Surface geochemical anomaly pattern of medium-to-high temperature geothermal systems in South China and its application

The existence of thermal storage will correspondingly increase the temperature of surrounding strata and promote the continuous expansion,volatilization,upward migration,and loss of gas in the strata.As a result,a low-concentration gas field will be formed in the strata above geothermal reservoirs.Geothermal reservoirs could in turn heat formation water and increase the solubility of soluble inorganic salts in the surrounding rocks and the total dissolved solids(TDS)content in the formation water.Since water can strongly wet and permeate strata,the dissolved inorganic salts migrate into upper strata along with water,giving rise to the formation of a high-concentration inorganic salt field in the strata above geothermal reservoirs.A higher geothermal reservoir temperature corresponds to more significant characteristics mentioned above.Therefore,a medium-to-high temperature geothermal system has a surface geochemical anomaly pattern of high inorganic salt concentrations and low gas concentrations(also referred to as the high-salt and low-gas pattern).This pattern is applied to the surface geochemical exploration of the two geothermal fields in Guangdong Province,i.e.,the Huangshadong geothermal field in Huizhou City and the Xinzhou geothermal field in Yangjiang City,revealing low-concentration gas fields above both.The application results also show that the exposed thermal spring water in both geological fields has higher concentration of dissolved inorganic salt than the surface water and nearby seawater,forming high-amplitude anomalies on the surface above geothermal reservoirs.These characteristics,as well as the measured temperature at known geothermal wells,verify the validity of the high-salt and low-gas pattern of medium-to-high temperature geothermal systems proposed in this study.Moreover,the high-salt and low-gas pattern proposed predicts three favorable medium-to-high temperature geothermal zones in the surface geochemical exploration of the Shiba Basin near the Huangshadong geothermal field.

Geochemical Anomalies Identified by Multifractal Modeling: Implications for Mineral Exploration in the Ziyoutun Cu-Au District, Jilin Province, China

The Ziyoutun Cu-Au district is located in the Jizhong–Yanbian Metallogenic Belt and possesses excellent prospects. However, the thick regolith and complex tectonic settings present challenges in terms of detecting and decomposition of weak geochemical anomalies. To address this challenge, we initially conducted a comprehensive analysis of 1:10,000-scale soil geochemical data. This analysis included multivariate statistical techniques, such as correlation analysis, R-mode cluster analysis, Q–Q plots and factor analysis. Subsequently, we decomposed the geochemical anomalies, identifying weak anomalies using spectrum-area modeling and local singularity analysis. The results indicate that the assemblage of Au-Cu-Bi-As-Sb represents the mineralization at Ziyoutun. In comparison to conventional methods, spectrumarea modeling and local singularity analysis outperform in terms of identification of anomalies. Ultimately, we considered four specific target areas(AP01, AP02, AP03 and AP04) for future exploration, based on geochemical anomalies and favorable geological factors. Within AP01 and AP02, the geochemical anomalies suggest potential mineralization at depth, whereas in AP03 and AP04 the surface anomalies require additional geological investigation. Consequently, we recommend conducting drilling, following more extensive surface fieldwork, at the first two targets and verifying surface anomalies in the last two targets. We anticipate these findings will significantly enhance future exploration in Ziyoutun.

Quantitative geochemical reconstruction of Eocene paleoenvironment in Fushun Basin,northeast China

The quantitative estimation of key parameters of paleotemperature and paleoprecipitation is crucial for paleoclimate reconstruction.Geochemical data from mod-ern sediments are highly consistent with climate data,and their relationship can provide an important reference for the quantitative reconstruction of the paleoclimate.In this study,detailed inorganic geochemical analysis was carried out using high-precision sampling of the Paleogene(LFD-1 well)Guchengzi,Jijuntun and Xiloutian Formations in the Fushun Basin located in the mid-latitudes of the Northern Hemisphere.The Eocene Guchengzi Formation(54.51–47.8 Ma)and Jijuntun Formation(47.8–41.2 Ma)in the Fushun Basin were found to have been deposited under a humid climate.The lower(41.2–40.1 Ma)and upper(40.1–37.8 Ma)parts of the Xiloutian Formation were character-ized by semiarid and semihumid–semiarid climates,respec-tively,which is very similar to the paleoclimatic information reflected by organic carbon isotopes.The Eocene Thermal Maximum 2(ETM2,~53.7 Ma),Early Eocene Climatic Optimum(EECO,~53.1–46.5 Ma),Eocene Thermal Maxi-mum 3(ETM 3,~52.8 Ma),and Middle Eocene Climatic Optimum(MECO,~40.7–40.1 Ma)events significantly enhanced chemical weathering during these periods.The rapid increase in pCO_(2)concentration leads to an increase in temperature,precipitation,and surface runoff,exhibiting strong chemical weathering.The mean annual temperature(MATa)and mean annual precipitation(MAPa,MAPb,and MAPc)were estimated using parameters,such as the corrosion index without potassium(CIA-K),CaO/Al_(2)O_(3),and(Na_(2)O+K_(2)O)/Al_(2)O_(3).Comparing MAPa,MAPb,and MAPc with the MAP estimated using pollen data,MAPa and MAPb were found to be more sensitive to the climate during high precipitation periods(precipitation>1000 mm,Guchengzi Formation),and the recovered average precipi-tation was similar to MAP.In contrast,MAPc was more sensitive to the climate during low precipitation periods(precipitation<1000 mm,Jijuntun,and Xiloutian Forma-tions),with higher accuracy.To fully consider the influence of soluble inorganic salts Ca^(2+)and Na^(+),multivariate linear equations of CIA-K and CaO/Al_(2)O_(3)with CIA,and CIA-K and CaO/Al_(2)O_(3)with MAP were constructed,namely MAPd and MAPe.The results show that MAPe has the highest per-formance and can be effectively used to estimate the change of paleoprecipitation in Northeast Asia.

Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales,southwest Yangtze Plate,China:Insights from geochemical and petrological evidence

Upper Ordovician-Lower Silurian Wufeng-Longmaxi Formation is the most developed strata of shale gas in southern China.Due to the complex sedimentary environment adjacent to the Kangdian Uplift,the favorable area for organic-rich shale development is still undetermined.The authors,therefore,focus on the mechanism of accumulation of organic matter and the characterization of the sedimentary environment of the Wufeng-Longmaxi Shales to have a more complete understanding and new discovering of organic matter enrichment and favorable area in the marginal region around Sichuan Basin.Multiple methods were applied in this study,including thin section identification,scanning electron microscopy(SEM)observations and X-ray diffraction(XRD),and elemental analysis on outcrop samples.Five lithofacies have been defined according to the mineralogical and petrological analyses,including mudstone,bioclastic limestone,silty shale,dolomitic shale,and carbonaceous siliceous shale.The paleo-environments have been reconstructed and the organic enrichment mechanism has been identified as a reduced environment and high productivity.The Wufeng period is generally a suboxic environment and the early Longmaxi period is a reducing environment based on geochemical characterization.High dolomite content in the study area is accompanied by high TOC,which may potentially indicate the restricted anoxic environment formed by biological flourishing in shallower water.And for the area close to the Kangdian Uplift,the shale gas generation capability is comparatively favorable.The geochemical parameters implied that new favorable areas for shale gas exploration could be targeted,and more shale gas resources in the mountain-basin transitional zone might be identified in the future.

New Data on Coal, Gypsum, Iron and Silica Sand Deposits and Geochemical Exploration (Pakistan): Revision of 25 Years History of Dinosaur Discoveries from Pakistan

Discoveries of many coal seams at depths by drilling carried by Geological Survey of Pakistan in Sor Range and Harnai Gochina, extended the coal seams at depth which is challenge for mine owners to exploit feasibly. Bed to bed gypsum samplings (and their chemical analyses) of huge gypsum deposits from Sulaiman foldbelt is a base for industrialist and also planers to develop cement and gypsum industries to increase export and foreign exchange for the development of area and Pakistan. Low and high grade sedimentary iron deposits, silica sand and uranium host rocks and their extensions in Sulaiman and Kirthar foldbelts are presented. Anomalies of a few base metals arise as a result of geochemical exploration carried at part of Loralai District of Balochistan. Theropod dinosaurs were frequent in India, while Poripuchian titanosaurs (Sauropoda, Dinosauria) were frequent in Pakistan. Besides some ichnotaxa, many bone taxa such as 1 titanosauriform, 14 titanosaurian sauropod (including one new titanosaur), and 3 theropod dinosaurs are established from Pakistan. Among these 12 titanosaur species and 3 theropod species are named in about 10 km2 area of Vitakri dome and 2 titanosaur species are named in about a few hundred square meter area of Mari Bohri (Kachi Bohri) which is about 10 km westward from Vitakri dome. Pakistan is a unique country which discoverd 14 diversified titanosaurs in a short area and also in a short period (67 - 66 million years ago/Ma). About 400 bones found from a few meter thick upper part of upper shale horizon of latest Maastrichtian Vitakri Formation which is base for titanosaur taxa. Cranial material is in low fraction (but include significant diverse snouts), caudal vertebrae are prominent, the cervicals, dorsals and sacrals have significant numbers, forelimb and hind limb bones have balanced fraction. Humeri, femora and tibiae are most common. To know the position of Pakistani titanosaurs among titanosaurs and sauropods, there is a need to extend list of characters for phylogenetic analyses. This broad feature list should include main characters of titanosaurs from Pakistan and also from global world.

Geochemical characteristics and diagenetic systems of dolomite reservoirs of the Changxing Formation in the eastern Sichuan Basin, China

In order to discuss the relationship between dolomite reservoirs and diagenetic systems of the Changxing Formation, we studied carbon, oxygen and strontium stable isotopes, iron, manganese and strontium trace elements and the Mg/Ca （mol%） ratio, dolomite order degree, and determined that burial dolomitization is the key to controlling the distribution of high quality dolomite reservoir in the Changxing Formation in the eastern Sichuan Basin. The dolomite of the Changxing Formation is divided into four diagenetic systems： （1） penecontemporaneous stage syngenetic brine diagenetic system, （2） early diagenetic stage strata seal brine diagenetic system, （3） middle-late diagenetic stage mixed hot brine diagenetic system and （4） tectonic uplift stage mixed hydrothermal fluid diagenetic system. New understanding of the controlling factors and distribution of dolomite reservoir development is discussed. Reef shoal facies belts controlled regional reservoir distribution and the scale of development. Burial dolomitization of a strata seal brine diagenetic system is the foundation of reservoir development, mainly developing pore reservoir. Burial dolomitization of mixed hot brine diagenetic system expanded the reservoir distribution and improved the reservoir quality, mainly developing pore-vug reservoir. Fracturing and dissolution of a mixed hydrothermal fluid diagenetic system is the key to improving the reservoir quality, mainly developing pore-vug-crack complex reservoirs.

Negative Haloes and Geochemical Field Systems of Hydrothermal Deposits

Primary haloes of hydrothermal deposits were previously considered as positive haloes. Although it has been recently suggested that primary haloes incude positive and negative ones, almost all the research work on primary haloes has still focused on positive haloes for various reasons. In order to understand the source of ore substances a number of large hydrothermal deposits related to magmatism including porphyry, skarn and vein type deposits have been studied. It has been found that negative haloes exist on the peripheries of positive haloes of a mineral deposit. On the basis of the study the authors propose the concept of the geochemical field system of ore-forming elements of hydrotherreal deposits, i. e., with the orebody as the centre outwards there occur the mineralized field, positive halo field, depleted field and background field successively.

Geochemical Characteristics of the Upper Permian Longtan Formation from Northeastern Sichuan Basin:Implications for the Depositional Environment and Organic Matter Enrichment

A set of organic-rich shales of the upper Permian Longtan Formation,which is widely developed in the northeastern part of the Sichuan Basin,is a key formation for the next step of exploration and development.At present,most studies on this set of formations have focused on the reservoir characteristics and reservoir formation mechanism of the shales,and basic studies on the palaeoenvironment and organic matter(OM)enrichment mechanism have not been fully carried out.In this paper,we recovered the sedimentary palaeoenvironment by mineralogical,elemental geochemical and organic geochemical analyses,and explored the enrichment mechanism of OM under the constraints of palaeoenvironmental evolution.The shales can be divided into two stages of sedimentary evolution:compared with the shales of the Lower Longtan Formation,the shales of the Upper Longtan Formation are relatively rich in quartz,poor in clay and carbonate minerals,and the OM type changes from typeⅢto typeⅡ_(2).The depositional environment has undergone a change from sea level rise,from warm and wet climate to dry and cold climate,and from oxygen-poor condition restricted to open reduction environment;the land source input has decreased,the siliceous mineral content has increased,the biological productivity has improved,and the deposition rate has changed from high to low.A depositional model was established for the shales of the Longtan Formation,reflecting the differential reservoir formation pattern of organic matter.For the Lower Longtan Formation shales,the most important factors controlling OM content are terrestrial source input and deposition rate,followed by paleoclimate and paleooxygen conditions.For the Upper Longtan Formation shales,the most important controlling factor is paleo-productivity,followed by sedimentation rate.The depositional model constructed for the Upper and Lower Longtan Formation shales can reproduce the enrichment of organic matter and provide a basis for later exploration and development.

Evaluation of hydro-chemistry in a phreatic aquifer in the Vindhyan Region, India, using entropy weighted approach and geochemical modelling

Groundwater quality monitoring and geochemical characterization in the phreatic aquifer are critical for ensuring universal and equitable access to clean,reliable,and inexpensive drinking water for all.This research was intended to investigate the hydrogeochemical attributes and mechanisms regulating the chemistry of groundwater as well as to assess spatial variation in groundwater quality in Satna district,India.To accomplish this,the groundwater data comprising 13 physio-chemical parameters from thirty-eight phreatic aquifer locations were analysed for May 2020 by combining entropy-weighted water quality index(EWQI),multivariate statistics,geochemical modelling,and geographical information system.The findings revealed that the groundwater is fresh and slightly alkaline.Hardness was a significant concern as 57.89% of samples were beyond the permissible limit of the World Health Organisation.The dominance of ions were in the order of Ca^(2+)> Na^(+)> Mg^(2+)> K^(+) and HCO_(3)^(-)> SO_(4)^(2-)> Cl^-> NO_(3)^(-)> F^(-).Higher concentration of these ions is mainly concentrated in the northeast and eastern regions.Pearson correlation analysis and principal component analysis(PCA) demonstrated that both natural and human factors regulate groundwater chemistry in the region.The analysis of Q-mode agglomerative hierarchical clustering highlighted three significant water clusters.Ca-HCO_3 was the most prevalent hydro-chemical facies in all three clusters.Geochemical modelling through various conventional plots indicated that groundwater chemistry in the research region is influenced by the dissolution of calcite/dolomite,reverse ion exchange,and by silicate and halite weathering.EWQI data of the study area disclosed that 73.69% of the samples were appropriate for drinking.Due to high salinity,Magnesium(Mg^(2+)),Nitrate(NO_(3)^(-)),and Bicarbonate(HCO_(3)^(-)) concentrations,the north-central and north-eastern regions are particularly susceptible.The findings of the study may be accomplished by policymakers and groundwater managers to achieve sustainable groundwater development at the regional scale.

A multiphysical-geochemical coupling model for caprock sealing efficiency in CO_(2) geosequestration

Precipitation or dissolution due to geochemical reactions has been observed in the caprocks for CO_(2) geosequestration.Geochemical reactions modify the caprock sealing efficiency with self-limiting or self-enhancement.However,the effect of this modification on the caprock sealing efficiency has not been fully investigated through multiphysical-geochemical coupling analysis.In this study,a multiphysical-geochemical coupling model was proposed to analyze caprock sealing efficiency.This coupling model considered the full couplings of caprock deformation,two-phase flow,CO_(2) concentration diffusion,geochemical reaction,and CO_(2) sorption.The two-phase flow only occurs in the fracture network and the CO_(2) may partially dissolve into water and diffuse through the concentration difference.The dissolved CO_(2) has geochemical reactions with some critical minerals,thus altering flow channels.The CO_(2) in the fracture network diffuses into matrix,causing the matrix swelling.This fully coupling model was validated with a penetration experiment on a cement cube and compared with two other models for CO_(2) storage plumes.Finally,the effects of geochemical reactions on penetration depth and pore pressure were studied through parametric study.The numerical simulations reveal that the coupling of geochemical reactions and matrix diffusion significantly affect the caprock sealing efficiency.Geochemical reactions occur at a short time after the arrival of CO_(2) concentration and modify the fracture porosity.The CO_(2) diffusion into the matrix requires a much longer time and mainly induces matrix swelling.These effects may produce selfenhancement or self-limiting depending on the flow rate in the fracture network,thus significantly modifying caprock sealing efficiency.

A New Geochemical Reaction Model for Groundwater Systems

Through a survey of the literature on geology, hydrogeology and hydrogeochemistry, this paper presents a hydrogeochemical model for the groundwater system in a dross-dumping area of the Shandong Aluminium Plant. It is considered that the groundwater-bearing medium is a mineral aggregate and that the interactions between groundwater and the groundwater-bearing medium can be described as a series of geochemical reactions. On that basis, the principle of minimum energy and the equations of mass balance, electron balance and electric neutrality are applied to construct a linear programming mathematical model for the calculation of mass transfer between water and rock with the simplex method.

Development and application of geochemical data processing system based on fractal theory

GC-GIS system is a geochemical data processing system based on fractal theory. The system realized quantity statistics function by calling Surfer and MapInfo software, and it is compiled with Visual Basic language. This system is designed to integrate the functions both quantity statistics of Surfer and spatial data management of MapInfo. A new algorithm of fractal is added up to GC-GIS. Taking example for Weichang region of Hebei to test the system, the processing results show that the model can match the real distribution of mine well.

Characteristics of B,Zn and Se in stream sediments of Tanzania and their agricultural applications:Based on 1∶1000000 geochemical survey

Tanzania is located in eastern Africa with a predominantly agricultural ecomomy,the potential for developing and utilizing cultivated land are promising,but scientific guidance is required.B,Zn and Se are essential micronutrients for plants and human body with crucial biological functions,in particular,Se is significant for human health and considered as“the king of anti-cancer”.As these elements required by human or plants are mainly absorbed from soil directly or indirectly,therefore,it is important to understand the contents and distributions of them in the soil of cultivated land for guiding agricultural production.In this work,low-density geochemical survey at the scale of 1∶1000000 was carried out in Tanzania,and the results show that the concentrations of B,Zn and Se in stream sediments are low and their distributions are heterogeneous.According to the distributions of geological units,the existing cultivated land resources can be divided into five regions in Tanzania.Compared with the national background values,the concentrations of B,Zn and Se are insufficient overall but enriched locally in these regions.In general,element concentrations in stream sediments and soil have a positive correlation because of their similar sources,which is essential in agriculture application.Based on the information provided by low-density geochemical data and maps,the Se-sufficient and Se-rich regions were delineated in Tanzania,where can be used to develop Se-rich industries.Finally,this paper believes that geochemical survey is a powerful tool for cultivated land evaluation,agriculture management and land development.

Mantle sources of Cenozoic volcanoes around the South China Sea revealed by geochemical and isotopic data using the principal component analysis

Principal component analysis(PCA)was employed to determine the implications of geochemical and isotopic data from Cenozoic volcanic activities in the Southeast Asian region,including China(South China Sea(SCS),Hainan Island,Fujian-Zhejiang coast,Taiwan Island),and parts of Vietnam and Thailand.We analyzed 15 trace element indicators and 5 isotopic indicators for 623 volcanic rock samples collected from the study region.Two principal components(PCs)were extracted by PCA based on the trace elements and Sr-Nd-Pb isotopic ratios,which probably indicate an enriched oceanic island basalt-type mantle plume and a depleted mid-ocean ridge basalt-type spreading ridge.The results show that the influence of the Hainan mantle plume on younger volcanic activities(<13 Ma)is stronger than that on older ones(>13 Ma)at the same location in the Southeast Asian region.PCA was employed to verify the mantle-plume-ridge interaction model of volcanic activities beneath the expansion center of SCS and refute the hypothesis that the tension of SCS is triggered by the Hainan plume.This study reveals the efficiency and applicability of PCA in discussing mantle sources of volcanic activities;thus,PCA is a suitable research method for analyzing geochemical data.

Geochemical characterization of rare earth elements in sediment profiles from the Oualida lagoon(Morocco)

The present work assesses the temporal distribution pattern and geochemical changes of rare earth elements and Yttrium, Scandium, Thorium, and Uranium delivery into the Oualidia lagoon. Two sediment cores were retrieved from the Oualidia lagoon and analyzed using neutron activation analysis. The results indicated that heavy rare earth elements are slightly enriched the sediment cores over light rare earth elements. The highest values of REEs were recorded in the top layers of the cores and depleted with depth, suggesting a possible change in factors controlling their accumulation, including mechanical, chemical, and environmental parameters such as weathering intensity, grain size, and Fe-Mn oxides. The sediments display positive Ce anomalies, which are probably related to the submarine weathering process and detrital input. Noting also the variation of hydrodynamics conditions and confinement of the upstream part of the lagoon played a key role in changing the sediment origins.Thus, further investigation of REEs origin in the Oualidia lagoon sediment is required to identify their sources,provenances, and the factors controlling their spatial and vertical distributions. However, these results provide baseline data of occurring changes in REEs geochemical composition and constitute a typical study case to understand the link between sedimentary and geochemistry processes in a lagoonal ecosystem.

Organic geochemical and petrographic characteristics of the Cambrian-Ordovician organic-rich marine shales in Scandinavia

This work used organic geochemistry and organic petrology to study the depositional environment,organic matter characteristics,and thermal maturity of the Cambrian-Ordovician organic-rich marine shales in the Baltic Basin.The main macerals in Cambrian samples include alginite,bituminite and solid bitumen,while zooclastic macerals become the major proportion of organic matter in the Ordovician samples.As the maturity increase,solid bitumen becomes abundant and dispersed.Semifusinite-like maceral was observed only in Furongian of well DBH15/73,which probably indicates the local intrusion of Permo-Carboniferous dolerite dikes.The programmed pyrolysis results show that immature,early mature,and over-mature samples are developed.However,the data of high-uranium Furongian samples were greatly altered by igneous intrusives from local dikes.HIo calculation model is simulated based on pyrolysis data and fitted according to the least-square fitting method.The simulated fitting HIo:400mg HC/g TOC(369.5 mg HC/g TOC,430.5 mg HC/g TOC as 95%confidence bounds)is within the worldwide marine shale HI_(o)and indicates a marine anoxia and transgressive sea with shallow water column(organofacies B).

Geochemical characteristics of temperature and pressure of Paleozoic reservoir fluid inclusions in Xuanjing region, Lower Yangtze area

In order to understand the geochemical characteristics of Paleozoic reservoir fluids in Xuanjing region,Lower Yangtze area,drilling core samples from Y and D wells were tested and analyzed to study the fluid inclusion types and composition.Pressure correction was undertaken to determine the temperature and pressure environment for inclusion formation,and the influence of fluid characteristics of the Upper Permian and Lower Triassic reservoirs on the preservation of shale gas was investigated.According to petrograph-ic observations,fluid inclusions are mainly brine and bitumen inclusions.Bitumen inclusions are mainly distributed in holes and fractures,and with smaller individuals.No visible fluorescence was observed,and the vitrinite reflectance is 3.39%–3.92%.This indicates that there had been oil and gas accumulation in the early stage of diagenesis in the study area,but due to the influence of magmatic hydrothermal solution,oil and gas underwent thermal metamorphism in the early stage,making liquid petroleum into solid bitumen.At present,oil and gas in the reservoir were largely formed in the late stage.During the continuous process in which shale was buried,light oil and gas were generated.Light oil and gas underwent magmatic and tectonic hydrothermal processes in some areas,resulting in high-temperature metamorphic cracking that formed dry gas.Moreover,nitrogen inclusions are found in fluid inclusions,forming metamorphic fluids caused by mag-matic hydrothermal activities.The study shows that Paleozoic reservoirs in Xuanjing area are characterized by self-generation and self-storage.Furthermore,the mechanism of shale gas accumulation is not only related to the buried hydrocarbon generation process of shale itself,but is also related to later magmatic activity and tectonic hydrothermal transformation.Therefore,preservation conditions are generally key factors of shale gas accumulation in this area.

Geochemical Mobility Associated to Gold and Base Metal Occurrences of Mangodara Sector, in Southern Burkina Faso, Banfora Greenstone Belts (West African Craton)

In the Mangodara area within the Banfora greenstone belts (Baoulé-Mossi domain of the West African Craton), our study focused on geochemical assessment of the mobility of major and trace elements. Gold and base metal occurrences are hosted in highly metamorphic felsic (metarhyolite) and intermediate (metadacite and metaandesite) formations. Common mineral assemblages made up of staurolite - kyanite - pyrophyllite are interpreted to represent the metamorphosed equivalent of aluminous hydrothermal alteration. Associated felsic and intermediate volcanic rocks are enriched in Fe2O3, K2O (metaandesite, metarhyolite) and depleted in MgO, Al2O3, CaO, P2O5, Na2O (metarhyolite) and Fe2O3, MgO, CaO (metaandesite). Al2O3 depletion in mineralized kyanite-staurotide bearing metarhyolites suggests corroded minerals. Mineralized metarhyolites show enrichment in Au, Ag, Ba, Bi, Cr, Cu, Eu, La, Mo, Ni, Pb, S, Sc, V and depletion in As Sb Co, Sn, Zn while mineralized metaandesites show enrichment in Au, Ag, As, Mo, S, Sb and depletion in Co, Sn, Zn, Bi, Cr, Cu, Eu, Ni, Pb, Sc. Ba, La, V are immobile in metaandesites. Finally, Ag, As, Sn appear as geochemical vectors for gold exploration in the study area since gold mineralization is characterized by Au + Ba + Cu + Eu + La + Mo + Ni + S association in metarhyolites and Au + S + Sb + As + Ag + Bi in metaandesites.

Geochemical Orientation Study of Stream Sediment Samples in the Southern Part of Nuggihalli Schist Belt: Ore Mineral Phases and Their Implications on the Bedrock Potential for Ores

Stream sediment sampling is a significant tool in geochemical exploration. The stream sediment composition reflects the bedrock geology, overburden cover, and metalliferous mineralization. This research article focuses on assessing selected trace element concentrations in stream sediments and interpreting their inter-element relationships using multivariate statistical methods. Tagadur Ranganathaswamy Gudda and its surroundings in the Nuggihalli schist belt of southern India have been investigated in the present work. The geology of the study area is complex, with a diverse range of litho units and evidence of strong structural deformation. The area is known for its mineralization potential for chromite, vanadiferous titanomagnetite, and sulfides. The topography of the region is characterized by an undulating terrain with a radial drainage pattern. Most part of the schist belt is soil covered except the Tagadur Ranganathaswamy Gudda area. For this study, a discrete stream sediment sampling method was adopted to collect the samples. Stream sediment samples were collected using a discrete sampling method and analyzed for trace elements using an ICP-AES spectrophotometer: Fe, Cr, Ti, V, Cu, Ni, Zn, Pb, Mn, Cd, and As have been analyzed. The analytical data were statistically treated using the SPSS software, including descriptive statistics, normalization of data using natural log transformation, and factor analysis with varimax rotation. The transformed data showed a log-normal distribution, indicating the presence of geochemical anomalies. The results of the study provide valuable insights into the geochemical processes and mineralization potential of the study area. The statistical analysis helps in understanding the inter-element relationships and identifying element groups and their implications on bedrock potential mineralization. Additionally, spatial analysis using inverse distance weighting interpolation provides information about the distribution of geochemical parameters across the study area. Overall, this research contributes to the understanding of stream sediment geochemistry and its application in mineral exploration. The findings have implications for future exploration efforts and can aid in the identification of potential ore deposits in the Nuggihalli schist belt and similar geological settings.

Features of sampling stream sediments of large river valleys under cryolithogenesis conditions in the Balygychan-Sugoy trough,North-East of Russia

Comprehensive research has been implemented to raise the efficiency of the geochemical survey of stream sediments(SSs)that formed under the cryolithogenesis conditions.The authors analysed the composition,structure and specific features of the formation of exogenous anomalous geochemical fields(AGFs)identified through SSs of large river valleys of IV order.In our case,these were the valleys of Maly Ken,Ken and Tap Rivers.These rivers are located in the central and southern parts of the Balygychan-Sugoy trough enclosed in the Magadan region,North-East of Russia.The authors proposed a new technique to sample loose alluvium of SSs in the large river valleys along the profiles.The profiles were located across the valleys.The AGFs of Au,Ag,Pb,Zn,Sn,Bi,Mo and W were studied.Correlations between elements have been established.These elements are the main indicator elements of Au-Ag,Ag-Pb,Sn-Ag,Mo-W and Sn-W mineralization occurring on the sites under study.The results obtained were compared with the results of geochemical surveys of SSs.It is concluded that the AGFs recognized along the profiles reflect the composition and structure of eroded and drained ore zones,uncover completely and precisely the pattern of element distribution in loose sediments of large water flows.The alluvium fraction<0.25 mm seems to be most significant in a practical sense,as it concentrated numerous ore elements.Sampling of this fraction in the river valleys of IV order does not cause any difficulty,for this kind of material is plentiful.The developed technique of alluvium sampling within large river valleys is efficient in searching for diverse mineralization at all stages of prognostic prospecting.It is applicable for geochemical survey of SSs performed at different scales both in the North-East of Russia,as well as other regions with similar climatic conditions,where the SSs are formed under the cryolithogenesis conditions.