade 2 and/or 3 anomalies in entire area except for NW. Ag with 3 stages enrichment shows grade 2 anomaly in NW part of district and Pb with 3 stages enrichment shows grade 3 anomaly in SW part of Haftsandoq district.

Sangan iron deposit is a magnetite iron skarn. Magnetometry is the most common method for the exploration of such kinds of deposits based on the magnetic properties of these minerals. This method specifies the depth, dip, shape, and strike of the sources causing the anomaly. Many explorations of this ilk have been done of which giant Gol e Gohar in Iran is an example. Based on geology and following magnetometry, a massive iron deposit was predicted during Sangan iron exploration, where 558 boreholes in 50×50 m net were designed and drilled in the west ore body, revealing very useful subsurface information. Intrusive bodies are mainly granitic and oxidant types which, because of the presence of fine grain and disseminated magnetite, have higher magnetic susceptibility (K) in comparison to other granites. These bodies are considered as source rocks for the creation of gigantic Sangan mines. Multiphase ground magnetic survey points (19376) with different specifications were equalized and interpreted in this study. The causative sources of most magnetic anomalies in the rotation to the pole (RTP) map were magnetite mineralization, confirmed by the drilling data. In this research, filters of first vertical gradient and upward continuation were used to guide drilling owing to the presence of the remnant magnetism in the magnetite skarn and the unavailability of such measurements that are necessary for specifying the accurate depth of the magnetic anomaly sources. The information pertaining to vertical gradient and upward continued maps correlated well with the depth obtained from drilling and 3D block modelling. The amount of ore reserve and its depth increased from the western anomaly (A') to the central anomaly (C) and had a dip direction to the east. Such change in the depth of mineralization correlated with upward continued responses which represent the central magnetic anomaly (C) as the deepest anomaly in Sangan iron ore deposit. Magnetic responses of the Upward continuation to 1000 m of this magnetic anomaly can be related to either the high depth of the mineralization (620 m drilled so far) or the deeper intrusive body which needed deeper drilling (more than 1000 m) for confirmation.

The East Atlantic-West Russia (EA–WR) teleconnection pattern is one of the low-frequency atmospheric phenomena that affects Europe and Asia, especially in the cold season. In this study, the effects of EA–WR on the climate of Southwest Asia are investigated using the NCEP/NCAR reanalysis dataset from 1950 to 2012 for winter months (Dec. to Feb.) and the monthly indices taken from the Climate Prediction Center (CPC). Because of the large zonal extension of the EA–WR teleconnection pattern, all data north of 20°N are taken into account for the analysis. In this paper, the method of composite maps is employed. Considering the critical positive and negative months, the average state of the troposphere is studied for each of the two phases from the synoptic viewpoint. To this end, a month is considered to be a critical positive (negative) month, if the monthly index of EA–WR is higher (lower) than the long-term mean value of EA–WR index plus (minus) its standard deviation. In this way, among 189 winter months during the 63-year period from 1950 to 2012, 26 positive critical months and 29 negative critical months are identified. For the part of analysis based on outgoing longwave radiation for which the data is available from 1974 onwards, there exist 20 positive critical months and 18 negative critical months. The composite map analyses include 500 hPa geopotential height and its anomaly, mean sea level pressure, 300 hPa wind field, 1000-500 hPa thickness, the outgoing longwave radiation and the Eady's parameter for the growth rate of baroclinic eddies: whereis the Coriolis parameter or inertial frequency, is the buoyancy frequency, and is the magnitude of the vertical wind shear. The growth rate is evaluated and compared between the two phases at 800 hPa. In the critical positive months of EA–WR, in 500 hPa geopotential height field, there is a trough from the western part of Russia to the Middle East and a ridge over the eastern part of the North Atlantic. In critical negative months of EA–WR, however, there is a ridge over the western part of Russia, a trough over Europe and a dominantly zonal flow is observed over the Middle East. In the critical positive months, the subtropical jet stream over the southwest of Asia is stronger, and at the same time, the exit region of the polar front is extended to the border between Europe and Asia, which together with the wind field anomaly result in significant cold air advection to the northwest of Iran. Furthermore, the stronger subtropical jet over the Southwest of Asia, the southwest of Iran, and Saudi Arabia in the critical positive months is associated with increased amounts of Eady's parameter for the growth rate and thus baroclinic instability. Overall, results point to a significant effect of EA–WR on the climate of the southwest Asia. Compared with the negative phase, the presence of a mid-tropospheric trough of geopotential height as well as the upper-tropospheric wind anomaly in the form of a stronger subtropical jet stream provide a better ground for the development and organization of synoptic systems and their impact on the climate of Iran in the positive phase. The dynamical effects mentioned are also helped by a more suitable lower-tropospheric moisture transport in the positive phase.

In this study, using single-station dispersion curves, two-dimensional tomographic maps of group velocity have been estimated for Kopeh Dagh region in the northeast of Iran. An investigation of the structure of the lithosphere and the asthenosphere of the Kopeh Dagh region is of great interest because of the complex tectonics of this area. The Kopeh Dagh forms an NW–SE range of mountains separating the Turkmen (Turan) shield from central Iran. The belt is up to 3000 m in elevation, rising 2000 m above the Turkmen plains. It is highest and narrowest in its center and the east, becoming broader and lower towards the west, where it merges with the lowlands of the SE Caspian shore. The range is asymmetric, with a steep, linear and narrow NE side on which short, straight streams run directly from the high ground to the Turkmen plain. Its SW flank contains gentler slopes, is less regular, and contains a broader, more developed drainage network. The NE flank of the Kopeh Dagh is assumed to be underlain by ‘Hercynian’ basement of the Turan shield, while the range itself contains thick Jurassic–Cretaceous marine sediments overlain by Eocene marls with some andesitic volcanoclastic horizons. These, in turn, are overlain by thick marine Pliocene units in the west (which continue into the South Caspian Basin) merging eastward into a continental sequence of equivalent age, reflecting the diachronous emergence of the range. Although there is some evidence for local structural detachments in Jurassic evaporites, most of the late Cenozoic and active folds in the Kopeh Dagh are thought to have developed in the hanging-walls of basement-cored thrusts. There is no evidence for major salt thicknesses that can produce large-scale regional decollement levels, as in the Zagros. Earthquakes in the Kopeh Dagh involve mostly right-lateral strike-slip faulting trending N to NNW or reverse faulting parallel to the NW regional strike. The abrupt linear topographic front forming the NE margin of the Kopeh Dagh follows a fault zone referred to as the Main Kopeh Dagh or Ashkabad Fault. The analysis of the lateral variations in group velocities in low, intermediate and long period is an optimal tool for the identification of the main different tectonic features present in the complex Kopeh Dagh region. These parameters are sampling crust and upper mantle structures as period increases from 3 s to 35 s. Generally, shorter periods bring information about velocity properties at shallow depths, whereas longer periods sample deeper into the Earth’s upper mantle. To explore two-dimensional tomographic maps, in the time period of 2006 to 2013, local earthquakes with high signal-to-noise ratio recorded in six broad-band stations operated by International Institute of Earthquake Engineering and Seismology (IIEES) are selected. In the first step, initial corrections were performed and surface wave fundamental modes for 1075 earthquakes are isolated. Frequency- time analysis software (FTAN) is used to isolate fundamental mode from higher modes. By using this approach, single-station dispersion curves are calculated. The estimated group velocity dispersion curves are used to explore two-dimensional tomographic maps. Yanovskaya–Ditmar linear inversion method was used to achieve this goal. According to the obtained two-dimensional tomography maps, in low periods of 3 s and 5 s (shallow depth), we find a high-velocity anomaly in the south of Kopeh Dagh region that has sharply separated Alborz–Binalud zone from the Kopeh Dagh zone; so we can consider a separation boundary between Alborz–Binalud zone and Kopeh Dagh zone. In the period of 20 s, we have a high-velocity anomaly from north to south. At the west of this high-velocity anomaly, also there is a low velocity that makes a sharp boundary. In the period of 35 s, the tomographic model obtained reveals high- and low-velocity anomalies in the near distances of the uppermost mantle which have been separated from each other with a sharp boundary.

The Qalikuh area,~35 km southwest of Aliqudarz, contains oil shale deposits in Garue and Sargelu formations(Jurassic-Cretaceous). Some 20 samples across two sections(Charun3-Deh ye Qali3) were ed and analyzed(Rock Eval – ICP – XRD – XRF) to study organic and mineral parameters(to determine type of organic material and kerogen, total organic carbon, thermal evolution, concentration, and classification of elements and minerals) and to model the relations between these parameters. The Qalikuh oil shale has a great potential for oil production with high levels of TOC (13.5 wt%), type 2 kerogen, low thermal maturity. However Qalikuh oil shale has metallic and nonmetallic element anomalies and high concentrations of strategic elements compared to Clark values. Dendritic diagrams suggest variable origins for elements and minerals in the samples. Some are associated with development of organic materials, TOC parameters, Resin and Asphaltene, and some are associated with clastic materials, aluminosilicates and source rock weathering.

Astarghan area is located in ~ 50 km of north of Tabriz, southeast of Kharvana, East-Azarbaidjn. The area is a part of Gharadagh- Arasbaran metallogenic belt. The most important units in the area is a hypabyssal prophyritic to granular granodioritic intrusive body of Oligo-Miocene and flysch- type sedimentry sequence of limestone, limy sandstone and marl (Paleocene-Eocene). Intrusion of the stock into the sedimentary rocks caused them to convert into a series of metasomatites and contact metamorphic rocks. Geostatistic studies on stream sediments and heavy mineral were done and include data processing, (i.e. normalization, univariate and multivariate analysis), and ultimately preparation of anomaly maps. The correlation coefficients among elements were determined. Elements that show positive correlations with gold are Cu, Hg, Pb, As, Sb, Ag, Bi and Mo. The results of preliminary regional geochemical explorations have led to discovery of two anomalous zones for gold; grade 1 and grade 2. The anomalies were verified by studies on heavy minerals in stream sediments and mineralized and altered samples taken gold anomalous zones. The most important indentified heavy minerals include magnetite, malachite, gold, micaseous hematite, pyrite, galena, cerussite, pyrite- limonite, goethite, limonite, barite, hematite, pyrite- oxide which are affiliated with alteration and mineralzation zones. The major alterations in the area are argillic, sericitic and propylitic developed along the vein’s walls. Field and analytic studies done on samples taken the gold anomalous zones led to identification of epithermal gold veins having over 4.5 ppm gold grade. The concordance of anomaly map with tectonic map and altered zones indicate that the faulted and fractured zones have played a crucial role in creation of gold anomalous zones. The incorporation of these data in the area led to introduction of several anomalous zones belonging to Au, Ag, Cu, As and Pb that can be used as passfinders for epithermal gold.

The Saghand Iron Ore is a type of magnesian skarn deposit formed by the intrusion of granitic igneous bodies of Jurassic into carbonate rocks. Four lithological units of micaschist, gneiss, skarn and limestone are present in the area. On the basis of the RTP magnetic map, three magnetic anomalies A, B and C are present in the area. The first vertical gradient map shows that anomaly A has shallow and near surface sources as part of it correlates with iron outcrop. Anomaly B which correlates with the alluvium shows also shallow sources in the western portion on the first vertical gradient map but the eastern portion of anomaly B has no responses. Anomaly C which also correlates with the alluvium, has no responses on the vertical gradient map. Considering the upward continued map, it is inferred that only anomaly A and the western portion of anomaly B have deep responses and their sources are possibly iron mineralization at depth. Due to the high magnetic susceptibility of magnetite in iron ores relative to the other rock units, the best causative source of the western portion of anomaly B which correlates with the alluvium can be magnetite in the covered iron bodies. Two anomalies are present in gravity data. Considering the first vertical and continued maps, the first priority of drilling is recognized over anomaly A which correlates with an iron ore outcrop. The second priority of drilling is identified over the western portion of anomaly B which correlates with the alluvium. This drilling results are consistent with the responses of the first vertical gradient and continued maps and confirm them.

The Panj area is located in the Esfahan province, 30 Km east of Ardestan with an area about 93 km2. The rock units in this area are recognized of sedimentary, igneous, pyroclastic, sub volcanic and volcanic Rocks with Eocene-pliocene age. The sampling was designed according to 253 sediments stream (- mesh) and 139 heavy mineral samples.The samples were analyzed for 44 elements with ICP,ES,AA. The accurancy of analysis has computed and then data processed.The processing is included normalize of raw data, drawing normalizing, determining of geochemical uni-multi variables map and finally PCA maps. For anomaly cheking and assesment of various element phase, is used by chip sampling in the following of this study 29 mineralized samples have taken from alteration district. Heavy mineral anomalies map was drawn based on different ore mineral groups on the basis of integrated and complicated data introduced 2 anomalies in this area, the first anomaly is located in west southern and the others in east southern.