Geological Journal最新文献

{"title":"The Geological Characteristics of Low-Permeability Sandstone Uranium Deposit in Ordos Basin, North China: Implications of Cause of Low Permeability and Corresponding In Situ Leaching Methods","authors":"Tongpan Wu,&nbsp;Xuebin Su,&nbsp;Lixin Zhao,&nbsp;Chunru Hou,&nbsp;Qingliang Wang,&nbsp;Chunze Zhou,&nbsp;Yuhan Zou,&nbsp;Guoping Jiang","doi":"10.1002/gj.5155","DOIUrl":"https://doi.org/10.1002/gj.5155","url":null,"abstract":"<div>\u0000 \u0000 <p>This study delves into the low-permeability sandstone uranium deposits in China's Ordos Basin, examining the Daying and Bayinqinggeli deposits. Employing x-ray diffraction, clay mineral analysis, x-ray fluorescence, core porosity, gas permeability tests, micrometre computed tomography (CT), and scanning electron microscopy (SEM), the research reveals the low-permeability genesis of these uranium deposits. The findings highlight a high presence of clay minerals, with Daying from 11.5% to 31.5%, and Bayinqinggeli at about 10%. Dense calcareous interlayers are common, with carbonate minerals like calcite and dolomite filling pore spaces and cementing rock-forming minerals, reducing pore sizes and ineffective connectivity, creating dead pore spaces and lowered permeability. The study concludes that the high montmorillonite content and calcareous cementation are the main causes of low permeability, providing a theoretical basis for future permeability enhancement and sustainable exploitation of uranium resources.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 7","pages":"1721-1735"},"PeriodicalIF":1.4,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144635553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrating GIS, MCDM, and Spatial Analysis for Comprehensive Flood Risk Assessment and Mapping in Uttarakhand, India","authors":"Dhaval R. Maru,&nbsp;Vijendra Kumar,&nbsp;Kul Vaibhav Sharma,&nbsp;Quoc Bao Pham,&nbsp;Anant Patel","doi":"10.1002/gj.5172","DOIUrl":"https://doi.org/10.1002/gj.5172","url":null,"abstract":"<div>\u0000 \u0000 <p>This study presents a comprehensive approach to flood risk assessment and mapping in the Uttarakhand region, India, by integrating geographic information system (GIS) and multi-criteria decision-making (MCDM). The methodology involves using digital elevation models (DEMs) to categorise elevation into five classes, slope analysis to evaluate the role of terrain steepness and drainage density assessment to identify areas less susceptible to flooding. Average annual rainfall data, classified from meteorological stations, land use/land cover patterns and distances from rivers and roads, were analysed within a GIS framework to assess flood susceptibility. The analytic hierarchy process (AHP) was employed to assign weights to these criteria and generate a flood risk index (FRI) map. Key findings indicate that extensive moderate-to-high-risk zones are present, particularly in the lower regions of Uttarakhand. The weighted overlay analysis using GIS and AHP effectively identified areas at greater risk of flooding. The results offer valuable insights for flood risk management, land-use planning and disaster preparedness, highlighting the need for targeted interventions to enhance flood resilience in the region.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 9","pages":"2263-2280"},"PeriodicalIF":2.2,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145013303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chinese Digital Economy and Urban Green Innovation Quality and Efficiency: The Threshold Effect Analysis Based on Chinese Cities Agglomeration","authors":"Li Yue,&nbsp;Yuan Yin,&nbsp;Yuxuan Cao,&nbsp;Fayyaz Ahmad","doi":"10.1002/gj.5168","DOIUrl":"https://doi.org/10.1002/gj.5168","url":null,"abstract":"<div>\u0000 \u0000 <p>This paper takes 277 Chinese cities data from 2011 to 2020 and measures the quality of green innovation and efficiency of green innovation based on super-efficiency SBM model. This paper uses the fixed effect model to analyse the digital economy on the influence of the quality and efficiency of urban green innovation, and uses the threshold effect model to test the threshold effect gathered in this effect. This paper found that the digital economy can promote urban green innovation quality and efficiency. The conclusion is still valid after robustness tests, such as recalculating the level of the digital economy and adjusting the sample time interval. Heterogeneity test shows that digital economy has a more obvious effect on improving the quality of green innovation in central and western cities, non-resource cities, cities with high-level innovation and cities with low-level enterprise density, while it has a more obvious effect on improving the efficiency of green innovation in eastern cities, non-resource cities, cities with high-level innovation and cities with high-level enterprise density. Furthermore, digital economy can enhance the quality and efficiency of urban green innovation by increasing the degree of urban economic agglomeration, talent agglomeration, industrial agglomeration and financial agglomeration. Additionally, the quality of green innovation, the improvement effect of the digital economy is stronger when the degree of economic agglomeration exceeds the threshold. Finally, when the degree of economic and financial agglomeration exceeds the threshold, the improvement of green innovation efficiency caused by the digital economy is stronger. Therefore, the government should improve the infrastructure of the digital economy, pay attention to the role of agglomeration, develop the digital economy according to local conditions and promote urban green innovation.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 9","pages":"2195-2212"},"PeriodicalIF":2.2,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145013186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zircon U–Pb Geochronology and Hf Isotope, Whole-Rock Geochemistry and Sr–Nd Isotopes of the Late Jurassic–Early Cretaceous Intrusive Rocks From North Shanxi Province: Insight on Petrogenesis and Magmatic Process in the Central North China Craton","authors":"Kai Qi,&nbsp;ZhanLi Ren,&nbsp;Junping Cui,&nbsp;Qian Ma,&nbsp;Guangyuan Xing","doi":"10.1002/gj.5145","DOIUrl":"https://doi.org/10.1002/gj.5145","url":null,"abstract":"<div>\u0000 \u0000 <p>The Late Jurassic to Early Cretaceous was a critical transformative period for the North China Craton (NCC), marked by a tectonic shift from compression to extension and the formation of numerous Yanshanian magmatic intrusions across Shanxi Province. This article presents zircon U–Pb geochronology and Hf isotope, whole-rock geochemistry and Sr–Nd isotopic compositions of Late Jurassic to Early Cretaceous intrusive rocks from the Hunyuan area in northern Shanxi Province. The Chakou, Liulengshan and Zhongzhuangpu intrusions yield zircon U–Pb ages of 150.9 ± 1.7 Ma, 137.9 ± 2.0 Ma and 115.4 ± 0.6 Ma, respectively. The Chakou monzogranites exhibit typical features of high-K calc-alkaline I-type granites, and they are enriched in Rb, Ba, K and U, and depleted in Nb and Ta. The Sr and Nd isotopes of these samples show (⁸⁷Sr/⁸⁶Sr)_i values ranging from 0.7062 to 0.7103 and <i>ε</i>\u0000 _Nd(<i>t</i>) values between −8.8 and −8.7. Additionally, zircon rims show highly variable <i>ε</i>\u0000 _Hf(<i>t</i>) values, spanning from −12.7 to −8.1. Geochemistry and isotopes suggest that the Chakou monzogranites originated primarily from the partial melting of the lower crust. The Liulengshan quartz syenites exhibit low SiO₂ and high K₂O contents, classifying them as shoshonitic I-type quartz syenites. They are enriched in LREE and LILE, depleted in HFSE with a weak negative Eu anomaly, and display moderate <i>ε</i>\u0000 _Nd(<i>t</i>) values between −17.1 and −17.0. Zircon Hf isotope composition is relatively uniform, with <i>ε</i>\u0000 _Hf(<i>t</i>) values ranging from −22.6 to −20.4. We propose that the quartz syenites from Liulengshan were formed by mixed products of mantle-derived and crust-derived magmas, with the latter being dominant. The Zhongzhuangpu biotite monzogranites are petrologically and geochemically uniform, showing enrichment in Pb and Ta, and strong depletion in Sr, Ba and Eu. We consider that they originated from the partial melting of crustal materials. Collectively, our data indicate that continuous crustal extension, thinning and asthenospheric upwelling facilitated partial melting of both lithospheric mantle and crustal materials. These processes were the primary drivers behind the formation of intrusions in the NCC during the Late Jurassic to Early Cretaceous.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 7","pages":"1576-1600"},"PeriodicalIF":1.4,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144635563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of Tropical Cyclone Yaas on Coastal Regions of Odisha and West Bengal, India: An Assessment Using Sentinel Datasets","authors":"Bahadur Das,&nbsp;Dipanwita Dutta,&nbsp;Ratnadeep Ray","doi":"10.1002/gj.5153","DOIUrl":"https://doi.org/10.1002/gj.5153","url":null,"abstract":"<div>\u0000 \u0000 <p>Coastal areas are increasingly susceptible to frequent cyclones driven by climate change. This leads to severe flooding, habitat loss, economic damage and community displacement, necessitating urgent adaptation measures. In this context, the present study aims to assess the impact of tropical cyclone Yaas on the coastal districts of Odisha and West Bengal combining SAR and optical satellite data. The Sentinel-1 data was used for flood inundation analysis, allowing for the identification and mapping of areas affected by the cyclonic flooding. In addition, Sentinel-2 data was employed for land use and land cover (LULC) analysis, enabling the evaluation of the cyclone's impact on various land cover classes. A fuzzy Analytic Hierarchy Process (AHP) was applied to analyse the changes in forest canopy cover. By integrating these diverse datasets and analyses, the study provides a holistic understanding of the cyclone's impact on the coastal region's environment and land cover. The findings reveal that the Yaas cyclonic flood affected an area of 2528.70 sq. km, accounting for 6.8% of the total region. In the coastal areas of West Bengal, more than 24% of cropland was affected particularly in the districts of Purba Medinipur, North 24 Parganas, Hoogly, Howrah and South 24 Parganas. In Odisha state, the most affected cropland areas were Bhadrak (945.11 sq. km) and Kendrapara (557.90 sq. km), while the districts of Bhadrak, Balasore, Jajpur, Khordha and Cuttack experienced the greatest impact on built-up areas. The findings of this comprehensive study contribute to a deeper understanding of the magnitude and extent of tropical cyclone Yaas's impacts. This study can be useful for the development of effective mitigation and adaptation strategies that is, restoration of mangrove forests, introduction of salt-tolerant crops and upgrading of existing embankments and levees to enhance the resilience of the coastal communities.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 5","pages":"1029-1045"},"PeriodicalIF":1.4,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143914652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geospatial Assessment and Mapping Landslide Susceptibility for the Garo Hills Division, Meghalaya, India","authors":"Naveen Badavath,&nbsp;Smrutirekha Sahoo","doi":"10.1002/gj.5166","DOIUrl":"https://doi.org/10.1002/gj.5166","url":null,"abstract":"<div>\u0000 \u0000 <p>Creating accurate and effective Landslide Susceptibility (LS) maps can aid disaster prevention and mitigation efforts and provide sufficient public safety. The primary aim of this study is to develop an LS map for the Garo Hills region in Meghalaya, India, using the weight of evidence (WoE), frequency ratio (FR), and Shannon entropy (SE) methods. A comprehensive landslide inventory catalogued 98 events from 2000 to 2023 for the analysis, and nine key geographical and environmental parameters were prepared. Conducted multicollinearity and correlation analysis to identify and mitigate collinearity issues between factors. The model's performance was analysed through the area under the curve (AUC) value of receiver operating characteristic (ROC) curves and three recent landslides. The results showed that FR method achieved the highest accuracy, with successive rate curve (SRC) AUC and predictive rate curve (PRC) AUC values of 0.860 and 0.940, respectively, and classified susceptibility at three sites as high, moderate, and low. The WoE method effectively identified three landslides site in high and very high susceptibility zones, achieving SRC AUC and PRC AUC values of 0.844 and 0.915, respectively. The SE method showed robust performance in predicting landslide-prone areas, with PRC AUC comparable to other methods (0.913), though its SRC AUC (0.771) was lower. Developed maps revealed that high and very high susceptibility zones account for approximately 10% and 3% of the study area, predominantly near roads, steep slopes, and higher elevations. The information in this study is valuable for civilians and the government authorities involved in hazard monitoring and management.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 5","pages":"1184-1201"},"PeriodicalIF":1.4,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143914727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chronology, Geochemical Characterisation and Tectonic Background of Early Cretaceous Volcanic Rocks in the Lengjimanda Plate, Da Hinggan Mountains","authors":"Wang ShiChang,&nbsp;Hao YuJie,&nbsp;Tang Zhen,&nbsp;Shi Lu","doi":"10.1002/gj.5151","DOIUrl":"https://doi.org/10.1002/gj.5151","url":null,"abstract":"<div>\u0000 \u0000 <p>The Lengjimanda Plate in the central Da Hinggan Mountains is mainly composed of a series of acid volcanic rocks such as rhyolites and rhyolitic crystal tuffs of the Early Cretaceous Baiyingaolao and Guanghua formations. LA-ICP-MS zircon U–Pb dating indicates that rhyolites of the Baiyingaolao Formation formed between 140 and 137 Ma, while rhyolites of the Guanghua Formation formed between 129 and 128 Ma. Rocks of the Baiyingaolao Formation exhibit the characteristics of high silica contents, alkali enrichment and aluminium depletion, thus resembling A-type granites. They show significant fractionation of light and heavy rare earth elements with a pronounced negative Eu anomaly. They zircon ¹⁷⁶Hf/¹⁷⁷Hf ratios range from 0.282932 to 0.252800, with an average <i>ε</i>\u0000 _Hf(<i>t</i>) value of +1.28; (⁸⁷Sr/⁸⁶Sr)_{\u0000 <i>i</i>\u0000} ranges from 0.68848 to 0.70068, with ε_Nd(<i>t</i>) ranging from +1.4 to +3.7; and <i>t</i>\u0000 _DM2 ranges from 629 to 817 Ma, indicating magma derived from newly formed young crustal material after the closure of the Mongolian-Okhotsk Ocean. The volcanic rocks of the Guanghua Formation have characteristics that are similar to I-Type granites, with silica and alkali enrichment and Ca and Mg depletion. They also show a right-skewed “V”-shaped pattern in their REE distribution curves, with a strong negative Eu anomaly. The zircon ¹⁷⁶Hf/¹⁷⁷Hf ratios range from 0.282887 to 0.282986, with an average <i>ε</i>\u0000 _Hf(<i>t</i>) value of +8.78; (⁸⁷Sr/⁸⁶Sr)_i ranges from 0.70060 to 0.70096, with <i>ε</i>\u0000 _Nd(<i>t</i>) ranging from +3.0 to +3.8; and <i>t</i>\u0000 _DM2 ranges from 616 to 677 Ma, indicating the partial melting of depleted mantle-derived mafic lower crustal material, influenced by the closure of the Mongolian-Okhotsk Ocean and subduction of the ancient Pacific Plate.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 7","pages":"1653-1681"},"PeriodicalIF":1.4,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144635199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oil Storage Capacity in Organic-Rich Chang 7 Shale, Ordos Basin: Comparing Evaluation Methods and Controlling Factors","authors":"Wei Dang,&nbsp;Menhui Qian,&nbsp;Haikuan Nie,&nbsp;Jun Liu,&nbsp;Kefeng Du,&nbsp;Yubo Feng,&nbsp;Yankai Xue,&nbsp;Xin Zhang","doi":"10.1002/gj.5167","DOIUrl":"https://doi.org/10.1002/gj.5167","url":null,"abstract":"<div>\u0000 \u0000 <p>This study examines the oil storage capacity and controlling factors of organic-rich Chang 7 shale in the Ordos Basin, using multistep Rock-Eval pyrolysis (MREP) and liquid hydrocarbon vapour adsorption (LHVA) techniques. The research evaluates the effectiveness of these techniques in determining oil content and identifies key geological and geochemical factors impacting free and adsorbed oil. Analyses of geochemical, mineralogical, and pore structure characteristics reveal that Chang 7 shale, with high total organic carbon (TOC) content and oil-prone kerogen, along with moderate thermal maturity, is a high-quality hydrocarbon source rock. A strong linear correlation between MREP and LHVA results demonstrate the reliability of both methods for assessing adsorbed oil content, though discrepancies emphasise the impact of hydrocarbon loss during sample preparation. Statistical analysis indicates TOC content (&gt; 2%, with &gt; 4% especially favourable) and thermal maturity (<i>R</i>\u0000 _o = 0.7%–1.0%) as the critical factors for shale oil accumulation and key indicators for identifying sweet spots. These findings improve the understanding of oil occurrence processes in shale and offer practical insights for optimising shale oil exploration and development.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 9","pages":"2176-2194"},"PeriodicalIF":2.2,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145013026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"3-D Crustal Structure Modelling of the Proterozoic Cuddapah Basin, Its Regional Geodynamic Evolution and Columbia–Rodinia Connection","authors":"Satendra Singh,&nbsp;Koteswara Chandrakala,&nbsp;Om Prakash Pandey","doi":"10.1002/gj.5165","DOIUrl":"https://doi.org/10.1002/gj.5165","url":null,"abstract":"<div>\u0000 \u0000 <p>The Cuddapah Basin located in the southern part of India, is one of the largest Proterozoic basins in the world. This basin witnessed multi-stage growth that involved sedimentation, magmatism and tectonism. This region has been studied geophysically for over nine decades, nevertheless, its subsurface structural configuration, underlying crust–mantle structure and its evolutionary relationship with east Antarctica during the Columbia and Rodinia supercontinental assembly periods, remain an enigma. In the present study, we provide a 3-D crustal structural configuration of this basin based on gravity modelling along 13 east–west and 3 north–south profiles, utilising density and subsurface depth constraints from crustal seismic studies. We have delineated the presence of a 15–20 km anomalously thick, high density differentiated magmatic layer above the Moho, which varies widely from 32 km below the Eastern Ghats Belt to about 50 km below the Nellore Schist Belt. It is invariably shallower at 37–38 km north of 14°45'N, compared with 43 to 46 km south of it, indicating possible tilting of the basin from north to south. Importantly, we also notice a high order translational movement of the crustal column across the Nallamalai Basin as revealed by conspicuous change in the Moho trend, which correlates with the absence of Eastern Ghats Belt for a distance of about 400 km south of Ongole, mimicking the translational movement. We infer that the Napier complex of east Antarctica, may form the missing part of Eastern Ghats Belt of India's east coast. Similarly, a high gravity over the Nellore Schist Belt region would possibly indicate presence of remanent slab material (or magmatic material) underneath which may be related to erstwhile supra-subduction during the Rodinia supercontinental assembly period. The present study further suggests that the Iswarakuppam dome, located in northern part of the Nallamalai Basin, contains a thin veneer of Cumbum shale (5.10 km/s) followed by a high velocity (Vp: 5.70 km/s) sequences containing Bairenkonda quartzites and possibly mantle derived mafic rocks that may be correlatable with the sills of southwestern part of the Cuddapah Basin. This domal structure probably formed due to underthrusting of the western Cuddapah Basin and the collision of Nellore Schist Belt/Eastern Ghats Belt terrains after the cessation of supra-subduction below eastern Dharwar Craton at the end of the Rodinia period (around 950 Ma).</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 9","pages":"2152-2175"},"PeriodicalIF":2.2,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145013028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry, Geochronology and Petrogenesis of the Proterozoic Betul–Chhindwara Bimodal Volcanics: Constraints on the Evolution of the Central Indian Tectonic Zone, Central Indian Shield","authors":"Ibrahim Yousuf,&nbsp;Talat Ahmad,&nbsp;D. V. Subba Rao,&nbsp;Roohi Irshad,&nbsp;S. Balakrishnan","doi":"10.1002/gj.5154","DOIUrl":"https://doi.org/10.1002/gj.5154","url":null,"abstract":"<div>\u0000 \u0000 <p>The Central Indian Tectonic Zone (CITZ) runs across peninsular India and includes Proterozoic bimodal volcanics (basalt-rhyolite), quartzite, mafic-ultramafic rocks, volcanic sediments and Banded Iron Formation (BIF). The bimodal volcanic rocks of Betul–Chhindwara belt have been subjected to upper greenschist to lower amphibolite-grade metamorphism and have well-preserved remnants of pillow structures. Total alkali vs. silica diagram clearly discriminates all the samples into subalkaline basalts and rhyolites which corresponds to their bimodal nature. Mafic volcanic sequence of Betul–Chhindwara belt is represented by high Ti and low Ti Groups. I. High Ti basalt has undergone low degree of partial melting (~5%), whereas low Ti basalt has undergone a high degree of partial melting (~20%) of the same source rock. Fe and Ca decrease with decreasing Ti indicating clinopyroxene and iron-titanium oxide fractionation in both the groups of basalt. These basalts are generally enriched in incompatible trace elements such as Rb and Ba and depleted in Nb, P and Ti, which collectively are good indicators of continental crust/lithosphere involvement in their genesis. The basalts show no Eu anomaly, which indicates little role of plagioclase during fractionation process. Positive anomalies of U–Th–Zr for the basalts indicate crustal involvement. Whole-rock Sm–Nd isochrons for the mafic volcanic rocks indicate an age of crystallisation for these volcanic rocks at about 1232 ± 37 Ma (initial ¹⁴³Nd/¹⁴⁴Nd = 0.510752 ± 0.000035, mean square weighted deviate [MSWD] = 1.20) which is much younger than the basement rocks ca. 1500 Ma. The <i>ε</i>\u0000 _{Nd<i>t</i>\u0000} (<i>t</i> = 1232 Ma) vary from −5.93 to −3.1 for the mafic volcanic rocks and between −5.81 and +0.14 for felsic volcanic rocks. Depleted mantle model ages of basalts vary from 2204 to 3040 Ma, and for rhyolites, these vary from 2174 to 2863 Ma, respectively. The <i>ε</i>\u0000 _Nd value for all the basaltic samples includes both the groups of basalts plot away from the CHUR line indicating their derivation from a depleted source and evolves to lower values, indicating longer crustal residence or more crustal contribution. Mafic magma might have been produced at the subduction zone interacted with the lower continental crust while ascending to the surface. This lowered the melting point of the continental crust which led to the production of felsic melt. Episodic mafic magma could have led to the production of rhyolite, produced at different levels of the continental crust.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 7","pages":"1701-1720"},"PeriodicalIF":1.4,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144635300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}