Mineral Occurrences Research Articles

Study of the Distribution of Rare-Earth Elements and Strontium in Apatite from Rocks of the Vuoriyarvi Carbonatite Complex by Total-Reflection X-Ray Fluorescence Spectrometry (TXRF): First Results and Prospects

Abstract —We have studied the trace element composition of apatite from several varieties of carbonatites and associated apatite ores of the Vuoriyarvi alkaline-ultrabasic carbonatite complex (Kola region, northwestern Russia), which hosts several commercial deposits of apatite–magnetite and pyrochlore ores and large-scale unexplored rare-earth mineral occurrences. The composition of apatite was analyzed by total-reflection X-ray fluorescence spectrometry (hereafter, TXRF). Verification of the obtained results was carried out by ICP-MS analysis of weighed portions of apatite monomineral samples. It is shown that during the evolution of the Vuoriyarvi carbonatites and associated apatite–magnetite ores, the contents of Sr and rare-earth elements (REE) and the degree of REE fractionation in apatite synchronously increased. The obtained TXRF data on the composition of apatite in the carbonatite complex demonstrate the efficiency of TXRF and its high potential in both applied and fundamental research concerned with apatite of various geologic objects.

Remote sensing of desertification and study of temporal variability of aeolian deposits in parts of the Arabian Desert for sustainable development in an arid environment

Aeolian deposit in part of the Arabian Desert is mapped using ASTER data to understand desertification, land encroachment, and degradation, and to assess agricultural development in arid regions. In this study, the interpretation of emissive spectra of sand deposits showed the presence of triplet absorptions in emissivity between 8 and 9.50 μm and studied with ASTER spectral bands to map the deposits. The ASTER quartz index (QI) images used to study the Abu Samra region, Qatar from 2000 to 2021 showed significant changes in desertification and land degradation. Analysis of temporal variability of deposits between 2000 and 2021 using ASTER band 12 by Parallelepiped image classification showed a decreasing trend from 9.70% to 2.94% in their distributions due to erosion and transportation. The changes are studied using FCC images (R:1; G:2; B:3) and hill-shaded images of 2000 and 2021. The results are confirmed from FCC (R:14; G:12; B:11) and Google Earth satellite images which showed the occurrence of sabkhas in 1985 and their disappearance from 2015, and the presence of agriculture in 2000 and their absence from 2005. The changes in desertification, land degradation, and agricultural development are verified in the field and evidenced. The grain size analysis of samples by ASTM method showed aeolian deposits have very fine to very coarse (63–2000 μm) sand types with silts of <3%. The samples analyzed by XRD and SEM-EDX methods showed the occurrence of dolomite, calcite, quartz, feldspar, and gypsum minerals with high sphericity and sub-angular to well-rounded characters and suggested transportations of grains from long distances. The geochemical elements analyses of samples reflected the chemistry of carbonates, aluminosilicates, and evaporites minerals which could have been derived from the carbonate, shale and sandstone formations, and sabkhas that occurred in Qatar and the Arabian Peninsula.

Spatial Relations between Geological Structures and Precious and Base Metal Deposits from Magnetic Investigation of the Pangar-Djérem Zone, Cameroon

The version three of Earth Magnetic Anomaly Grid (EMAG2-v3) used in this work is aimed at establishing the spatial relationships between tectonic structures and gold and associated mineralization in the Pangar-Djérem area, central and southern Cameroon. Various processing and transformation of image data such as the reduction to the equator, horizontal gradient, generalized derivative, and pseudogravity allowed the identification and delineation of numerous faults related to Syn-D1, Syn-D2, and Syn-D3 deformations. The main orientations, W-E, SW-NE, and SE-NW, obtained from these faults define the intensity of the Pan-African and Eburnian tectonics in the Cameroonian basement. Correlations between mapped faults and mineral occurrences define a structural control of gold mineralization in the study area. Furthermore, the spatial relationships between these faults and the igneous/metasedimentary rocks demonstrate that the Eburnian and Pan-African orogenies favoured the circulation of gold-enriched fluids along faults and shear zones. Gold mineralization in the Pangar-Djérem zone is of the vein type (primary gold), resulting from the intrusion of type I granites and the circulation of enriched fluids in a brittle to ductile shear context. The pseudogravity anomalies associated with the sedimentary deposits/rocks and the SW-NE structures of the Sanaga and Bétaré-Oya Faults define an environment of detrital sedimentary deposits, consisting of metavolcanic and metasedimentary rocks, and justify the existence of gold-bearing quartz veins.

Mineralogical mosaics from the Carpathian-Pannonian region 5

Further mosaic-like data were recorded on the mineral occurrences of the Carpathian–Pannonian region in this fifth member of the series arranged by countries and localities. Each “mosaic” contains a concise mineral description, mainly based on XRPD, SEM-EDX and EPMA measurements and a concise description of the mineral paragenesis. Some minerals are first-time descriptions from the entire discussed region, but all are newly documented occurrences for at least the described locality. From Hungary humboldtine and weddellite are described from the coalbed of Csordakút (Bicske), and data from Sr-rich and other Aluminium Phosphate Sulphate (APS) minerals from the ore mineralization of the Lahóca Hill at Recsk are also reported. Chemical data of Mg-rich tourmaline from the Harghita volcanic ridge are given, and also kyrgyzstanite is described from the ore mineralization of Baia Sprie, Romania. From Slovakia Na-containing sulphates (kröhnkite, ferrinatrite, tamarugite) from the ore mineralization of Farbište (Poniky) and an arsenate (bariopharmacosiderite) from the ore mineralization of Rožňava are also introduced.

154 Toward a General Approach to Risk Assessment of Naturally Occurring Asbestos and Asbestos-Like Minerals: the case of Fibrous Antigorite

Abstract The natural occurrence of asbestos and asbestos-like minerals (NOA) poses a risk to the environment and human health, notably when natural processes and anthropic activities promote fibre dispersion. Hundreds of potentially hazardous elongated mineral particles (EMPs, NIOSH 2011 definition) exist, and their toxicological profile is often unknown. We aim here to define a general approach, from field analysis to nano-structural investigation, to assess whether a fibrous mineral occurring in a specific site could pose a risk to human health. To evaluate the hazard associated with NOA, a multi-scale and multi-analytical integrated approach was adopted. Specifically, the geological factors that control the occurrence and distribution of NOA on site, and the mechanisms of formation and liberation of airborne fibres were investigated. In parallel, we explored the key bulk and surface properties of several natural mineral fibres and defined crystallographic, chemical, and morphological aspects that should be considered during hazard assessment. Also, the effect of standardized mechanical stress was used to simulate variation on morphometric parameters of investigated minerals and allowed us to quantitatively evaluate the potency to generate inhalable fibres. This property was connected with the mineral characteristic and the rock fabric. Isolated fibre specimens were used to assess solubility in simulated body fluids, surface reactivity, and toxicological endpoints in vitro and in vivo. Taken together, these findings allowed us to build a multidimensional description of the hazard parameters of a mineral fibre and paved the way for a science-based risk assessment in an unexplored NOA site.

Predicting new mineral occurrences and planetary analog environments via mineral association analysis.

The locations of minerals and mineral-forming environments, despite being of great scientific importance and economic interest, are often difficult to predict due to the complex nature of natural systems. In this work, we embrace the complexity and inherent "messiness" of our planet's intertwined geological, chemical, and biological systems by employing machine learning to characterize patterns embedded in the multidimensionality of mineral occurrence and associations. These patterns are a product of, and therefore offer insight into, the Earth's dynamic evolutionary history. Mineral association analysis quantifies high-dimensional multicorrelations in mineral localities across the globe, enabling the identification of previously unknown mineral occurrences, as well as mineral assemblages and their associated paragenetic modes. In this study, we have predicted (i) the previously unknown mineral inventory of the Mars analogue site, Tecopa Basin, (ii) new locations of uranium minerals, particularly those important to understanding the oxidation-hydration history of uraninite, (iii) new deposits of critical minerals, specifically rare earth element (REE)- and Li-bearing phases, and (iv) changes in mineralization and mineral associations through deep time, including a discussion of possible biases in mineralogical data and sampling; furthermore, we have (v) tested and confirmed several of these mineral occurrence predictions in nature, thereby providing ground truth of the predictive method. Mineral association analysis is a predictive method that will enhance our understanding of mineralization and mineralizing environments on Earth, across our solar system, and through deep time.

Analysis of Groundwater Quality In Areas Surrounding Mining Sites In Kolaka Regency

This rearch was conducted around mining sites is Pomalaa district, Kolaka. Nickel mining activities have an impact on water pollution which can reduce water quality in both rivers and groundwater. The decrease in water quality around the mining area can be caused by the flow of runoff from rainwater which carries soil particles to water bodies which makes the water cloudy and may contain heavy metals. This study aims to determine the quality of the soil around the mining area of ​​Pomalaa District. Sampling of surface water and subsurface water was carried out using the purposive sampling method. The Pollution Index method is used to analyze the level of water pollution. The results of the analysis show that mining activities in the study area do not have a significant impact on decreasing air quality even though some hazardous metal elements are found such as Arsenic (Ar), Khomium VI (Cr+6), Iron , Cadmium, Copper (Cu) and Lead (Pb). The dominant influence is the high content of BOD and DO in the waters which makes several locations of minor occurrences according to the calculation of indexing calculations. Geological factors that play a role in decreasing air quality are morphological, lithological and structura

Evaluation of Kaolin Mineral Emplacement at Amaihe-Ukpor, Anambra Basin, Southeastern Nigeria Using Spatial Layer Electrical Resistivity Tomography

Spatial layer Resistivity tomography was carried out at a Kaolin Mining site in Amaihe-Ukpor of Anambra Basin, southeastern Nigeria. The tomograms were obtained at various depths with the aim of assessing the depths of emplacement of the Kaolin at the site. Firstly, apparent resistivity data Schlumberger-B electrode configuration was obtained from Seventy-five (75) Vertical Electrical Tomography (VES) along 6 transverses at the site. Using the VES data, tomographic plots of spatial distribution of the Kaolin minerals at depths were obtained. Interpreted tomograms showed the occurrence of Kaolin minerals bearing apparent resistivity values in the range of about (900 - 28,900 Ωm) occurrence within the depth range of 0.5 m at layer 2 to 115 m at layer 4 of the site. The tomograms show that layers 2 to 5 indicate traces of the occurrence of Kaolin, layers 2, 3 and 4 particularly showed prominence of the Kaolin. Layers 1 and 6 show no trace of the Kaolin formation enrichment on them. The spatial layer tomograms showed that the prominence of the Kaolin remains at the site occur mostly at the northern and southern zones of the surveyed site. Further mining at the site could lead to tertiary exploitation of the mineral. The site is therefore in threat of gross depletion of the environment. Hence, there is need for suspension of the ongoing extraction of the Kaolin at the site to give room for deposition and sufficient formation of the target mineral.

The occurrence and genesis of HREE-rich minerals from the giant Bayan Obo deposit, China

The carbonatite-related Bayan Obo deposit, China is the largest REE resource in the world. This deposit has long been a major light REE (LREE) producer, with heavy REE (HREE) rarely exploited. In order to better understand the occurrence of HREE in the deposit, this paper conducts a study of HREE-rich minerals at Bayan Obo. Overall, four types of HREE-rich minerals are identified, including fergusonite-group mineral [(Y, REE)(Nb, Ta, Ti)O4], samarskite-group mineral [(Y, REE, Fe)2(Nb, Ta, Ti)2O8], aeschynite-group mineral [(Y, REE, Ca, Th, U)(Nb, Ta, Ti)2O6], and a type of unknown Pb-rich mineral. These minerals have HREE contents varying from 3.4 wt% to 46.4 wt%, mostly between 19.7 wt% and 34.3 wt%. Yttrium, Dy and Gd are the major REE constitute. Textual relations indicate that the HREE-rich minerals were mainly precipitated from carbonatite-related fluids, with small amounts of grains crystallized from the carbonatitic magma or deposited from post-ore modification fluids. The HREE-rich minerals occur in close temporal and/or spatial association with LREE minerals (e.g., monazite and bastnäsite), so formation of these HREE-minerals does not mean strong LREE-HREE fractionation during the ore-formation or post-ore modification process. Given that certain niobium oxides strongly prefer HREE relative to LREE in the mineral structure, a local physiochemical environment that allowed for the deposition of niobium oxides may be significant for efficient HREE deposition. Although HREE-rich minerals are not widely present in the deposit, they tend to occur as clusters in places. To determine what proportions of HREE can be hosted in the HREE-rich minerals, the weight proportions and REE contents of major REE-bearing minerals were measured in three representative ore samples. The results show that ∼ 25–57 % HREE can be hosted in fergusonite, samarskite, and/or aeschynite. Therefore, the newly identified HREE-rich minerals are non-negligible targets for future exploitation of HREE in the Bayan Obo deposit.

Distinct pumice populations in the 74 ka Youngest Toba Tuff: Evidence for eruptions from multiple magma chambers

Whether the magma storage system is responsible for the formation of the 74 ka Youngest Toba Tuff (YTT) is still debatable. It is currently believed that the YTT super-eruption was formed either by a single voluminous chamber or by multiple magma chambers. This paper presents a detailed component analysis of eruption products, comprehensive stratigraphy, mineralogy, and geochemistry of phenocrysts and matrix glass to shed light on the issue. Based on the componentry, mineral assemblages, mineral and glass compositions, and vesicle texture, we identified four distinct pumice types: YtA–YtD. Of these, YtA is an amphibole-bearing pumice containing an average of 77.1 wt% SiO2. This type of pumice is characterized by abundant matrix vesicles, with plagioclase showing a wide range of anorthite content (An20–An90) and disequilibrium texture. The YtB and YtC types are the most evolved pumices, with 77.5 and 77.6 wt% SiO2, respectively. The plagioclase of these pumices commonly has an unzoned texture with low anorthite content (~An30). The YtB pumice is biotite-bearing, distinctively characterized by abundant pheno-vesicles; while the YtC pumice includes rare pheno-vesicles, skeletal-polyhedral quartz, and no biotite. The YtD type is a quartz- and sanidine-free pumice, with a less-evolved glass composition (76.3 wt% SiO2), and is characterized by dominant matrix-vesicles and crystal clots of plagioclase, amphibole, pyroxene, and biotite. The plagioclase of the YtD pumice shows a hollow texture and high anorthite content (~An50). In situ trace element analysis for the matrix glass of YtA, YtB, YtC, and YtD showed very distinct geochemical signatures, which correlated with the four pumice types. Bivariate plots (Ba vs. Y, Sr vs. Y, and Ba vs. Sr) showed that YtA pumice is characterized by medium Ba (400–875 ppm) and Sr (41–67 ppm), and variable Y (20–53 ppm) content. YtB and YtC pumices are characterized by low Ba (8–136 ppm) and Sr (13–37 ppm), and highly variable Y (27–77 ppm) content. YtD pumice is characterized by high Ba (1173–1340 ppm) and Sr (95–124 ppm), but a narrow range of Y (21–31 ppm) content. The trace-element geochemical signatures, occurrence and absence of certain minerals (i.e., biotite and quartz), and vesicle type from the distinct pumice type, suggest the presence of four distinct magma bodies before the eruptions, namely YtA, YtB, YtC, and YtD. The number of distinct glass shards and pumices with the same geochemical signatures represents the volume fraction of each magma type. The approximate total volume of the magma (5300 DRE km3) and the geographical distributions of each pumice type demonstrated that the voluminous YtA (3406 km3), medium YtB (1354 km3), and smallest YtD (168.5 km3) chambers in the northern direction, and the small YtC chamber (371.5 km3) in the southern caldera, were evacuated during the 74 ka YTT eruption. Eruptions from multiple magma chambers were initiated by a high supersaturation of pheno-vesicle-rich magma (YtB magma), triggering the subsequent eruptions of the YtA, YtB, YtC, and YtD magmas.

Provenance and transport mechanism of gravity core sediments in the deep-water area of the Qiongdongnan Basin, northern South China Sea

Reconstructing the role of provenance and transport mechanism of sediments deposited in deep-water environments is often complex because of myriad of factors such as variability in sediment sources, tectonics, bottom morphology, climatic changes and sea level fluctuations as well as current regime. The South China Sea (SCS) is situated at the tectonic intersection of the Pacific, Eurasian, and Indo-Australian plates, and provides an excellent natural laboratory for understanding source-to-sink transport processes of fluvial sediments. The Qiongdongnan Basin (QDNB) is located in the northern part of the SCS, and the deep-water area (>300 m) of the QDNB has a good hydrocarbon source and hydrocarbon accumulation conditions with a tremendous thickness since the late Miocene-Quaternary. However, the complex sources and transport mechanisms of sediments in the QDNB are undefined. In previous study QDNB may have a major provenance or a mixture of sources. In this paper, the sediments of two cores from the deep-water area of QDNB have been analyzed using several sedimentological and geochemical approaches, including measurements of grain size distribution(433 samples), the occurrence of minerals, and trace element geochemistry(37 samples)as well as strontium and neodymium isotopes(20 samples).The granularity analysis results first show that the 19S37 core can be divided into three stages while the 19S40 core is divided into two stages by clear vertical variations in grain size characteristics. Chlorite (62.0%) and Muscovite (33.6%) appear to be the predominant minerals in the 19S37 core, while the mineral assemblage of sediments from 19S40 mainly consists of kaolinite (37.4%), muscovite (29.2%) and chlorite (27.1%). The primitive mantle standardization curves and chondrite standardized distribution patterns of 19S37 and 19S40 are consistent and display enrichments in Th, U, Pb, and Nd and depletions in Ba, Nb, Sr, and Eu. In addition, the content of Sr fluctuates greatly with depth, which should reflect the influences of sea level changes and the relative proportion of various provenance components. The 143Nd/144Nd ratios and εNd values of the sediments from 19S37 are higher than those of the sediments from 19S40, and all the εNd values show narrow variations and range from −10.085 to −11.080. We conclude that the sediments of the deep-water area in the upper Pleistocene-Holocene were mainly from the sources of the Red River, Taiwan, Pearl River, Hainan Island, and Vietnam. The transport mechanism of the sediments from Hainan Island can be explained by the short distance between the source region and the sedimentary site, while the large amounts of terrigenous sediment inputs derived from the Red River and advantageous morphology make the Red River the largest sediment source to cores 19S37 and 19S40. The transport distance and amount of Deep Water Current could be even more powerful to make Taiwan be the second largest source of modern sediments in QDNB.

Application of GOCE Satellite Gravimetric Data For Mineral Exploration

Gravity is directly proportional to density thereby making possible the use of measurable gravity in mapping the density variations in the earth’s interior. The use of density as a means of mineral exploration is cost-effective for wider area coverage. GOCE gravity data, collected by ESA’s GOCE satellite at 255km altitude and 10km intervals leading to the acquisition of multiple gravity points over the globe made possible the application of gravimetry in mineral exploration. Gravity disturbance data sourced from BGI- was corrected with WGM2012 corrections computed using EGM2008 geoid and ETOPO1 models, with reference gravity computed using the Somigliana formula. The gravity disturbances were mapped over Zambia using Surfer and Q-GIS, with over 600 control points of known mineral occurrences plotted together with other surface features like roads, rivers, railways, etc. By relating the control points to the varying gravity disturbances using the triple integral principle, a cautious analysis led to the geological classification of the gravity disturbances which essentially involved mapping predominant mineral occurrences across different parts of Zambia. During ground truthing, it was observed that the results within a particular area of interest on the classified map, and those obtained using four (4) different metal detectors as well as another remote sensing method tallied. The metal detectors used were the GR-100MINI, AKS, AKS plus 3D, and Garrett Ace 400, each with its own characteristics. From the map outputs, the results showed that GOCE data can be used for geological classification and delineation of terrain types. The delineation of terrain types on the classified map output matched that on existing geological maps and also offered the delineation of sub-terrain types.

Geochemical characteristics of sediment and pore water affected by cold seeps in southern South China Sea

Cold seep, characterized by active material circulation and methane seepage, is of great importance to reconstruct the paleo-marine environment and trace the origin of life and the occurrence of minerals. Southern South China Sea (SCS) with ample oil and gas resources is an ideal platform for cold seep study, but information and researches on cold seeps here are rather deficient. We studied the geochemical characteristics of sediment cores and pore water combined with seismic profile information in the Beikang Basin, aiming to further understand the nature of cold seeps in this area. Results show the extremely low δ 13CDIC of pore water in each core and we also found sulfate content decreases with depth, the high content of inorganic carbon (DIC) and the corresponding minimumδ 13CDIC in pore water, the kink-type depth profiles of Sr, Ba and Ni enrichment factors and Sr/Mg in the sediments of BH-CL37, the reducing sedimentary environment constrained by the features of Mo, U and REE. The extremely negative δ 13CDIC in the pore water of the sediment cores indicates strong AOM effect in cold seeps and the main biogenic origin of methane. The SO42- depth variation trends of pore water, the high DIC content and the lowest value of δ 13CDIC can define the approximate SMTZ depth of each sediment core effectively. We thought that fluid fluxes and tectonic settings greatly influence the sedimentary environment and geochemistry, leading to the manifest regional differences in the properties and activities of cold seeps. This study of cold seep in southern SCS proves the variation of cold seep in time and space, stressing the necessity of further region-specific analysis towards different cold seeps; and the complex conditions of SCS do function well in offering multiple types of cold seeps.

Anomalous concentrations of rare earth elements in acid mine drainage and implications for rare earth resources from late Permian coal seams in northern Guizhou

Rare earth elements (REEs) have attracted much attention in recent decades due to their growing applications in high-tech industries. Coal and acid mine drainage (AMD) are considered promising alternative sources due to their high concentrations of REEs. Here, AMD with anomalous REEs concentrations was reported in a coal-mine area in northern Guizhou, China. The AMD had a total concentration as high as 22.3 mg/l, suggesting that regional coal seams may be enriched with REEs. Five segments from borehole samples, which contained coal, rocks from the roof and floor of the coal seam were collected from the coal mine site to investigate the abundance, enrichment, and occurrence of REE-bearing minerals. Elemental analysis showed that the REE contents in the coal, mudstone and limestone from the coal seam roof, and claystone from the floor (all dating to the late Permian) varied greatly, with averages of 388, 549, 60.1 mg/kg and 2030 mg/kg, respectively. Encouragingly, the REEs content in the claystone is over an order of magnitude higher than the average content reported in most other coal-based materials. The enrichment of REEs resources in regional coal seams is particularly associated with the contribution of REEs in the claystone that comprises the coal seam floor, rather than just the coal, as considered in previous studies. The minerals in these claystone samples were dominated by kaolinite, pyrite, quartz and anatase. Two types of REE-bearing minerals, bastnaesite and monazite, were detected in the claystone samples by SEM–EDS analysis, and they were found to be adsorbed by a large amount of clay minerals, mainly kaolinite. Additionally, the results of chemical sequential extraction also confirmed that the majority of the REEs in the claystone samples are mainly in their ion-exchangeable, metal oxide and acid-soluble forms, which are viable prospects for REE extraction. Therefore, the anomalous concentrations of REEs and most of them are in extractable phases, which demonstrates that the claystone from the floor of the late Permian coal seam should be a potential secondary source of REEs. Future studies will further consider the extraction model and the economic benefits of REEs from the floor claystone samples.

Ultrahigh-Pressure Mineral Inclusions in a Crustal Granite: Evidence for a Novel Transcrustal Transport Mechanism

Spherical crystals in minerals from prismatine-bearing rock from Waldheim, including ultrahigh-pressure (UHP) minerals such as stishovite and coesite, were previously described in uncommon crustal environments. To determine if this was an outlier phenomenon, we searched for equivalent inclusions in other rocks, which we indeed discovered in a Variscan tin-bearing granite sensu stricto from the Erzgebirge/Germany. The identification of more examples of this phenomenon implies a novel, very rapid transcrustal transport mechanism, which, however, is not unique. We demonstrate the unusual occurrence of UHP minerals (moissanite, diamond, lonsdaleite, stishovite, coesite, kumdykolite, and cristobalite-II) in topaz the investigated granitic samples, which reflects the direct interaction of mantle and crust via supercritical fluids or extremely volatile-rich melts. Mostly, the UHP minerals we recognized occur as tiny inclusions in moissanite. The trapping by this mineral prevents a fast reaction in an exogenous environment.

Cassiterite geochemistry and U–Pb geochronology of the Shihuiyao Rb–(Nb–Ta–Be–Sn) deposit, Northeast China: Implication for ore‑forming processes and mineral exploration

The Shihuiyao giant Rb deposit in association with Nb–Ta–Be–Sn occurs within the Southern Great Xing’an Range tin belt known for its Sn, W, Cu, Ag, and base-metal deposits. The trace element compositions of four types of cassiterites hosted in the granite, greisen, unidirectional solidification texture (UST) quartz layer, and the hydrothermal quartz vein, respectively (abbreviated as Cst-I to Cst-IV) were measured by laser ablation inductively coupled plasma mass spectrometry and electron probe microanalysis to establish chemical criteria for the application of cassiterite as a useful geological tracer mineral. In situ U–Pb dating of Cst-I, Cst-III, and Cst-IV yielded Tera–Wasserburg intercept ages of 150.3±5.2, 145.8±4.6, and 146.9±3.5 Ma, respectively. These ages are consistent with the previously published monazite and columbite U–Pb ages of 150.2–141.0 Ma for the Shihuiyao ore-bearing granites, indicating a genetic relationship between granite magmatism and Ta–Nb–Sn mineralization. The composition of the studied cassiterites within the whole magmatic–hydrothermal evolution process yields some petrographic dissimilarities and geochemical trends from xenothermal to epithermal environments, which can be used to fingerprint the fluid evolution of the Shihuiyao deposit. For example, the magmatic cassiterites (Cst-I and Cst-II) are strongly enriched in Ta and yield low Nb/Ta ratios compared to the Cst-IV cassiterites from shallow hydrothermal veins. The occurrence of wodginite-group minerals and the highest W concentrations in cassiterite from the UST quartz layers suggests that the main enrichment in W is primarily controlled by magmatic fluid exsolution during the magmatic–hydrothermal transition stage. Additionally, hydrothermal cassiterite is generally lighter in color and characterized by complex internal oscillatory zoning with alternate dark (Cst-IVa) and light (Cst-IVb) bands. Cst-IVa cassiterites have similar W, Nb, and Ta contents but much higher Ti contents compared to Cst-IIIb cassiterites related to primary magmatic fluid, whereas Cst-IVb cassiterites exhibit sharply decreasing W but elevated Ti contents, suggesting pulsed exsolution of magmatic ore‑forming fluids and the involvement of external fluid in a distal open-fluid systems during the late mineralization stage. Therefore, the chemical variations of cassiterites are not only robust tracers pointing to magmatic–hydrothermal centers but also effective in discriminating the primary source of alluvial cassiterite and evaluating its metallogenic potential during a natural heavy mineral survey, supporting the use of cassiterite as an indicator mineral for exploration targeting.

Ultramafic-Hosted Ni-Cu-Co-(As) Mineralization from an Ancient Oceanic Transform Fault Zone in the Troodos Ophiolite, Cyprus: An Analogue for Ultramafic Sea-Floor Massive Sulfide Mineralization?

Abstract Accumulations of sulfide minerals that are enriched in Ni-Cu-Co-(As) occur as sea-floor massive sulfide (SMS) deposits associated with ultramafic rock types on the sea floor and in ophiolite terranes as Outokumpu-type mineralization. In this study we focus on similar mineralization at Lakxia tou Mavrou in the Limassol Forest Complex of Cyprus, which represents the on-land exposure of an oceanic transform fault zone preserved within the Troodos ophiolite. Mineralization here consists of massive lenses of pyrrhotite associated with veins of isocubanite, chalcopyrite, Co pentlandite, and chrome spinel hosted in serpentinized mantle peridotite. We reexamine the field context of mineral occurrences and use in situ mineral chemistry, element mapping, and sulfur isotope ratios (δ34S) to constrain metal sources and provide an updated paragenetic model for Lakxia tou Mavrou. Highly variable S/Se ratios (304–108,571), a depletion in platinum group elements relative to mantle values, and an average δ34S value of –3.7 ± 2.4‰ (1σ, n = 17) in sulfide minerals support a hybrid hydrothermal and magmatic origin for the mineralization. Metals at Lakxia tou Mavrou were sourced from both the serpentinization of peridotites and from crosscutting intrusions, with later intrusions into the already serpentinized mantle lithosphere host providing a heat source to drive prolonged hydrothermal circulation. The reexamination of the field context of mineralization shows that the Ni-Cu-Co-(As) mineralization at Lakxia tou Mavrou originally formed because of the fault-guided intrusion of hot primitive magma bodies into serpentinized shallow mantle lithosphere in the active domain of an ocean-floor transform fault zone. The mineralization was subsequently partially disrupted by structures related to emplacement of the Troodos ophiolite. We show that the relationship between serpentinization, magmatism, and hydrothermal circulation at Lakxia tou Mavrou can be used to understand the formation of ultramafic-hosted SMS deposits in transform fault and other ultramaficdominated slow- and ultraslow-spreading mid-ocean ridge settings.

Delineation of hydrothermal alteration zones associated with mineral deposits, using remote sensing and airborne geophysics data. A case study: El-Bakriya area, Central Eastern Desert, Egypt

El-Bakriya area is situated in the Central Eastern Desert of Egypt. It includes several mineral occurrences and/or deposits. Data from remote sensing and airborne geophysics (gamma-ray and magnetic) were combined to identify the hydrothermal alteration zones and structures related to these occurrences. Various processing of ASTER satellite images revealed fifteen zones of high probability for metallic mineralizations. Airborne gamma-ray spectrometric data clarify K-enrichment zones, which are correlated geologically with the distribution of calc-alkaline, alkali feldspar granites (Younger granites), and calc-alkaline quartzdiorites to granodiorites (Older granites), as well as basement metavolcanics and metasediments. An integrated hydrothermal alteration map was constructed, based on both ASTER remote sensing and airborne gamma-ray spectrometric data. This map delineates some metallic mineral occurrences and/or deposits, which are located in the detected hydrothermal alteration zones. Besides, it displays new potential zones for mineralization, such as: Gabal (G.) El-Shalul, G. El-Bakriya, G. Siwat El-Arsha and G. Umm Bisilla. The geologic and airborne magnetic maps demonstrate five structural lineament trends of E–W, ENE–WSW, NE–SW, NW–SE, and NNW–SSE directions, which might act as pathways to transport the hydrothermal solutions in the study area.

Aeromagnetometric data aplication to investigate the magnetic basement - Caçapava do Sul, RS

The evolution and understanding of the granitic intrusive rock structures in the southern Rio Grande Shield (SRGS) are fundamental to supporting the investigation of mineral occurrences in the state of Rio Grande do Sul, Brazil. This mineral province is classified as complex with igneous, metamorphic, and sedimentary rocks of the Archean to Neopaleoproterozoic age. The main objective of the present study was to investigate the Caçapava do Sul Shear Zone (CSSZ), of which, despite its role as a terrain boundary, its kinematic importance at a regional scale is still questioned. With this objective, aeromagnetometry data were used to enhance the lineaments, trace the domains and estimate the depth of the basement surface related to the formation of the Caçapava do Sul Granitic Complex (CSGS) and consequently the CSSZ. In addition, 3D Euler deconvolution and Source Parameter Imaging (SPI) techniques were applied to estimate the depth of the magnetic basement surface. The 3D Euler deconvolution provided the estimated depth of structural features internal and external to the CSGS. Among the identified features, they include the transcurrent shear zones located at the internal boundaries of the CSGS associated with the tectonic evolution of the granitic body. The joint interpretation of the SPI technique with the 3D Euler deconvolution evidenced the influence of the CSSZ on the magnetic basement, showing even less influence of this feature on its southwestern limits (decrease in the depth of the magnetic basement). This work, through the application of enhancement techniques, evidenced the influence of the Shear Zones on the surface of the magnetic basement. In this way, the results found in this work provide subsidies with greater weights for future geological mappings and studies focused on the evolution of the CSGS.

Regimentation of geochemical indicator elements employing convolutional deep learning algorithm

Recently, deep learning algorithms have been popularly developed for identifying multi-element geochemical patterns related to various mineralization occurrences. Effective recognition of multi-element geochemical anomalies is essential for mineral exploration, and effective recognition is extremely dependent on integral clustering. Deep learning algorithms can achieve impressive results in comparison to the prior methods of clustering indicator elements correlated to mineralization for a region of interest due to their superb capability of extracting features from complex data. Although numerous supervised and unsupervised deep learning algorithms have been executed for the recognition of geochemical anomalies, employing them for clustering geochemical indicator elements is rarely observed. In this research, a convolutional deep learning (CDL) algorithm was architected to recognize and regiment geochemical indicator elements in Takht-e Soleyman District, Iran. Various opinions and experiments were considered to reach optimum parameters of this architecture. Fortunately, the achieved root mean square error (RMSE) values were in the appropriate range (&amp;lt;20%) which display the predicted values of the dependent variables (Pb as a pioneer of the first group and Ag as a pioneer of the second group) through their independent variables that are so close to their actual values. Also, the great R2adj calculated (more than 90%) for the last stage of regimentation confirms impressive accuracy and performance of the convolutional deep learning algorithm for clustering geochemical indicator elements of the study area.