Geological Journal最新文献

{"title":"Intra-Craton Faults Characteristics, Development and Its Hydrocarbon Accumulation Significance in Mesozoic Strata at Southwestern Ordos Basin, China","authors":"Yun Jiang,&nbsp;Lei Pu,&nbsp;Fangpeng Du,&nbsp;Xinkai Chen,&nbsp;Chiyang Liu,&nbsp;Jianqiang Wang,&nbsp;Heng Peng,&nbsp;Yang Zhou","doi":"10.1002/gj.5085","DOIUrl":"https://doi.org/10.1002/gj.5085","url":null,"abstract":"<div>\u0000 \u0000 <p>The Ordos Basin is among China's largest petroliferous basins, with its southwestern part being a key exploration area. Prior studies indicated that the basin's internal structure was relatively simple, featuring minor developmental faults and primarily stratigraphic–lithologic reservoirs. However, recent research has identified numerous strike-slip faults in the basin, and their relationship to oil and gas accumulations remains unclear. This study, using integrated interpretations of field outcrops, imaging logging and 3D seismic reflection data, clarifies the characteristics, morphology and formation mechanisms of multi-period faults in the southwestern Ordos basin. Additionally, the study investigates the relationship between these faults and oil and gas accumulations. Results show that Mesozoic fractures in the southwestern basin are primarily NE- and NW-trending. Seismic profiles reveal that these faults exhibit complex geometries, including upright structures in the Middle to Upper Triassic and floral structures in the Cretaceous. Coherence slices show that Lower Jurassic faults have linear structures NE- and NW-trending, while Cretaceous faults exhibit parallel linear structures ENE-trending. The study of fault displacement and morphology suggests two evolutionary patterns for Mesozoic faults in the basin: layered development and basement-activated faulting. The widespread ENE- and NW-trending faults represent a specific mode of tectonic stress transfer in stable cratonic areas with minimal basement fault influence. Conversely, some ENE-trending faults are significantly influenced by basement activation during various geological periods, penetrating deeply into strata and exhibiting distinct segmentation on a planar scale. This differential fault development results in an uneven distribution of Jurassic oil and gas reservoirs. Significant accumulations of Jurassic oil and gas are found in the ENE-trending tension–torsional strike-slip sections, whereas many NW-trending faults may negatively impact oil and gas reservoirs. This study elucidates the characteristics of Mesozoic faults in the southwestern Ordos Basin, offering valuable guidance for oil and gas exploration and development in the region.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"583-595"},"PeriodicalIF":1.4,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530640","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":"Assessment of Geothermal Energy in Aluto-Langano and Tulu-Moye, Central Ethiopia","authors":"Mamaru Genetu","doi":"10.1002/gj.5073","DOIUrl":"https://doi.org/10.1002/gj.5073","url":null,"abstract":"<div>\u0000 \u0000 <p>This study aims to identify the primary issues leading to the pause in geothermal energy development at Aluto-Langano and Tulu-Moye sites, while also exploring opportunities in new drilling wells and assessing compliance with occupational safety, health and environmental standards. The geothermal energy development status was evaluated through focus group discussions, site visits and field data collection. The Tulu-Moye Geothermal Operation (TMGO) project is underway to establish a power plant, with a phased development spanning 6 years targeting a total capacity of 150 MW, comprising 50 MW for Phase 1 and 100 MW for Phase 2, though with some constraints. The Aluto-I Geothermal Pilot Plant marked the initial efforts to produce electricity from geothermal sources but faced shutdown due to declining thermal energy in some wells, turbine corrosion, pentane leakage, frequent in efficiency of fans and instability of foundations. Consequently, Phase 2 of the project aims to integrate with Phase 1 wells to mitigate potential thermal energy losses. Geothermal energy development demands substantial initial investment but entails minimal ongoing costs and workforce requirements. Its eco-friendliness benefits communities, offering higher efficiency and lower maintenance compared to hydroelectricity. Leveraging Ethiopia's geothermal potential is crucial for electricity generation, mineral extraction, and water supply, with plans involving nationwide field expansion to enhance renewable energy capacity.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 1","pages":"64-72"},"PeriodicalIF":1.4,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143118842","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 Silurian Granitoids in the Western Segment of the North Qilian Accretionary Belt, China: Insights Into the Closure of the Northernmost Branch of the Proto-Tethys Ocean","authors":"Weidong He,&nbsp;Yunpeng Dong,&nbsp;Jiaopeng Sun,&nbsp;Lei He,&nbsp;Zonglin Li,&nbsp;Yukun Qi,&nbsp;Kai Ye,&nbsp;Zhigang Wang,&nbsp;Teng Wang","doi":"10.1002/gj.5090","DOIUrl":"https://doi.org/10.1002/gj.5090","url":null,"abstract":"<div>\u0000 \u0000 <p>The North Qilian Accretionary Belt, situated at the northernmost extent of the Proto-Tethys tectonic domain, preserves key tectonic events such as Proto-Tethys Ocean subduction and accretion. Despite ongoing debates about the closure mechanisms and timing of the North Qilian Ocean, our study presents novel findings on granitoids from the Changma region in the western segment of the North Qilian Accretionary Belt. Zircon U–Pb dating indicates an emplacement age of 436 Ma for the Qingshixia pluton and 425 Ma for the Heixialao pluton. The <i>ε</i>\u0000 _{\u0000 <i>Hf</i>\u0000}(<i>t</i>) values of the Qingshixia granodiorite range from +8.25 to +10.89, with T_DM2 model ages estimated between 614 and 716 Ma. In contrast, the <i>ε</i>\u0000 _{\u0000 <i>Hf</i>\u0000}(<i>t</i>) values of the Heixialao monzogranite range from +1.79 to +4.48, with T_DM2 model ages spanning from 1127 to 1291 Ma. The Qingshixia granodiorite displays adakitic traits, characterised by high Sr, low Y, low Yb, and a low K₂O/Na₂O ratio, whilst the Heixialao monzogranite exhibits peraluminous, high-potassium calc-alkaline features. The low concentrations of Ni and Cr, along with moderate Mg# values, suggest that the Qingshixia granodiorite likely originated from the partial melting of a subducting slab. By comparison with experimental melts, the relatively low Rb/Ba and Rb/Sr ratios and higher zircon saturation temperatures of Heixialao monzogranite suggest that it may have formed from partial melting of the mafic middle and lower crust. Integrating these findings with regional geological features and differences between east and west segments, we propose that the western segment of the North Qilian Ocean basin may have closed during the Late Silurian, contributing to a diachronic closure process from east to west and offering insights into the tectonic evolution of the Proto-Tethys Ocean.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 2","pages":"431-454"},"PeriodicalIF":1.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438950","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":"Multi-Parameter Investigation of Cretaceous to Palaeocene Sedimentary Sequences in the Anambra and Niger Delta Basins, Nigeria: Organic Matter Characterisation, Palynofacies and Implications for Palaeoclimate and Sea-Level Changes","authors":"Erepamo J. Omietimi,&nbsp;Nils Lenhardt,&nbsp;Renchao Yang,&nbsp;Annette E. Götz,&nbsp;Aitalokhai J. Edegbai,&nbsp;Adam J. Bumby","doi":"10.1002/gj.5084","DOIUrl":"https://doi.org/10.1002/gj.5084","url":null,"abstract":"<p>The Anambra Basin of Nigeria, part of the larger West and Central African Rift System (WCARS) across Africa, contains primarily Cretaceous to Palaeocene shallow to marginal marine and freshwater sedimentary deposits. The organic-rich deposits of the Cretaceous Nkporo and Mamu formations within the Anambra Basin and the Palaeocene Imo Formation of the Niger Delta Basin constitute important conventional source rocks. Despite its economic significance, research on organic matter characterisation, palynofacies, sea-level fluctuations, palaeoclimate, hydrogeography, basin restriction, palaeobathymetry and the factors controlling organic matter preservation remains largely undocumented. The here presented new inorganic and organic geochemical and organic petrography data of the Cretaceous to Palaeocene deposits serve to refine the regional interpretation at a basinal scale and within the supra-regional context of the WCARS. Geochemical palaeotemperature proxies suggest a warm and humid tropical palaeoclimate during the Late Cretaceous within the study area. Furthermore, the measured TOC values indicate poor to very good organic content. Palynofacies analysis revealed high abundances of opaque and translucent phytoclasts and low amounts of palynomorphs with negligible amorphous organic matter (AOM) in the studied mudrocks. Two palynofacies groups suggest shallow-marine conditions in a proximal shelf setting and a heterolithic oxic basin. The palynofacies of the upper Imo Formation reveal higher percentages of dinoflagellate cysts during the early highstand phase, with equidimensional, opaque phytoclasts representing the maximum flooding phase, accompanied by warmer conditions. Additionally, abundant terrestrial phytoclasts, <i>Deltoidospora</i> spp., <i>Classopollis</i> spp. and geochemical indicators collectively indicate warm tropical climatic conditions consistent with geochemical interpretations. The palaeobathymetry reconstructions suggest a shallow seaway during the Upper Cretaceous in the Anambra Basin.</p>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 1","pages":"196-222"},"PeriodicalIF":1.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/gj.5084","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143117614","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":"Assessment of Landslide Susceptibility using Geospatial Techniques: A Comparative Evaluation of Machine Learning and Statistical Models","authors":"Subrata Raut,&nbsp;Dipanwita Dutta,&nbsp;Debarati Bera,&nbsp;Rajeeb Samanta","doi":"10.1002/gj.5080","DOIUrl":"https://doi.org/10.1002/gj.5080","url":null,"abstract":"<p>This study delineates landslide susceptibility zones in the Kalimpong district by integrating multi-sensor datasets and assessing the effectiveness of statistical and machine learning models for precision mapping. The analysis utilises a comprehensive geospatial dataset, including remote sensing imagery, topographical, geological, and climatic factors. Four models were employed to generate landslide susceptibility maps (LSMs) using 16 influencing factors: two bivariate statistical models, frequency ratio (FR) and evidence belief function (EBF) and two machine learning models, random forest (RF) and support vector machine (SVM). Out of 1244 recorded landslide events, 871 events (70%) were used for training the models, and 373 events (30%) for validation. The distribution of susceptibility classes predicted by The RF and SVM models produced similar susceptibility distributions, predicting 13.30% and 14.30% of the area as highly susceptible, and 2.42% and 2.82% as very highly susceptible, respectively. In contrast, the FR model estimated 20.98% of the area as highly susceptible and 4.30% as very highly susceptible, whereas the EBF model predicted 17.42% and 5.89% for these categories, respectively. Model validation using receiver operating characteristic (ROC) curves revealed that the machine learning models (RF and SVM) had superior prediction accuracy with AUC values of 95.90% and 86.60%, respectively, compared to the statistical models (FR and EBF), which achieved AUC values of 74.30% and 76.80%. The findings indicate that Kalimpong-I is most vulnerable, with 6.76% of its area categorised as very high susceptibility and 24.80% as high susceptibility. Conversely, the Gorubathan block exhibited the least susceptible, with 0.95% and 6.48% of its area classified as very high and high susceptibility, respectively. This research provides essential insights for decision-makers and policy planners in landslide-prone regions and can be instrumental in developing early warning systems, which are vital for enhancing community safety through timely evacuations and preparedness measures.</p>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 5","pages":"1129-1149"},"PeriodicalIF":1.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143914766","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":"Instability Mechanism of Cohesive Soil Slope Based on Discrete-Continuous Coupled Method","authors":"Yuqi Li,&nbsp;Yuting Jing,&nbsp;Zhaoyu Yang","doi":"10.1002/gj.5088","DOIUrl":"https://doi.org/10.1002/gj.5088","url":null,"abstract":"<div>\u0000 \u0000 <p>This paper employed PFC^3D and FLAC^3D to conduct a three-dimensional discrete-continuous dual-scale coupled simulation and stability analysis of cohesive soil slope through discrete-continuous coupled algorithm and the gravity increase method. In the discrete element model zone, the progressive failure process of cohesive soil slope was studied by setting particles with different displacements to different colours, the evolutions of porosity and coordination number in the shear, sliding and stability zones of slope were analysed by arranging measurement spheres, and the variation law of particle position was obtained by the vertical layering of the soil. In the continuous model zone of coupled slope model, the horizontal and vertical stresses were verified with those of a pure FLAC^3D model of slope. Furthermore, a comparative instability analysis of cohesive soil slope and gravelly soil slope was also performed. The safety factor for the cohesive soil slope in this work was determined to be 1.7 according to the mesoscopic fabric evolution of slope particles and the gravity increase method. The work in this paper broadens the application scope of the dual-scale coupled algorithm, highlights the differences in the mesoscopic instability mechanism between cohesive soil slop and gravelly soil slop, and provides new theoretical support for slope design and risk assessment in engineering practice.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 5","pages":"1093-1105"},"PeriodicalIF":1.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143914764","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 Evolution of the Baiyun Sag, Northern South China Sea Margin","authors":"Wei Guan,&nbsp;Lei Huang,&nbsp;Guangrong Peng,&nbsp;Chiyang Liu,&nbsp;Han Li,&nbsp;Chao Liang","doi":"10.1002/gj.5092","DOIUrl":"https://doi.org/10.1002/gj.5092","url":null,"abstract":"<div>\u0000 \u0000 <p>The northern South China Sea (SCS) divergent margin developed on a heterogeneous crust that inherited the structures of the Mesozoic convergent margin. However, in the past, studies focused mainly on Cenozoic structures and neglected Mesozoic basement structures. On the basis of the latest high–resolution 3D seismic volumes, we first identify the fault features and evidence in the granite basement. We then identify three sets of Mesozoic fault systems in the northern SCS and discuss their properties and genesis. The NE–trending thrust system (Seismic Reflection 1), formed by forward compression, corresponds to the NW-ward subduction of the palaeo-Pacific plate; the NE–trending extensional system (Seismic Reflection 2 and small residual half-grabens) is related to post-orogenic extension caused by slab rollback and retreat of the palaeo-Pacific plate; and the NNE–trending thrust system (Seismic Reflection 3) formed by a transpressional effect related to the palaeo-Pacific plate and the Eurasian plate changed from the long-term NW-ward orthogonal convergence to a NNW-ward oblique convergence. Finally, by combining previous results on the regional tectonic evolution of onshore and offshore South China, we establish a model for the late Mesozoic evolution of the northern SCS from the Andean-type margins to the western Pacific-type margins.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"629-641"},"PeriodicalIF":1.4,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530379","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":"New Euungulate Fossils from the Middle Siwalik Subgroup of the Potwar Plateau of Northern Pakistan","authors":"Chaman Ara,&nbsp;Riffat Yasin,&nbsp;Hafiz M. Ishaq,&nbsp;Shakila Naz,&nbsp;Tayyaba Sultana,&nbsp;Khizar Samiullah,&nbsp;Fahad A. Al-Misned,&nbsp;Kifayait Ullah,&nbsp;Holly E. Anderson,&nbsp;Sergi López-Torres,&nbsp;Asghar Abbas","doi":"10.1002/gj.5081","DOIUrl":"https://doi.org/10.1002/gj.5081","url":null,"abstract":"<div>\u0000 \u0000 <p>This article provides a detailed taxonomic study of mammalian fossil fauna from five localities situated within the Middle Siwalik subgroup including the Nagri and Dhok Pathan formations in Punjab, Pakistan. Twenty-three euungulate specimens comprised of isolated teeth, and maxillary and mandibular fragments, are described. This collection includes the bovid, <i>Elachistoceras</i>; a very rare faunal element in the Siwaliks of Pakistan, as well as <i>Elachistoceras khauristanensis</i>, <i>Pachyportax latidens</i>, <i>Giraffa punjabiensis</i>, <i>Bramatherium grande</i>, <i>Merycopotamus dissimilis</i>, <i>Dorcatherium minus</i>, <i>Dorcatherium majus</i>, <i>Hippopotamodon sivalense</i>, <i>Sivalhippus theobaldi</i>, <i>Sivalhippus nagriensis</i> and <i>Brachypotherium perimense</i> These fossil remains add important new insights into the taxonomy and diversity of Late Miocene mammal faunas of the Middle Siwaliks. The data is important for understanding the biogeographical and palaeoenvironmental history of the region. The characteristics of the fossils described in this study further support the currently hypothesised presence of a massive open land environment with variable wet and dry seasons alike to that of the current climate in Eurasia and Africa. The variable habitat niches of these co-existing fauna also give further support to the supposition that there was a much more mixed array of palaeoenvironments ranging from a prevalence of woodland to expansive savannah territory during the deposition of Nagri and Dhok Pathan formations.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 1","pages":"133-162"},"PeriodicalIF":1.4,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143115194","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 of Mudstones Atop the Sangonghe Formation, Shuixigou Group, Turpan-Hami Basin: New Insights and Their Implications for Petroleum Geology","authors":"Weiming Wang,&nbsp;Meishuo Hu,&nbsp;Xuan Chen,&nbsp;Qingguo Liu,&nbsp;Weihao La,&nbsp;Hua Zhang,&nbsp;Yuzhong Yang,&nbsp;Changsheng Miao,&nbsp;Tingting Li","doi":"10.1002/gj.5094","DOIUrl":"https://doi.org/10.1002/gj.5094","url":null,"abstract":"<div>\u0000 \u0000 <p>As the exploration of deep-seated oil and gas resources in the Turpan-Hami Basin intensifies, there is an urgent need to thoroughly depict the geological characteristics of newly uncovered, underexplored strata in sub-sag centers. This study undertakes the inaugural systematic geochemical analysis of mudstones atop the Sangonghe Formation, including palynological identification, maceral identification, biomarker analysis, total organic carbon (TOC) analysis, and pyrolysis. The findings reveal that the mudstone sequence, as the target layer, was deposited in a warm and moist paleoclimate and a weakly reducing to weakly oxidising saline water environment, fostering the growth of prolific algae and bacteria, thus ensuring substantial foundational materials for source rock formation. The organic matter in the mudstone sequence displays pronounced laminar accumulation. Despite the overall modest abundance, the organic matter features notable hydrocarbon-generating potential per unit of organic carbon and favourable types. Humic-sapropelic kerogens (type II₁) are found in the mudstones, with organic matter generally reaching a mature to highly mature stage. These characteristics establish the mudstones as effective source rocks, furthermore, the hydrocarbon expulsion in the Xishanyao Formation precedes that of the Sangonghe Formation and that both formations constitute a sequential process in terms of hydrocarbon generation and expulsion timing and hydrocarbon contribution. Reanalyzing this mudstone sequence not only revises prior geological understanding of it as direct cap rocks, but also facilitates the reclassification of deep-seated strata into three distinct petroleum systems. Centered around this source rock layer, dual modes, namely the “lower-source rock and upper-reservoir” and the “ lower-reservoir and upper-source rock” modes can be formed. These new insights will offer profound implications for hydrocarbon resource evaluation and future hydrocarbon exploration endeavours in the Shuixigou Group within the Taibei sag.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 3","pages":"659-673"},"PeriodicalIF":1.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143530751","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":"RAMAN Analysis of Carbonaceous Material and Deduced Peak Metamorphic Temperatures of Metasediments From Western Himalaya, NW Pakistan","authors":"Nasir Ahmad,&nbsp;Shah Faisal,&nbsp;Asad Khan,&nbsp;Hafiz U. Rehman","doi":"10.1002/gj.5083","DOIUrl":"https://doi.org/10.1002/gj.5083","url":null,"abstract":"<p>Raman spectroscopy of carbonaceous materials (RSCM) was applied to 10 carbonaceous material (CM) -rich low- to medium-grade metasedimentary rock samples of Western Himalaya, Pakistan to assess their optimum thermal evolution. The RSCM thermometry is based on the degree of graphitisation of CM as a function of peak metamorphic temperature. Petrographic observations of the studied samples revealed two dominant CM morphologies. Type-I CM, represented by fine-grained discontinuous dust-like and scattered to thin sporadic layers, was more prevalent in low-grade metamorphic samples. Type-II CM, corresponding to continuous and extended thick fibres and elongated grain constellations, was dominant in medium- to high-grade metamorphic samples. The degree of crystallinity of CM and subsequent metamorphic temperatures were quantified by considering the intensity-based <i>R</i>1 and the area-based <i>R</i>2 ratio parameters. Low-grade samples from the Lesser Himalayan Sequence (LHS), having Type-I CM, resulted in RSCM peak temperatures between 306°C and 403°C. Medium- to high-grade samples from Higher Himalayan Crystalline (HHC), containing Type-II CM, yielded peak temperatures in the 482°C–560°C range. The extremely deformed sample from a fault zone in the LHS produced relatively higher temperature of 403°C, thereby suggesting heat associated with shearing due to fault activities resulting in CM recrystallisation and elevated temperature values. The study revealed that the peak metamorphic temperatures increase from south towards north following a progressive path of metamorphism in the region.</p>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 2","pages":"387-403"},"PeriodicalIF":1.4,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/gj.5083","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143439229","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}