Pub Date : 2024-11-01DOI: 10.1016/j.geogeo.2024.100308
Swetasree Nag , Malabika Biswas Roy , Pankaj Kumar Roy
This study employs the SWAT hydrologic model to integrate climatological and hydrological processes for an in-depth analysis of the Mayurakshi River Basin. Utilizing the Markov chain model, the study evaluates water availability, flow patterns, and the basin's response to various climatic and land-use scenarios. Over 30 years of daily observed river discharge data were rigorously calibrated, validated, and analyzed for uncertainty, with critical data from the Massanjore Dam and Tilpara Barrage gauge stations characterizing the river's hydrological behavior. The result suggests the watershed received an average annual precipitation of 1432.4 mm, with evapotranspiration accounting for 40% of total water loss (578.4 mm). Surface runoff constituted over 90% of the total discharge, highlighting its importance for agricultural practices, particularly during the dry season. However future projections (2021–2031) indicate a significant decrease in mean annual precipitation (1404.7 mm) and a drop in evapotranspiration (542.1 mm or 38% of mean precipitation), attributed to reduced vegetation cover and increased settlement, leading to enhanced surface runoff. By quantifying internal renewable blue water, evapotranspiration, and soil water, this research provides crucial data for long-term water resource planning and assessment. The findings are valuable for national, regional, and transboundary water management agencies, offering insights into sustainable water resource management under changing climatic and different land-use conditions.
{"title":"Integrated hydrological modeling and water resource assessment in the Mayurakshi River Basin: A comprehensive study from historical data to future predictions","authors":"Swetasree Nag , Malabika Biswas Roy , Pankaj Kumar Roy","doi":"10.1016/j.geogeo.2024.100308","DOIUrl":"10.1016/j.geogeo.2024.100308","url":null,"abstract":"<div><div>This study employs the SWAT hydrologic model to integrate climatological and hydrological processes for an in-depth analysis of the Mayurakshi River Basin. Utilizing the Markov chain model, the study evaluates water availability, flow patterns, and the basin's response to various climatic and land-use scenarios. Over 30 years of daily observed river discharge data were rigorously calibrated, validated, and analyzed for uncertainty, with critical data from the Massanjore Dam and Tilpara Barrage gauge stations characterizing the river's hydrological behavior. The result suggests the watershed received an average annual precipitation of 1432.4 mm, with evapotranspiration accounting for 40% of total water loss (578.4 mm). Surface runoff constituted over 90% of the total discharge, highlighting its importance for agricultural practices, particularly during the dry season. However future projections (2021–2031) indicate a significant decrease in mean annual precipitation (1404.7 mm) and a drop in evapotranspiration (542.1 mm or 38% of mean precipitation), attributed to reduced vegetation cover and increased settlement, leading to enhanced surface runoff. By quantifying internal renewable blue water, evapotranspiration, and soil water, this research provides crucial data for long-term water resource planning and assessment. The findings are valuable for national, regional, and transboundary water management agencies, offering insights into sustainable water resource management under changing climatic and different land-use conditions.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100308"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141843241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Late Cretaceous (89–65 Ma) Sarnu-Dandali alkaline complex is intrusive into the Neoproterozoic (∼750 Ma) Malani Igneous Suite of rocks in North-Western India. This complex represents a polychronous setup owing to the available age groups of varied rock types involving nephelinites, alkali pyroxenites, syenites, phonolites, ijolites, carbonatites and lamprophyres. In this study, we report xenoliths of ijolite up to 2 mm in size, comprising minerals such as aegirine, nepheline, sodalite, apatite, sphene, fluorite, Ti-rich andradite, and perovskite entrained in the host nephelinite from this complex. Pyroxene thermobarometry for both host and xenoliths reveals that the xenoliths crystallized around 876–1114°C; 4.6–18 kbar (Kdcpx−melt ∼0.164), whereas the host magma crystallized around 800–1165°C and 4.5–17.9 kbar (Kdcpx−melt ∼0.44). The redox conditions of the magma are also estimated from Fe-Nb oxy barometry of perovskite and the log oxygen fugacity varies from -2.5 to -3.7 (ΔNNO), showing a resemblance with that of the world-wide kimberlites derived from the cratonic mantle. Furthermore, the composition as well as the barometric study of clinopyroxenes from both the host and the xenoliths, suggest multiple shallower magma chambers composed of ijolite and nephelinite magmas which were activated by different magmatic pulses, thereby forming a complex magmatic plumbing system.
晚白垩世（89-65 Ma）萨尔努-丹达利碱性复合岩是印度西北部新近纪（750 Ma）马拉尼火成岩组的侵入岩。这个复合体是一个多时相设置，因为它有不同岩石类型的年龄组，包括霞石、碱性辉长岩、正长岩、辉绿岩、黝帘石、碳酸盐岩和灯泡岩。在这项研究中，我们报告了来自这一复合体的尺寸达 2 毫米的黝帘石异长岩，其中包括夹杂在宿主霞石中的埃吉林石、霞石、钠长石、磷灰石、榍石、萤石、富钛安山岩和透辉石等矿物。主岩浆和氙石的辉石热压计显示，氙石的结晶温度约为 876-1114°C; 4.6-18 kbar (Kdcpx-melt ∼ 0.164)，而主岩浆的结晶温度约为 800-1165°C 和 4.5-17.9 kbar (Kdcpx-melt ∼ 0.44)。岩浆的氧化还原条件也是通过包晶的Fe-Nb氧压测定法估算出来的，对数氧富集度在-2.5到-3.7（ΔNNO）之间，这与世界上源自板块地幔的金伯利岩相似。此外，对主岩和鳞片辉石的成分以及气压研究表明，由黝帘石和霞石岩浆组成的多个较浅的岩浆室被不同的岩浆脉冲激活，从而形成了一个复杂的岩浆管道系统。
{"title":"Petrology of ijolite xenoliths entrained in a nephelinite dyke from the Kamthai area, Late Cretaceous polychronous Sarnu-Dandali alkaline complex, North-West India: Evidence for recurrent magmatic pulses and magma mixing","authors":"Sudipa Bhunia , N.V. Chalapathi Rao , Debojit Talukdar , Rohit Pandey , Bernd Lehmann","doi":"10.1016/j.geogeo.2023.100248","DOIUrl":"10.1016/j.geogeo.2023.100248","url":null,"abstract":"<div><div>The Late Cretaceous (89–65 Ma) Sarnu-Dandali alkaline complex is intrusive into the Neoproterozoic (∼750 Ma) Malani Igneous Suite of rocks in North-Western India. This complex represents a polychronous setup owing to the available age groups of varied rock types involving nephelinites, alkali pyroxenites, syenites, phonolites, ijolites, carbonatites and lamprophyres. In this study, we report xenoliths of ijolite up to 2 mm in size, comprising minerals such as aegirine, nepheline, sodalite, apatite, sphene, fluorite, Ti-rich andradite, and perovskite entrained in the host nephelinite from this complex. Pyroxene thermobarometry for both host and xenoliths reveals that the xenoliths crystallized around 876–1114°C; 4.6–18 kbar (<em>Kd<sub>cpx</sub></em><sub>−melt</sub> ∼0.164), whereas the host magma crystallized around 800–1165°C and 4.5–17.9 kbar (<em>Kd<sub>cpx</sub></em><sub>−melt</sub> ∼0.44). The redox conditions of the magma are also estimated from Fe-Nb oxy barometry of perovskite and the log oxygen fugacity varies from -2.5 to -3.7 (ΔNNO), showing a resemblance with that of the world-wide kimberlites derived from the cratonic mantle. Furthermore, the composition as well as the barometric study of clinopyroxenes from both the host and the xenoliths, suggest multiple shallower magma chambers composed of ijolite and nephelinite magmas which were activated by different magmatic pulses, thereby forming a complex magmatic plumbing system.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100248"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139023265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Preliminary studied lower crust and Moho of Baikal Rift (BR) was investigated using pyroxenite xenoliths and xenocrysts from Cenozoic volcanoes to determine the structure, thermal conditions and composition of the transitional zone from the crust to mantle and influence of plumes on it. Samples from Vitim Plateau (Miocene picrite basalts) SW part of BR, Dzhida River Basin (Bartoy volcanoes) located at SE of BR and Tunka axial Valley (Karierny volcanoes) to the West from Baikal were studied for major components using electron microprobe and electron microscope and for trace elements with the inductively connected mass-spectrometry with laser ablation. For the comparison, the lower crust xenocrysts from the Angara Vitim batholite were also included in this study. The PT estimates for minerals are mostly refer to the Moho boundary or are locating just beneath it giving the vast range of temperatures. Beneath the Moho, they trace 90 mw/m2 geotherm. Within the crust, temperature regime varies from the conductive to advective. Pyroxene xenocrysts and pyroxenite xenoliths mainly trace 90 mw/m2 SEA plume geotherm. The levels of the melt intrusions are overheated to 1350°C. The granulites are typically represent the colder conditions than SEA geotherm. Xenocrysts from Angara Vitim batholith magmas reveal more depleted material of lower crust than those found in Cenozoic lavas and possibly are skialites. The xenocrysts and granulite xenoliths in Cenozoic lavas are mainly basic cumulates. The rocks of the lower crust became more acid to the upper part.
The lateral variations in the lower crust sampled material show enrichment in K2O at the boundary with the Siberian Craton in Tunka, more metasomatic and hydrous nature in Dzhida zone and more basic and CaO rich characteristic in Vitim area. These data give the evidence for the conditions of origin of the magmas of Angara-Vitim Batholith (AVP) (275–310 Ma), which was created due to interaction of hot spot with the crust in Baikal and Transbaikalia. Initially this hot generated kimberlites and basalts in northern (420–390 Ma) and central part of Yakutia (370–440 Ma) in time, migrated to – and eeastern Sayan Mountain formed Ingashi lamproites -kimberlites (310 Ma), than plume was spreading to south beneath the crust in Transbaikalia and created AVP. After it returned to central and northern Siberia, it generated Permo-Triassic Siberian trap province.
{"title":"Thermal state and nature of the lower crust in the Baikal Rift Zone: Insight from xenoliths of Cenozoic and Paleozoic magmatic rocks","authors":"I.V. Ashchepkov , A.A. Tsygankov , G.N. Burmakina , N.S. Karmanov , S.V. Rasskazov , I.S. Chuvashova , Y. Ailow","doi":"10.1016/j.geogeo.2024.100305","DOIUrl":"10.1016/j.geogeo.2024.100305","url":null,"abstract":"<div><div>Preliminary studied lower crust and Moho of Baikal Rift (BR) was investigated using pyroxenite xenoliths and xenocrysts from Cenozoic volcanoes to determine the structure, thermal conditions and composition of the transitional zone from the crust to mantle and influence of plumes on it. Samples from Vitim Plateau (Miocene picrite basalts) SW part of BR, Dzhida River Basin (Bartoy volcanoes) located at SE of BR and Tunka axial Valley (Karierny volcanoes) to the West from Baikal were studied for major components using electron microprobe and electron microscope and for trace elements with the inductively connected mass-spectrometry with laser ablation. For the comparison, the lower crust xenocrysts from the Angara Vitim batholite were also included in this study. The PT estimates for minerals are mostly refer to the Moho boundary or are locating just beneath it giving the vast range of temperatures. Beneath the Moho, they trace 90 mw/m<sup>2</sup> geotherm. Within the crust, temperature regime varies from the conductive to advective. Pyroxene xenocrysts and pyroxenite xenoliths mainly trace 90 mw/m<sup>2</sup> SEA plume geotherm. The levels of the melt intrusions are overheated to 1350°C. The granulites are typically represent the colder conditions than SEA geotherm. Xenocrysts from Angara Vitim batholith magmas reveal more depleted material of lower crust than those found in Cenozoic lavas and possibly are skialites. The xenocrysts and granulite xenoliths in Cenozoic lavas are mainly basic cumulates. The rocks of the lower crust became more acid to the upper part.</div><div>The lateral variations in the lower crust sampled material show enrichment in K<sub>2</sub>O at the boundary with the Siberian Craton in Tunka, more metasomatic and hydrous nature in Dzhida zone and more basic and CaO rich characteristic in Vitim area. These data give the evidence for the conditions of origin of the magmas of Angara-Vitim Batholith (AVP) (275–310 Ma), which was created due to interaction of hot spot with the crust in Baikal and Transbaikalia. Initially this hot generated kimberlites and basalts in northern (420–390 Ma) and central part of Yakutia (370–440 Ma) in time, migrated to – and eeastern Sayan Mountain formed Ingashi lamproites -kimberlites (310 Ma), than plume was spreading to south beneath the crust in Transbaikalia and created AVP. After it returned to central and northern Siberia, it generated Permo-Triassic Siberian trap province.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100305"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141713730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.geogeo.2024.100315
M. Lavanya, M. Muthukumar
Recent advances in space technology are being widely utilized in resource mapping and management as they provide a high level of accuracy over a short duration and at a lower cost, when compared to traditional methods. Remote sensing and the geographical information system (GIS) play a vital role in collecting and analyzing information used to map resources and earth surface features. For example, anthropogenic activities and climate change affect the natural interaction between the surface and ground water making the monitoring and management of groundwater resources mandatory for future sustainable development. In this study, we attempt to identify the groundwater potential zones in the Dindigul district of Tamil Nadu, India using these emerging technologies. To map regions with groundwater potential, the analytical hierarchical process (AHP) was used to assign weights to all classes in each thematic layer based on groundwater-influencing factors. The sub-features of every parameter were also ranked, using a pairwise comparison method, based on the groundwater-influencing factors and expert knowledge. The parameters selected for the analysis were geology, geomorphology, soil, land use/land cover, drainage density, lineament density, slope, rainfall, thickness of top-soil, thickness of fractured zone, thickness of weathered zone, topographic wetness index, roughness and curvature. The weighted overlay analysis method was adopted for all the thematic layers, with technical support from the AHP for assigning weightages. The results were classified into five categories viz., very high, high, moderate, low, and very low potential zones, and used to prepare a groundwater potential map. This map revealed a nuanced distribution of groundwater potential across the district, with varying degrees of potentiality in different regions. Very high potential zones occupy a minimal area (0.07%) but are strategically located in areas characterized by high weathered zone thickness and conducive soil characteristics. High potential zones cover a significant area (22.33%) and are dispersed throughout the district, with specific concentrations in regions featuring highly fractured zones and favorable geological attributes. Moderate potential zones (35.12%) are primarily located in the northeastern part of the study area, while low and very low potential regions cover 19.56% and 22.92% of the study area. The low and very low potential zones appear particularly in hilly terrains, with unfavorable top soil and geological conditions. The validation of the groundwater potential zone (GWPZ) map using the annual average water level data demonstrates a substantial match (60.53%) between the identified groundwater conditions and actual well depths, affirming the reliability and significance of the findings from this study.
{"title":"AHP and geospatial technologies for identifying groundwater exploration target regions in Dindigul, southern India","authors":"M. Lavanya, M. Muthukumar","doi":"10.1016/j.geogeo.2024.100315","DOIUrl":"10.1016/j.geogeo.2024.100315","url":null,"abstract":"<div><div>Recent advances in space technology are being widely utilized in resource mapping and management as they provide a high level of accuracy over a short duration and at a lower cost, when compared to traditional methods. Remote sensing and the geographical information system (GIS) play a vital role in collecting and analyzing information used to map resources and earth surface features. For example, anthropogenic activities and climate change affect the natural interaction between the surface and ground water making the monitoring and management of groundwater resources mandatory for future sustainable development. In this study, we attempt to identify the groundwater potential zones in the Dindigul district of Tamil Nadu, India using these emerging technologies. To map regions with groundwater potential, the analytical hierarchical process (AHP) was used to assign weights to all classes in each thematic layer based on groundwater-influencing factors. The sub-features of every parameter were also ranked, using a pairwise comparison method, based on the groundwater-influencing factors and expert knowledge. The parameters selected for the analysis were geology, geomorphology, soil, land use/land cover, drainage density, lineament density, slope, rainfall, thickness of top-soil, thickness of fractured zone, thickness of weathered zone, topographic wetness index, roughness and curvature. The weighted overlay analysis method was adopted for all the thematic layers, with technical support from the AHP for assigning weightages. The results were classified into five categories viz., very high, high, moderate, low, and very low potential zones, and used to prepare a groundwater potential map. This map revealed a nuanced distribution of groundwater potential across the district, with varying degrees of potentiality in different regions. Very high potential zones occupy a minimal area (0.07%) but are strategically located in areas characterized by high weathered zone thickness and conducive soil characteristics. High potential zones cover a significant area (22.33%) and are dispersed throughout the district, with specific concentrations in regions featuring highly fractured zones and favorable geological attributes. Moderate potential zones (35.12%) are primarily located in the northeastern part of the study area, while low and very low potential regions cover 19.56% and 22.92% of the study area. The low and very low potential zones appear particularly in hilly terrains, with unfavorable top soil and geological conditions. The validation of the groundwater potential zone (GWPZ) map using the annual average water level data demonstrates a substantial match (60.53%) between the identified groundwater conditions and actual well depths, affirming the reliability and significance of the findings from this study.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100315"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.geogeo.2024.100266
A.A. Tsygankov, G.N. Burmakina, V.B. Khubanov, A.V. Ukraintsev, N.D. Guslyakov
Late Paleozoic granites of the Angara-Vitim batholith (AVB) occupy an area of 200,000 km2 in Western Transbaikalia (the eastern part of the Central Asian fold belt). Batholith granitoids form a sheet-like body with an average thickness of 7–10 km and a volume of about 1 million km3. The granitoid massifs that make up the batholith are composed of high-potassium calc-alkaline and subalkaline quartz monzonites, quartz syenites, amphibole-biotite granodiorites, and biotite granites of autochthonous and allochthonous facies. An extremely high heterogeneity of the batholith isotopic structure was established, which basically corresponds to the parameters of uneven-aged crustal metaterrigenous protoliths. There are significant variations in εNd(Т) and accordingly T(DM-2) in granitoids of different complexes. It is assumed that the isotopic heterogeneity of AVB was formed due to the melting of a limited protoliths number that are maximally contrasting in isotopic and lithological composition: the Paleoproterozoic continental crust with εNd(Т) ≈ -20 ÷ -22 and T(DM-2) = 2.9–2.5 Ga and Neoproterozoic mafic granulites of increased potassium alkalinity, enriched in the juvenile component (εNd(Т) ≈ -3.0; T(DM-2) = 1.2–1.3 Ga). The latter were the main magmas source of postbatholitic alkali granites. Melts from these contrasting protoliths were only in some cases complementary to the salic melts sources. The main mechanism that determined the isotopic composition of AVB granitoids was the mixing of isotopically contrasting magmas in different proportions. Mingling dikes, mafic inclusions in granitoids, and synplutonic mafic intrusions in the AVB indicate an additional mixing component. It was mafic magma from an enriched mantle reactivated in the Late Paleozoic under the mantle plume influence on the heated plastic crust of a young (Hercynian) orogen.
{"title":"Nd isotope systematics of Late Paleozoic granitoids from the Western Transbaikalia (Russia): Petrological consequences and plume model testing","authors":"A.A. Tsygankov, G.N. Burmakina, V.B. Khubanov, A.V. Ukraintsev, N.D. Guslyakov","doi":"10.1016/j.geogeo.2024.100266","DOIUrl":"10.1016/j.geogeo.2024.100266","url":null,"abstract":"<div><div>Late Paleozoic granites of the Angara-Vitim batholith (AVB) occupy an area of 200,000 km<sup>2</sup> in Western Transbaikalia (the eastern part of the Central Asian fold belt). Batholith granitoids form a sheet-like body with an average thickness of 7–10 km and a volume of about 1 million km<sup>3</sup>. The granitoid massifs that make up the batholith are composed of high-potassium calc-alkaline and subalkaline quartz monzonites, quartz syenites, amphibole-biotite granodiorites, and biotite granites of autochthonous and allochthonous facies. An extremely high heterogeneity of the batholith isotopic structure was established, which basically corresponds to the parameters of uneven-aged crustal metaterrigenous protoliths. There are significant variations in εNd(Т) and accordingly T(DM-2) in granitoids of different complexes. It is assumed that the isotopic heterogeneity of AVB was formed due to the melting of a limited protoliths number that are maximally contrasting in isotopic and lithological composition: the Paleoproterozoic continental crust with εNd(Т) ≈ -20 ÷ -22 and T(DM-2) = 2.9–2.5 Ga and Neoproterozoic mafic granulites of increased potassium alkalinity, enriched in the juvenile component (εNd(Т) ≈ -3.0; T(DM-2) = 1.2–1.3 Ga). The latter were the main magmas source of postbatholitic alkali granites. Melts from these contrasting protoliths were only in some cases complementary to the salic melts sources. The main mechanism that determined the isotopic composition of AVB granitoids was the mixing of isotopically contrasting magmas in different proportions. Mingling dikes, mafic inclusions in granitoids, and synplutonic mafic intrusions in the AVB indicate an additional mixing component. It was mafic magma from an enriched mantle reactivated in the Late Paleozoic under the mantle plume influence on the heated plastic crust of a young (Hercynian) orogen.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100266"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140088105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mantle xenoliths from Zarnitsa pipe studied in gray eruptive breccias (early) brown autholitic breccia (BAB) and black macrocrystic kimberlites (last dike; BMK), include garnet and spinel dunites-harzburgites, pyroxenites, eclogites, glimmerites and megacrysts. PT reconstructions using xenoliths reveal sharply layered structure (8 levels), estimated with the single grain mineral estimates mark hot (Cpx, Ilm) and cold (OPx, Gar) inflected geotherm. The interaction with plume melts is found at the lithosphere asthenosphere boundary (LAB), pyroxenite layer (3-4 GPa), Gar-Sp transition and Moho. Eclogites reveal Fe# growth from LAB to middle pyroxenites layer. Clinopyroxenes and ilmenite estimates marks melt refertilisations in interlayers between coupled subduction slabs. Source of capture from first to third stage deepening to LAB and Cr- rich garnets (to 19.5 Cr2O3) are below the LAB.
The grey erupted breccia (GEB) includes mainly depleted and deformed peridotites. The later BAB includes pyroxenites, eclogites, and refertilised, deformed, and veined peridotites in BMK. Geochemistry of minerals changes from primary mid ocean ridge basalts (MORB) and back arc peridotites with low REE and large ion lithophile elements (LILE) and deeps in high field strength elements (HFSE) to metasomatized by alkaline (high Na and LILE) and adakitic melts (high Al, Na, Sr, and elevated HFSE) varieties and refertilised lherzolites due to plume at last stage. Mantle column metasomatized with scattered phlogopites in early grey eruptive breccia to amphibole-phlogopite ilmenite veins at last stages. Amphiboles trace mantle from lithosphere – asthenosphere boundary to Moho.
Growth of the diamond grade from early eruptive breccia to later kimberlite phases refer to decreasing of the crust material and deepening of the xenoliths capture level. Metasomatism dissolve the diamonds but growth of megacrystic diamond crystals increase diamond grade.
{"title":"Trace element geochemistry of mantle xenoliths from Zarnitsa kimberlite pipe, Daldyn field, Yakutia: Complex history of melts interactions with lithospheric mantle","authors":"I.V. Ashchepkov , N. Ntaflos , N.S. Medvedev , G.P. Shmarov","doi":"10.1016/j.geogeo.2024.100313","DOIUrl":"10.1016/j.geogeo.2024.100313","url":null,"abstract":"<div><div>Mantle xenoliths from Zarnitsa pipe studied in gray eruptive breccias (early) brown autholitic breccia (BAB) and black macrocrystic kimberlites (last dike; BMK), include garnet and spinel dunites-harzburgites, pyroxenites, eclogites, glimmerites and megacrysts. PT reconstructions using xenoliths reveal sharply layered structure (8 levels), estimated with the single grain mineral estimates mark hot (Cpx, Ilm) and cold (OPx, Gar) inflected geotherm. The interaction with plume melts is found at the lithosphere asthenosphere boundary (LAB), pyroxenite layer (3-4 GPa), Gar-Sp transition and Moho. Eclogites reveal Fe# growth from LAB to middle pyroxenites layer. Clinopyroxenes and ilmenite estimates marks melt refertilisations in interlayers between coupled subduction slabs. Source of capture from first to third stage deepening to LAB and Cr- rich garnets (to 19.5 Cr<sub>2</sub>O<sub>3</sub>) are below the LAB.</div><div>The grey erupted breccia (GEB) includes mainly depleted and deformed peridotites. The later BAB includes pyroxenites, eclogites, and refertilised, deformed, and veined peridotites in BMK. Geochemistry of minerals changes from primary mid ocean ridge basalts (MORB) and back arc peridotites with low REE and large ion lithophile elements (LILE) and deeps in high field strength elements (HFSE) to metasomatized by alkaline (high Na and LILE) and adakitic melts (high Al, Na, Sr, and elevated HFSE) varieties and refertilised lherzolites due to plume at last stage. Mantle column metasomatized with scattered phlogopites in early grey eruptive breccia to amphibole-phlogopite ilmenite veins at last stages. Amphiboles trace mantle from lithosphere – asthenosphere boundary to Moho.</div><div>Growth of the diamond grade from early eruptive breccia to later kimberlite phases refer to decreasing of the crust material and deepening of the xenoliths capture level. Metasomatism dissolve the diamonds but growth of megacrystic diamond crystals increase diamond grade.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100313"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.geogeo.2024.100321
Omid Memarian Sorkhabi
Peatlands represent vital carbon reserves; however, once ignited, they release stored carbon, inflicting lasting environmental harm and necessitating prolonged recovery periods. An innovative method merging Sentinel-1 satellite imagery and deep learning (DL) is proposed to monitor burnt peat across diverse regions of Ireland, regardless of weather conditions or time of day. Sentinel-2 images and field measurements were used to train deep neural networks (DNN) and the accuracy in detecting burnt peat areas reached 80 %. This was achieved by combining the VV (vertical transmit, vertical receive) and VH (vertical transmit, horizontal receive) from Sentinel-1. Time-series analysis of Sentinel-1 VV backscatter change for Wicklow Mountains in 2018 highlights the Sentinel-1's capacity to detect various phenomena, including snowfall and burnt peat, evident prior to the peat fire event. Furthermore, an examination of peat fire occurrences in Wicklow Mountains from 2018 to 2023 through time series and mapping shows a significant escalation, with the largest burnt areas detected in 2023 spanning over 40 km².
{"title":"Deep learning of Sentinel-1 SAR for burnt peatland detection in Ireland","authors":"Omid Memarian Sorkhabi","doi":"10.1016/j.geogeo.2024.100321","DOIUrl":"10.1016/j.geogeo.2024.100321","url":null,"abstract":"<div><div>Peatlands represent vital carbon reserves; however, once ignited, they release stored carbon, inflicting lasting environmental harm and necessitating prolonged recovery periods. An innovative method merging Sentinel-1 satellite imagery and deep learning (DL) is proposed to monitor burnt peat across diverse regions of Ireland, regardless of weather conditions or time of day. Sentinel-2 images and field measurements were used to train deep neural networks (DNN) and the accuracy in detecting burnt peat areas reached 80 %. This was achieved by combining the VV (vertical transmit, vertical receive) and VH (vertical transmit, horizontal receive) from Sentinel-1. Time-series analysis of Sentinel-1 VV backscatter change for Wicklow Mountains in 2018 highlights the Sentinel-1's capacity to detect various phenomena, including snowfall and burnt peat, evident prior to the peat fire event. Furthermore, an examination of peat fire occurrences in Wicklow Mountains from 2018 to 2023 through time series and mapping shows a significant escalation, with the largest burnt areas detected in 2023 spanning over 40 km².</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100321"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.geogeo.2024.100295
Sergei V. Rasskazov , Irina S. Chuvashova , Tatyana A. Yasnygina , Elena V. Saranina
Representative sampling of the Dariganga volcanic field was conducted to decipher its inner structure in terms of its deep magma sources. Rocks with a high La/Yb ratio (40–54) and a high MgO content (11–15.8 wt%) are identified among the predominantly moderate La/Yb ratio (7–40) and a moderate MgO content (5–11 wt%) rocks. These rock markers, traced along linear volcanic zones, are considered as indicators of high and low temperature magma generation processes. A general agreement exists that partial melting predominated in the transitional asthenosphere–lithosphere region; however, between 10 and 5 Ma, these processes were complicated by melts that either adiabatically ascended from a residual slab source in the deep mantle at a high potential temperature (Тр = 1489°С) or were generated due to mantle fluid degassing at a low temperature or both these processes, simultaneously. Magmas were subsequently adiabatically upraised from an OIB-like source in the deep mantle with potential temperatures (Tp) of up to 1423°C and were also generated by mantle fluids at low temperature. The rock markers yield Pb-isotope age estimates of the proto-mantle (at 4.47 and 4.45 Ga) and the age-modified mantle (at 3.11 and 2.74 Ga) beneath Dariganga. In the last 16 Ma, encompassing the late geodynamic epoch of Earth's mantle, similar high and low temperature magmas have erupted across vast sections of the Japan-Baikal Geodynamic Corridor; these magmas are not reported from the adjacent Abaga and Dalinuoer areas, with the exception of the final (Holocene) fluid-derived compositions.
{"title":"Late Cenozoic high and low temperature magma generation from primordial and age-modified mantle materials beneath Dariganga in Southeast Mongolia: Factors of mantle degassing and adiabatic upwelling","authors":"Sergei V. Rasskazov , Irina S. Chuvashova , Tatyana A. Yasnygina , Elena V. Saranina","doi":"10.1016/j.geogeo.2024.100295","DOIUrl":"10.1016/j.geogeo.2024.100295","url":null,"abstract":"<div><div>Representative sampling of the Dariganga volcanic field was conducted to decipher its inner structure in terms of its deep magma sources. Rocks with a high La/Yb ratio (40–54) and a high MgO content (11–15.8 wt%) are identified among the predominantly moderate La/Yb ratio (7–40) and a moderate MgO content (5–11 wt%) rocks. These rock markers, traced along linear volcanic zones, are considered as indicators of high and low temperature magma generation processes. A general agreement exists that partial melting predominated in the transitional asthenosphere–lithosphere region; however, between 10 and 5 Ma, these processes were complicated by melts that either adiabatically ascended from a residual slab source in the deep mantle at a high potential temperature (Т<sub>р</sub> = 1489°С) or were generated due to mantle fluid degassing at a low temperature or both these processes, simultaneously. Magmas were subsequently adiabatically upraised from an OIB-like source in the deep mantle with potential temperatures (T<sub>p</sub>) of up to 1423°C and were also generated by mantle fluids at low temperature. The rock markers yield Pb-isotope age estimates of the proto-mantle (at 4.47 and 4.45 Ga) and the age-modified mantle (at 3.11 and 2.74 Ga) beneath Dariganga. In the last 16 Ma, encompassing the late geodynamic epoch of Earth's mantle, similar high and low temperature magmas have erupted across vast sections of the Japan-Baikal Geodynamic Corridor; these magmas are not reported from the adjacent Abaga and Dalinuoer areas, with the exception of the final (Holocene) fluid-derived compositions.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100295"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.geogeo.2024.100267
Ankur Ashutosh, Amiya K. Samal, Gulab C. Gautam, Rajesh K. Srivastava
The Bastar craton of the Indian Shield hosts several generations of mafic dyke swarms of various trends, compositions, and ages, which span from ca. 2.7 Ga to 1.42 Ga. This study focuses on geochemical attributes of the ca. 1.89–1.88 Ga NNW-trending Bastanar swarm, aiming to address a perceived discrepancy between its arc-like geochemistry and the influence of a heterogeneous mantle source. To resolve the intra-swarm geochemical variations, we conducted a comprehensive geochemical characterization and petrogenetic interpretation of the ca. 1.89–1.88 Ga Bastanar swarm. The samples from this swarm are categorized into two distinct groups, primarily based on their geochemical composition. The Group 1 samples exhibit higher TiO2 (1.06–1.86 wt%), (La/Yb)N (7.2–8.6), (Gd/Yb)N (2- 2.27), Nb (14.6–16.6 ppm), Th (1.23–3.03 ppm) and Zr (104–118.72 ppm) concentrations than the Group 2 samples. Furthermore, rare-earth element patterns and variations in high-field strength element contents in the Group 1 samples suggest derivation from a deeper, less depleted mantle source resembling an OIB/less MORB-type. This inference is further supported by higher TiO2/Yb, Zr/Nb, and Nb/Y ratios. In contrast, the Group 2 samples indicate derivation from a shallower, more MORB/less OIB-type depleted mantle source, as evidenced by lower TiO2/Yb, Zr/Nb, and Nb/Y ratios. Variations in Dy/Yb and Gd/Yb ratios confirm the involvement of variable mantle sources, implying the derivation of the Group 1 and 2 samples from garnet-rich and spinel-rich lherzolite mantle sources, respectively. The absence of consistent negative Nb-Ta-Ti anomalies in the Group 1 samples suggests an uncontaminated nature, ruling out any role of crustal contamination. On the other hand, the Group 2 samples display negative Nb-Ta-Ti anomalies with enriched LREE and LILE patterns, indicating the involvement of crustal components in their genesis. A trace-element modelling suggests that the ca. 1.89–1.88 Ga mafic dyke swarm exhibits significant intra-swarm variability, with at least two distinct source components contributing to its genesis – a depleted MORB-type and an enriched OIB-type mantle. Notably, the geochemical characteristics of the Group 2 samples suggest interaction with a metasomatized mantle source, possibly enriched by fluids from an earlier subducted slab. Geochemical evidence presented in this work supports Archean subduction-related processes for the crustal growth of the Bastar craton and highlight the enduring influence of a metasomatized sub-continental lithospheric mantle on subsequent magmatism over millions of years.
印度地盾的巴斯塔克拉通（Bastar craton of the Indian Shield）孕育了几代岩浆岩堤群，其趋势、成分和年龄各不相同，从大约 2.7 Ga 到 1.42 Ga 不等。本研究的重点是约 2.7 Ga 至 1.42 Ga 的岩浆岩的地球化学属性。1.89-1.88 Ga NNW走向的巴斯塔纳尔岩浆群的地球化学属性，旨在解决其弧状地球化学与异质地幔源影响之间的差异。为了解决星群内部的地球化学变化，我们对大约 1.89-1.88 Ga 的巴斯塔纳尔星群进行了全面的地球化学特征描述和岩石成因解释。1.89-1.88 Ga 的巴斯塔纳尔岩群进行了全面的地球化学表征和岩石成因解释。该岩群的样品主要根据其地球化学成分被分为两个不同的组。第 1 组样品的 TiO2（1.06-1.86 wt%）、(La/Yb)N（7.2-8.6）、(Gd/Yb)N（2- 2.27）、Nb（14.6-16.6 ppm）、Th（1.23-3.03 ppm）和 Zr（104-118.72 ppm）浓度高于第 2 组样品。此外，第 1 组样品的稀土元素模式和高场强元素含量的变化表明，它们来自更深、贫化程度更低的地幔源，类似于 OIB/less MORB 类型。较高的 TiO2/Yb、Zr/Nb 和 Nb/Y 比率进一步支持了这一推论。与此相反，第 2 组样品表明其来源于更浅、更 MORB/less OIB 型贫化地幔源，较低的 TiO2/Yb、Zr/Nb 和 Nb/Y 比率证明了这一点。Dy/Yb和Gd/Yb比率的变化证实了可变地幔源的参与，这意味着第1组和第2组样品分别来自富含石榴石和富含尖晶石的蛭石地幔源。第 1 组样本中没有持续的 Nb-Ta-Ti 负异常，这表明样本未受污染，排除了地壳污染的可能。另一方面，第 2 组样品显示负 Nb-Ta-Ti 异常，并伴有丰富的 LREE 和 LILE 模式，表明其成因涉及地壳成分。痕量元素建模表明，约1.89-1.88Ga岩浆岩堤群表现出显著的群内变异性，至少有两种不同的成因--贫化的MORB型地幔和富集的OIB型地幔。值得注意的是，第 2 组样品的地球化学特征表明，它们与一个变质地幔源发生了相互作用，该地幔源可能被来自早期俯冲板块的流体富集。这项研究提供的地球化学证据支持了巴斯塔环形山地壳生长过程中与奥陶纪俯冲有关的过程，并强调了在数百万年的时间里，变质的次大陆岩石圈地幔对后续岩浆活动的持久影响。
{"title":"Petrogenetic and geochemical constraints on ca. 1.89–1.88 Ga Bastanar mafic dyke swarm, Bastar craton, India: Insights into MORB- and OIB-type contributions and interactions with metasomatized subcontinental lithospheric mantle","authors":"Ankur Ashutosh, Amiya K. Samal, Gulab C. Gautam, Rajesh K. Srivastava","doi":"10.1016/j.geogeo.2024.100267","DOIUrl":"10.1016/j.geogeo.2024.100267","url":null,"abstract":"<div><div>The Bastar craton of the Indian Shield hosts several generations of mafic dyke swarms of various trends, compositions, and ages, which span from ca. 2.7 Ga to 1.42 Ga. This study focuses on geochemical attributes of the ca. 1.89–1.88 Ga NNW-trending Bastanar swarm, aiming to address a perceived discrepancy between its arc-like geochemistry and the influence of a heterogeneous mantle source. To resolve the intra-swarm geochemical variations, we conducted a comprehensive geochemical characterization and petrogenetic interpretation of the ca. 1.89–1.88 Ga Bastanar swarm. The samples from this swarm are categorized into two distinct groups, primarily based on their geochemical composition. The Group 1 samples exhibit higher TiO<sub>2</sub> (1.06–1.86 wt%), (La/Yb)<sub>N</sub> (7.2–8.6), (Gd/Yb)<sub>N</sub> (2- 2.27), Nb (14.6–16.6 ppm), Th (1.23–3.03 ppm) and Zr (104–118.72 ppm) concentrations than the Group 2 samples. Furthermore, rare-earth element patterns and variations in high-field strength element contents in the Group 1 samples suggest derivation from a deeper, less depleted mantle source resembling an OIB/less MORB-type. This inference is further supported by higher TiO<sub>2</sub>/Yb, Zr/Nb, and Nb/Y ratios. In contrast, the Group 2 samples indicate derivation from a shallower, more MORB/less OIB-type depleted mantle source, as evidenced by lower TiO<sub>2</sub>/Yb, Zr/Nb, and Nb/Y ratios. Variations in Dy/Yb and Gd/Yb ratios confirm the involvement of variable mantle sources, implying the derivation of the Group 1 and 2 samples from garnet-rich and spinel-rich lherzolite mantle sources, respectively. The absence of consistent negative Nb-Ta-Ti anomalies in the Group 1 samples suggests an uncontaminated nature, ruling out any role of crustal contamination. On the other hand, the Group 2 samples display negative Nb-Ta-Ti anomalies with enriched LREE and LILE patterns, indicating the involvement of crustal components in their genesis. A trace-element modelling suggests that the ca. 1.89–1.88 Ga mafic dyke swarm exhibits significant intra-swarm variability, with at least two distinct source components contributing to its genesis – a depleted MORB-type and an enriched OIB-type mantle. Notably, the geochemical characteristics of the Group 2 samples suggest interaction with a metasomatized mantle source, possibly enriched by fluids from an earlier subducted slab. Geochemical evidence presented in this work supports Archean subduction-related processes for the crustal growth of the Bastar craton and highlight the enduring influence of a metasomatized sub-continental lithospheric mantle on subsequent magmatism over millions of years.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100267"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140085401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.1016/j.geogeo.2024.100319
Joseph Omeiza Alao , Kolawole Muideen Lawal , Bala Bello Muhammad Dewu , Jimoh Raimi
Prediction of the exact location and depth of underground targets with the very low-frequency electromagnetic (VLF-EM) technique is one of the most important and difficult tasks in geophysical investigations. This study examined and compared the conventional 2D KIFFILT inversion pseudo-section and the use of Thumb's rule technique in the Fraser filter plot to estimate the top depth of underground targets. The VLF-EM measurement was performed over several empirical buried target models to identify anomalies or geophysical responses corresponding to subsurface targets. The Karous-Hjelt and Fraser filtering techniques were applied to estimate the depth of the identified anomalies using Thumb's rule and the conventional 2D KIFFILT inversion. The signal behaviours of the VLF-EM current density pseudo-sections and the application of Thumb's rule effectiveness in delineating empirical buried target models were examined. Thumb's rule shows 65 % accuracy with the actual depth of the empirical buried target models, while the conventional 2D KHFFILT inversion shows 30 % accuracy with the actual depth of burial. Thumb's rule is more effective and precise in predicting the accurate depth of underground targets. The influences of conductive and resistive materials on VLF-EM signals and the challenges of VLF-EM surveys were discussed. Thumb's rule is suggested as a substantial technique for estimating top depth to the underground target where depth estimation is of prime interest due to its large degree of accuracy. In addition, the total depth of the current density distribution was noted to be increased when the distance between measuring points increased. This means that VLF-EM signals with longer wavelengths indicate deeper depth penetration into the ground than signals with shorter wavelengths. The accuracy of Thumb's rule regarding top depth estimation of the anomalies has been successfully tested and validated, which can be used for VLF-EM investigation where accurate depth estimation is required. The VLF-EM technique can be considered reliable for depth estimation using Thumb's rule approach, which applies to a wide range of subsurface investigations.
{"title":"Estimation of top depth to underground targets of Karous-Hjelt and Fraser filtering of VLF-EM measurements: The Thumb's rule approach","authors":"Joseph Omeiza Alao , Kolawole Muideen Lawal , Bala Bello Muhammad Dewu , Jimoh Raimi","doi":"10.1016/j.geogeo.2024.100319","DOIUrl":"10.1016/j.geogeo.2024.100319","url":null,"abstract":"<div><div>Prediction of the exact location and depth of underground targets with the very low-frequency electromagnetic (VLF-EM) technique is one of the most important and difficult tasks in geophysical investigations. This study examined and compared the conventional 2D KIFFILT inversion pseudo-section and the use of Thumb's rule technique in the Fraser filter plot to estimate the top depth of underground targets. The VLF-EM measurement was performed over several empirical buried target models to identify anomalies or geophysical responses corresponding to subsurface targets. The Karous-Hjelt and Fraser filtering techniques were applied to estimate the depth of the identified anomalies using Thumb's rule and the conventional 2D KIFFILT inversion. The signal behaviours of the VLF-EM current density pseudo-sections and the application of Thumb's rule effectiveness in delineating empirical buried target models were examined. Thumb's rule shows 65 % accuracy with the actual depth of the empirical buried target models, while the conventional 2D KHFFILT inversion shows 30 % accuracy with the actual depth of burial. Thumb's rule is more effective and precise in predicting the accurate depth of underground targets. The influences of conductive and resistive materials on VLF-EM signals and the challenges of VLF-EM surveys were discussed. Thumb's rule is suggested as a substantial technique for estimating top depth to the underground target where depth estimation is of prime interest due to its large degree of accuracy. In addition, the total depth of the current density distribution was noted to be increased when the distance between measuring points increased. This means that VLF-EM signals with longer wavelengths indicate deeper depth penetration into the ground than signals with shorter wavelengths. The accuracy of Thumb's rule regarding top depth estimation of the anomalies has been successfully tested and validated, which can be used for VLF-EM investigation where accurate depth estimation is required. The VLF-EM technique can be considered reliable for depth estimation using Thumb's rule approach, which applies to a wide range of subsurface investigations.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100319"},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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