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":"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":"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":"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}

{"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}