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Precambrian metamagmatic complexes of the Zhingeldy and Kendyktas blocks of the Zheltau and Chu-Kendyktas terranes of the SW part of the Central Asian Orogenic Belt (CAOB) consist of predominant Neoproterozoic orthogneisses with the estimated protolith ages of ca. 790–800 Ma, and subordinate epidote and garnet amphibolites, metabasalts and metadolerites of the lower metamorphic grades. The orthogneisses are characterized by negative eNd(t) values of −12 to −4 with Nd model ages of 2.3–1.7 Ga, indicating their protoliths could have formed by a reworking of the Palaeoproterozoic crustal materials. Precambrian metavolcanic rocks in the studied region are rhyolites with the estimated crystallization ages of ca. 800–830 Ma, and are associated with metabasalts. Metasedimentary complexes in the studied region consist of intensively retrogressed garnet-mica schists interlayered with marmorized limestones, metasilicic rocks, epidote and garnet amphibolites and strongly altered eclogites. The inferred protoliths of the garnet-mica schists are terrigenous rocks accumulated during the latest Ediacaran – middle Cambrian and formed from Mesoproterozoic (ca. 1.0 Ga) and to a lesser extent Palaeoproterozoic felsic source rocks (ca. 1.6–1.7 Ga and ca. 2.5 Ga). The garnet-mica schists of the Kendyktas block have negative eNd(t) of −13.4 and a model age tNd(DM) of 2.2 Ga, implying formation of their protolith from Palaeoproterozoic crustal source. The studied Zheltau and Chu-Kendyktas terranes from the SW part of the CAOB have much in common in terms of Precambrian and Early Palaeozoic evolution and chemical compositions of the key rock types. The presence of the Early Precambrian rocks (Zheltau terrane), an abundance of the Late Mesoproterozoic (1000–1100 Ma) detrital zircons in the Ediacaran-Cambrian metasedimentary complexes and a wide distribution of the Late Neoproterozoic magmatism, are distinctive features of the studied terranes. We refer such Precambrian terranes of the western CAOB to the Ulutau-Moyunkum group where tectono-magmatic evolution is consistent with that observed from the northern part of the Tarim craton. Our results also aid comprehensive correlation of metamorphic complexes of the Precambrian terranes from the SW CAOB.

Mechanisms for invisible gold enrichment hosted within Paleoproterozoic Fe-rich metamorphic rocks (marble, biotite schist, and quartz-feldspar schist) in the Liaodong Peninsula, NE China are still unclear. In this study, we choose the Xiaotongjiapuzi deposit as a case study, and present a detailed ore deposit geology and dataset of in situ chemical compositions of Fe-sulfides to address this issue. Fe-sulfides have the following paragenesis: metamorphic pyrite (Py0), first-ore stage pyrite (Py1, Py2), and a second-ore stage comprising arsenopyrite (Apy1, Apy2) and two phases of marcasite (Mas(a-b)). Early metamorphic pyrite (Py0) has relatively low concentrations of Au (

Discovering ore deposits is becoming increasingly difficult, and this is particularly true in areas of glaciated terrains. As a potential exploration tool for such terrains, we test the vectoring capacities of trace element and sulfur isotope characteristics of pyrite, combined with quantitative statistical methods of whole-rock geochemical datasets. Our target is the Rajapalot gold–cobalt project in northern Finland, where metamorphosed Paleoproterozoic volcanic and sedimentary rocks of the Peräpohja belt host recently discovered gold prospects, which also have significant cobalt enrichment. The focus is particularly put on a single gold–cobalt prospect, known as Raja, an excellent example of this unusual cobalt-enriched gold deposit, common in the metamorphosed terranes of northern Finland. The major lithologies at Rajapalot comprise amphibolite facies metamorphosed and polydeformed calcsilicate rocks that alternate with albitic units, mafic volcanic rocks, mica schist and quartzite. Mineralization at Rajapalot prospects is characterized by an older Co-mineralizing event and a younger high-grade Au mineralization with re-mobilization and re-deposition of Co. Detailed in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful technique that produces robust trace element and sulfur isotope databases from paragenetically and texturally well-characterized pyrite from the Raja prospect. The results are treated with appropriate log-ratio transformations and used for multivariate statistical data analysis, such as the computation of principal components. Application of these methods revealed that elements such as Co, Ni, Cu, Au, As, Ag, Mo, Bi, Te, Se, Sn, U, Tl and W have high vectoring capacities to discriminate between Co-only and Au–Co zones, as well as between mineralization stages. The systematic pyrite study suggests that homogenous sulfur isotopic characteristics (+1.3 ‰ to +5.9 ‰) and positive loadings of Co, Se, As, Te, Bi and Au onto PC1 are reflective of an early stage of Co mineralization, while the opposing negative loadings of Mo, Ni, W, Tl, Cu and Ag along PC1 are associated with pyrites from the Au-mineralizing event. The sulfur isotopic signature of the latter pyrite type is between −1.2 ‰ and +7.4 ‰. Subtle patterns recognized from the whole-rock geochemistry favor an As–Au–Se–Te–W–U signature along the positive axis of PC1 for the localization of high-grade Au–Co zones, whereas the element group Ni, Cu, Co, Te, Se and As, which has negative loadings onto PC2, will predict Co-only zones. This study shows the efficiency of trace element geochemistry in mineral exploration targeting, which has the capacity to define future targets by characterizing the metallogenic potential of a host rock, as well as distinguishing various stages of mineralization.

Remote sensing methods are a vital alternative for regional exploration surveys. Many ore deposits (e.g., epithermal, porphyry-related, volcanogenic massive sulphides, etc.) have distinct distribution patterns of alteration zones that can be used for recognizing this mineralization. Several known goldfields are distributed within the basement rocks of western Nigeria. The area of interest, Malumfashi Schist Belt, is located in North-Western Nigeria and is characterized by gneisses and metasediments that were intruded by Pan-African granitoids. Gold mineralization occurs as veins and veinlets that are associated with hydrothermal alteration zones (i.e., argillic, phyllic, and propylitic). Hence, the discrimination of these alteration zones is one of the key indicators for new prospective zones of gold mineralization in this metallogenic belt. In the present study, Landsat Enhanced Thematic Mapper+ (Landsat-7 ETM+) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data were processed and integrated with the aim to identify possible locations for gold mineralization within the Malumfashi Schist Belt. For this purpose, the band ratio techniques and Principal Component Analysis (PCA) were applied to identify, enhance and map the different alteration types, while fractal analysis was utilized to quantify the degree of alteration within each processed image. Using the multi-criteria evaluation method, the discretized images obtained from the fractal analysis were weighted and integrated into an enhanced possible location for gold occurrences. A receiver operating curve/Area under curve analysis was then used to evaluate the reliability of the predictive model. Both spatial and GIS analyses indicate that gold mineralization displays a proximal relationship to hydrothermal alteration data. We can map sets of alteration minerals which mainly represent new and good ore prospects for the investigated area. A sensitivity analysis points out a predictive accuracy of 78%, which suggests the model is capable of predicting gold occurrences within the study region. Besides, the results showed that the prospective zones of gold accumulations mainly occur within metasedimentary units. It is recommended that the studied dataset provide a potential tool for mapping alteration minerals related to gold deposits that can be applied in other regions with analogous geological setting.

Lineament are extended mappable linear or curvilinear feature of a surface which can be utilized in mineral, oil, gas, and underground water studies. They are obvious in satellite images, aerial images or aerial photographs. The aim of this study is to analyse an automatically generated lineament from part of the Maru schist belt using a combination of Digital Elevation Model (DEM) data and Aeromagnetic data. The area of study is within the Maru schist belt in Zamfara State. A shaded relief map was produced from the two data sources and the lineament was extracted automatically from them. The extracted lineament was combined to obtain a final lineament map of the area. Trends such as N-S, NW–SE, ENE–WSW and NW–SE, with very little E-W were all present. The areas of very high, high, moderate and low population of lineaments was delineated. Regions with very high lineament intersections and lineament concentration, covers an area of 153.6 km2 and accounts for 16.1% of the study area, these regions are known to harbour gold and iron ores from literature reviews. These target regions are located at the Northern and South part of the study area. Also, the gold artisan miners have dominated these same regions and they have only started from exposed vein of gold mineralization. With this rather fast and easier approach of obtaining such a map, it could be used as a start point for planning a more detailed geophysical or geological survey

Remote sensing technology has advanced significantly, making it useful for geological applications such as structural and lithological mapping, as well as mineral prospecting and mapping. This study looks at how certain enhancement techniques on Landsat 7 ETM+ data can be used to map surface geology, resulting in color composite imagery that can be interpreted and validated through field mapping exercises. Because some of these rocks are poorly exposed and some portions of the research region are inaccessible, field mapping was supplemented by remote sensing lithological mapping techniques. False Color Composite images for bands (7:4:1 and7:5:4), Principal Component analysis (PC1, 2, 3 and PC4, 5, 6) and RGB composite images of Landsat band ratios (1/3:5/7:3/5 and5/1:5/7:4) proved useful in determining the approximate boundaries of the various lithology in the research area. Gneiss and quartzites occur in the central and western quadrants of the study area, mylonites and schist in the eastern quadrant, and amphibolite in the southern and southeastern quadrants, according to GPS sample locations of the individual rock types found in the study area plotted on the processed images. The contact relationships between these rocks are mostly gradational and interlayered. As a result, a thorough examination of satellite optical imagery, such as Landsat data, can greatly aid lithological inquiry and the creation of more detailed geological maps in areas that are inadequately understood.

Integrated airborne and ground geophysical studies were conducted in parts of Ilesha schist belt, southwestern Nigeria. The goal was to provide a useful guide for mineral prospecting, with the hope of considerably narrowing down the future search for mineral deposits within the study area. Aeromagnetic and aeroradiometric data were analyzed for the reconnaissance study. In addition, the reduction-to-equator transform, analytic signal, tilt derivative, and Euler deconvolution filters were applied to the aeromagnetic data to enhance shallow and deep geologic features. The aeroradiometric data were used to determine spatial variations in the concentrations of uranium (U), thorium (Th), and potassium (K) in near-surface rocks and to map spatial lithologic changes. The 2D-magnetic sections, radiometric profiles, inverted resistivity, and induced polarization (IP) sections were generated from the integrated geophysical data. The electrical resistivity tomography (ERT) results reveal the subsurface heterogeneity (to a depth of approximately 197 m) and varied geoelectric layers (topsoil, lateritic-clay, weathered rock, and basement rock). The IP sections show varying degrees of chargeability and features that suggest the presence of disseminated mineralized bodies concealed in some areas. The overburden thickness varies between 4 and 85 m as determined from the 2D-magnetic and electric resistivity sections. Anomalous peaks on profiles of elemental ratios (eTh/K, eTh/eU, and K/eU) correlate with the results of IP and ERT. Data sets are well correlated and highlight areas with relevant structural and lithologic signatures favorable for mineral deposition. The methodology adopted in our research is well adapted, and the interpretation techniques provided insight into regional and local lithostructural settings. These anomalous areas are suggested as targets for future exploration works.

The recent paper by Chaves and Porcher published in Gondwana Research (2020, v.87, 224–237) asserts the presence of 2.2 Ga eclogite facies rocks in the Itaguara Sequence, Sao Francisco craton (SFC), Brazil. They present images in which the diagnostic high-pressure minerals either occur on cracks (rutile), or as fragmentary matrix grains with unclear mineral relationships (omphacite and phengite). Here I discuss the sample petrology in order to identify the equilibrium assemblage, and utilise a P-T phase modelling approach, integrating the major mineral compositions, to show that these rocks are not retrogressed eclogites. The modelling presented here indicates that peak conditions were likely in the amphibolite facies, reaching maximum pressures of no more than 8 kbar and peak temperatures of ca. 700 °C (at 5 kbar). This result is consistent with that found by Massonne (2020, JSAMES, v.99, 102495) who suggested that mica schists from Itaguara reached maximum pressures of 13–14 kbar, and possibly lower than 10 kbar at 600 °C (i.e. within the medium to high-pressure amphibolite facies). This work shows that declarations of eclogite facies conditions, particularly from Paleoproterozoic terrains, should be accompanied by carefully evaluated petrography and thermodynamic investigations based on minerals (or mineral replacement textures) that indicate equilibrium relationships.

The Mw6.4 earthquake on November 18, 2017 in Milin County, Nyingchi City, Tibet triggered thousands of landslides. By comparing visual interpretation of satellite images acquired shortly before and after the earthquake and field survey, we have created a new landslide database which includes 3 130 coseismic landslides, each with an area of 0.01 to 4.35 km2. Six factors (elevation, slope angle, slope aspect, lithology, distance from the epicenter and distance from the seismogenic fault) were selected to correlate with the coseismic landslides. In addition, the area and density of landslides were counted as indicators. Results show that most landslides occurred where the elevation is between 2 000–3 000 m, with a 40°–50° slope angle and S, E or SE slope aspect, schist or gneiss lithologies, 10–15 km from the epicenter, and 5 km within the seismogenic fault. Most of the landslides, triggered by the Mw6.4 earthquake, are concentrated near the seismogenic fault rather than at the epicenter, indicating that the seismogenic structure is more influential than the location of the epicenter. Our findings may differ from other landslide database due to temporal image acquisition, interference from weather, and image resolution.

Remote sensing and aeromagnetic data analyses were conducted for the characterization of basement structural elements that influence iron ore deposits and other mineralization over kabba and its surroundings. Spectral analysis suggests depth to magnetic sources range from deep, intermediate, and shallow with depths (i.e., 2.8 km, 1.5 km, and 0.3 km respectively). Three lithological zones were revealed on the Analytic Signal (AS) image which includes Meta-Sedimentary Complex, migmatite-gneiss-quartzite complexes, and undifferentiated schist and metavolcanic rocks. Structures interpreted based on first vertical derivatives (FVD), total horizontal derivatives (THD), and AS of the aeromagnetic images enabled delineation of long, deep, regional, inter-terrain linear structural features that are different f rom shallow, relatively short local intra-terrain structures. Typical potential mineralized zones are regions where the delineated structures on the AS coincide with FVD anomalies vis-a-vis zones exhibiting THD peak anomalies and high magnetic susceptibility. These characterized zones also coincide with the location of known geologically deposits of iron - ore and marble. Mineral deposits tend to be dominated regionally by the dominant structural patterns (NE-SW to ENE-WSW, NW-SE to WNW-ESE, and E-W) delineated from SRTM and aeromagnetic analysis.

Aeromagnetic and vertical electrical sounding around Ijano, southwestern Nigeria, was investigated for groundwater potential. Aeromagnetic dataset and vertical electrical sounding were acquired and used to investigate the study area. Oasis Montaj, Microsoft Excel and Arc GIS were used to present the results in maps, images and profiles. In order to map out the geological structures of the study area, magnetic image enhancing filters applied to the total magnetic intensity using Geosoft (Oasis Montaj) are reduction to equator, vertical derivative, total horizontal derivative and upward continuation. These filters helped define the lithological boundaries, geological structures, faults, folds and contacts. The lineament of aeromagnetic map was generated from derived field intensity gradients and solutions of Euler deconvolution carried out on the aeromagnetic data using structural index of 0.5 and 1. The processed image shows the lineaments trends majorly towards NE–SW directions. From these combined results of the study area, consistent aeromagnetic lineament map was generated showing the probable positions and trends of the suspected fractured/faulted zone as well as other basement structures. Hydro-lineament density maps based on lineament were produced from the generalized structure trends in the area. The result from the depth sounding data interpretation indicates three curve types which are H, HA and KH, where curve type H has the highest occurrence. The results from the vertical electrical sounding data revealed that the areas with the highest hydro-lineament density are good for groundwater prospect and development. The study has led to the delineation of areas where groundwater occurrences are most promising for sustainable supply, suggesting that an area with high concentrations of lineament density has a high tendency for groundwater prospecting. The results from the study show that the aeromagnetic technique is capable of extracting lineament trends in an inaccessible tropical forest.

In this study, micro and uniaxial compression tests were performed on two types of quartz mica schist. The effect of schistosity orientation on their mechanical properties was discussed in terms of the critical characteristic strength (CCS) and energy. Furthermore, the microscale mechanism of the mechanical properties of schistose rocks was revealed. In view of the good correspondence between the energy evolution curves and stages of rock damage, the damage evolution process of rock before failure can be divided into five stages. Energy evolution curves can be used to quickly and accurately determine the CCS of specimens, including the initiation, closure, and damage strength of cracks. This suggests that the energy and CCS of schist depend closely on the schistose angle α. The specimen with α = 30° has the minimum crack initiation strength and the highest level of crack initiation stress, while the specimen with α = 90° has the lowest level of crack damage stress and higher elastic and dissipation energy. The mechanical anisotropy, closely related to the orientation dependence of crack initiation and propagation, is essentially controlled by the typical interbedded quasi-microstructure composed of clustered mica layers and granular mineral layers. The CCS and energy are significantly different for the two tested schist samples, and they are determined by microscale factors, such as the proportions of soft and hard minerals, aggregation degree of flaky minerals, and continuity of oriented mica clusters. The CCS and energy of schistose rocks are more sensitive to the various microscale factors at α = 30° than at α = 90°.

The newly discovered Bibole banded iron formations are located within the Nyong Group at the northwest of the Congo Craton in Cameroon. The Bibole banded iron formations comprise oxide (quartz-magnetite) and mixed oxide-silicate (chlorite-magnetite) facies banded iron formations, which are interbedded with felsic gneiss, phyllite and quartz-chlorite schist. Geochemical studies of the quartz-magnetite banded iron formations and chlorite-magnetite banded iron formations reveal that they are composed of >95 wt % Fe2O3 plus SiO2 and have low concentrations of Al2O3, TiO2 and high field strength elements. This indicates that the Bibole banded iron formations were not significantly contaminated by detrital materials. Post-Archaean Australian Shale–normalized rare earth element and yttrium patterns are characterized by positive La and Y anomalies, a relative depletion of light rare earth elements compared to heavy rare earth elements and positive Eu anomalies (average of 1.86 and 1.15 for the quartz-magnetite banded iron formations and chlorite-magnetite banded iron formations, respectively), suggesting the influence of low-temperature hydrothermal fluids and seawater. The quartz-magnetite banded iron formations display true negative Ce anomalies, while the chlorite-magnetite banded iron formations lack Ce anomalies. Combined with their distinct Eu anomalies consistent with Algoma- and Superior-type banded iron formations, we suggest that the Bibole banded iron formations were deposited under oxic to suboxic conditions in an extensional basin. SIMS U–Pb data indicate that the Bibole banded iron formations were deposited at 2466 Ma and experienced metamorphism and metasomatism at 2078 Ma during the Eburnean/Trans-Amazonian orogeny. Overall, these findings suggest that the studied banded iron formations probably marked the onset of the rise of atmospheric oxygen, also known as the Great Oxidation Event in the Congo Craton.

Geological and geochemical studies of gold mineralization in Bode-Saadu axis, Southwestern Basement Complex, Nigeria have been conducted in order to study their mode of occurrence, structural settings, pattern of distribution and potential. Geological studies reveal that granite and gneiss granite are the prominent rocks in the area and exist in the north-eastern, north-western and southwestern part of the area whereas mica and amphibole schist occur as low-lying exposure. Petrographic studies reveal spatial association between gold mineralization and the fractured zones. Geochemical studies show that the gold concentration in rocks and stream sediments from the region is low with the exception of a few areas with high values ​​and is related to the occurrence of fissure in the northeast-west direction. The distribution pattern of gold in the region is skewed NE-SW, indicating that gold mineralization is structurally controlled. Keywords: Geochemical prospecting; Geological studies; Gold mineralization; Structurally controlled.

Appreciable amount of copper mineralisation dominated by chalcopyrite along with incidence of uranium within the Mayurbhanj granite batholith in Kesharpur-Madansahi-Dudhiasol sector has been established through preliminary exploration (UNFC-G3). Chalcopyrite-pyrite-pyrrhotite assemblages along with minor pentlandite seems to be preferably controlled through secondary structural shear fabric and vein selvages along the contact zones of granite and country rocks viz. hornblende biotite schist and metabasics. Hydrothermal alteration is notably marked by potassic, propyllitic and phyllic zones besides wide chloritisation and silicification in close proximity and within mineralised zone. Three potential prospects of significant copper mineralisation in terms of thickness and grade have been brought out at Kesharpur, Madansahi and Dudhiasol. These prospects show a linear lensoidal synformal disposition of the ore body trending NE-SW in eastern part to E-W in central part and NW-SE in the western part with moderate to steep northerly dipping. Out of these three prospects, Madansahi is quite promising where thickness of copper lodes varying from 2.00 m to 18.35 m and grade varies from 0.20% Cu to 1.76% with maximum nickel concentration of up to 0.13% Occurrence of copper mineralisation along with nickel concentration and anomalous uranium values up to 0.045% U3O8 is a significant achievement in establishing polymetallic mineralisation and augmenting the mineral resources in eastern India.

WorldView-3 (WV-3) is the first high spatial resolution and super-spectral commercial satellite which has the capability in improvement of geological mapping. The VNIR-SWIR data of this satellite are evaluated in this study for mapping the lithological units of a metamorphic-igneous terrain in Chadormalu area, Central Iran, by the use of support vector machine (SVM) classification method. Applying principal component analysis (PCA) as an image transformation technique on the WV-3 data, and interpretation of its results, supported by field observations, petrography, and spectroscopy, lead to identifying training areas which are input to the SVM algorithm. This method not only produces a detailed lithological map of all exposed rock units, but also well discriminates diorite-gabbro diorite from granite, and gneissic granite from green schist and garnet mica schist, which are not revealed in 1:100,000 geological map of the area, published by Geological Survey of Iran (GSI), with overall accuracy of 88.36% and the Kappa coefficient of 0.86. Furthermore, the efficacy of each applied band of WV-3 is assessed in promoting classification accuracy using SVM method. Results show that band 7 of SWIR region has increased the overall accuracy 4.81% relative to SWIR dataset, and improves the classification accuracy of green schist and diorite. Moreover, bands 5, 6, and 8 of SWIR dataset are more efficient in improvement of the overall accuracies than other bands. This study concludes that WV-3 data provides a good facility to generate large scale geological maps owing to its high spatial and radiometric resolution and appropriate SWIR bands.

The Sambagawa Belt is a subduction-related high-pressure intermediate type metamorphic complex with its protoliths characterized by the ocean plate stratigraphy. The Iyo-nada Sea area of this belt at western Shikoku, Southwest Japan exposes lenticular bodies of metagabbro. Besides, low P/T type metamorphosed Karasaki mylonites occur in this area as an upper structural unit of the Sambagawa Belt. LA-ICP-MS zircon U-Pb dating of the metagabbros in the Sambagawa Belt revealed their crystallization ages of 139–135 Ma as a magmatic event. Trace element composition of zircon suggests that the metagabbros were formed under the arc tectonic setting. Metagabbros do not show any evidence of high P/T metamorphism, instead, they indicate low P/T metamorphism based on the chemical compositional analysis of the hornblende. From the present study, it is constrained that the 139–135 Ma metagabbros were possibly originated as the hanging-wall arc crust. Zircon U-Pb dating of the Karasaki mylonites revealed imprints of multiple tectono-thermal events of 114.3 ± 1.5 Ma (magmatic event), ∼108–105 Ma (metamorphic with or without magmatic event), and 102.4 ± 0.9 Ma (metamorphic event). The first two tectono-thermal events can be correlated with those of the Higo Belt, central Kyushu. However, the last metamorphic event is younger than the tectono-thermal events of the Higo Belt, instead, it coincides with the initial stage tectono-thermal events of Ryoke-San’yo igneous province. Detrital zircon age of the pelitic schist in Karasaki mylonites revealed their origin as Jurassic to earliest Cretaceous sedimentary rock and its age distribution pattern is likely comparable to the previously reported age spectra of Higo metasedimentary rocks and their equivalent rock units. The newly obtained dataset indicates that the Karasaki mylonites are the eastern extension of the late Early Cretaceous Higo Belt.

The mining sector’s share in Ethiopia’s economy is gradually increasing. Among metallic mines, Legadembi for gold and Kenticha for tantalum are the main contributors. At Kenticha, the Ethiopian Mineral Development Share Company is producing tantalite concentrate of 40-60% grade by open pit mining. The mine area is comprised of the rocks of Neoproterozoic age, pegmatite, granite, serpentinite, and talc-chlorite schist. The ore-bearing pegmatite intruding the basement serpentinite, and talc schist rocks, is asymmetric, N-S trending, and locally affected by fractures and local faults. Mining, at present, is being done using conventional methods not by developing benches. An optimum open pit design is developed and its impact on the run of mine is evaluated based on the field data, technical mine report data, borehole data, tonnage data, grade data, and mine survey. The suggested design has taken into account the mine drainage, bench design, haul road design, and mine waste dump design. Also keeping in view the future mining and production requirements. The suggested open pit mine design can minimize the dilution and improve the ore recovery.

To identify the required parameters of grouting operations in scrutinising the design and execution of seal curtain of the Balvabin dam site, the test grouting operations were conducted in a part o...

In this study, uniaxial compression testing was carried out to investigate the response of quartz mica schist to water in terms of strength and energy anisotropy. The micromechanism and water action mechanism of the anisotropic properties of the schist were further discussed based on microscopic observations of the rock fabric and analysis of the mineral composition of the solid precipitant after immersion. Mechanical tests reveal that both the failure strength and crack initiation strength of dry schist change in a U shape with the schistose angle; moreover, the strength anisotropy of schist generally increases with increasing immersion time. The specimen with α = 30° has the minimum energies, while that with α = 90° exhibits the maximum total and elastic energies. The total and elastic energies of dry specimens decrease significantly after saturation, but the influence degree of water on the energy of schist differs with the schistosity orientation. The energy response of specimens with α = 30° and 0° to water is more sensitive than that with α = 90°. The internal energy allocation of schist was found to be associated with the schistosity orientation and immersion time. Based on the analysis of microcrack propagation and macro-failure, it is concluded that the fabric of schist plays an essential controlling role in the strength and energy anisotropy. The response of anisotropy to water is closely dependent on the lubrication and disintegration of flaky minerals and the hydraulic action on the tips of voids in response to external compression.

Geochemistry of schists of Obudu area was carried out using ICP-MS and ICP-ES techniques in order to determine the geochemical evolution of the area. 40 samples were analyzed for their major, trace and REE composition. Field mapping revealed that gneisses, amphibolites and schists comprising migmatitic schists (MS), quartz-mica schists (QMS), garnet-mica schists (GMS), and hornblende biotite schists (HBS), intruded by granites, granodiorites, quartzofeldspathic rocks and dolerites occur in the area. Structural studies revealed that the schists trend approximately NE–SW (5 – 30o ) indicating the Pan-African event. Modal analysis revealed that the schists have average concentration of quartz (15vol.%), plagioclase (An45-19 vol.%), biotite (15vol.%), garnet (9.0vol.%) and muscovite (6vol.%), the remaining consists of accessory minerals. Geochemistry showed that all the schists have molecular Al2O3 > CaO+K2O+Na2O, indicating they are peraluminous metasedimentary pelites. Trace and REE element results show that all the analyzed schist samples are depleted in Hg, Ag, Be, Bi, and Sb below < 1.0ppm, but relatively enriched in Ba, Sr and Zr with average concentration of 996, 675.73, 243.13 ppm respective. The HREE are depleted with ΣHREE < 10.2, but the LREE are relatively enriched with ΣLREE > 289.54. The ΣLREE/ΣHREE ratio ranges from 9.17 to 33.4, with a large positive delta V at Eu. These findings indicate that the schists of Northwest Obudu area are highly fractionated and had attained at least the uppermost amphibolite metamorphic grade. The schists had contributed to the development of the Pan-African continent.

Graphite deposits may form alternatively by metamorphism of sedimentary rocks and from fluids. Both types occur in supracrustal successions within the Lewisian Complex of Northwest Scotland, and similarly in Palaeoproterozoic supracrustal rocks across the North Atlantic region in Canada, Greenland and Scandinavia. Carbon isotope compositions show that the graphite in Scotland had a mixed origin from metamorphism of sedimentary organic matter (schists) and the decarbonation of limestones (marbles). Raman spectroscopy shows that most of the graphite in Scotland exhibits some structural disorder, unlike the complete order in graphite vein ore deposits across the region. Exceptionally, where graphite was precipitated from fluid, in albitized rock in Tiree and Scardroy, it is fully ordered. While organic matter may survive granulite facies metamorphism without being transformed to fully ordered graphite, it can yield commercially more valuable ordered graphite when mobilized in a fluid.

Petrographic and provenance studies of heavy minerals in Ifelodun sediment were carried out. Sediment samples from eight locations were obtained from the study area; sieved to allow only sand-size lithology. The result was achieved after subjecting this sieved lithology obtained to analyses using a binocular (transmitted and reflected light) microscope. Minerals were separated in a funnel using bromoform with a specific gravity of about 2.89 (gravity method). The heavy minerals present in lithologic sand units are mainly staurolite, tourmaline, zircon and other opaque minerals including cassiterite. The most dominant non-opaque mineral is staurolite with 27.5% of the total minerals counted in the area. Staurolite is very appreciable in locations AR1 with 60% presence (which is 80% of the non-opaque minerals), AR3, AR5, AR7 and OL15b (each with 30%). OL15b also recorded a better amount of tourmaline (20%); Zircon is better in OL6b with 20% of the heavy minerals available in this location. The source rock predicted is porphyroblastic schists.

The origin of sediment-hosted copper-cobalt deposits (SCDs) within metamorphic terranes remains contentious, particularly in regard to the timing of mineralization relative to basin evolution. Here, we link the timing of Cu-Co mineralization in the Zhongtiao Mountains district, central China, to basin closure during development of the Trans-North China Orogen. Metamorphic apatite from meta-evaporite has a U-Pb age (1844 ± 25 Ma) within error of a Re-Os age for molybdenite from Cu- and Co-bearing veins (1819 ± 10 Ma), implying that mineralization and metamorphism were coincident. In situ trace element and Fe-S isotope analyses of deformed sedimentary pyrite (Py I) and younger euhedral metamorphic pyrite (Py II) in pyritic graphite schist indicate that Co was mobilized from Py I via fluid-mediated dissolution and reprecipitation. In the graphite schist, representing a sulfidic shale metamorphosed at upper greenschist facies conditions, relic Py I has high δ34S values (22.9 ± 0.4‰, n = 10) and δ56Fe values (0.90 ± 0.16‰, n = 8). These values are consistent with bacterial sulfate reduction and pyrite formation in a Paleoproterozoic sulfidic sea (i.e., after the first great oxygenation event). In addition, Py I has unusually high Co contents (0.8–3.0 wt.%), suggesting that transition metals, including Co and Ni, were originally concentrated in sedimentary pyrite in an evaporative setting. The evaporitic setting is supported by the presence of sylvite in sulfidic schists and adjacent scapolitic calc-silicates. Younger Co-poor Py II has slightly lower δ34S values (21.4 ± 0.2‰, n = 19) and higher δ56Fe values (1.61 ± 0.15‰, n = 9), supporting the hypothesis that Co was released from sedimentary sulfide during dissolution and reprecipitation. The great variability of δ34S (14.8 to 22.9‰) and δ56Fe (0.13 to 2.30‰) in hydrothermal pyrite (Py III) associated with Cu-Co mineralization suggests that an external Cu-rich oxidizing fluid was involved in the ore-forming process. Copper and Co in this type of deposit are typically both considered to be derived from fertile basement rocks. This study, however, highlights another potential source for the Co, with its enrichment in a sulfidic sea along an evaporative margin and its upgrading through mobilization during orogenesis that leads to formation of a relatively high-temperature group of SCDs. Tectonometamorphic processes causing such Co enrichments took place during the Paleoproterozoic and Neoproterozoic oxygenation events, implying that the most prospective targets for Co resources are concentrated in ca. 2.2–2.0 Ga and 0.9–0.7 Ga deformed passive margin marine sequences.

The present study combined analysis of satellite, aeromagnetic and radiometric data for evaluation of structural features within the Ife-Ilesha schist belt. Shuttle Radar Topographic Mission digital elevation data have been enhanced using hill-shading technique for the delineation of morphological features. The superposition of total gradient amplitude lineaments on the 3-D Euler deconvolution map revealed the trends and depth of structural features within the study region. The major trends are NE–SW, NNE–SSW, E–W and minor trends in the N–S direction, including the Ifewara shear zone that trends in the NNE–SSW. The estimated depths to the top of the sources within the shear zone varies from 90 to 200 m. Complementary analysis of the airborne radiometric data revealed that the Ifewara shear zone and adjacent regions are characterized by radiometric anomalies, indicating regional mineralization alteration zone. Generally, there is a good correlation between the satellite, radiometric, aeromagnetic maps which provides new insights and re-evaluation of structural features.

To understand the protracted accretionary evolution along the Central Indian Tectonic Zone (CITZ), we investigated garnet-staurolite schists and associated lithologies from the central Maha...

The Beishan complex, located along the Liuyuan suture in the southern Beishan, separates the Dunhuang terrane from the southern Central Asian Orogenic Belt. The ages and origins of the Beishan complex are still controversial. Based on integrated field investigation and petrological, geochronological, and geochemical work, the Beishan complex is interpreted to consist of four diachronous lithologic units with different tectonic origins. Unit I is mainly composed of meta-clastic and minor carbonate rocks; these metaclastic rocks were derived from a proximal source with dominantly intermediate–acidic magmatic materials, and were deposited in a continental arc setting during 430–280 Ma. Unit II exhibits a block-in-matrix structure with variably sized blocks of ultramafic rock, meta-gabbro, Nb-enriched pillow meta-basalt, amphibolite, calc-alkaline mylonitized diorite, marble, argillaceous slate, and quartzitic meta-chert embedded in a matrix of sheared fine-grained sandstone; this tectonic melange was emplaced during 284–267 Ma. Unit III consists of coherent quartzite, paragneiss, and biotite schist with maximum depositional ages of 1214 Ma, 817 Ma, and 1210 Ma, respectively. Unit IV was formed in a continental arc setting, and predominantly contains early Paleozoic diorite (430 Ma), TTG (455–437 Ma), and tonalite (430–429 Ma), as well as biotite–quartz schist (507–420 Ma). Consequently, we propose that the Beishan complex represents an assemblage of a continental arc and a fore-arc accretionary complex resulting from subduction of the Paleo-Asian oceanic slab. Our results indicate long-lived subduction–accretion of the Paleo-Asian Ocean and the final closure may have occurred posterior to the middle Permian.

Assessment of drillability of rocks is vital in the selection, operation, and performance evaluation of cutting tools used in various excavation machinery deployed in mining and tunneling. The commonly used rock drillability prediction methods, namely, drilling rate index (DRI) and Cerchar hardness index (CHI) have limitations in predicting the penetration rate due to differential wear of the cutting tool in rocks with varied hardness and abrasivity. Since cutting tools get blunt differently in different rocks, the stress beneath the tip of the bit decreases until it reaches a threshold value beyond which the penetration rate becomes constant. In this research, a new composite penetration rate index (CPRI) is suggested based on the investigations on four metamorphic rocks viz. quartzite, gneiss, schist and phyllite with varied hardness-abrasivity values. The penetration-time behavior was classified into active, moderate, passive, and dormant phases based on the reduction in penetration rate at different stages of drilling. A comparison of predicted penetration rate values using DRI and CPRI with actual penetration rate values clearly establishes the supremacy of CPRI. Micro-structure and hardness-based index was also developed and correlated with CPRI. The new indices can help predict cutting tool penetration and its consumption more accurately.

The results of studying the mineralogy of metamorphic schists from the Pre-Jurassic base of the Arctic part of the West Siberian plate are presented. The accessory and ore mineralization of schists from the Zapadno-Yarotinsky license area located in the southern part of the Yamal Peninsula is studied. The schists was uncovered by the Zapadno-Yarotinskaya No. 300 well at a depth of 2762 m. Above the section, the metamorphic rocks are overlain by a young Meso-Cenozoic cover. The schists are mainly composed of quartz, plagioclase (albite), carbonates (dolomite and siderite), mica (muscovite) and chlorite (donbassite). The discovered accessory and ore minerals in the metamorphic schists of the Zapadno-Yarotinsky area can be divided into two groups. The first group includes minerals that were formed during the metamorphism of schists, or were preserved as detrital matter. These minerals include zircon, fluorapatite, and rutile as the most stable compounds. The remaining mineralization (pyrite, sphalerite, chalcopyrite, cubanite, galena, cobaltite, barite, xenotime-(Y), goyazite, synchysite-(Nd), native silver and copper) is clearly secondary and was formed as a result of superimposed metasomatic processes. Judging from the described mineralogy, the schists underwent changes as a result of superimposed propyllitization. The temperature range of this process is determined by the formation of cubanite in association with chalcopyrite at a temperature of 200-210 оС.

This work presents the experiences gained during the construction of the Perthus high-speed railway tunnel (8.4 km long), as regards water inflow management, analysis of the impact on surface-waters and groundwater, monitoring of piezometers and water quality control, soil injections. The excavation met granodiorites, schists, diorites, gneisses, black schists and coarse river deposits (pebbles and blocks) near the north portal. Some important tectonic structures, and associated groundwater flow, were also crossed. Finally, a geothermal study on the hydrothermal springs Le Boulou, which were not impacted, is presented.

Hydrothermal mineralizations (Pb–Zn, Ba, F, Cu) of the Aouli mining district are hosted by Paleozoic schists and granitoids, as well as Triassic arkoses and basalts. These mineralizations are geographically distributed in five vein systems that are spread out over the Paleozoic Aouli inlier. Geological mapping, structural analyses and paleostress reconstruction were carried out in each of these vein systems, and they show that mineralizations are mainly controlled by three fracture networks: (i) NNE-SSW to NE-SW system; (ii) ENE-WSW to E-W system; (iii) WNW-ESE system. All of these fractures are developed under an extensive tectonic regime consistent with a NW-SE to NNW-SSE sub-horizontal σ3 axis and a subvertical σ1 axis. This extensive tectonic regime, related to the Atlas rifting stage during the Upper Triassic-Early Liassic period, allowed the development of vein structures along NNE-SSW to E-W trending normal faults and tension gashes, as well as WNW-ESE trending normal faults with strike-slip component. The relative age of mineralizations emplacement is interpreted to be the end of the Triassic period, with veins cross cutting Upper Triassic detrital and volcanic formations, but never affecting Early Liassic formations.

Xenolithic structures are considered to be natural defects in theigneous rocks that highly affect their physicochemical and mechanicalproperties. They are foreign rock fragments trapped in the magmaor lava during the cooling process. They are totally unrelated to theigneous rocks, as they compose from different types of rock piecesthat enclosed in the monumental granites during their emplacement.This paper aims to study and characterize the xenolith fragmenttrapped in the studied granitic obelisk. The analytical study wascarried out using different techniques such as polarizing microscope,x-ray diffraction, scanning electron microscope, EDS elementalanalysis and BET surface area. The results clarified that the studiedxenolith fragment is classified as biotite schist xenolith. In addition, itwas observed that the xenolith fragment not only affects theaesthetic appearance of the studied granitic obelisk but also itrepresents a serious weakness point in its structure.

Manganese is one of the most widely distributed elements in the earth’s crust and mapping of these deposit are of high economic interest. Manganese occurs as diverse genetic types that is vital for iron and steel production. It occurs usually in the form of oxide, hydroxide, carbonate and silicate which is an important raw material for iron, steel industry, chief manufacturer of chemicals and dry cells in the form of manganese dioxides. Advanced analysis of hyperspectral signatures and GPS applications have opened a newest approach in exploration and systematic mapping of economic ore deposits. The present study aims to integrate the hyperspectral signatures with major elements of manganese ore deposits of Halekal band in Bhahaddurghatta-Hosahatty village of Chitradurga Schist Belt. The samples collected from field are studied in the laboratory using thin and polished sections under microscope and X-Ray Diffraction (XRD) analysis. Efforts are created to assess the spectral signatures of four representative random ore samples collected and analyzed through ASD Spectro-radiometer instrument operative in Visible and InfraRed (325 to 2500 nm) region with concentration of major elements. This study clearly demonstrated and documented the spectral absorption features of the selected rock samples in the study area mainly depend on the optical and physico-chemical characters of the rock and major elemental composition as well as mineral constituents of the samples.

The airborne Time-domain electromagnetic data acquired over the Ilesha Schist Belt in southwestern Nigeria were filtered, enhanced and analysed to generate ground conductivity responses at differen...

Banded iron formations (BIFs) are the most significant source of iron in the world. The present study addresses the petrographic and geochemical characterization of the BIF from Chundi-Malakonda-Ayyavaripalle area in the Nellore schist belt of Prakasam district, Andhra Pradesh, their genesis and iron enrichment processes. Six bands of banded magnetite quartzite (BMQ) of Archaean age occur in the area. Field investigations and petrography revealed that the studied BIF samples are hard, compact, weathered and composed of alternate layers of magnetite/martite and subordinate quartz, biotite and muscovite. The BIFs occur in three associations: volcanic (Band 1,3,4,5), sedimentary (Band 6) and volcano-sedimentary (Band 2). The geochemical composition of the whole rock reveals that iron and silica represent 78.48% to 91.74% of the average composition. The total iron (TFe) contents range from 16.25 to 61.80 wt % (average of 38.47 wt %) and is consistent with low-grade siliceous BIF by global standards. All BIFs have high SiO2/Al2O3, Fe/Ti, and low Al/(Al+Fe+Mn), which suggest a mixed hydrogenous and hydrothermal origins. Geochemical results for the BIFs lead to the conclusion that all the BIFs are of Algoma-type with Precambrian affinity and formed in small sloped or terraced silled basins in the back-arc areas with MORB affinity, surrounding an immature island arc. Depending on the degree of replacement and shape of the magnetite crystals, two textural types of magnetite (Magnetite-I and Magnetite-II) are observed. Ore formation occurs in three stages: Magnetite (protore), Martites and Martite-goethites.

The mineral assemblage Pl + Bt + Qtz + Grt + Sil + Ilm + Rt ± St (without cordierite) found in metapelites at the Kitela garnet deposit in the North Ladoga Metamorphic Complex, southeastern Fennoscandian Shield, was produced by Barrovian-type (elevated-pressure) medium- to high-temperature metamorphism. The P–T parameters of the metamorphic processes were evaluated using the technique of multiequilibrium thermobarometry (TWEEQU) at 610–700°C and 6–8 kbar. The metamorphism was associated with deformations and anatexis (partial melting) in a water-saturated system. The U–Pb monazite age (ID‑TIMS) of the Kitela schists is 1800 Ma (the final stage of the Svecofennian orogeny). Evidence for the identified metamorphic event is found locally in high-strain zones among schists with low- to medium-pressure mineral assemblages that are common to the North Ladoga Metamorphic Complex and the Svecofennian Orogen as whole (Buchan-type metamorphism). The Kitela schists were retrogressed at temperatures lower than 300°C. This retrogression occurred not during the final stage of the Late Svecofennian metamorphic event but was related to a younger low-temperature fluid-assisted overprinting.

There is growing evidence that the earliest Paleozoic ocean experienced fluctuations in ocean redox chemistry, with anoxic ferruginous conditions being a prevalent feature at certain times. However, the general absence of early Paleozoic banded iron formations (BIFs) means that direct supporting evidence for ferruginous conditions inferred from geochemical proxy data is currently limited. Here, we describe an early-Paleozoic BIF (Tiande No.2) from the late Silurian Habahe Group in Altay, NW China. The BIF is hosted in meta-volcano-sedimentary rocks, and is characterized by alternating iron-rich and silica-rich laminae. In addition to abundant magnetite and quartz, Fe-silicates (garnet and amphibole) are dominant minerals in the BIF. Like most earlier Precambrian examples, the BIF horizons are dominated by high Si and Fe contents, but also contain significant Al, Ti and rare earth element concentrations, consistent with a dominant chemical origin, but with significant terrigenous contribution. We observe slightly positive Eu anomalies (1.17 to 1.57) and low eNd(t) values (−4.2 to −0.8) in BIF samples, indicating a mixed seawater and submarine hydrothermal source for the iron. The BIF also generally displays negative Ce anomalies, and homogeneous and slightly negative δ56Fe values. This suggests near-quantitative oxidation of dissolved Fe(II) from the water column, likely following upwelling into oxygenated surface waters as sea level decreased, in a region where the terrigenous input was low relative to the dissolved Fe2+ flux. The Tiande No.2 BIF is conformably bedded within schist, which also has high concentrations of Fe (up to 12.67 wt%), generally elevated Fe/Al ratios (>1.0), and no Ce anomaly, while magnetite in the schist has heavy and variable δ56Fe values. This suggests that the schist precursor, which likely comprised a significant contribution from deposited marine sediment, was also deposited from ferruginous waters, but with only partial oxygenation of dissolved Fe2+ in a dominantly anoxic water column. The occurrence of this late Silurian BIF and associated ferruginous rocks provides new constraints on the nature of ocean redox chemistry at this time, and supports continued dynamic Fe cycling and at least intermittent ferruginous deeper water conditions in this location during the late Silurian.

At the Basement Complex geological province of central Nigeria, in the state of Niger, just northeast of the Bida Sedimentary Basin, there is the character of non-complexity and high uniformity in the local geology over an appreciable linear spread. This appreciation makes it a standard practice to do one-dimensional vertical electrical sounding surveys in the search for groundwater resources at this area with the expectation of reliable results. This seeming “simplicity” means that intense manual labour can be invested in acquiring a large data-field at a local area of survey where resources are not readily available to do a standard two-dimensional survey of the conventional kind. This is especially significant for the proposed area of development at the Gidan Kwano Campus of the Federal University of Technology, Minna, Thus, with this awareness and the use of the ABEM Terrameter 4000 equipment, the aim of this study was to do an intense acquisition of one-dimensional electrical resistance and concomitant induced polarization programme for this proposed area of development so as to achieve the objective of garnering information about exploitable groundwater locations before structural developments cover these points up. Typical point-to-point one-dimensional tandem electrical resistance and concomitant induced polarisation surveys were completed along east-west profile lines for about 309 survey stations of the available 441 principal locations of the 4 km2 extent of the proposed new development. After due processing and interpretation of the data-field of this survey, whilst remarking that the induced polarisation data-set was used herein as quality control “refiner” only, clusters of reliable groundwater locations were observed at the southwest end of the 4 km2 areal extent of the proposed new development. It conforms to the dip of the landform and comparatively significant overburden-material thicknesses observed over there. Interestingly, in a twist of serendipity, the series of diagonal subsurface “fault-lines” that connect one promising groundwater prospect with the other, describable by a prominent northeast-southwest dip, aligns exactly with the Kazaure-Karaukarau-Kushaka-Ilesha Schist Belt. In the modern geography setting of the present time, the Kazaure-Karaukarau-Kushaka-Ilesha Schist Belt actually traverses a lengthy diagonal across the landscape of Nigeria, cutting through such Nigerian states as Jigawa, Kano, Kaduna, Niger, Kwara, Ekiti, and Osun. There is virtually no surface indicator of this once-prominent schist belt and what this study reveals is its vestigial signature

Morphologic and placer features were used to characterize, determine the provenance, and transport distances of gold grains within the River Gagare drainage basin of the Wonaka Schist Belt. Field studies, scanning electron examination coupled with energy dispersive spectrometry and binocular microscopy were utilized to study the spatial distributions, shape, size, inclusions, primary and fluvial transport-induced deformations, as well as Cailleux flatness indices. The grains are dominantly subrounded (71%), with the length between 35 – 800 µm and width of 10 – 778 µm while the rounded grains have a mean length of 292.5 µm and width of 179 µm. Similar values for circularity and sphericity are observed in the sub-rounded grains, with slight variations of 2.7 circularity and 2.6 sphericitydistinguished in the rounded grain subset. The Cailleux flatness index range from 2.5 to 9 for subrounded grains and 2 – 15.5 for the rounded, indicating the multisource nature of the grains. The grains are consistent with short to moderate transport distances from the lode sources. The similarities in physical features, lack of delicate secondary growth structures and irregular grain outlines point to a detrital source for the placer deposits. Evidence of emulsion crystallisation type is indicated by the presence of sub- to anhedral inclusions within the Au grains. Keywords: Placer gold, Cailleux flatness indices, Wonaka Schist Belt, Provenance, Northwest Nigeria

The Orocopia Schist and related schists are sediments subducted during the Laramide orogeny and are thought to have been underplated as a laterally extensive layer at the base of the crust in the southwestern United States Cordillera. This concept is hard to reconcile with the existence of continental mantle lithosphere in southeastern California and western Arizona. Analytical solutions and numerical modeling suggest that the Orocopia Schist may have ascended through the mantle lithosphere as sediment diapirs or subsolidus crustal plumes to become emplaced in the middle to lower crust. Modeled time-temperature cooling paths are consistent with the exhumation history of the Orocopia Schist and explain an initial period of rapid cooling shortly after peak metamorphism. The Orocopia Schist represents a potential example of relaminated sediment observable at the surface.

The study of lineaments derived from optical imagery provides insights to the location of mineral deposits as they reflect geologic structures. The present study employs lineament extraction from Landsat-8 Operational Land Imager (OLI) to identify possible areas of epigenetic mineralization in the rocks of Dagbala-Atte District. Fifty-one (51) geologically significant lineaments of varying lengths and directions were extracted. Lineament map revealed three promising zones of epigenetic mineralization. These zones are those in the northeastern, central, and southwestern parts of the district. Previous reconnaissance stream sediment geochemical survey in the larger region comprising the district had selected areas that correlate well with these zones as the more prospective for metallic mineralization. Also, pedogeochemical surveys in the district revealed plausible areas underlain by rocks most likely contain different metallic mineralizations that synchronize well with these promising zones. Geological mapping and preliminary lithogeochemical survey in these zones have unveiled uranium bearing pegmatite in the northeastern zone; gold bearing marble deposit and iron oxide-copper-gold-silver mineralized silicified sheared rock along the central zone; and lead-zinc mineralized metaconglomerate in the southwestern zone. Ample geological studies of these mineralized rocks are recommended.

An extensive dataset of major- and trace-element and B-isotope composition related to the compositional variation of the tourmalines from the S-type granite and pegmatite from the Upper Bonai and Gangpur Group granitoids, eastern India, is provided. The Gangpur Schist Belt, consisting of the Upper Bonai and Gangpur Group, lies at the eastern end of the Proterozoic Central Indian Tectonic Zone. An attempt to constrain the source of the boron isotope and describe the magmatic–hydrothermal evolution of the granite–pegmatite system is made. The tourmalines record generally low trace-element concentrations, with the exception of some elements such as Zn, Li, Ga, Mn and Ti. The Zn and Li concentration increases from the tourmalines in the granites to the tourmalines in the pegmatite. Trace-element compositions also vary slightly from the core tourmaline to the rim tourmaline. Tourmalines in granites/pegmatites are mostly Fe-rich schorl, and have S-type B-isotopic signature (δ11B = −10‰ to −12‰). Their chemistries reflect changing salinities of the granitic melts as well as vapour exsolution during progressive crystallization. This study indicates that the tourmalines in the pegmatites crystallized from evolved flux-element-rich (F, B, Li) melt, probably after the crystallization of granite-forming melt.

This study was carried out in the Lom series in Cameroon, at the border with Central African Republic, located between the latitudes 5∘30′–6∘ N and the longitudes 13∘30′–14∘45′ E. A multi-scale analysis of aeromagnetic data combining tilt derivative, Euler deconvolution, upward continuation, and 2.75D modelling was used. The following conclusions were drawn. (1) Several major families of faults were mapped. Their orientations are ENE–WSW, E–W, NW–SE, and N–S with a NE–SW prevalence. The latter are predominantly sub-vertical with NW and SW dips and appear to be prospective for future mining investigations. (2) The evidence of compression, folding, and shearing axis was concluded from superposition of null contours of the tilt derivative and Euler deconvolution. The principal evidence of the local tectonics was due to several deformation episodes (D1, D2, and D4) associated with NE–SW, E–W, and NW–SE events, respectively. (3) Depths of interpreted faults range from 1000 to 3400 m. (4) Several linear structures correlating with known mylonitic veins were identified. These are associated with the Lom faults and represent the contacts between the Lom series and the granito-gneissic rocks; we concluded the intense folding was caused by senestral and dextral NE–SW and NW–SE stumps. (5) We propose a structural model of the top of the crust (schists, gneisses, granites) that delineates principal intrusions (porphyroid granite, garnet gneiss, syenites, micaschists, graphite, and garnet gneiss) responsible for the observed anomalies. The 2.75D modelling revealed many faults with a depth greater than 1200 m and confirmed the observations from reduced-to-Equator total magnetic intensity (RTE-TMI), tilt derivative, and Euler deconvolution. (6) We developed a lithologic profile of the Bétaré-Oya basin.