Indicator Minerals Research Articles

Temporal and spatial distribution and genesis of primary indium deposits around the world

Because rare dispersed elements including indium play an increasingly extensive and indispensable role in the field of modern high technology, the exploration, development and research of its resources are in full swing. The abundance of indium in the earth's crust is extremely low, and its original independent deposits have not been found so far. Indium is mainly parasitic in bulk non-ferrous metal deposits in the form of associated by-products. Because of its origin, the genetic types of indium deposits are as diverse as those non-ferrous metal deposits it parasitizes. The distribution of indium in geological time and earth space is uneven. The formation of indium ore deposit is closely related to tectonic-magmatic activity. It is the product of plate tectonic movement, continental rifts and mantle plumes or mantle hotspots in the interior of ancient continents. The emergence of indium ore deposit is inseparable from magmatic activity, especially granite magmatic activity. Ore-forming materials mainly come from the upper mantle and/or deep crust. Indium deposits formed under high temperature conditions have enrichment mechanisms. In addition to the enrichment factors of traditional metal deposits, the enrichment of nano-scale indium minerals through the nano effect is also a very important enrichment method. The indium deposits formed at the end of the differentiation and evolution of granite magma may not be enriched in one go, but is the result of multiple enrichments.

О некоторых особенностях региональной поисковой алмазной минералогии

Analysis of the results of carried out investigations of mantle modules in kimberlite diatremes of main diamondiferous regions of the Siberian platform was made. Morphology and chemistry of garnets, chrome-diopsides, clinopyroxenes, picroilmenites, chromites and chrome-spinellids were investigated. Generally, the quantity of diamond association minerals is proportional to diamondiferousness of certain variety of kimberlite for each type of kimberlite rocks composing pipes. It is stated that comprehensive studying of kimberlites and diamond property are very important, because the diamond is a mineral with a broad complex of physical-chemical and crystal-morphological features, reflecting peculiarity of thermodynamic and geochemical conditions of their formation, which can be used as typomorphic indicators. Detailed complex investigations of diamond and its paragenetic accessory minerals allow establishing material-indicative parameters of kimberlite magmatism of various productivity and geologic-structural position of kimberlite bodies, and address issues about primary sources of placer diamonds, as well. Upgrading the line of research on creation of more efficient ore processing flowsheets and providing crystalintegrity technologies, expansion of diamond application areas with consideration of their real structure and physical features, as well as revelation of natural targets with increased quality of diamond raw material, are all related with investigation of primary indicator minerals of kimberlites.

Reconstruction of the composition and structure of the lithospheric mantle based on the major element composition of garnet and chromium diopside xenocrysts from rocks of the crater part of a kimberlite pipe (the example of the V. Grib pipe, Arkhangelsk diamondiferous province)

The article reports data on the concentrations of the major elements in garnet (1104 grains) and clinopyroxene (238 grains) xenocrysts extracted from rocks of the crater part of the highly diamondiferous V. Grib kimberlite pipe, located within the Arkhangelsk diamondiferous province. All garnet grains were divided into five color groups: violet (35% of the total sample), orange (40%), red (23%), red-orange (<1%) and dichroic (1.3%). The composition of garnets indicates the presence in the lithospheric mantle of lherzolites (39 %), harzburgite-dunites (up to 8 %, including 4 % of potentially diamond-bearing), as well as a significant amount of megacrysts (23 %), low-chromium pyroxenites (up to 19 %), and eclogites (11 %). The temperature varies from 900 to 1200 °С, which is the most common temperature range of diamond stability in the lithospheric mantle rocks, corresponds to 78 % of lherzolite garnets and 88 % of garnets of the harzburgite-dunite paragenesis, including 95 % of “diamond association” garnets. The bestfit geotherm was determined using the software "Gtherm" according to the calculated P-T values of chrome diopside xenocrysts and was consistent with 36.8 mW/m2 surface heat flux. Reconstruction of the structure of the lithospheric mantle indicates the location of garnets of lherzolite paragenesis throughout the entire section of the lithospheric mantle from ~ 80 to ~ 205 km, harzburgite-dunites, including potentially diamond-bearing varieties, mainly in its central and lower parts from ~ 130 to ~ 180 km. The lower boundary of the lithospheric mantle was established at a depth of ~ 230 km. The thickness of the “diamond window” is ~ 85 km. The results of the study showed that kimberlite indicator minerals from the crater parts could be suitable to predict the potential diamond content of kimberlite objects at the drilling stage.

Об особенностях некоторых индикаторных минералов кимберлитовых пород

Analysis of the results of carried out investigations of mantle modules in kimberlite diatremes of main diamondiferous regions of the Siberian platform was made. Morphology and chemistry of garnets, chrome-diopsides, clinopyroxenes, picroilmenites, chromites and chrome-spinellids were investigated. Generally, the quantity of diamond association minerals is proportional to diamondiferousness of certain type of kimberlite rocks composing pipes. Both comprehensive investigation of kimberlites and study of diamond itself are very important, as diamond is a mineral with a broad complex of physical-chemical and crystal-morphological features, reflecting peculiarity of thermodynamic and geochemical conditions of their formation, which can be used as the typomorphic characteristics. Detailed complex investigations of diamond and its paragenetic accessory minerals allow establishing material-indicative parameters of kimberlite magmatism of various productivity and geologicstructural position of kimberlite bodies, and address issues about primary sources of placer diamonds, as well. The presence in kimberlites of definite groups of depth xenoliths and xeno-grains of their minerals, chemical and geochemical composition of kimberlites allowed formulating a concept about properties of upper mantle formations, which are the source of magma for each of distinguished type of kimberlites. The existing point of view that bedding depth of magma chambers roots is the reason of differing productivity of kimberlites is confirmed. As a rule, the roots of commercially productive kimberlites occur at a greater depth than of low productive. Upgrading the line of research on creation of more efficient ore processing flowsheets and providing crystalintegrity technologies, expansion of diamond application areas with consideration of their real structure and physical features, as well as revelation of natural targets with increased quality of diamond raw material, are all related with investigation of primary indicator minerals of kimberlites.

Trends in the Unit Cell Parameter for Kimberlitic Versus Non-Kimberlitic and Diamond-Indicating Chromite

Abstract Spinel-group minerals are among the best-known and widely used minerals in diamond exploration due to their ubiquity, resistance to weathering, and utility as petrogenetic indicators. The kimberlite indicator mineral chromite is investigated in this study using micro-X-ray diffraction (µXRD) to measure chromite unit cell parameter ao. We used epoxy-mounted chromium-rich spinel (henceforward called ‘chromite’) mineral separates with known chemical composition from kimberlitic and non-kimberlitic sources to evaluate structural-chemical correlations for potential use in diamond exploration. Chromite grains of <300 µm size from the Koala, Misery, and Sheiba kimberlites in the Ekati property (Northwest Territories, Canada), as well as from exploration programs in Botswana and Gabon, Africa, were examined in situ, as mounted for standard electron probe microanalysis (EPMA). Unit cell parameter ao was measured by µXRD for several natural kimberlitic and non-kimberlitic chromite grains, and these data have been correlated with chemical composition as determined by EPMA on a grain-by-grain basis. Conventional chemical discrimination plots with unit cell size denoted by color demonstrate clearly discernable unit cell trends that are useful for classification. Two kimberlitic chromite compositional trends can be discriminated by chromite unit cell size. The kimberlitic phenocryst trend is delineated by a distinct increase in unit cell size (ao > 8.336 Å), whereas the kimberlitic xenocryst trend is delineated by a distinct decrease in the unit cell (ao < 8.322 Å). The latter trend is also followed by the Gabon non-kimberlitic samples. Notably, the unit cell parameters for chromite in the diamond-indicating field have a tightly determined value of ao = 8.329 (± 0.007) (or 8.322–8.336 Å). This field partially overlaps with the unit cell values for some non-kimberlitic chromites (e.g., Botswana). Unit cell values of chromite grains recovered from heavy mineral concentrates could serve as a preliminary screening technique for identifying diamond-indicating chromites prior to chemical analysis if their kimberlitic provenance is known. More broadly, the μ-XRD unit cell technique is a useful, non-destructive tool that shows promise for application to other kimberlite indicator minerals.

Dynamics of the microorganisms’ number in the soil mass of podzolized chernozem after treatment with fungicides of various origins

In a laboratory model experiment, the dynamics of the number of bacteria and micromycetes in the soil mass of podzolized chernozem after a one-time treatment of its surface with fungicides of various origins investigated. Chemical fungicides based on the active substances carbendazim, tebuconazole and azoxystrobin, and biological fungicides based on the antagonistic fungi Trichoderma viride (lignorum) and Chaetomium cohliodes were used. The soil mass for the experiment was taken from the arable layer of the soil on the site without fertilizers in the field experiment of the Department of Agrochemistry NSC "Institute for Soil Science and Agrochemistry Research named after O. N. Sokolovsky" (NSC "ISSAR") on the territory of SE "EF Hrakivske" (Noviy Korotych village, Kharkiv district, Kharkiv region). During 110 days of composting at a constant temperature, changes in the state of microbial communities, in particular soil micromycetes, and the speed and completeness of their recovery compared to soil not treated with fungicides evaluated. The state of the microflora was monitored four times during the study period according to the parameters of the number of microorganisms belonging to various ecological-trophic and taxonomic groups, the total biological index (TBI) and indicators reflecting the functional state of microbial coenoses (oligotrophy and mineralization indices, the coefficient of microbial transformation of soil organic matter (MTSOM). On the fifth day after treatment with fungicides, the number of bacteria and micromycetes in the samples of the treated soil mass was slightly higher higher than in the control samples, and on the twentieth day, on the contrary, it was significantly lower. The number of bacteria was lower by 20-46 %, micromycetes by 16-34 % compared to the control. On the fortieth day, a partial restoration of the number of bacteria to the level of the untreated control soil observed, and the number of micromycetes remained lower by 9-36 % compared to the control in the case of chemical fungicides. When using biological fungicides, the number of micromycetes approached the values in control soil and accounted for 84-94 % of them. On the one hundred and tenth day, the number of microflora in the soil treated with chemical fungicides according to TBI was 79-89 % of the control values, and in the soil treated with biofungicides it was 102-104 %. The number of micromycetes decreased to a lesser extent and recovered most completely and quickly in the case of the application of the biological fungicide Hetomic. Given the important role of soil micromycetes in the functioning of soils, a decrease in their number due to the accumulation of residual amounts of chemical fungicides in the soil can have a negative impact on many soil-biological processes, in particular the decomposition of plant residues and further transformation of organic matter, as well as on the phytosanitary state of the soil. Therefore, in order to avoid the possible consequences of their excessive or repeated application and the associated threat of soil contamination, it is necessary to carry out microbiological monitoring of soils in areas with a high fungicide load.

Mineral Indicators of Geologically Recent Past Habitability on Mars.

We provide new support for habitable microenvironments in the near-subsurface of Mars, hosted in Fe- and Mg-rich rock units, and present a list of minerals that can serve as indicators of specific water-rock reactions in recent geologic paleohabitats for follow-on study. We modeled, using a thermodynamic basis without selective phase suppression, the reactions of published Martian meteorites and Jezero Crater igneous rock compositions and reasonable planetary waters (saline, alkaline waters) using Geochemist's Workbench Ver. 12.0. Solid-phase inputs were meteorite compositions for ALH 77005, Nakhla, and Chassigny, and two rock units from the Mars 2020 Perseverance rover sites, Máaz and Séítah. Six plausible Martian groundwater types [NaClO4, Mg(ClO4)2, Ca(ClO4)2, Mg-Na2(ClO4)2, Ca-Na2(ClO4)2, Mg-Ca(ClO4)2] and a unique Mars soil-water analog solution (dilute saline solution) named "Rosy Red", related to the Phoenix Lander mission, were the aqueous-phase inputs. Geophysical conditions were tuned to near-subsurface Mars (100 °C or 373.15 K, associated with residual heat from a magmatic system, impact event, or a concentration of radionuclides, and 101.3 kPa, similar to <10 m depth). Mineral products were dominated by phyllosilicates such as serpentine-group minerals in most reaction paths, but differed in some important indicator minerals. Modeled products varied in physicochemical properties (pH, Eh, conductivity), major ion activities, and related gas fugacities, with different ecological implications. The microbial habitability of pore spaces in subsurface groundwater percolation systems was interrogated at equilibrium in a thermodynamic framework, based on Gibbs Free Energy Minimization. Models run with the Chassigny meteorite produced the overall highest H2 fugacity. Models reliant on the Rosy Red soil-water analog produced the highest sustained CH4 fugacity (maximum values observed for reactant ALH 77005). In general, Chassigny meteorite protoliths produced the best yield regarding Gibbs Free Energy, from an astrobiological perspective. Occurrences of serpentine and saponite across models are key: these minerals have been observed using CRISM spectral data, and their formation via serpentinization would be consistent with geologically recent-past H2 and CH4 production and sustained energy sources for microbial life. We list index minerals to be used as diagnostic for paleo water-rock models that could have supported geologically recent-past microbial activity, and suggest their application as criteria for future astrobiology study-site selections.

Identifying Potential Areas for Oil and Gas Well Location Planning Using Support Vector Machine Algorithm

To fulfill national energy needs for the National Energy Grand Strategy (GSEN), it is necessary to increase the productivity of oil and gas exploration by involving technology that provides alternative solutions, cuts work time, and overcomes the risk of failure. This research aims to identify potential areas for planning new oil and gas well locations using a machine learning algorithm called Support Vector Machine (SVM). This research chooses four splitting ratios of 80:20, 75:25, 60:40, and 50:50 on training and testing data to produce four models and to identify the most robust model for Blora Regency. The algorithm involves fourteen conditioning parameters comprising altitude, slope, aspect, distance from the river network, land cover, distance from the road network, soil type, Normalized Difference Vegetation Index (NDVI), clay mineral index, iron oxide index, surface temperature, complete Bouguer anomaly (CBL), distance from the fault, and rock type. This research uses the confusion matrix and the ROC-AUC to evaluate all models and determine the best one. The result witnesses the best model is SVM 75:25 with an accuracy (Acc), sensitivity (Sen), specificity (Spe), and predictive value (PPV) of 0.8333; Matthew’s correlation coefficient and Cohen’s kappa of 0.6667; and area under the curve (AUC) of 0.9444. In addition, the conditioning parameter contributing the most significant influence on the best model is the slope equal to 100%.

Mineral exploration using trace element composition of pyrite grains from till: A case study from the Petäjäselkä Au occurrence, northern Finland

Geochemical anomalies and indicator mineral studies in glacial sediments are commonly used to define mineral exploration targets in glaciated areas. Trace element composition of sediment-hosted heavy minerals, such as pyrite and chalcopyrite, can be potentially used to fingerprint mineral deposits. This study presents results from trace element compositions of pyrite in the heavy mineral concentrates of till and mineralized bedrock samples from the orogenic gold ore occurrences in the Petäjäselkä area, Central Lapland belt, northern Finland.The trace element contents of pyrite grains were evaluated by using a robust compositional data analysis workflow, including symmetric pivot coordinates and robust principal component analysis (PCA). Four different pyrite textures (A-D) were identified from the gold ore occurrences. Compositional data analysis showed that the heavy mineral pyrite correlated with Pyrite D in the ore occurrence and confirmed the discrimination power of pyrite in the heavy mineral grains as a tool for source characterization of transported sedimentary material. The study also discusses the difficulties of finding suitable grains for the LA-ICP-MS, highlighting the importance of proper heavy mineral grain recovery procedures and the factors of oxidization and weathering processes influencing the geochemical compositions of the pyrite grains.

Symbiosis with endophyte leads to greater C accumulation in grassland soils

Epichloë coenophiala forms aboveground symbiotic relationships with tall fescue (Festuca arundinacea) and provides the host with better fitness. This study investigated the effects of endophyte symbiosis on carbon mineralization in soil. Two soils were amended with endophyte-infected (E+) or endophyte-free (E−) residues of two tall fescue genotypes. At the end of the experiment, CO2 evolution rates were monitored to quantify the mineralized carbon. The indices of carbon mineralization were significantly greater (LSD, P < 0.05) in the E−compared to E+ plant residue treated soils. Cellulose, hemicellulose, lignin contents, C:N and lignin:N ratios were significantly greater (LSD, P < 0.05) in soils with the E+ residues than in those with E− residues. Additionally, the E+ plant residues consistently contained significantly less N (LSD, P < 0.05). Overall, it is concluded that grass-endophyte symbiosis results in the production of less biodegradable plant residues, in turn reducing the residue biodegradability and promoting greater C accumulation in the soils.

Review of till geochemistry and indicator mineral methods for mineral exploration in glaciated terrain

Since the 1970s, till geochemical and indicator mineral methods for mineral exploration, provenance studies and environmental research in glaciated terrain have been developed, tested and refined. This review summarizes these methods, focusing on field and laboratory methods for till geochemical, indicator mineral and boulder surveys. This review of protocols is intended as a guide for the mineral exploration industry and publicly funded agencies. It summarizes till as a sample medium, and describes the formation of glacial dispersal trains, along with methods for till sample collection, sample processing, matrix geochemistry, indicator mineral analyses, quality assurance/quality control procedures and data reporting and interpretation. The methods described here can be used to conduct reconnaissance- to deposit-scale till sampling surveys to assess mineral resource potential and establish environmental baselines. Supplementary material: Appendix A – Photographs of till types described in text; Appendix B – Logistical and geological factors to consider in till sample survey design; Appendix C – Photographs of glaciate terrain types described in text; and Appendix D – Till sample processing and analysis flow charts are available at https://doi.org/10.6084/m9.figshare.c.6786087 Thematic collection: This article is part of the Reviews in Exploration Geochemistry collection available at: https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry

Stream sediment geochemistry in mineral exploration: a review of fine-fraction, clay-fraction, bulk leach gold, heavy mineral concentrate and indicator mineral chemistry

Stream sediment surveys support early-stage reconnaissance mineral exploration and regional assessment programmes, enhanced by recent improvements in analytical method detection limits, continuously improving mineral chemistry, and new approaches to the interpretation of geochemical data. Sediment surveys may be used to predict catchment basin lithology, mineralization type based on pathfinder geochemistry, and geological features based on indicator mineral chemistry. Sediment surveys that target a finer-fraction sediment sample led to the discovery of the La Colosa gold deposit, Colombia. The Batu Hijau porphyry Cu–Au deposit in Indonesia was discovered based on an anomalous clay-sized fraction sample 12 km downstream. In an arid region with poorly developed drainages and minor topographic relief, the Ag-base-metal Navidad District in Argentina was discovered with clay-fraction sediment geochemistry. Heavy mineral concentrate (HMC) sediment surveys that include mineral chemistry determinations have led to global diamond discoveries. HMC surveys contributed to discovery of the Ring of Fire Ni–Cu–PGE and chromite district, Ontario, Canada. Discoveries and geochemical mapping can assist advancement of the application of stream sediment geochemistry in those global areas for which lithologies and deposits are exposed. Stream sediment surveys continue to be one of the most cost-effective geochemical methods for covering large areas for mineral exploration. Thematic collection: This article is part of the Reviews in Exploration Geochemistry collection available at: https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry

Negative δ13Ccarb excursions within early part of the Lomagundi event recorded in the Paleoproterozoic sedimentary carbonates, Aravalli Supergroup, Rajasthan India: Chemostratigraphy and basin evolution

High resolution stable isotopic (C and O) and geochemical studies of Paleoproterozoic carbonates were carried out in the Umra sub-basin of the Aravalli Supergroup, Rajasthan, India. All the sections, Umra-Dedkiya (UM), Umra-Jampa (BD), and Matoon (MU and GU), have yielded characteristic Lomagundi type positive values, with δ13Ccarb > 4 ‰ VPDB (maximum up to 6.86 ‰). Samples of two sections (UM and BD) have also yielded several distinct negative δ13Ccarb values (up to −6.14 ‰ VPDB). Geochemical validation of trace element and REE data indicate both these types of excursions to be of pristine character, with no signature of organic-remineralisation or hypersaline depositional condition. Mineralogical assemblages lack hypersalinity indicator minerals, such as Na-tourmaline, Na-Albite or scapolite, in the positive δ13C bearing carbonate samples. This supports the inference regarding the observed positive δ13C excursions mimicking the global Paleoproterozoic Lomagundi event. Chemostratigraphic correlation within the basin and with one of the global strato-type Paleoproterozoic carbonate unit from Paso Severino Formation, Uruguay, indicate interruptions in the initial part of the Lomagundi episode marked by several negative δ13C excursion events before achieving a stable positive δ13C character. This phenomenon is also evident from variation in paleoproductivity proxies, such as TOC, TN, Ba and P values, consistent with δ13C fluctuations. Mathematical model calculations have corroborated such a conclusion. All these observations motivated us to present a modified version of the global Paleoproterozoic δ13Ccarb curve and a six stage basin evolution model to explain the evolution of δ13C vis-à-vis variation in atmospheric oxygen.

Caries preventive efficacy of 2-,3-,4-aminophenylacetic acids hexafluorosilicates

In recent years, ammonium hexafluorosilicates have been actively studied as new potential anti-caries agents, which may compete with traditional fluoride preparations in the future. The pharmacological potential of hexafluorosilicates with substituted phenylammonium cations remains unexplored. The purpose of the work is to study the caries-prophylactic effectiveness of 2-,3-,4-aminophenylacetic acids hexafluorosilicates in the experiment on a model of experimental caries.&#x0D; 2-,3-,4-aminophenylacetic acids hexafluorosilicates (I–III, respectively) were synthesized according to the previously proposed method, reference drugs – NaF and (NH4)2SiF6. The studied drugs were applied to the teeth and gums of rats as part of a gel based on Na-salt of carboxymethylcellulose. The activity of alkaline and acid phosphatases was determined and the mineralization index was calculated in the pulp of incisors. The number and depth of carious lesions of the teeth were calculated and the caries prevention efficiency was calculated. The concentration of calcium ions was determined in the alveolar bone homogenate, the level of malondialdehyde, the activity of elastase, urease, and lysozyme was determined in the mucous membrane of the oral cavity homogenate.&#x0D; It was established that the caries-prophylactic efficiency of NaF, (NH4)2SiF6, I–III is 38.1%, 33.3%, 28.6%, 59.5%, 64.3%, that is, the anti-caries effect of compounds II and III exceeds the similar indicator of NaF by more than 1,6 and 1,7 times, respectively. The results of determining the phosphatases activity in the pulp of incisors showed that I–III almost completely normalize the mineralizing index. Compounds I–III provide an effective reduction of inflammatory markers, and the maximum effect is achieved when using gels with the participation of compounds II and III. The studied fluoropreparations reduce the activity of urease; the effect of all hexafluorosilicates is more effective compared to the reference drug – NaF. All hexafluorosilicates significantly return lysozyme activity to the control level compared to NaF, with compounds II and III being the most effective. Calculations using the PASS online method demonstrate an increased probability of anti-inflammatory (intestinal), anti-infectious, antiviral (influenza), antiseptic activity in the case of 3-,4-aminophenylacetic acids in the composition of salts II and III, which can lead to potentiation of their joint action and strengthening of anti-caries effect of these compounds. It is planned to continue research on the biological activity of 3-,4-aminophenylacetic acids hexafluorosilicates as potential means of caries treatment and prevention.

POSSIBLE EVIDENCE FOR THE EXISTENCE OF VOLCANOGENIC MAGMATISM IN THE SINYAYA RIVER BASIN AT THE SOUTHERN FLANK OF THE VILYUI SYNECLISE

The results of different-extension geological survey, exploration and thematic work methods show that the Vilyui syneclise is relatively amagmatic. However, the recent factual evidence in this region indicates the occurrence of magmatism of a different composition and age. This evidence includes kimberlite indicator mineral found in the sedimentary cover of the syneclise. Kimberlites or magmatic rocks of a different composition are not yet known there, so that any other signs of the presence of this type of rocks therein are of importance. As such a sign the authors consider a boulder of metamorphic rock found in the Archean greenstone succession in the lower reaches of the Sinyaya River at the southeastern flank of the Vilyui syneclise. The rock is similar in its mineral composition to garnet-staurolite-kyanite schist typical of the Barrovian metamorphic rocks series. The rocks of this mineral composition are common in the greenstone belts of the Aldan-Stanovoy Shield. In particular, they are typical of the Tungurchin metapelite unit of the TemulyakitTungurchin greenstone belt exposed in the western part of the shield. The straight line distance between the sratotype area of the Tungurchin Formation development and the place where the boulder was found is more than 600 km southwest of the Sinyaya River. So it is unlikely that the boulder was just transported along the Lena River basin and then to the Sinyaya River by, for example, the Quaternary glacial ice. A more realistic way the boulder appeared in the place where it was found would be its transportation from depth by volcanic pipe, i.e. the boulder is a xenolith from volcanic pipe. The volcanic pipe can be within a radius of a few tens of kilometers or less. The Archean basement therein lies at at a depth of a few hundreds of meters to 100 meters which implies transportation of so large xenolith to the surface during the volcanic pipe formation. Therefore, it can be implied that magmatic events occurred in the form of the Jurassic-Cretaceous or probably Middle Paleozoic volcanic pipe intrusion into the Sinyaya River basin area where the metamorphic xenolith was found.

Editorial for the Special Issue “Native Gold as a Specific Indicator Mineral for Gold Deposits”

Native gold is the most common and significant industrial gold mineral [...]

Extracting hydrothermally altered information using WorldView-3 data: a case study of Huitongshan, NW Gansu, China

Introduction: The Huitongshan skarn-type deposits, in which ore bodies primarily occur in the outer contact zone between K-feldspar granite and marble in the Beishan area, are evidently related to hydrothermal alteration of the surrounding rock. Key mineral alteration processes include serpentinization, epidotization, chloritization, carbonatization, jarosite, ferritization, and hematitization.Methods: WorldView-3 (WV-3), a satellite-recorded high-spatial resolution multispectral image, has been widely used in the exploration and prediction of different types of deposits around the world. In this study, WV-3 multispectral images were used to extract the spatial distribution data of the main altered minerals in the Huitongshan area. Dedicated radiometric calibration, atmospheric correction, and image fusion were used to pre-process the extracted spectral information related to hydrothermal alteration. In addition, directed principal component analysis (PCA) and a unique mineral index were designed based on the effective use of the WV-3 data band corresponding to the spectral absorption characteristics of altered minerals.Results: The findings of this study show that the PCA model and mineral index pro-posed herein are reliable both in theory and for practically obtaining extraction information. Additionally, the WV-3 data are well suited for identifying hydroxy-bearing alterations with rich short-wave infrared bands that distinguish Fe-OH–bearing alterations from Mg-OH–bearing alterations. The results obtained were applied to identify potential targets for skarn-type copper deposits and the implementation of prospecting practices.Discussion: This study provides a basis for the application of WV-3 data as an important and effective tool for alteration information extraction and determination of prospecting practice, thereby proving the validity of multispectral remote sensing images in mineral resource exploration.

Trace Element Composition of Chalcopyrite from Volcanogenic Massive Sulfide Deposits: Variation and Implications for Provenance Recognition

Abstract Chalcopyrite from 51 volcanogenic massive sulfide (VMS) and sea-floor massive sulfide (SMS) deposits from six lithostratigraphic settings was analyzed for trace elements by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to evaluate its potential as an indicator mineral for exploration. Partial least squares discriminant analysis (PLS-DA) results reveal that chalcopyrite from different lithostratigraphic settings has different compositions reflecting host-rock assemblages and fluid composition. Three random forest (RF) classifiers were developed to distinguish chalcopyrite from the six lithostratigraphic settings with a divisive approach. This method, which primarily classifies according to the major host-rock affinity and subsequently according to VMS settings, yielded an overall accuracy higher than 0.96 on test data. The model validation with literature data having the same elements required by the models yielded the highest accuracies (&amp;gt;0.90). In validation using published data with missing elements, the accuracy is moderate to high (0.60–1); however, the performances decrease significantly (&amp;lt;0.50) when the most important elements are missing. Similarly, RF regression models developed using all sets of analyzed elements to determine ccp/(ccp + sp) ratio (ccp = chalcopyrite; sp = sphalerite) in chalcopyrite within a single VMS setting reported high performances, thus showing a potential to predict the Cu/Zn ratio (Cu-rich vs. Zn-rich) of the mineralization based on chalcopyrite composition. This study demonstrates that trace element concentrations in chalcopyrite are primarily controlled by lithotectonic setting and can be used as predictors in an RF classifier to distinguish the different VMS subtypes.

Substantiation of the use of digital methods for assessing the dental status of the oral cavity in normal and pathological conditions

Relevance. Diseases and processes of microbial nature in the oral cavity, such as caries, the hygienic condition of the oral cavity and its individual biotopes in terms of their diagnosis and sanogenetic therapy, are still an urgent problem in dentistry.&#x0D; The purpose of the study. To conduct pathogenetic and clinical substantiation of the use of an objective digital express method of Raman-fluorescence diagnostics to assess the dental status of the oral cavity "in situ" in patients with cardiac arrhythmia while taking anticoagulants.&#x0D; Material and method. Based on the use of a hardware and software complex of the "InSpectrM" type, 150 people aged 35-55 years with cardiac arrhythmia on the background of taking anticoagulants or without them (in a comparative aspect) were examined. Patients are divided into 2 groups. In each group, the indicators of oral homeostasis at the metabolic, morphometric, functional and clinical levels were evaluated using both digital and classical "ad oculum" method before and after controlled and/or uncontrolled oral hygiene treatment. The following indicators were diagnosed: tissue aerobicity/anaerobicity, type of metabolism, saliva volume and saliva microbial contamination index, digitized Schiller-Pisarev sample, oxygenation index, mineralization, periodontal and hygienic indices, represented by a pie chart to assess the clarity of the results obtained in their relationship.&#x0D; Results. It is shown that the proposed digital, express Raman-fluorescent technology for assessing the dental status of the oral cavity eliminates the presence of errors amounting to 200-400% when measuring the "ad oculum" hygienic status of the oral cavity and allows obtaining results in the relationship of all elements of oral homeostasis.It was shown p0.05 that in patients taking anticoagulants with controlled hygienic treatment of the oral cavity, its hygienic condition approaches the norm, unlike patients with uncontrolled hygienic treatment. All the studied indicators p0.05 have positive dynamics. The necessity of remineralizing therapy after each hygienic treatment of hard tooth tissues is substantiated.It is proved that for a comprehensive assessment of the hygienic condition of the oral cavity, it is necessary to use both the method of Raman-fluorescence diagnostics and separate methods of "ad oculum", which complement each other in the relationship.

Minerals of the apatite group from ultramafic lamprophyres of the Zima alkaline-ultramafic carbonate complex (Urik-Iya graben, Eastern Sayan region)

Research subject. This paper presents the results of a study of minerals of the apatite group from aillikites of the Zima alkaline-ultramafic carbonatite complex. Aim. To determine the composition of apatites to characterize the studied rocks and to elucidate the patterns of element distribution in the magma of aillikites in the late crystallization stages. Materials and Methods. Minerals of the apatite group from 6 samples (4 from dikes of the Bol'shetagninsky massif, 1 from the Bushkanai dike, 1 from the Beloziminskaya pipe) were studied. The samples showed similar textural-structural features, differing in the mineral composition of the groundmass. Results. Minerals of the apatite group are widespread in the groundmass of all the studied rocks. They are characterized by idiomorphic, subidiomorphic crystals of homogeneous composition, 10-100 microns in size. Minerals of the apatite group were identified as fluorapatite and hydroxyapatite characterized by a significant SiO2 content (up to 5 wt %), low SrO content (up to 1.5 wt %) and REE2O3 (up to 2 wt %). The studied apatites also include MgO, FeO, Na2O, SO4, and CO3. Fluorapatites from dyke aillikites are characterized by a higher silicon content as compared to apatites from the Beloziminskiy pipe. Apatites from fresh aillikites of the Bushkanai dyke have a relatively higher content of Sr, REE, and F than minerals from serpentinized samples. Conclusions. The composition of the studied apatites has a lower Sr and Ba content than orangeite and lamproite apatites. In terms of Sr, Si and REE contents, the studied apatites are similar to kimberlite and ailikite apatites. Such a difference allows minerals of the apatite group to be used as an indicator mineral for classification of kimberlites and related rocks, but only in combination with petrography and composition of other minerals of the groundmass.