Geological Journal最新文献

{"title":"Origin of Indosinian W–Sn Deposits in the Nanling Region, China: Case Study of the Nanzhuhe Sn Polymetallic Deposit in the Dupangling Area","authors":"Zhang Hui,&nbsp;Bai Lingan,&nbsp;Pang Chongjin,&nbsp;Dai Yu,&nbsp;Feng Zuohai,&nbsp;Liu Xijun,&nbsp;Meng Chunlan,&nbsp;Lin Lizhuan","doi":"10.1002/gj.5118","DOIUrl":"https://doi.org/10.1002/gj.5118","url":null,"abstract":"<div>\u0000 \u0000 <p>Great breakthroughs have been made in the Indosinian W–Sn ore exploration in the Nanling region of China in recent years, but there is still relatively little research on its metallogenic mechanism. Nanzhuhe Sn polymetallic deposit is located on the southeast side of Dupangling complex in the western part of Nanling and is a typical altered fracture zone type of Sn polymetallic deposit. The ore body is controlled by the NE-trending fault and occurs in the Indosinian granite in the Indosinian contact zone and the secondary tension–torsion fault zone. In this article, zircon and cassiterite were selected for U–Pb dating and trace element analysis, and quartz was studied by microthermometry, Laser Raman compositional analysis and H and O isotopes. The results show that the zircon U–Pb age of the biotite granite is 224.2 ± 6.4 Ma (MSWD = 1.5), and the cassiterite U–Pb age is 217.9 ± 7.2 Ma (MSWD = 1.6). The cassiterite is enriched in high-field-strength elements such as Nb, Ta, Ti, Sc, V and Hf, which indicates that the deposit was formed by the highly evolved granitic magmatic activity in the late stage of the Indosinian. The fluid inclusions are mainly liquid-rich two-phase, and a little gas-rich two-phase. The gas component is mainly water vapour. The initial ore-forming fluid is NaCl–H₂O system with medium to high temperatures and medium to low salinity. Hydrogen and oxygen isotopes indicate that about 40% of the atmospheric precipitation is mixed along the extensive fault. The comprehensive study shows that the mixing of magmatic–hydrothermal fluid and meteoric water occurred in the Indosinian period of the Nanzhuhe Sn polymetallic deposit, which led to the continuous decrease of temperature and salinity of the ore-forming fluid, the increase of oxygen fugacity, the increase of pH value and the decrease of ligand activity, which destroyed the stability of tin complex and caused a large number of tin and other metal ions to break off from the complex carrier, and finally the precipitation of tin and other metals.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 4","pages":"1000-1023"},"PeriodicalIF":1.4,"publicationDate":"2025-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749689","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":"Late Mesozoic Tectonic Transfer in the Southern Great Xing'an Range, NE China: Evidence From Geochronology, Geochemistry and Lu–Hf Isotopes of Intermediate-Acid Intrusions in Eastern Inner Mongolia","authors":"ZhiXiong Zhao,&nbsp;GuoChen Dong,&nbsp;M. Santosh,&nbsp;XiangPing Bao,&nbsp;YingWei Ren,&nbsp;ZhuoLin Xie","doi":"10.1002/gj.5121","DOIUrl":"https://doi.org/10.1002/gj.5121","url":null,"abstract":"<div>\u0000 \u0000 <p>The geodynamic background of late Mesozoic magmatism in eastern Inner Mongolia remains debated owing to multi-plate influences. Here, we present zircon U–Pb geochronology, geochemistry and Hf isotope data for Late Jurassic diorite and Early Cretaceous quartz monzonite porphyry and granite porphyry to investigate the petrogenesis and tectonic setting. Zircon U–Pb data suggest that multiphase magmatism extended from the Late Jurassic to the Early Cretaceous, that is, 161.0 ± 1.0 Ma (diorite), 129.9 ± 1.4 Ma (quartz monzonite porphyry), 125.8 ± 1.1 Ma and 126.8 ± 1.1 Ma (granite porphyry). The dioritic samples have lower SiO₂ (55.41–56.75 wt%), higher MgO (4.22–4.57 wt%) and Mg^# (52–55). The quartz monzonite shows mediate SiO₂ contents (63.17–64.89 wt%), belonging to the high-K, calc-alkaline series. The granite porphyry samples exhibit higher SiO₂ (74.49–77.03 wt%) and Na₂O + K₂O (6.37–7.38 wt%) contents, while lower Mg# (20–25). The diorites and quartz monzonite porphyry show slight negative Eu anomalies (δEu = 0.85–0.88 and 0.78–0.90, respectively), while Eu anomalies are intensely for the granite porphyry (δEu = 0.45–0.67). All these rocks show enrichments in LILEs (U and Pb) and depletions in HFSEs (Nb, Ta, P and Ti). The clinopyroxenes are classified as augite and diopside, and they show slightly inverted U-shaped patterns in the chondrite-normalised REE diagram. The plagioclases are mainly andesine from the diorites, while they are albite from the quartz monzonite porphyry and granite porphyry. The ε_Hf (<i>t</i>) values of zircon crystals range from +3.04 to +5.90, +2.04 to +4.10 and +1.93 to +4.35. These data indicate that the diorite formed by low degree partial melting of a depleted mantle wedge metasomatized by fluids. The quartz monzonite porphyry was generated by partial melting of the lower crust triggered by the underplating of depleted mantle-derived basaltic magma. The granite porphyry is classified as S-type granite and was sourced from greywacke. Combined with previous data, we conclude that Late Jurassic magmatism was related to the southward subduction of the Mongol-Okhotsk Ocean, while the Early Cretaceous magmatic rocks formed in a post-collision extensional setting.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 5","pages":"1233-1251"},"PeriodicalIF":1.4,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143914000","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":"Hydrochemical Characterisation and Genesis Mechanism of Li-Rich Geothermal Waters in the High-Temperature Geothermal Areas of Western Sichuan, China","authors":"Xingcheng Yuan,&nbsp;Yunhui Zhang,&nbsp;Jinhang Huang,&nbsp;Shiming Yang,&nbsp;Ying Wang,&nbsp;Yangshuang Wang,&nbsp;Ji Zhang","doi":"10.1002/gj.5119","DOIUrl":"https://doi.org/10.1002/gj.5119","url":null,"abstract":"<div>\u0000 \u0000 <p>Lithium (Li) is a valuable resource with significant economic benefits and strategic importance. The extraction of Li from Li-rich geothermal fluids has low production costs and may be an essential source of Li in the future. The Li contents in the high-temperature geothermal systems of western Sichuan are high (most exceeding 1 mg/L) and reach the exploration standard. However, the Li source and enrichment processes of high-temperature geothermal fluids are not well known. Therefore, 30 groups of natural hot springs with Li ≥ 1 mg/L from Batang, Litang, and Kangding high-temperature geothermal systems were selected to analyse the Li enrichment mechanism in high-temperature geothermal water. The average exposed temperatures of Batang, Litang, and Kangding geothermal waters were 82.4°C, 53.7°C, and 61.9°C, respectively, and the hydrochemical types were HCO₃-Na. The average concentrations of Li in the geothermal waters of Batang, Litang, and Kangding were 2.32, 3.29, and 3.54 mg/L. Based on the δD and δ¹⁸O characteristics, the geothermal waters in the study area originated from meteoric water and snow-melt water. Magmatic water was also mixed during circulation, with Kangding geothermal water being the most mixed (25.0%). Strong water–rock interactions occurred during geothermal water runoff ascent, including silicate mineral dissolution, geothermal gas dissolution, and cation exchange. The deep reservoir temperatures in the geothermal systems of Batang, Litang, and Kangding were estimated to be 239°C, 200°C, and 242°C, and the shallow reservoir temperatures were 175°C, 86°C, and 116°C. Finally, two Li enrichment mechanisms were proposed: (1) Li in the geothermal waters of Batang and Litang geothermal systems mainly came from the leaching of lepidolite and spodumene during water–rock interactions. (2) Li in the Kangding geothermal system mainly originated from the input of magmatic water. This research deepens the understanding of Li enrichment mechanisms in high-temperature geothermal systems, which will be helpful for the exploration of geothermal Li resources.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 8","pages":"2033-2048"},"PeriodicalIF":2.2,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144815164","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":"Diagenesis and Reservoir Evolution of Low Permeability Sandstones: A Case Study of the Second Member of the Jurassic Sangonghe Formation, Central Junggar Basin, China","authors":"Zheng Cao,&nbsp;Hairuo Qing,&nbsp;Karem Azmy,&nbsp;Lei Zhang,&nbsp;Zhipeng Li,&nbsp;Shijie Zhu,&nbsp;Changcheng Han,&nbsp;Qinglian Wei,&nbsp;Nanxin Yin","doi":"10.1002/gj.5109","DOIUrl":"https://doi.org/10.1002/gj.5109","url":null,"abstract":"<div>\u0000 \u0000 <p>The low-permeability oil-bearing tuffaceous sandstones of the second member of the lower Jurassic Sangonghe Formation (J₁s₂) in the Well Pen-1 west sag of the central Junggar Basin occur in a deep burial setting (&gt; 4000 m). They contain abundant oil and gas shows and hold promising exploration prospects. However, the reservoir heterogeneity is strong due to complex lithofacies and diagenesis, leading to significant productivity differences between adjacent wells. Therefore, identifying the lithofacies and diagenesis of the J₁s₂ sandstones and elucidating their influence on the evolution of relatively high-quality reservoirs is of utmost importance for oil and gas exploration and development in this area. Samples from the Well Pen-1 west sag, representing the J₁s₂ sandstones, were investigated utilising core and thin section observations, scanning electron microscopy, X-ray diffraction, fluid inclusions and carbon and oxygen isotope analyses. The J₁s₂ sandstones are mainly medium- to fine-grained and moderate- to-well-sorted feldspathic litharenites and litharenites. The tuffaceous contents range from 2.6% to 25% and the authigenic clay contents, produced by diagenesis, range from 0.6% to 12%, although carbonate cements are not abundant (av. 3.1%). Four sandstone lithofacies have been identified based on mineral compositions, leading to variations in diagenetic evolution and reservoir quality. Early diagenetic events included compaction, alteration of tuffaceous matrix and feldspar, and development of smectite, chlorite, kaolinite and early calcite. Mesogenic alteration included feldspar and tuffaceous matrix dissolution, alteration of kaolinite, chlorite and illite, and precipitation of quartz, anhydrite, late calcite and ferrocalcite. The alteration of the tuffaceous matrix resulted in a complex pore-throat structure in the J₁s₂ sandstones. The pebbly sandstone and conglomerate (SC) and fine-grained sandstone (Sm) lithofacies are generally characterised by high compaction resistance, low tuffaceous matrix and cement contents, and abundant secondary dissolution pores, and they exhibit better reservoir quality and great potential for oil and gas enrichment.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 4","pages":"883-903"},"PeriodicalIF":1.4,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749878","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":"Development Characteristics of Fractures in the Upper Palaeozoic Along the Northeastern Edge of the Ordos Basin and Their Controlling Effects on Hydrocarbon Accumulation","authors":"Shuai Yin,&nbsp;Ziqiang Xu,&nbsp;Yuanyuan Lu,&nbsp;Ahmed E. Radwan","doi":"10.1002/gj.5125","DOIUrl":"https://doi.org/10.1002/gj.5125","url":null,"abstract":"<div>\u0000 \u0000 <p>The northeastern edge of the Ordos Basin is characterised by low-amplitude structures and the presence of intrusive rock bodies in the Upper Palaeozoic strata. Tectonic movements and stratal denudation during the Mesozoic and Cenozoic have resulted in the development of well-defined and effective fractures in the area. However, the controlling role of fractures on the Upper Palaeozoic gas reservoirs is not yet clear. This paper uses the Linxing Block as a case study to conduct a comprehensive analysis of the role of fractures in controlling gas distribution. The study shows that the Upper Palaeozoic in this area is primarily characterised by the development of vertical fractures, which are of a tensile-shear nature and have a low degree of filling. The formation and evolution of fractures are controlled by the generation of hydrocarbons, denudation, and tensile strain during the sedimentation-erosion process. Tensile fractures are more likely to occur when the horizontal minimum principal stress is lower than the formation pressure during hydrocarbon generation. During the denudation process, the horizontal minimum principal stress in tight sandstone decreased, facilitating the formation of near-vertical tensile fractures. At the same time, the strata also produce a stress tensor, with the reduction in sandstone strata being greater than that in mudstone strata. Ultimately, fractures are more developed in reservoirs with high brittle mineral (quartz and feldspar) content in the uplifted and sloped areas of low-amplitude structures, which is favourable for the accumulation of natural gas. In contrast, fractures in the trough zones are usually underdeveloped, and fractures are extremely developed near the Zijinshan Pluton, which is detrimental to the preservation of natural gas.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 6","pages":"1329-1345"},"PeriodicalIF":1.4,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206987","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":"Low-Temperature Thermochronologic Analysis and Geologic Significance of the Northern Part of the Western Margin of the Ordos Basin: A Case Study of the Moergou Profile in the Zhuozishan Area, Inner Mongolia, China","authors":"Xing Guangyuan,&nbsp;Ren Zhanli,&nbsp;Qi Kai,&nbsp;Guo Sasa,&nbsp;Liu Yanzhao","doi":"10.1002/gj.5108","DOIUrl":"https://doi.org/10.1002/gj.5108","url":null,"abstract":"<div>\u0000 \u0000 <p>The northern part of the western margin of the Ordos Basin is located between the Alxa Block, the Central Asian Orogenic Belt, and the Ordos Basin, with a special structural location, making it an ideal area for studying surface action processes and tectonic dynamic evolution. Since the Mesozoic era, the region has undergone multiple stages of tectonic deformation and exhumation, but the exhumation events of different strata have significant differences. In this paper, we use apatite fission track (AFT) to study the Middle–Upper Proterozoic to Upper Paleozoic samples from the Moergou profile in the Zhuozishan area of Wuhai City. The central ages of the three sandstone samples are 153 ± 6.6, 125 ± 6, and 135 ± 5 Ma. The thermal history simulation results indicate that the area has undergone multiple cooling periods since the Mesozoic era, including (i) Late Jurassic (160–150 Ma), (ii) Late Early Cretaceous (130–110 Ma), and (iii) Cenozoic (~20 Ma). Additionally, we have discovered that the Changcheng System near the core of the Zhuozishan anticline was uplifted earlier and at a faster rate than the Taiyuan Formation located on both wings. The research area was affected by the Yanshanian orogeny and began to rapidly uplift from the Late Jurassic to the Early Cretaceous. The maximum paleogeothermal temperature was reached in the Late Jurassic and then rapidly uplifted to a partial annealing zone. Since the Miocene, it rapidly rose to the surface. The Late Jurassic tectonic exhumation indicated by thermochronology corresponds to the formation of thrust-fold structures in the western margin.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 4","pages":"871-882"},"PeriodicalIF":1.4,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749904","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":"Detrital Zircon U–Pb Geochronological Records and Geological Significance of the Cambrian–Devonian Strata in the Southern Part of South China","authors":"Fei Liu,&nbsp;Kun Li,&nbsp;Asui Liu,&nbsp;Lejia Yan,&nbsp;Yushuai Yu,&nbsp;Shunbo Cheng,&nbsp;Xiaofei Qiu,&nbsp;Qidi Yang,&nbsp;Xiaokun Huang,&nbsp;Yun Zhou,&nbsp;Xirun Tong","doi":"10.1002/gj.5098","DOIUrl":"https://doi.org/10.1002/gj.5098","url":null,"abstract":"<div>\u0000 \u0000 <p>The southern part of South China records an unconformity between the Devonian and the underlying Cambrian strata, which responded to the Caledonian Movement during the Early Palaeozoic period. Zircon U–Pb dating and in situ Lu–Hf isotope analyses were conducted on four samples from the Cambrian and Early Devonian strata near the unconformity on the west side of Qin-Fang Belt, and their significance for palaeogeographic evolution was discussed followed by regional provenance comparisons. The results show that the Early Devonian and Cambrian samples share the similar detrital zircon age spectra with two prominent peaks at ~985 and ~ 530 Ma, respectively. Based on comparisons of the detrital zircon age spectra and <i>ε</i>\u0000 _Hf(<i>t</i>) values with contemporary igneous zircons inside and outside of South China, the provenances of the Cambrian strata are deduced to be mainly supplied by the old strata in the East Gondwana margins. But the ultimate provenances were mainly from the East Ghats-Rayner orogenic belt and South Indian Granulite Terrane, and partly from Musgrave Province. The provenances of the Early Devonian strata were mainly derived from the recycling of the underlying Cambrian strata. Both sides of the Qin-Fang Belt share the same detrital zircon age spectra in the Cambrian period, indicating that there existed not the South China Residual Ocean. The Early Palaeozoic (460–430 Ma) detrital zircons are absent in the Early Devonian strata on the Qin-Fang Belt and its west side, but are widely distributed in the Middle Devonian strata on the Qin-Fang Belt and eastern margin of the Yunkai Massif, indicating that the most of the Yunkai Massif was submerged below the sea level in the Early Devonian period and emerged above the sea level in the Middle Devonian period.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"716-736"},"PeriodicalIF":1.4,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530708","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":"Preparation of High-Selectivity Li+ Adsorbents Based on Bauxite via Liquid-Phase Alkaline Thermal Activation","authors":"Tao Ding,&nbsp;Yiran Hu,&nbsp;Cheng Qian,&nbsp;Mianping Zheng,&nbsp;Zhen Nie,&nbsp;Enyuan Xing,&nbsp;Xinlei Wang,&nbsp;Yubin Li","doi":"10.1002/gj.5100","DOIUrl":"https://doi.org/10.1002/gj.5100","url":null,"abstract":"<div>\u0000 \u0000 <p>Bauxite, as the main aluminium-bearing mineral in China, is a crucial resource for the industrial production of aluminium and aluminium-related products. In this study, bauxite-based aluminium composite Li⁺ adsorbents were prepared using a liquid-phase alkaline thermal activation—acid in situ method. The effects of various factors on Li⁺ adsorption from brine were investigated through single-factor experiments. Multiple techniques, such as scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) method, Fourier transform infrared spectroscopy (FT-IR), and x-ray photoelectron spectroscopy (XPS), were employed to characterise and analyse the microstructure, pore size distribution, chemical element distribution, and mineral structure of the adsorbents. In addition, the changes in bauxite structure and properties before and after functionalization were investigated. Results indicate that the adsorption capacity of LATA-AIS-LDH-BX adsorbent prepared by the acid in situ method reached 1.15 mg/g at pH = 7; the adsorption capacity of LATA-Al-LDH-BX adsorbent prepared by the aluminium salt conversion method reached 2.16 mg/g. The adsorption behaviour of both adsorbents followed the pseudo-second-order kinetic model and the Langmuir model. In the presence of interfering ions (Na⁺, K⁺, SO₂\u0000 ⁴⁺, Mg²⁺), the composite adsorbents showcased strong selective adsorption capacity for Li⁺. After five cycles of adsorption–desorption, the adsorption rates decreased by 12.19% and 11.48%, respectively, demonstrating good recycling stability. Furthermore, the Li⁺ adsorption capacities in salt lake brine reached 0.82 mg/g and 1.48 mg/g, indicating promising potential for industrial application.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 8","pages":"1799-1811"},"PeriodicalIF":2.2,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144815129","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":"Petrogenesis of Paleoproterozoic Khalari Hornblende-Pyroxenite Intrusion Within the Dongargarh Supergroup, Bastar Craton: Insights From Petrological and Geochemical Studies","authors":"Amiya K. Samal,&nbsp;Gulab C. Gautam,&nbsp;Ankur Ashutosh,&nbsp;Rajesh K. Srivastava","doi":"10.1002/gj.5099","DOIUrl":"https://doi.org/10.1002/gj.5099","url":null,"abstract":"<div>\u0000 \u0000 <p>This study investigates Paleoproterozoic hornblende pyroxenite, a lithological unit within the Khalari Ultramafic-Mafic Complex (KUMC), which is intruded into the Neoarchean-Paleoproterozoic Dongargarh Supergroup near Khalari village in the northern Bastar Craton. A comprehensive characterisation has been conducted through petrological analysis, bulk-rock geochemistry, mineral chemistry, and platinum group elements (PGEs)-Au geochemical studies to understand its petrogenesis and geotectonic implications. The presence of primary amphibole, specific pyroxene chemistry (low Ti and Cr), and enriched LILE, LREE and fluid-mobile elements alongside negative Nb–Ta–Ti anomalies suggest these rocks were crystallised from a mantle melt originated from a metasomatized sub-continental lithospheric mantle (SCLM) source. This metasomatization could be due to fluids derived from a subduction event predating the emplacement of the studied rocks. The proposed melt composition is estimated to have formed from 5% to 10% partial melting of a garnet-rich peridotite mantle source. The crystallisation conditions are estimated to have occurred at an average pressure of 7.85 kbar and a temperature of 902°C, indicating moderately shallow depths influenced by fractional crystallisation and slow cooling rates. The emplacement of the KUMC is contemporaneous with several other magmatic activities in the Bastar Craton, around ca. 2.50–2.47 Ga, suggesting that mantle plume might have played a significant role in their formation. Low concentrations of PGEs in the studied samples indicate a PGE-depleted mantle source.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"737-761"},"PeriodicalIF":1.4,"publicationDate":"2024-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530648","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":"Geological and Geochemical Characterisation of Shale as an Unconventional Gas Source and Reservoir Within the Lesser Himalaya, Nepal","authors":"Kumar Khadka,&nbsp;Shuxun Sang,&nbsp;Sijie Han,&nbsp;Junjie He,&nbsp;Upendra Baral,&nbsp;Saunak Bhandari","doi":"10.1002/gj.5112","DOIUrl":"https://doi.org/10.1002/gj.5112","url":null,"abstract":"<div>\u0000 \u0000 <p>The Gondwana and the Foreland shales in the Tansen and Surkhet areas within the Lesser Himalayas, Nepal, have been studied in detail, focusing on unconventional gas potentiality. The geochemical analysis indicates that the Eocene shales have a total organic carbon (TOC) content of up to 1.56%, and the Gondwana shales exhibit ≤ 0.75%. Pyrolysis results show Tmax values above 480°C, and the modified van Krevelen diagram and Hydrogen Index (HI) versus Tmax cross-plot confirm the presence of type III (gas-prone) kerogen. Vitrinite reflectance (Ro) values ranging from 1.06% to 2.96% indicate high thermal maturity. Mineralogical analysis reveals a distinct contrast between the shales, with the Gondwana shales showing higher silica content within a brittle-ductile zone and the Eocene Foreland shales are more richer in clay minerals (56%) and quartz (31%), with superior porosity (2.1% to 8.3%) and organopores, enhancing their reservoir potential. Scanning electron microscopy (SEM) and petrographic observations further highlight the dominance of vitrinite macerals and organic pores in the Eocene shales. The Eocene Foreland shales of the Bhainskati Formation have favourable carbon content and pyrolytic properties and present a promising target for unconventional gas exploration compared to the Gondwana Sisne Formation. The over-maturity of the shale resulted from the thrusting over the Lesser Himalaya in the early Miocene. The Main Boundary Thrust, activated from 11 Ma, is active and other tectonic activity impacts gas preservation. Regionally, the Bhainskati Formation is more thermally mature than the Patala Formation in Pakistan and shares similarities with the Subathu Formation in India. Despite having lower TOC content than globally established shales, the Eocene shales warrant further exploration for detailed exploration of their potential as unconventional gas reservoirs.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 4","pages":"923-941"},"PeriodicalIF":1.4,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749522","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}