Geological Journal最新文献

{"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}

{"title":"Intracontinental Mesozoic Composite Magmatism in Central North China Craton—A Tectonic Response to the Westward Subduction of the Paleo-Pacific Plate","authors":"Junyi Sun,&nbsp;Jiawei Cui,&nbsp;Xiaolong Wang,&nbsp;Sushan Wang","doi":"10.1002/gj.5107","DOIUrl":"https://doi.org/10.1002/gj.5107","url":null,"abstract":"<div>\u0000 \u0000 <p>The influence, extent, intensity, and spatiotemporal evolution of the subduction of the Paleo-Pacific Plate on West-Central North China Craton during the middle-late Mesozoic remains unknown. Detailed petrological investigations, systematic zircon U–Pb dating, whole-rock geochemistry, and in situ zircon Lu-Hf isotopic analysis were conducted on various lithologies of the composite pluton in the central part of the North China Craton. The composite pluton can be divided into four distinct periods: quartz-porphyry (162 ± 1 Ma), porphyritic biotitic granite (152 ± 1 Ma), quartz diorite (142 ± 1 Ma), granite (136 ± 2 Ma). These rocks are belonged to high silica, potassium-calcareous alkalinity, aluminium content and enriched in large-ion lithophile elements such as Rb and K, and depleted in high-field-strength elements such as Nb and Ta. The <i>ε</i>Hf(<i>t</i>) values and the TDMC ages of the quartz-porphyry, porphyritic biotitic granite indicated these igneous rocks originated from the lower crust to the mid-lower crust which exhibit a lithospheric evolution process consistent with that of the North China Craton. The <i>ε</i>Hf(<i>t</i>) values of quartz diorite and granite indicate that the igneous rocks originated from the ancient lower crust with contributions of mantle-derived material, and from a mixture of the ancient mid-lower crust and the Late Palaeozoic younger lower crust. Considering the regional geological background, it is believed that this magmatism indicates a transition in the central North China Craton from compression to extension from the Late Jurassic to the Early Cretaceous. This transition is associated with the subduction of the Paleo-Pacific Plate, which began subducting under eastern Asia in the Early Jurassic and led to an extensional state in the Cretaceous due to the retreat of the Pacific subduction slab.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 4","pages":"844-870"},"PeriodicalIF":1.4,"publicationDate":"2024-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749872","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":"Geology, Mineralogy and Sulphur Isotope Constraints of the Buffalo Reef Gold Deposit, Central Belt, Peninsular Malaysia: Implications for Ore Genesis","authors":"Mazlinfalina Mohd Zin,&nbsp;Mohd Basril Iswadi Basori,&nbsp;Kenzo Sanematsu,&nbsp;Takayuki Manaka,&nbsp;Khin Zaw,&nbsp;Christian Dietz,&nbsp;Habibah Jamil,&nbsp;Abhisit Salam","doi":"10.1002/gj.5106","DOIUrl":"https://doi.org/10.1002/gj.5106","url":null,"abstract":"<div>\u0000 \u0000 <p>The Buffalo Reef deposit is a developed gold mine located in the northern part of Pahang State, within the Central Belt of Peninsular Malaysia. The gold deposit is hosted by the Permo-Triassic Gua Musang Formation, which consists of shale, carbonaceous shale, mudstone, siltstone, volcanic rocks and low-grade metamorphic rocks. Gold ore at Buffalo Reef is found in quartz veins and alteration selvages, which fill ductile-brittle structures along N–S and NE–SW striking faults and shear zones. The sulphide minerals associated with gold ore include pyrite, arsenopyrite, stibnite and minor amounts of galena. Geochemical studies of gold grains reveal that the gold is alloyed with less than 10 wt% Ag and contains no other minor elements, with fineness of gold grains ranging from 882 to 990. Sulphur isotope analysis of sulphide minerals extracted from auriferous veins shows a narrow range of δ³⁴S values from −2.40‰ to +2.70‰ (<i>n</i> = 29). The δ³⁴S composition close to zero relative to VCDT for all sulphide minerals indicate that these minerals are isotopically uniform and derived from a single source. The overlapping sulphur isotope data between the sulphide minerals from the Buffalo Reef and those from other gold deposits in the Central Belt suggest that the sulphur in the ore-forming fluids responsible for the auriferous quartz veins at Buffalo Reef is likely related to devolatilisation from metamorphic fluids at depth in an orogenic system. However, the substantial contribution of magmatic fluid cannot be ruled out due to the narrow range of sulphur isotopic compositions around zero per mil. The results of this study indicate that gold mineralisation in the study area and in other gold deposits along the Bentong-Raub Suture Zone in the Central Belt is of the orogenic type.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 4","pages":"824-843"},"PeriodicalIF":1.4,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749317","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":"Advances in Magmatic Ni–Cu–(PGE) Sulphide Deposits and Their Constraints on Neoproterozoic Tectonic Settings of China","authors":"Huidong Yu,&nbsp;Haoran Chen,&nbsp;Huawen Cao,&nbsp;Nuru Said,&nbsp;Changcheng Huang,&nbsp;Zihan Ma,&nbsp;Bin Xiao,&nbsp;Haifeng Chen,&nbsp;Hao Zou","doi":"10.1002/gj.5105","DOIUrl":"https://doi.org/10.1002/gj.5105","url":null,"abstract":"<div>\u0000 \u0000 <p>Magmatic Ni–Cu–(PGE) sulphide deposits are the primary global sources of nickel, copper and platinum group elements (PGE). The study of these deposits is critical for mineral exploration and holds important economic implications. This paper reviews recent advances in understanding magmatic Ni–Cu–(PGE) sulphide deposits and their related magmatism. Findings reveal that these deposits have an uneven global distribution and a wide range of classifications. The Proterozoic era represents the main period of mineralisation, and the mineralisation setting is closely related to continental rifts, mantle plumes and collision orogenic belts. An ongoing debate exists between the ‘magma conduit’ and ‘deep-multiple magma chamber segregation’ models, which differ in mineralisation location, magma intrusion mechanisms and the role of external sulphur addition. The primary mechanisms of sulphide segregation include rapid cooling, crystal differentiation and crustal contamination. Furthermore, this paper examines the spatial–temporal distribution and mineralisation dynamic settings of Neoproterozoic magmatic Ni–Cu–(PGE) sulphide deposits in China and their relationship to the convergence and breakup of the Rodinia supercontinent. These Neoproterozoic deposits are located along the margins of the Yangtze, North China and Tarim blocks. They formed in five different stages, 1000–960, 900–850, 830–800, 760–740 and 650–620 Ma, corresponding to the following tectonic settings, respectively: (1) a back-arc extensional setting before the convergence of the Yangtze and Cathaysia blocks; (2) a post-orogenic extensional setting following the convergence between the Yangtze and North China blocks; (3) a rift setting related to the first Neoproterozoic mantle plume event (830–795 Ma) within the Yangtze Block or North China Block; (4) a rift setting related to the second Neoproterozoic mantle plume event (780–745 Ma) within the Tarim Block and (5) an intraplate rift setting within the Yangtze Block. The evolving mineralisation dynamic settings of these deposits indicate that their mineralisation is directly related to large-scale mafic–ultramafic magmatism during the Neoproterozoic and the convergence and breakup of the Rodinia supercontinent.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 4","pages":"807-823"},"PeriodicalIF":1.4,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749726","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":"Identification of Multiple Thermal Events in High-Grade Metacarbonate Rocks Using Carbon Isotope Thermometry: An Example From the Sør Rondane Mountains, East Antarctica","authors":"M. Satish-Kumar,&nbsp;Sasidharan Kiran,&nbsp;Fumiko Higashino,&nbsp;Tetsuo Kawakami,&nbsp;Tomokazu Hokada","doi":"10.1002/gj.5095","DOIUrl":"https://doi.org/10.1002/gj.5095","url":null,"abstract":"<p>Nine metacarbonate layers from the regionally metamorphosed terrane of the Sør Rondane Mountains in the Eastern Dronning Maud Land in East Antarctica were examined in detail for constraining the thermal events using carbon isotope exchange between dolomite/calcite and graphite. Equilibrium carbon isotope fractionation between dolomite and graphite suggested peak metamorphic temperature conditions reaching up to 802°C ± 29°C were estimated at the Balchenfjella locality, where multiple samples from six thick layers of metacarbonate rocks were examined. However, some of the samples exhibit lower carbon isotope fractionation reflecting the possibility of ultrahigh-temperature metamorphic conditions, which is consistent with recent reports. Furthermore, several metacarbonate rock samples display large variations in δ¹³C_VPDB values for graphite grains, despite dolomite and calcite showing homogeneous carbon and oxygen isotopic composition indicating signatures of retrograde metamorphism and fluid infiltration events. Detailed textural observation suggested alteration of δ¹³C_VPDB values of graphite during retrograde metamorphism might have resulted due to the overgrowth of graphite crystals by the infiltration of low δ¹³C_VPDB-bearing fluids, the extent of alteration being a direct function of the fluid–rock ratio. Field evidence indicates the presence of carbonate veins cutting across the metacarbonate rocks suggesting that carbon isotope thermometry can also be utilised to understand the effect of external fluid infiltration. At Perlebandet locality the metamorphic temperature conditions were estimated to be around 915°C, whereas those from Tanngarden and Menipa gave lower temperature estimates. Detailed textural analysis of graphite in combination with isotopic composition provided clear evidence for retrograde events. Thus, our results provide tight constraints of peak and post-peak metamorphic temperature conditions and a regional thermal structure for the Sør Rondane Mountains and further testify the usefulness of carbon isotope thermometry in polymetamorphic terrains.</p>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 2","pages":"455-483"},"PeriodicalIF":1.4,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/gj.5095","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification of Fracture Extension Modes During Hydraulic Fracturing in Coalbed Methane Vertical Wells: A Case Study From the Southern Shizhuang Area of the Qinshui Basin, China","authors":"Jin Yan,&nbsp;Xiaoming Ni,&nbsp;Yafei Zhang,&nbsp;Wensheng Wang,&nbsp;Ruize Niu","doi":"10.1002/gj.5101","DOIUrl":"https://doi.org/10.1002/gj.5101","url":null,"abstract":"<div>\u0000 \u0000 <p>The accurate identification of fracture extension patterns in hydraulic fracturing can provide important guidance for the optimisation of fracturing parameters. In this paper, factors such as effective hole friction and wellbore flow friction during fracturing are fully considered, and a calculation model of net bottom-hole pressure of fracturing is constructed. By introducing the change rate of net bottom-hole pressure and the changing characteristics of the fracturing curve, seven fracture extension modes during hydraulic fracturing in coalbed methane vertical wells are established. The accuracy of the identification method is verified by the fracture monitoring and production results in Shizhuang South Block. The results show that fracture elongation is mainly controlled by in situ stress difference, angle between natural fracture and maximum principal stress, coal tensile strength, fracturing time, proppant and angle between other factors. When the fracture construction parameters are fixed, the smaller the difference between maximum and minimum horizontal principal stresses and the smaller the natural fractures and maximum horizontal principal stresses. When the reservoir potential is similar, the effective extension index is positively correlated with the gas production effect, and the effective extension index can effectively judge the fracturing effect. The higher the proportion of effective extension mode, the longer the extension time and the higher the stable daily gas production. The research results provide a method and reference for clearly identifying the fracture extension and the occurrence conditions of different extension modes in the hydraulic fracturing process.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"762-775"},"PeriodicalIF":1.4,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530112","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":"Cambrian–Ordovician Arc-Related Magmatism in the Central Southeast Asian Continents and Its Significance on Early Palaeozoic Tectonics of the Indochina Block","authors":"Xuan Thanh Ngo,&nbsp;Nguyen Quoc Hung,&nbsp;Yoonsup Kim,&nbsp;Sanghoon Kwon,&nbsp;Vinh Hau Bui,&nbsp;Thanh Hai Tran,&nbsp;Yirang Jang,&nbsp;Vinod O. Samuel","doi":"10.1002/gj.5102","DOIUrl":"https://doi.org/10.1002/gj.5102","url":null,"abstract":"<div>\u0000 \u0000 <p>Knowledge of the early Palaeozoic tectonic evolution of the Indochina Block is critical for reconstructions of the Gondwana supercontinent in relation with other microcontinents. In the central Indochina Block, the Early Palaeozoic Tam Ky–Phuoc Son Suture Zone (TPSZ) and Po Ko Suture Zone (PKSZ) demarcate the boundary between the Truong Son Belt in the north and Kon Tum Massif in the south. In the southern parts of Truong Son Belt, we have identified meta-mafic and meta-intermediate rocks associated with plagiogranite, metapelitic and meta-siliceous rocks. Here we present integrated field, geochemical and geochronological results of the meta-gabbroic and amphibolitic samples in the southern Truong Son Belt to unravel the tectonic evolution of the Indochina Block during the Early Palaeozoic. The MC–LA–ICP–MS zircon U–Pb ages indicate magmatism at ca. 504–460 Ma. Based on geochemical composition, the samples range from gabbro to gabbro-diorite. The gabbroic samples have slightly higher Mg# (58.9–62.8) than those of the gabbro-dioritic samples (Mg# = 56.3–61.5), and both types of rock show low TiO₂ contents (0.68–0.98 wt%), displaying enriched LREE ((La/Sm)_{\u0000 <i>N</i>\u0000} = 1.66–3.23) and LILE (e.g., Rb, Ba, Th and U), and pronounced negative HFSE (e.g., Nb, Ta and Ti anomalies) with low εHf(t) zircon values (from −6.34 to +0.71). These geochemical characteristics suggest that the metabasic rocks are of subduction-related arc magmatic processes, and also indicate infiltration of sediment melt from subducting slab to mantle-wedge prior to its partial melting. The new data suggests that northward subduction under the Truong Son Belt might have initiated during the Early Cambrian, and lasted until around the Middle Ordovician. On a regional scale, the ages of the Early Palaeozoic arc magmatism in the Truong Son Belt are comparable with the ages of tectonic events that occurred in Himalaya, West Qiangtang and East Tibet at the northern margin of the Gondwana supercontinent.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"776-791"},"PeriodicalIF":1.4,"publicationDate":"2024-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530606","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":"Isotopic and Sedimentologic Proxies of Palaeoexposure Events and Oceanic Anoxic Event 2 (OAE2) in the Cenomanian–Turonian Neritic Carbonates (the Sarvak Formation) in the Abadan Plain, Zagros Basin, Iran","authors":"Emad Yahyaei,&nbsp;Hamzeh Mehrabi,&nbsp;Ramin Abbasi","doi":"10.1002/gj.5089","DOIUrl":"https://doi.org/10.1002/gj.5089","url":null,"abstract":"<div>\u0000 \u0000 <p>The shallow marine carbonate deposits of the Sarvak Formation have been deposited in an active tectonic setting under warm and humid climatic conditions during the Cenomanian–Turonian (C–T). The focus of this study is on the sedimentological and geochemical analysis of this formation in the Abadan Plain, Zagros Basin. Petrographic studies led to the identification of five microfacies deposited in the restricted lagoon, tidal flat, reef, shoal and open marine environments. They indicate deposition of the Sarvak Formation on a homoclinal ramp–like carbonate platform. Sequence stratigraphy studies have led to the identification of two third-order sequences named Cenomanian sequence (DSS-1) and Turonian sequence (DSS-2), along with six fourth-order sequences. The upper boundary of DSS-1, known as the C–T disconformity (CT-ES), is subjected to meteoric diagenetic processes, as evidenced by meteoric dissolution (karstification), collapsed brecciation and the development of palaeosols. The upper SB of DSS-2 is marked by the mid-Turonian disconformity (mT-ES), characterised by silicification, brecciation, meteoric dissolution and iron oxide staining of core samples. The significant decreases in δ¹⁸O_carb and δ¹³C_carb values indicate a strong effect of meteoric diagenesis beneath the palaeoexposure surfaces. The calculation of sea surface temperatures (SSTs) based on the δ¹⁸O_carb values measured from the unaltered carbonates indicated that the average SST for the C–T is 31.8°C and 30.9°C in K-01 and K-02 wells, respectively. A decrease of about 1.5°C is measured during the C–T transition, which indicate a cooling trend of the Late Cretaceous in the Tethyan realm. The carbon isotopic pattern observed in the analysed sections shows correlation with previous studies conducted in the Tethyan region. Additionally, the isotopic composition indicative of Oceanic Anoxic Event 2 (OAE2) is identified around the C–T boundary. Nevertheless, the signature of OAE2 has been somewhat obscured by diagenetic processes associated with C–T palaeoexposure.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"596-613"},"PeriodicalIF":1.4,"publicationDate":"2024-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530602","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":"The Genesis and Circulation of Geothermal Water in the Riduo–Cuona Rift, Eastern Tibetan Plateau, Based on Hydrochemistry and Stable Isotopes Geochemistry","authors":"Yunhe Liu,&nbsp;Xiaocheng Zhou,&nbsp;Sheng Wang,&nbsp;Zhe Chen,&nbsp;Miao He,&nbsp;Jiao Tian,&nbsp;Ying Li,&nbsp;Xiaoyi Zhu,&nbsp;Zhipeng Liu,&nbsp;Baolong Lu,&nbsp;Yi Huang","doi":"10.1002/gj.5093","DOIUrl":"https://doi.org/10.1002/gj.5093","url":null,"abstract":"<div>\u0000 \u0000 <p>Studying initial geothermal fluids and tectonic active zones is crucial for exploiting intermediate high-temperature geothermal resources. This study aims to investigate the genesis, circulation and environmental implications of geothermal water in the Riduo–Cuona Rift (RCR) of the eastern Tibetan Plateau. By integrating hydrochemical analysis, stable isotope geochemistry (δ²H, δ¹⁸O and ⁸⁷Sr/⁸⁶Sr), and noble gas isotope characteristics, the research seeks to develop comprehensive geothermal circulation models in the RCR. (M1) The spatial distribution of geothermal waters near the molten magmatic domes indicated ⁸⁷Sr/⁸⁶Sr ranges consistent with those of the rock, respectively. The high Ca, Mg ‘hardness’ spring waters were attributed to strata surrounding the dome resulting from the last leaching, as confirmed by the estimated higher hydraulic head, mainly located in ‘immature water.’ (M2) The spatial distribution of geothermal waters corresponding to an orogenic belt revealed HCO₃·SO₄–Na as the dominant hydrochemical facies in the northern RCR. Research suggests that springs exhibit greater circulation depths and that spring solute SO₄ is related to the Gangdise magmatic arc leaching. (M3) However, the active tectonic zone's springs ⁸⁷Sr/⁸⁶Sr (0.705763–0.709754) indicated evaporite characteristics. The thermal reservoir temperature in this structural junction zone is the highest (256.75°C–287.03°C). The high trace alkali element concentrations, particularly of B, F and As, exceeded the WHO guideline; the drainage system analysis indicates regional nonnegligible environmental risks in the Gudui. Establishing these models can clarify the relationships between geothermal fluids, tectonic structures and regional faults, providing insights into geothermal resource potential, environmental risks and possible strategies for sustainable resource exploitation in the region.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"642-658"},"PeriodicalIF":1.4,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530812","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":"Garnet as a Proxy for Deciphering Polymetamorphic Histories: An Example From the Sanandaj-Sirjan Zone of Iran","authors":"Mirmohammad Miri,&nbsp;Federico Lucci,&nbsp;Ali A. Sepahi,&nbsp;Mohammad Maanijou,&nbsp;John Charles White","doi":"10.1002/gj.5104","DOIUrl":"https://doi.org/10.1002/gj.5104","url":null,"abstract":"<p>In the central sector of the Sanandaj-Sirjan zone of Iran, the Triassic-to-Jurassic ‘Hamedan Phyllites’ metamorphic complex shows a polymetamorphic evolution characterised by a main Barrovian- to Buchan-type garnet+staurolite+kyanite/andalusite regional sequence, locally overprinted by a low-pressure thermal event generated by vigorous Jurassic magmatic activity and the emplacement of voluminous composite plutonic complexes (e.g., Alvand). In this work, we explore the Hamedan phyllites enveloping the Jurassic Alvand granite batholith, particularly in the eastern sector at the transition from cordierite-bearing hornfels to staurolite-bearing schists. In this study, we present for the first time the textural characterisation and mineral chemistry of a previously undescribed minor population of post-kinematic Mn-rich garnet from the staurolite schists. We developed phase equilibria modelling to define the pressure-temperature condition of its genesis. We then integrated the existing literature on metapelites from the study area to develop new thermobarometric models with those data to propose a revised evolution of the metapelites enveloping the Alvand batholith and the extent of its contact aureole. On a wider scale, this study provides evidence for the relevance of garnet, as chemical-physical archive, in deciphering complex polymetamorphic histories where thermal events affect previously regional metamorphosed rocks under relatively hot gradients.</p>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 4","pages":"793-806"},"PeriodicalIF":1.4,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/gj.5104","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}