Mineral Zones Research Articles

Insights into the Metallogenesis of the Felsic Volcanic Hosted Mundiyawas-Khera Cu Deposit, Alwar Basin, Western India

Copper and associated gold mineralization in the Mundiyawas-Khera area of western India is hosted by the Proterozoic felsic volcanic rocks of rhyo-dacite composition. Signatures of hydrothermal alteration represented by sericite, epidote, scapolite and carbonates are well observed around the ore mineralization zone. The felsic volcanic rocks with gently to flat sloping REE pattern, variable negative Eu anomaly, intermediate abundances of HFSE and moderate to low Zr/Y anomalies are suggested to be FII, FIIIa and FIV type rhyolite. The felsic volcanic host rock for copper mineralization has a depleted and flat HREE pattern and indicates the crustal source, which is garnet free. Negative Eu anomaly in the rock is probably because of the intracrustal partial melting formed in a rift related environment. The high temperature magmatic activities are probably evolved due to the partial melting of crust at shallow to moderate depths, suggesting an evolved continental crust. The δ13C values of the mineralized carbonate veins range between −10.4‰ and −0.9 ‰ (min = −10.6‰, n = 27), whereas the δ18O values show a range of 16.35‰ to 25.23‰ (min = 21.49‰, n = 27), ideally suggesting a mixed source for the ore bearing fluid. Geological, geochemical and stable isotope data of the Mundiyawas-Khera copper deposit suggest it to be a VMS/VHMS setup and these insights will lead to finding new deposits in the nearby areas, having same stratigraphic horizons and similar lithogeochemical assemblages.

Exploring mineralization zones using remote sensing and aeromagnetic data, West Allaqi Area, Eastern-Desert, Egypt

Wadi-Allaqi district, in the southern part of the Eastern Desert of Egypt, is a historic well-known gold resource that has been exploited since the Pharaonic era. The study area represents the western segment of Wadi-Allaqi, about 220 km southeast Aswan city, Upper Egypt. It covers approximately 4702 km2. Exploring new potential mineralization zones was conducted by integrating the Landsat-8 and aeromagnetic data to map different surfaces of alteration zones and trace shallow and deep mineralized bodies. The corrected Landsat-Operational Land Imager (OLI) bands were processed using the Band Ratio (BR), Crosta, selective for the Minimum Noise Fraction (MNF) transformation, and False-Color Composition (FCC) techniques were used to detect the hydrothermal alteration zones and recognize the different geological units. The enhanced eigenimage (MNF1) was processed to delineate the fractures and weakness zones over the west Allaqi-Heini Suture (AHS). The shallow residual mineralized sources have been detected and mapped using the Tilt Derivative (TDR), First Derivative (FVD) and high pass filter techniques of aeromagnetic data. The depths to the mineralized magnetic sources, and hence the roots of gold and other minerals, were obtained using the power spectrum and Euler techniques. Accordingly, new gold and mineralization potential zones were successfully delineated over the study area's ophiolitic, metavolcanics, and granitic rocks. Lineaments deduced from aeromagnetic and remote sensing data represent the pathways of the ascending hydrothermal fluids. The main trends of the dominant structural systems were detected through the statistical analyses of these lineaments.

Automatic detection of geological lineaments in central Turkey based on test image analysis using satellite data

The Hamurcu and Başdere study areas, part of the Central Anatolian Volcanic Provence (CAVP), are associated with metalliferous ore deposits. The assumption that hydrothermal alterations might be related to faults and fractures makes mapping the lineaments around the study areas vital. Accordingly, geological lineaments in the vicinity of the studied areas in Central Anatolia (Turkey) were delineated using Landsat-8 and Phased Array type L-band Synthetic Aperture Radar (PALSAR) data. We adopted a new methodology for determining the optimal values of six parameters used in a fully automated extraction of lineaments. The lineaments identified in the region including the study areas strike mainly the NW-SE direction in the PALSAR data. Moreover, hydrothermal alterations around the towns of Hamurcu and Başdere are directly related to the NW-SE oriented faults, indicating that the lineations in the region might be carefully scrutinized in the exploration of mineralization zones. As a result, it was demonstrated in this study that the most appropriate parameter values specified for automatic lineament extraction successfully map geological structures around both study areas and can confidently be employed in different geographical locations.

MAPPING THE MINERAL ZONATION AT THE ERNEST HENRY IRON OXIDE COPPER-GOLD DEPOSIT: VECTORING TO Cu-Au MINERALIZATION USING MODAL MINERALOGY

Abstract Iron oxide copper-gold (IOCG) deposits form in spatial and genetic relation to hydrothermal iron oxide-alkali-calcic-hydrolytic alteration and thus show a mappable zonation of mineral assemblages toward the orebody. The mineral zonation of a breccia matrix-hosted orebody is efficiently mapped by regularly spaced samples analyzed by the scanning electron microscopy-integrated mineral analyzer technique. The method results in quantitative estimates of the mineralogy and allows the reliable recognition of characteristic alteration as well as mineralization-related mineral assemblages from detailed mineral maps. The Ernest Henry deposit is located in the Cloncurry district of Queensland and is one of Australia’s significant IOCG deposits. It is known for its association of K-feldspar altered clasts with iron oxides and chalcopyrite in the breccia matrix. Our mineral mapping approach shows that the hydrothermal alteration resulted in a characteristic zonation of minerals radiating outward from the pipe-shaped orebody. The mineral zonation is the result of a sequence of sodic alteration followed by potassic alteration, brecciation, and, finally, by hydrolytic (acid) alteration. The hydrolytic alteration primarily affected the breccia matrix and was related to economic mineralization. Alteration halos of individual minerals such as pyrite and apatite extend dozens to hundreds of meters beyond the limits of the orebody into the host rocks. Likewise, the Fe-Mg ratio in hydrothermal chlorites changes systematically with respect to their distance from the orebody. Geochemical data obtained from portable X-ray fluorescence (p-XRF) and petrophysical data acquired from a magnetic susceptibility meter and a gamma-ray spectrometer support the mineralogical data and help to accurately identify mineral halos in rocks surrounding the ore zone. Specifically, the combination of mineralogical data with multielement data such as P, Mn, As, P, and U obtained from p-XRF and positive U anomalies from radiometric measurements has potential to direct an exploration program toward higher Cu-Au grades.

3D zoning of barium in alkali feldspar

Abstract Interpretation of chemical zoning within igneous minerals is critical to many petrologic studies. Zoning in minerals, however, is commonly observed in thin sections or grain mounts, which are random 2D slices of a 3D system. Use of these 2D sections to infer 3D geometries requires a set of assumptions, often not directly tested, introduces several issues, and results in partial loss of zoning information. Computed X-ray microtomography (microCT) offers a way to assess 3D zoning in minerals at high resolution. To observe 3D mineral zoning using microCT, however, requires that zoning is observable as differences in X-ray attenuation. Sanidine, with its affinity for Ba in the crystal lattice, can display large, abrupt variations in Ba that are related to various magma reservoir processes. These changes in Ba also significantly change the X-ray attenuation coefficient of sanidine, allowing for discrete mineral zones to be mapped in 3D using microCT. Here we utilize microCT to show 3D chemical zoning within natural sanidines from a suite of volcanic eruptions throughout the geologic record. We also show that changes in microCT grayscale in sanidine are largely controlled by changes in Ba. Starting with 3D mineral reconstructions, we simulate thin-section making by generating random 2D slices across a mineral zone to show that slicing orientation alone can drastically change the apparent width and slope of composition transitions between different zones. Furthermore, we find that chemical zoning in sanidine can commonly occur in more complex geometries than the commonly interpreted concentric zoning patterns. Together, these findings have important implications for methodologies that rely on the interpretation of chemical zoning within minerals and align with previously published numerical models that show how chemical gradient geometries are affected by random sectioning during common sample preparation methods (e.g., thin sections and round mounts).

A numerical experiment for geological sequestration of CO[formula omitted] in the pre-Comondú sandstones of Las Tres Virgenes geothermal area, Baja California Sur, Mexico

The most recent studies on geological sequestration of CO2 in Mexico point towards high sequestration potential associated with geologically stable zones and high-emission centres. These studies overlook however, the potencial that high heat flow areas in the country can offer to geological sequestration of CO2 by mineral precipitation. Here we present an assessment of the CO2 sequestration capacity of the Pre-Comondú sandstones, that overlie the productive granitic basement of the Las Tres Virgenes geothermal field (10 MWe). Both, the physical properties and mineralogical description of the sandstone are defined from drilling core analyses reported by the Federal Commission of Electricity. The initial formation water saturating the sandstone is determined by means of a batch simulation of equilibrium between the primary minerals in the rock and a 1 M solution of NaCl in water. Injection of supercritical CO2 is then numerically simulated. Simulations are based on the TOUGHREACT software and the equation of State Module ECO2N. Our results show Pre-Comondú sandstone favour mineralization of CO2 through the precipitation of carbonates in moderate geologic times (100–300 yr). Mineral changes occur within two main zones in the CO2-impacted reservoir, the zone lying close to the injection point is dominated by precipitation of low-albite, kaolinite, calcite, and minor siderite, whereas the distal zone responds with moderate changes in the system illite-smectite. Changes in porosity are moderate and consistent with the two mineralization zones. Furthermore, the decline in porosity occurs in the long term, which suggests moderate risk for injection operations. Although high reservoir temperature is unfavorable to CO2 solubility, high pressure can counteract this effect, so the system can benefit from higher mass diffusivity and reactivity. This manifests in an accelerated sequestration rate.

Combined satellite and portable XRF exploration mapping of the Zaaiplaats tin field, South Africa

Abstract The Zaaiplaats tin field is host to two of the historically most significant tin mines in South Africa. The geological maps of Zaaiplaats and Groenfontein have not been updated since the 1980s and 1950s respectively and warrant a renewed investigation. Cassiterite is hosted in the Bobbejaankop and Lease granites, of the Zaaiplaats and Groenfontein tin mines, which are part of the Lebowa Granite Suite of the Bushveld Complex. Tin mineralisation is primarily hosted as low-grade disseminations and within networks of high-grade hydrothermal pipes and lenticular ore-bodies. One difficulty in mapping such formations arises from the limited lithological variability between mineralised and unmineralised granitic facies. In order to map the granitic lithologies and discriminate alteration zones, an integrated approach is applied by combining remote sensing and in situ portable X-ray fluorescence (pXRF) mapping. The pXRF large ion lithophile (LIL) element distribution mapping, specifically correlating Rb, Sr and Ba with Sn, points to the concentration of late-stage magmatic-hydrothermal fluids, which are associated with endogranitic mineralisation. The use of the Rb/Ba ratio highlights regions of late-stage magmatic-hydrothermal alteration, effectively delineates granitic facies and identifies zones of potential tin mineralisation. Spectral image processing techniques were used as tools to support the mapping of these granites, their variable degrees of magmatic-hydrothermal alteration and regions of endogranitic disseminated mineralisation. We thus exemplify that an expert-based and synergic approach, combining inexpensive in situ pXRF and freely available satellite remote sensing data, supports the mapping and identification of endogranitic mineralisation in early exploration stages. Furthermore, due to its versatility, this approach can easily be applied to other styles of plutonic mineralisation.

Geological, geochemical and fluid inclusion investigations on the Duna Pb-Ba-(Ag) deposit, Central Alborz, North Central Iran

The Duna Pb-Ba-(Ag) mine is located ca. 155 km north of Tehran in the central Alborz structural zone, northern Iran. The ore mineralization occurs as stratabound, epigenetic, E-W and WSWENE trending veins and veinlets in fracture-controlled as well as massive and open-space filling textures within a Permian dolomitic limestone host rock. Field observations as well as mineralogical and petrographic studies show dolomitization, silicification and possibly haematisation in the host rock. In the mineralization zone, galena and barite are the main minerals, followed by pyrite, quartz, chalcopyrite, tetrahedrite, sphalerite, calcite and supergene minerals such as covellite, malachite, azurite, cerussite, anglesite, and Fe-oxides. The chemical analyses of the highgrade ore samples show an average grade of 18.66 wt. % for Pb, 19.99 wt. % for Ba, and 120 ppm for Ag together with substantial quantities of Zn (0.15 wt. %), As (690 ppm), Cu (0.86 wt. %), Sb (0.25 wt. %), and Sr (0.56 wt. %). The amount of silver in some samples from the tunnel and discordant layers is up to 7030 ppm. The positive Eu/Eu⃰ ratio and the weak negative Ce/Ce⃰ anomaly in the ore samples were most likely inherited from magmatic water. The presence of minerals such as pyrite and chalcopyrite together with the co-precipitation of sphalerite and chalcopyrite suggest a high-temperature for mineralizing fluids. The homogenization temperatures of fluid inclusions from barite in concordant layers span between 135 and 165 ºC with salinities between 18.54 and 23.65 wt. % NaCl equivalent, while the homogenization temperatures of fluid inclusions from barite of discordant layers span between 113 and 285 ºC with salinities between 7.34 and 23.65 wt. % NaCl equivalent. The structural, geological, geochemical, and mineralogical studies together with the paragenesis of the ore minerals and fluid inclusion data allow consideration of the Duna Pb-Ba-(Ag) mine as a two stage mineralization scenario; 1st stage /older/MVT-type (Early Cimmerian tectonic phase), and the second stage/younger/Irish-type (Laramide orogenic movements). The structural data, high temperature of the fluid inclusions, positive Eu/Eu⃰ ratio and high silver content, especially in the discordant layers, indicate the involvement of a magmatic water mixed with meteoric and connate fluids comparable to the Irishtype mineralization in the second stage, which formed along brecciated zones of the thrust faults. The second stage of mineralization was most likely influenced by the Akapol granitoid intrusive mass, which overprinted the 1st stage/older/MVT-type.

Establishing the mining deposit groups and the gold exploration network patterns in the Attapeu area, Lao PDR

This paper initially clarified the context of primary gold mineralization in the Attapeu area, Lao People's Democratic Republic. It proposed the priority for the exploration, using the conventional technique combined with the geological mathematic method. The research essentially summarized that the study area had a complex geological and structural setting; the mineralization zones or gold orebodies most likely formed as a lens shape and/or mineralized single vein or vein zone, extending from a few tens of meters to greater than 500 meters long, within a single dipping angle of 450÷800; the geometric of orebodies likely illustrated as small to medium size. The mineralization zone significantly extended following the geological setting, indicating consistent to the strongly inconsistent group (Vm = 8.9÷116.8%). Medium- to high-grade gold ores are commonly found in each ore body and identified as a homogeneous to strongly inhomogeneous group (Vc = 58.3÷785%). Regarding the exploration criteria, exploring primary gold mineralization in the Attapeu area fits well with the mineral exploration group III. To estimate the ore reserve in category 112 significantly requires conducting the parallel exploration grid or rectangular grid with the exploration grid interval of 40÷60 meters within the space of the exploration grid line between 20 to 30 meters. The exploration guidelines proposed in this research are efficiently applicable for exploring other primary gold mineralization elsewhere with the geological settings and mineralogical characteristics identically to the primary gold mineralization in the Attapeu area.

Diagenetic barite-calcite-pyrite nodules in the Silurian Longmaxi Formation of the Yangtze Block, South China: A plausible record of sulfate-methane transition zone movements in ancient marine sediments

The sulfate-methane transition zone (SMTZ) serves as an important geochemical transition especially during early diagenesis. Organoclastic sulfate reduction (OSR), sulfate-driven anaerobic oxidation of methane (SD-AOM), fermentation, and methanogenesis, the dominant diagenetic processes near the SMTZ, play key roles in marine sulfur and carbon cycling. However, the paleo-SMTZ has rarely been identified in the geologic record because of equivocal evidence. The presence of barite-calcite-pyrite assemblages (abundant nodules and pyritic laminae) concentrated over a 1-m thick interval of the Silurian Longmaxi Formation, Yangtze Block, South China, provide a unique opportunity to investigate possible vertical movements of the paleo-SMTZ in ancient sediments. The inferred paleo-SMTZ comprises nodules made up of barite (BaSO4), calcium carbonate (CaCO3), and pyrite (FeS2), and pyritic laminae. Strong 34S enrichment of barite (50 to 62.1‰ VCDT) and modestly 13C-depleted calcite (−11.4‰ to −5.3 VPDB) of the nodules associated with positive δ34S values of pyritic laminae (4 to 6.2‰ VCDT) suggest precipitation of these minerals sourced by mixed carbon and sulfur sources close to and/or within the paleo-SMTZ. Nodules from center to edge display mineral zonation that may reflect the effects of depth fluctuations of the paleo-SMTZ. Initial (stage 1) barite mineralization in nodule centers appears to have occurred within the base of the sulfate reduction zone (SRZ). By the time if stage 2 mineralization, the stratigraphic locus of precipitation had migrated closer to highly alkaline SMTZ resulting in barite dissolution and calcium carbonate precipitation. Higher proportions of calcium carbonate exhibiting some enrichment of 12C associated with cubic pyrite crystals in nodule centers are consistent with the occurrence of SD-AOM within the SMTZ. Stage 3 acicular barite mineralization along nodule edges likely took place near at the base of SRZ immediately above the SMTZ, whereas the replacement of barite by calcite during stage 4 mineralization occurred again within the SMTZ. Vertical movement of paleo-SMTZs suggested by the occurrences of barite-calcite-pyrite assemblages in the Longmaxi Formation across Yangtze Block, are likely the consequence of the complex interplay of varying sedimentation rate, organic matter quality, methane flux, and perhaps seawater sulfate concentration.

Spatial distribution of heavy metals contamination in sediments of alpine lakes and potential risk indices, Northern Pakistan

ABSTRACT The current study worked on heavy metals concentrations in sediments of the alpine lakes in Gilgit-Baltistan, Northern Pakistan. Sediments samples (n = 41) from alpine lakes: Sadpara Lake, Rama Lake, Upper Kachura Lake, and Shausar Lake were collected. Sediments samples were digested according to standard protocol and analysed by atomic absorption spectrometry. Among heavy metals, Mn exhibited the highest mean concentration (333 mg/kg) in the sediments of alpine lakes, while Cd showed the lowest (1.48 mg/kg). The Ni, Cu, Cr, Mn, and Zn showed the highest mean concentrations in Sadpara Lake compared to other lakes. Sediments heavy metals concentrations were used for the calculation of pollution factors of alpine lakes, such as contamination factor (CF), pollution loads index (PLI), and ecological risk assessment (ERA). Among alpine lakes, the Sadpara Lake showed the highest PLI and CF values for most of the heavy metals. However, the highest mean (74.2 and 104) values of ERA and risk index (RI) were noted in the Rama Lake and exhibited a low-level risk to the alpine lake’s system. Statistical analyses showed that weathering of bedrock and rich mineralised zone in the vicinity were dominating contributors of heavy metals contaminations.

Towards a deeper understanding of the third millennium BC Iranian metallurgy: Use of synchrotron light for characterizing arsenic‐bearing minerals in metal objects from Espidej

New excavations at Espidej at the Kerman Province of the Halil Basin corridor in Iran offer a unique opportunity to reconsider the third millennium BC (i.e. Bronze Age) metallurgical practices related particularly to arsenical copper (Cu‐As) alloying and to explore arsenic‐bearing raw materials. This paper presents results of optical microscopy and environmental scanning electron microscopy (ESEM) on a selected group of copper‐based artefacts from Espidej. Additionally, we have benefited from synchrotron light for further investigations on a dagger sample. The scientific examinations on metal corpora adds new information regarding the microchemistry and production techniques of metals of the south‐eastern cultural zone of Iran. Synchrotron micro X‐ray diffraction (SR‐μXRD) data of the sample demonstrates traces of arsenic‐bearing minerals in the corrosion products indicative of types of ores used in alloying processes. Preliminary research on copper ores indicates possible extraction of local ore deposits that were outcropped along the south‐east Makran orogeny zone of Iran. This area is part of hydrothermal mineralization zone consisting of arsenopyrite (FeAsS), sinnerite (Cu6As4S9), bornite (Cu5FeS4) and algodonite (Cu6As). Noticeable arsenic‐bearing phases within the metallic core of the sample were frequently characterized as sinnerite and algodonite.

Analysis of structure and material in the southwest of the Talnakh ore cluster

The issues of metallogenetic modeling of ore-forming systems for search purposes when studying sides and deep horizons of the mined deposits are considered. The object of the study is the geological and geochemical conditions of ore accumulation of various mineral composition and the concentration of useful components in various sections of the Talnakh ore-forming system. Mineral and geochemical zoning of the deposits reflect the degree of contamination of primary silicate and magmatic melts with crustal material. On the western and southern sides of the ore-forming system, ore mineralization is represented by low-sulfur associations of chalcopyrite minerals and is specialized in Cu–Ni–Co. The geochemical analysis of isotopes δ34S, 40Ar/36Ar, δ65Cu, 87Sr/86Sr suggests that the process of ore formation on the sides of the Talnakh ore cluster occurs under intense influence of the crust (sulfur source evaporite rocks) and near-surface water on the fluid in melting-fractionated sulphide magma enriched with copper, which results in the formation of chalcopyrite ore.

Detection of alteration zones using the Dirichlet process Stick-Breaking model-based clustering algorithm to hyperion data: the case study of Kuh-Panj porphyry copper deposits, Southern Iran

Detection of hydrothermal alteration zones (HAZs) associated with porphyry copper systems using remote sensing imagery is a crucial stage for discovering high potential zone of ore mineralization. Statistical model-based clustering methods have great potential for automatic and accurate detection of hydrothermal alteration minerals using hyperspectral remote sensing imagery. In this research, the Dirichlet Process based on Stick-Breaking (DPSB) model-based clustering algorithm was implemented to hyperion remote sensing imagery to discriminate HAZs associated with the Kuh-Panj porphyry copper deposit, south, Iran. The DPSB clustering algorithm was implemented and subsequently compared with the k-means algorithm, CLARA clustering, hierarchical clustering, Gaussian finite mixture model (GFMM), Gaussian model for high-dimensional (GMHD) and spectral clustering as well as spectral angle mapping (SAM). Results derived from the DPSB model-based clustering algorithm show 88.6% accuracy in distinguishing propylitic, argillic, advanced argillic, propylitic-argillic and phyllic alteration zones. The DPSB algorithm can be broadly implemented to hyperspectral remote sensing imagery for detecting alteration zones associated with porphyry systems.

Analysis of VLF-EM Data for Potential Cassiterite Mineralization Delineation Zone in Rafin-Bareda Area North-Western Nigeria

VLF-EM geophysical technique was employed to delineate potential cassiterite mineralization at Rafin Bareda, Dutsen-Wai, Kubau Local Government area of Kaduna state, North Western, Nigeria. A total area of 3.025 km2 was covered along eleven (11) traverses separated by 25 m with a measurement interval of 10m taken in the East-West direction. The response of the in-phase component revealed various anomalous zones while Fraser-filtered plots of the in-phase peaked over the anomalous zones and the Karous-Hjelt filtered response of the in-phase correlates quite well with the results of the Fraser filtered data. In order to achieve the aim of the investigation, and since the VLF data was collected in the magnetic mode, enhancement procedures such as reduced to equator and analytical signal techniques were applied to the Fraser Filtered response of the In-phase component and correspondingly, Center for Exploration Targeting (CET), Source Parameter Imaging and Euler Deconvolution algorithms of the Oasis Montaj were successively employed to delineate potential mineralization zones and best locations for drilling productive cassiterite in the study area. Enhanced maps show linear features trending in the NE-SW and NW-SE directions with minor traces in the N-S direction. Most of the delineated zones of high analytical signal signature were either intercepted or flanked by the extracted lineament which is indicative of positive correlation between the extracted lineament and the high amplitude response of the analytical signal and also, validated the occurrence and positioning of the cassiterite mineral deposits is greatly controlled by the lineament system across the study area and the development of conductive zones of high apparent current with positive values reflects inferred subsurface structural fractures and/or mineralized zones. Depths evaluation analysis from the Euler Deconvolution (ED) technique using structural index of 1, ranged from 5 m to 15 m while depths varying from 4.9 m to 13.7 m were obtained from the Source parameter imaging technique.

Mapping carbonate-hosted Pb-Zn mineralization zones in Yahyali Province (Eastern Taurus - Turkey) using ASTER data

The first record of the carbonate-hosted Pb-Zn deposits in Turkey dates back to the Roman period. The carbonate-hosted Pb-Zn deposits in Turkey are economically important and found in the Aladağlar - Zamantı Province. Mineral exploration and geological mapping through the utilization of the traditional geological method still remain very challenging in many high terrains (High mountains). In this study, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) remote sensing data were used for mapping the carbonate-hosted Pb-Zn deposits in the Yahyali region of Turkey. The Band Ratio (BR), Least square fitting methοd (Ls–fit), Band Ratio Color Composite (BRCC), and Principal Cοmpοnent Analysis (PCA) were used tο map the Pb-Zn mineralization zone. The results of this investigation show the spatial distribution of Fe-Mg – OH/CO3, hydroxyl-bearing and iron oxide minerals. Field work and laboratory analysis were carried out to verify the occurrence of alteration zones and highly prospective locations and to confirm the availability of alteration and potential zones of carbonate-hosted Pb-Zn mineralization in the study area. Spatial correlation and distribution were observed between the previous geological map, active and abandoned mines, and the result obtained from the remote sensing data. Different techniques applied to the Aster data image in this study are recommended fοr carbonate-hosted Pb-Zn and lithological mapping in hostile terrains.

ГЕОХИМИЧЕСКИЕ ОСОБЕННОСТИ САМОРОДНОГО ЗОЛОТА ЮГЛЕРОВСКОГО РУДНО-РОССЫПНОГО ПОЛЯ (СЕВЕРО-ВОСТОК РОССИИ)

We have used the “Leader” and “PROFILE” software programs to analyze spectral study results for 242 native gold samples from lode deposits and placer relics of the Yugler mineral district. The Yugler black shales host gold mineralization characterized by the geochemical specialization in lead and copper, which assigns it to the style of gold mineralization at the Degdekan deposit but distinguishes it from the majority of similar deposits in Russia and abroad. Native gold in ore bodies and placers displays a distinct geochemical specialization. Native gold from ore bodies is high in As, Bi and Pb, from the Yugler placer in Cu, Pb, Fe and Mn, and Spokoiny and Matrosov’s placers in Sb and Ag. Vertical zoning of mineralization manifests itself as low-grade antimonious grains of native gold in eroded parts of the sequence and high-grade bismuth-lead-arsenious grains in its preserved parts. The mineral-geochemical formation model of the Yugler lode-placer district is a space-time succession of copper-polymetallic mineral assemblages replaced by arsenic-bismuth-polymetallic and then by silver-antimony-polymetallic assemblages. Antimonious mineral assemblages were most abundant in the southwest of the ore field.

Identification of Gold Mineralization Zones Using Magnetic Data at Gunung Gupit Area, Magelang, Central Java

Indonesia is one of the biggest gold producing countries in the world. the discovery of new gold reserves makes the passion of the gold mining industry increase. The Gunung Gupit area of Magelang Regency in Central Java has discovered new gold potential, but has not been thoroughly explored. The magnetic method is applied to identify and determine the distribution of the presence of gold mineralized zones based on the magnetic properties of rocks. A total of 1001 points on 41 magnetic line were acquired using Proton Precession Magnetometer (PPM) Geometrics model G-856 in an area of 2.5 km2. Field data is obtained as Magnetic Field Anomaly. Reduction to pole (RTP) and low-pass filter process is applied to the magnetic anomaly. The results showed the Gunung Gupit area was divided into 4 zones based on magnetic anomaly responses, i.e strong, medium, weak anomaly and igneous rock zones. The 2.5 D modeling result shows the presence of northwest-southeast normal fault and strike slip fault that is perpendicular to the normal fault. These faults control the hydrothermal alteration in Gunung Gupit and its surroundings. A strong mineralization zone lies between these two faults. The presence of gold and other metal minerals lies in this strong mineralization zone, and moderate alteration. The coverage area is quite wide and distributed along the two faults.

An Application of Remote Sensing Imagery for Geological Lineaments Extraction over Kaybarkuh Region in East of Iran

Kaybarkuh (Mount Kaybar) consists of intrusive igneous bodies with two age periods, located in North of Dasht-e-Bayaz left-lateral fault terminal. The spatial and structural analysis of fractures and dike networks may allow for the accurate identification of mineralization zones in the area. This study aims to characterize lineament network in the study area by automatic method using multispectral satellite images from Landsat 8 Operational Land Imager (OLI), visual extraction of lineaments from Landsat-8 and SENTINEL-2 images, and extraction of drainage network as lineament based on digital elevation models (DEMs) and their validation, compared with fault network of the area. The results showed that there is a significant relationship between the trend of studied lines in the region by the three methods mentioned and the overall trend is about N330⁰. This can indicate a tensile regime with a trend perpendicular to the mentioned orientation, which results from the activity of the Dasht-e-Bayaz fault. Finding more evidences requires further studies.

Three-Dimensional Audio-Magnetotelluric Imaging including Surface Topography of the Cimabanshuo Porphyry Copper Deposit, Tibet

Cimabanshuo deposit is a newly discovered porphyry copper (Cu) deposit with giant metallogenic potential, found in the western segment of the Gangdese metallogenic belt, Tibet. The average elevation of the deposit is greater than 5500 m and the terrain on which it is found is steep and complex. Therefore, it is untraversed, and the existing exploration works on it are weak. We used 59 AMT sites belonging to an array covering the main, proven mineralization zone and ore bodies of this deposit for an analysis of its underground electrical structure. Dimensionality and strike analysis revealed the apparent three-dimensional (3D) features near the Cu ore bodies. 3D inversion with topography was conducted for the AMT array data. A large range of high-resistivity anomaly (~500–2000 Ωm) appears beneath the proven Cu mineralization zone and ore bodies, which is interpreted as intrusive rocks with potassic alteration. Although containing chalcopyrite, it is characterized by middle–high resistivity due to a low sulfide content and poor connectivity. Moreover, a series of scattered conductors (~10–300 Ωm) around the Cu ore bodies are distributed in the shallow layer from near the surface to ~200 m, possibly indicating phyllic alteration containing pyritization and connected metal sulfides. The proven ore bodies of Cimabanshuo are mainly located at the junction regions between high-resistivity intrusive rocks and high-conductivity sericitization alteration zones. According to this research, the 3D inversion with topography of AMT data can visually display the 3D distribution of intrusive rocks and alteration zones beneath porphyry Cu deposits in high-elevation regions, and provides a reference for further exploration works.