Structural Lineaments Research Articles

Probabilistic constraints on structural lineament best fit plane precision obtained through numerical analysis

Understanding the orientation distribution of structural discontinuities using the limited information afforded by their trace in outcrop has considerable application, with such analysis often providing the basis for geological modelling. However, eigen analysis of 3D structural lineaments mapped at decimetre to regional scales indicates that discontinuity best fit plane estimates from such datasets tend to be unreliable. Here, the relationship between digitised lineament vertex geometry (coplanarity/collinearity) and the reliability of their estimated best fitting plane is investigated using Monte Carlo experiments. Lineaments are modelled as the intersection curve between two orthonormally oriented fractional Brownian surfaces representing the outcrop and discontinuity plane. Commensurate to increasing lineament vertex collinearity (K), systematic decay in estimated pole vector precision is observed from these experiments. Pole vector distributions are circumferentially constrained around the axis of rotation set by the end nodes of the synthetic lineaments, reducing the rotational degrees of freedom of the vertex set from three to one. Vectors on the unit circle formed perpendicular to this arbitrary axis of rotation conform to von Mises (circular normal) distributions tending towards uniform at extreme values of K. This latter observation suggests that whilst intrinsically unreliable, confidence limits can be placed upon orientation estimates from 3D structural lineaments digitised from remotely sensed data. A probabilistic framework is introduced which draws upon the statistical constraints obtained from our experiments to provide robust best fit plane estimates from digitised 3D structural lineaments.

A sub-crustal piercing point for North Atlantic reconstructions and tectonic implications

Plate tectonic reconstructions are usually constrained by the correlation of lineaments of surface geology and crustal structures. This procedure is, however, largely dependent on and complicated by assumptions on crustal structure and thinning and the identification of the continent-ocean transition. We identify two geophysically and geometrically similar upper mantle structures in the North Atlantic and suggest that these represent remnants of the same Caledonian collision event. The identification of this structural lineament provides a sub-crustal piercing point and hence a novel opportunity to tie plate tectonic reconstructions. Further, this structure coincides with the location of some major tectonic events of the North Atlantic post-orogenic evolution such as the occurrence of the Iceland Melt Anomaly and the separation of the Jan Mayen microcontinent. We suggest that this inherited orogenic structure played a major role in the control of North Atlantic tectonic processes.

Hydrogeological investigation of shallow aquifers in an arid data-scarce coastal region (El Daba’a, northwestern Egypt)

Hydrogeological investigations in arid regions are particularly important to support sustainable development. The study area, El Daba’a in northwestern Egypt, faces scarce water resources as a result of reported climate change that particularly affects the southern Mediterranean coast and increases stress on the local groundwater reserves. This change in climate affects the area in terms of drought, over-pumping and unregulated exploration of groundwater for irrigation purposes. The hydrogeological investigation is based on a multidisciplinary data-layer analysis that includes geomorphology, geology, slope, drainage lines, soil type, structural lineaments, subsurface data, stable isotopes, and chemical analyses. The study area contains Pleistocene and middle Miocene marine limestone aquifers. Based on lithology and microfacies analysis, the middle Miocene aquifer is subdivided into two water-bearing zones. The area is affected by sets of faults and anticline folds, and these structures are associated with fractures and joints that increase permeability and facilitate the recharge of groundwater. Stable isotope data indicate that groundwater of both the Pleistocene and middle Miocene aquifers is recharged by modern precipitation. The high salinity values observed in some groundwater wells that tap both aquifers could be attributed to leaching and dissolution processes of marine salts from the aquifers’ marine limestone matrix. In addition, human activities can also contribute to an increase in groundwater salinity. A future water exploration strategy, based on the results from the multidisciplinary data-layer analysis, is proposed for the area. The derived scientific approach is transferable to other arid coastal areas with comparable conditions.

Surface-subsurface structural architecture and groundwater flowof the Equi Terme hydrothermal area, northern Tuscany Italy

A multidisciplinary integrated approach was used to study the structural architecture influencing the circulation pattern of geother -mal fluids in the Equi Terme area (NW Alpi Apuane, Tuscany). Geological-structural surveys were carried out to define the structural setting of the area and to characterize geometries and kinematics of fault systems. Chemical (major components) and isotopic analyses (δ18O‰, δ2H‰, 3H, δ13C‰[DIC], δ34S‰[SO4]) were performed on thermal water and cold springs. A geophysical survey was also conducted by means of both Magnetotelluric and Electrical Resistivity Tomography methodologies, in order to gain insight into the resistivity distribution at depth and to indirectly image the subsurface structure. This multidisciplinary approach proved to be a powerful tool, since it unravels the complexity of this natural geothermal system and provides useful suggestion for reconstructing the fluid circulation outflowing at the Equi Terme thermal spring. Results pointed out how the E-W oriented fault system (the Equi Terme Fault) play a key role in controlling the thermal groundwater outflow, and the chemical-physical features of this resource. This structural lineament separates high permeability carbonate complexes (footwall), in which both shallow and deep flow paths develop, from a medium-low permeability succession (hangingwall) that contains evaporitic formations from which thermal water acquires a high salinity and a composition of the Na-Cl (Ca-SO4) type. During the uprising along the fault system, the thermal water is also affected by a mixing with shallow fresh-cold waters that lead to a strong seasonal variation in the chemical-physical properties of the thermal springs.

Mapeamento do risco de ravinamento na área de proteção ambiental Fernão Dias, sudeste do Brasil, a partir de lógica de decisão FUZZY

É apresentado um modelo espacial que utiliza regressão logística, classificação fuzzy e SIG, para mapear o risco de ravinamento. Este modelo utiliza os mapas: índice de vegetação; declividade; densidade de lineamentos estruturais e de estradas vicinais. A possibilidade de ocorrência de um evento de ravinamento, em relação a estes mapas, foi estimada através do odd ratio (OR). O modelo calcula o risco de ravinamento em cada pixel, a partir da soma ponderada de mapas temáticos, e utiliza como peso o valor de r2 obtido pela frequência de pontos de ravinamento observados em cada classe dos mapas temáticos.

Interpretation of gravity and magnetic anomalies at Lake Rotomahana: Geological and hydrothermal implications

We investigate the geological and hydrothermal setting at Lake Rotomahana, using recently collected potential-field data, integrated with pre-existing regional gravity and aeromagnetic compilations. The lake is located on the southwest margin of the Okataina Volcanic Center (Haroharo caldera) and had well-known, pre-1886 Tarawera eruption hydrothermal manifestations (the famous Pink and White Terraces). Its present physiography was set by the caldera collapse during the 1886 eruption, together with the appearance of surface activities at the Waimangu Valley. Gravity models suggest that subsidence associated with the Haroharo caldera is wider than the previously mapped extent of the caldera margins. Magnetic anomalies closely correlate with heat-flux data and surface hydrothermal manifestations and indicate that the west and northwestern shore of Lake Rotomahana are characterized by a large, well-developed hydrothermal field. The field extends beyond the lake area with deep connections to the Waimangu area to the south. On the south, the contact between hydrothermally demagnetized and magnetized rocks strikes along a structural lineament with high heat-flux and bubble plumes which suggest hydrothermal activity occurring west of Patiti Island. The absence of a well-defined demagnetization anomaly at this location suggests a very young age for the underlying geothermal system which was likely generated by the 1886 Tarawera eruption. Locally confined intense magnetic anomalies on the north shore of Lake Rotomahana are interpreted as basalt dikes with high magnetization. Some appear to have been emplaced before the 1886 Tarawera eruption. A dike located in proximity of the southwest lake shore may be related to the structural lineament controlling the development of the Patiti geothermal system, and could have been originated from the 1886 Tarawera eruption.

Magnetometric exploration in intrusive basic with evidence of gold in northern region of the Camaquã Sedimentary Basin (RS)

AbstractThis study involved magnetometric exploration in the region of São Sepé (RS), southern Brazil, to evaluate the potential for gold mineralization in a gabbro using evidence previously obtained from the geochemical exploration of stream sediments. The gabbro named Santa Catarina is intruded in the Metamorphic Complex Vacacaí, a metassedimentary sequence where several gold deposits were recognized. In this study, nine lines of land magnetometry were performed with 1.200m in length each, a total of 10.800m and 720 reading stations. The results suggest the presence of filonian mineralization in fractures, some of which are subject to weathering action, releasing and transporting gold by water action and depositing it along the stream sediments downstream from the gabbro. The analytical signal map outlines areas of high magnetic susceptibility within its boundaries, coinciding with structural lineaments in the NS and EW directions, associated with the last of the four stages of regional deformation, possibly responsible for both fracturing and opening of spaces in the gabbro, as by remobilization of sulfide and gold recognizably described in several gold deposits within the Vacacaí Metamorphic Complex.

Prospecting for new gold-bearing alteration zones at El-Hoteib area, South Eastern Desert, Egypt, using remote sensing data analysis

Gold has been mined in the Eastern Desert of Egypt since the time of the Pharaohs, yet the geological settings of such ore deposits and how certain deposits link to each other are still not fully understood. The application of remote sensing in identifying variations in surface mineralogy, structural elements, and lithologic contacts can help in identifying such relations. Signatures collected from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data is used to map the hydrothermal alteration zones of El-Hoteib area, which is located to the northwest of Iqat and Al-Fawi gold mines and prospective for gold. SPOT5 data is used to highlight the preliminary structural lineaments in the area. Band ratioing and principal component analysis techniques are used to refine the different lithologic units in the area. A simplified Crósta technique has been applied to the ASTER data to identify both the location and spatial extent of the different alteration zones around the Iqat-Al-Fawi area. A new gold-bearing alteration zone is detected to the north of Gabal El-Hoteib. It is structurally controlled by E–W to WNW–ESE structures with evidence of reactivation of such trends during the Quaternary. Ore microscopy examination, induced coupled plasma mass spectrometry and fire assay analysis revealed the presence of gold associated with excess zinc in most samples.

Utilization of airborne gamma ray spectrometric data for geological mapping and radioactive mineral exploration of Gabel Umm Tineidba area, south eastern desert, Egypt

The present work utilizes airborne gamma ray spectrometric data in a trial to refine surface geology of igneous, metamorphic and sedimentary rocks, detect any radioactive mineralization at Gabel Umm Tineidba area South Eastern Desert, Egypt. The study area is covered by rock exposures ranging in age from the Precambrian to Quaternary. Airborne gamma ray spectrometry can be very helpful in mapping surface geology. This provides estimates of the apparent surface concentrations of the most common naturally occurring radioactive elements, such as potassium (K), equivalent uranium (eU) and equivalent thorium (eTh). This is based on the assumption that, the absolute and relative concentrations of these radioelements vary measurably and significantly with lithology. The composite image technique is used to display simultaneously three parameters of the three radioelement concentrations and their three binary ratios on one image. The technique offers much in terms of lithological discrimination, based on color differences and showed efficiency in defining areas, where different lithofacies occur within areas mapped as one continuous lithology. The integration between surface geological information and geophysical data led to detailing the surface geology and the contacts between different rock units. Significant locations or favourable areas for uranium exploration are defined, where the measurements exceed (X+2S), taking X as the arithmetic mean of eU, eU/eTh and eU/K measurements and S as the standard deviation corresponding to each variables. The study area shows the presence of fifteen relatively high uraniferous zone. In addition, the trend analysis based on the total count map and the published geological map shows that, most of the well-developed structural lineaments have NS, ENE, NNE and NNW trends.

Rifting and mafic magmatism in the Hebridean basins

Basalt dykes from the regional dyke swarm of the British Palaeogene Igneous Province (BPIP) were emplaced parallel to structural lineaments linking onshore and offshore volcanic edifices. Basalts that underwent minimal interaction with the crust have Mg# 60–75, εNd 58 c . 8, 206 Pb/ 204 Pb c . 17.5, δ 18 O 5.9 ± 0.3‰, and 87 Sr/ 86 Sr <0.7040. Basalts with convex-upwards REE profiles ([La/Sm] N <1; [Sm/Yb] N >1) were generated by limited extents of melting (<10%) in the garnet–spinel transition of the upper mantle. Basalts with LREE-depleted ([La/Sm] N <1) or flat REE profiles require substantial (up to 20%) melting of spinel lherzolite. Modelling of major element compositions and olivine equilibration temperatures indicates that the mantle potential temperature was a maximum of 1530 °C beneath the BPIP at 58–60 Ma. Magmatism occurred at the periphery of a mantle thermal anomaly (proto-Iceland plume; T P ≤ 1560 °C) centred beneath western Greenland. The distribution of BPIP magmas was controlled by extensional tectonism driven by plate boundary forces resulting from plate reorganizations in the northern hemisphere starting at c . 62 Ma. The well-known mildly alkaline lava piles of Skye and Mull represent volcanoes on the flanks of the resulting rift system.

Geophysical and Geochemical Signature of Rare Metal Granites, Central Eastern Desert, Egypt: Implications for Tectonic Environment

Magnetic survey is usually used to delineate magnetic-structural lineaments, analyze their relationships to the inherited ductile fabrics and estimate the depth of perturbing body sources, probably granitic intrusions. These were conducted on the total magnetic intensity reduced to the pole map as well as First vertical derivative and Euler deconvolution maps to show various aeromagnetic structural lineaments which were interpreted as fault systems on the interpretation maps. The early deformational event (D1) produced sets of NE-SW striking local and regional fractures and faults. The second deformational event (D2) generated mainly NNW-SSE and NW-SE faults and fractures some of which intersected earlier (D1) structures. At the northern and eastern parts of the study area (D1/D2) intersections are observed. The last event (D3)created NNE-SSW set of fractures and faults brought out by splay of dykes and reactivated some (D1 and D2)fractures and faults. The study area is also characterized by a major, N-S trending, late-stage dyke system that extend through the area. In order to estimate source depths from gridded aeromagnetic data, 3-D Euler deconvolution method was applied. The calculated source depths are in the range of 200 m to 3500 m. The deepest structures are in the ENE-WSW direction and have depths ranging from about 1100 m to 3000 m in the southeastern part of the study area. On the other hand, the network of parallel major structures trending in NNW-SSE direction have a shallow depth of about 700 m. Rare-metal granites of the Central Eastern Desert of Egypt are classified chemically into alkaline to peralkaline and peraluminous granites. They display the typical geochemical characteristics of A-type granites, with high SiO₂, Na₂O+K₂O, Rb, Zr, Nb, Ta, Sn, and Y, and low CaO, MgO, Ba and Sr. The magmatism of the rare metal granites of the Central Eastern Desert are related to anorogenic, within-plate, A-type, subvolcanic setting and emplaced in the extensional tectonic regime along to the inherited ductile fabrics.

Management of female infertility with traditional Chinese Herbal Medicine: An updated meta-analysis

Remote sensing and aeromagnetic data provided significant information for detecting potential areas of mineralization in Wadi Allaqi in the South Eastern Desert of Egypt. Application of band ratios and Crosta technique of Principal Component Analysis (PCA) using Landsat-8 successfully highlighted the hydrothermal alteration zones and the structural elements represented by lithologic contacts and faults/fracture zones. Structural lineaments were also successfully extracted using remote sensing and aeromagnetic data. Center for Exploration Targeting (CET) Grid analysis and CET Porphyry Analysis techniques were applied for constructing the structural complexity heat map and probable near circular features of porphyry intrusions respectively. Combining data of lineaments, alteration zones and porphyry intrusions after obtaining a consequence of each map allowed predicting and mapping areas of probable high mineral resources. Overlaying the present sites of mineralization on the final map validated the prepared mineral predictive map. Overall results clearly revealed that areas of high structural complexity, fractures/faults density are in agreement with the detected areas of hydrothermal alterations which also matched with the known mineralization mines in the study area.

Volcano-tectonic control of Merapi's lava dome splitting: The November 2013 fracture observed from high resolution TerraSAR-X data

Volcanism at active andesite–dacite volcanoes is often associated with the formation and collapse of circular-shaped protrusions of extruded, highly viscous lava, the so-called domes, which are emplaced in the near summit region. Growing domes may experience stable and instable structural phases, with a gradual transition in between. Dome collapse and the break-off of instable blocks of viscous lava may lead to pyroclastic flows, one of the most lethal hazards at stratovolcanoes. At Merapi volcano, Indonesia, a new dome started growing in the summit region in the amphitheater formed in the course of the climactic 2010 eruption. Three years later, the dome reached a height of approximately 100m and diameters of 220 and 190m with a plateau-like surface area of 40,000m2 approximately. On 18/11/2013, an explosion occurred without identified precursors, leaving a major fracture cutting the complete dome structure. Based on high resolution TerraSAR-X satellite radar imagery, we could identify the linear fracture, traceable over ~200m in the long axis, up to 40m wide. After geocoding of the radar amplitude imagery, the fractures azimuthal trend could be compared to other structural lineaments, indicative of a significant NNW–SSE structural direction that has formed on Merapi volcano in the past. The Merapi dome fractured in a NW–SE direction, and is consistent with the alignment of regional tectonic structures and of anticipated directions of pyroclastic flows. The fracture may be part of a larger volcano-tectonic system and may affect the dynamics and the stability of the Merapi dome.

Geological – structural outlines of the southern Madonie Mts. (Central northern Sicily)

Geological and structural surveys were undertaken in central-northern Sicily along the southern slope of the Madonie Mts., a portion of the Sicilian Fold and Thrust Belt. Collected data have allowed the compilation of a new map of this region at 1:30,000 scale. The map is the result of a classic field survey supported by a combined analysis of 1:33,000 aerial photographs, 1:10,000 ortho-photos, and the use of a high-resolution Digital Elevation Model.The cartographic product displays the distribution of the distinct sedimentary successions and the geometric setting of the major tectonic lineaments, providing further constraints on the geology of the area. The mapped rocks mostly consist of Neogene syn-tectonic sedimentary successions deposited within basins developed in a SE-migrating piggy-back/foredeep system. Thrust-top deposits are floored by a clayey substratum pertaining to a former oceanic domain.The tectonic setting has been reconstructed through the mapping of structural lineaments and compared to available seismic sections. The geometries and orientation of the observed/measured faults and folds and the age of the sediments involved, suggest that since Miocene times the area experienced a multi-phased deformation with previously formed (middle Miocene) large flat thrusts and associated folds, re-deformed by a younger (Upper Miocene to Early Pliocene) and deep-seated thrust and folds system.Strike-slip deformation affected the area after the Early Pliocene with the nucleation of NW-SE-oriented right-lateral faults whose propagation produced vertical axis rotations with a general re-orientation of previously formed structures.

Structural control of fluvial drainage in the western domain of the Cape Fold Belt, South Africa

The purpose of the study was to examine the extent to which drainage morphology has been influenced by faulting, folding and bedrock lithology in the Cape Fold Belt (CFB) of South Africa. This region was formed during Paleozoic–Mesozoic convergence along the south-western margin of Gondwana. An extensive structural geology database, terrain characteristics and stream network data were analysed using Geographical Information Systems (GIS) to examine the possible linkages between structure and fluvial drainage. Results indicated that the contemporary geomorphology of the area reflects the influence of folding and faulting as well as differential erosion. The following drainage anomalies suggestive of strong structural control were identified: orientation of flow direction of major streams corresponding to structural lineaments, abrupt changes in stream direction influenced by anticline fold axes, faults and joints, and fault-aligned streams. Drainage development in the study area responded noticeably to the underlying structure. The study raises questions with regard to the implications of one major or multiple dominant structural controls on drainage morphology and pattern. The findings have relevance with regard to the understanding fluvial drainage development and landform evolution in tectonically deformed regions.

Origin of the Easter Submarine Alignment: morphology and structural lineaments

The Easter submarine alignment corresponds to a sequence of seamounts and oceanic islands which runs from the Ahu-Umu volcanic fields in the west to its intersection with the Nazca Ridge in the east, with a total length of about 2.900 km and a strike of N85°E. Recent bathymetric compilations that include combined satellite derived and shipboard data (Global Topography) and multibeam bathymetric data (from NGDC-NOAA) are interpreted both qualitatively and quantitatively by using a morphological analysis, which was comprised of the determination of bathymetric patterns, trends in lineations and structures; height measurements, computation of basal areas and volumes of seamounts, in order to establish clues on the origin of this seamount chain and to establish relationships with the regional tectonics. In the study region 514 seamounts were counted, of which 334 had a basal area less than the reference seamount (Moai). In general, the largest seamounts (>1000 m in height) tend to align and to have a larger volume, with an elongation of their bases along the seamount chain. On the other hand, smaller seamounts tend to be distributed more randomly with more circular bases. As a consequence of the morphological analysis, the best possible mechanism that explains the origin of the seamount chain is the existence of a localized hotspot to the west of the Salas y Gomez Island. The corresponding plume would contribute additional magmatic material towards the East Pacific Rise through canalizations, whose secondary branches would feed intermediate volcanoes. It is possible that within the Easter Island region there would be another minor contribution through fractures in the crust, due to the crustal weakening that was produced by the Easter Fracture Zone.

Evolution of a dynamic paleo-hydrothermal system at Mangatete, Taupo Volcanic Zone, New Zealand

Recent quarrying and active faulting at Mangatete, Taupo Volcanic Zone (TVZ), New Zealand, illuminate a rare spatial and temporal window on a dynamic Late Quaternary geothermal system. Detailed geological mapping, stratigraphic logging, AMS 14C dating, and textural and mineralogical analyses were used to construct a complex history of hydrothermal, volcanological and tectonic activity from ~36 to 2ka. Extinct, surface hydrothermal manifestations occur over a ~2km2 area, and include in situ siliceous sinters distributed on normal fault terraces, an inferred hydrothermal eruption breccia (HEB) containing acid-etched sinter blocks, another probable HEB that was bathed in silicifying thermal fluids, and sinter clasts that were entrained in a debris flow associated with a volcanic ash event. Preserved sinter textures typical of near-neutral pH, alkali chloride spring discharge channels, aprons, terraces and affiliated marshes comprise plant-rich, palisade, tufted bubble mat, and domal stromatolitic fabrics. In addition, a packed fragmental sinter facies is shown herein to constitute silicified microbial mats that were broken, transported and deposited as point bar deposits in thermal spring-fed streams. Moreover, four unusual siliceous sinter fabrics—vuggy, globular spongy, scalloped, and arcuate wavy layered—are interpreted to have formed from local acid-sulfate-chloride thermal springs, possibly associated with paleo-fumaroles. The reconstructed history of paleo-hydrothermal activity indicates that the oldest sinters (~36ka) at Mangatete developed in alkali chloride hot springs, but then underwent post-depositional alterion/overprinting by acid-sulfate steam condensate and were dismembered, possibly by a hydrothermal eruption. Low pH hot-spring discharges forming the unusual, inferred acid sinter fabrics were localized in the same area. A shift in paleo-hydrology is evidenced by unaltered, alkali chloride sinters dated between ~22 and 3ka. A cluster of sinter dates between 22.7 and 20.7ka denote thermal fluid emissions around the time of the Okareka eruption (~22.1ka). An ~11kyr gap in sinter ages followed, which overlaps with a time of relative quiescence in local fault movement in between the Rotorua and Rotoma eruptions, as determined from previous paleo-seismicity studies on the Whirinaki Fault in the Mangatete area. At ~9.4ka, hot spring activity in thermally fed streams slightly post-dated the Rotoma eruption (~9.5ka). The locations and ages of the youngest (post-9.4ka) alkali chloride sinters and silicified paleosols in relation to Whirinaki Fault movements indicate an overall westward migration of siliceous spring discharge. Dated charcoal (~1.8kyr) in ash at the base of a locally extensive, volcaniclastic debris flow, containing sinter blocks of a range of ages and mineralogical maturity, suggests its affiliation with the Taupo eruption. Mangatete sinters occur along SW–NE striking faults parallel to the regional trend of the TVZ, which dissect the topography into stepped terraces. Inferred basement cross-faults in the study area, i.e. structural lineaments orthogonal to this trend, may have served as fluid pathways at depth, initiating and maintaining hydrothermal activity at Mangatete for more than 30kyr. Within the larger Ngakuru Graben (~150km2), the ages and distributions of sinters and hydrothermal eruption breccias, including those at Mangatete, show that significant hydrothermal activity occurred for more than 60kyr, in an area lacking such activity today. Thus, Mangatete retains a rare stratigraphic record within the TVZ sinter archive of changing geothermal fluids, resulting from shifts in paleo-phreatic water levels. Moreover, although limited, the presented age data imply a relationship among seismic activity, volcanic ash fall events, and the occurrence of permeable pathways for upward migration of thermal fluids. Finally, whereas currently active TVZ geothermal fields appear to be stable over tens of thousands of years or more, the fossil hydrothermal systems in the wider Mangatete area demonstrate the possibility of much greater temporal variability in the lateral expression of local surface manifestations of thermal fluid discharge through time.

Application of remote sensing for gold exploration in the Fawakhir area, Central Eastern Desert of Egypt

Eastern desert of Egypt is well-endowed with noble mineral resources that provide challenges for the future economy and development in Egypt. Such mineral resources are not yet well-mapped and fully understood; however, various geological maps are available. The newly advanced sensors of earth observations such as advanced space thermal emission and reflection radiometer (ASTER) images were functioned to map the lithology, the structural patterns and the alteration zones related to gold mineralization at the Fawakhir area, Central Eastern Desert of Egypt. Integration of band rationing and principal component analysis (PCA) clearly determined the lithological units of the study area. The alteration zones of the study area were efficiently mapped from the ASTER radiance data using reference spectra based on two supervised classification techniques including the spectral angle mapper (SAM) and spectral information divergence (SID). Field visits and laboratory microscopic examination of thin and polished sections were used for validating the process. The final resulted map of the alteration mineral zones consists of sericite, clay minerals, quartz, carbonate, and pyrite. Auto-detection of the structural lineaments, which are zones of deformation and fracturing that implies secondary porosity, was mapped from the satellite image. These structures represent significant pathways for migration of hydrothermal solutions, which influence the creation of the alteration zones and become potential zones for mineral resources. The spatial analysis showed the high correlation between the density of lineaments and the occurrence of the alteration zones, which represent high probability of the presence of gold deposits that validated against the old gold mines.

FEATURES CONTROLLING RADIOELEMENTS DISTRIBUTION IN AL AGLAB REGION, NORTH EASTERN DESERT, EGYPT

This work is an approach to integrate multi-discipline set of data including geological and remote sensingas well as airborne, ground radiometry and aeromagnetic geophysical data aiming to establish the controllingfeatures of the radioelement potential distribution within Al Aglab area. The investigated area of Al Aglabregion is located within the Northern Eastern Desert litho-structural domain where the outcropping rock typescomprise: metavolcanics (oldest), quartz diorites, Dokhan volcanics, Hammamat sediments and gabbrogranophyreassociations intruded by monzogranite, syenogranite and post granitic dykes (youngest). Thegranitic rocks display sharp contact with the older pre-existing rock. The radioactive anomalies lay at theintersections between NNW-SSE to N-S and NE-SW to ENE-WSW trending structure lineaments (joints,faults and shear zones) within the syenogranites pluton of G. Al Aglab and along the NE-SW to ENE-WSWtrending felsitic dykes, jasperoid veines and pegmatite bodies.Landsat Thematic Mapper (TM) remote sensing map in great concordance with airborn gamma rayspectrometric data delineate most of the surface geology over the compiled geological map. The extractedstructural lineaments are coherent to those inferred from the analytical signal magnetic maps in completeharmony with the NNW-SSE to N-S and NE-SW to ENE-WSW trending fault systems obtained from theground geological and radiometric investigation. Moreover, different types of alterations such as hematitization,Kaolinitization, chloritization and silicification are recorded within the synogranite, where their distributionis mainly controlled by the intersections between the NNW-SSE to N-S and NE-SW to ENE-WSW trendingstructural lineaments.The studied structural lineaments are arranged according to three main trend clusters around NNW-SSEto N-S, NE-SW to ENE-WSW and NW-SE to WNW-ESE directions representing the main factor controllingthe emplacement of the different granitic intrusions in Al Aglab area. Moreover, most of these lineaments, asobtained from field measurements, show strike-slip movement criteria within an extensional context. All therecorded mineralized occurrences are related to extensional events that create the necessary space either formineral entrapment and/or the percolation of the hydrothermal carrying solutions along these structural trendsespecially at their intersections.Spectrometric data (K, U and Th) shows a very high consistency between the radioelement distributionsand the differentiated outlines of different rock types. Results from integrated field studies, Landsat ThematicMapper (TM) remote sensing data and geophysical data analyses provide important constraints on the tectonicevolution of Al Aglab area and importantly, demonstrate the strength of combining remote sensing data withgeophysical data and geological observations in resolving the surface geometry of major fault systems andtheir impact on the radioelement potential distribution within Al Aglab area.

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.