Geological Journal最新文献

{"title":"Reply to Comment on “Singh R, Vadlamani R, Bajpai S & Maurya AS (2024) Strontium Isotope Stratigraphy of Marine Oligocene–Miocene Sedimentary Successions of Kutch Basin, Western India. Geological Journal, 1–20. DOI: 10.1002/gj.4961”","authors":"Rimjhim Singh,&nbsp;Ravikant Vadlamani,&nbsp;Sunil Bajpai,&nbsp;Abhayanand Singh Maurya","doi":"10.1002/gj.5074","DOIUrl":"https://doi.org/10.1002/gj.5074","url":null,"abstract":"<div>\u0000 \u0000 <p>This response addresses the comments made by Saraswati et al. on our recent publication in Geological Journal. In our study, we used a multi-analytical screening approach, including visual, XRD and trace element analysis, to evaluate diagenetic alteration of carbonate shell samples. Contrary to the claims made by Saraswati et al. our findings are based on well-preserved samples with minimal alteration. The Sr-isotope data from the Khari Nadi Formation (23.07–18.09 Ma) are largely consistent with existing biostratigraphic constraints, but suggest a possible extension of the upper age limit into the Burdigalian. Our Sr-isotope ages for the Chhasra Formation (15.11–12.29 Ma) are younger than those suggested previously, based on larger benthic foraminifers, but largely corroborate recent nannoplankton data. As a result of the new age data from Kutch, we suggest that the sedimentation rates, derived from multiple samples, increased significantly from the Oligocene to Miocene. We assert that ‘established’ ages are also subject to refinements as the rock units become amenable to new dating techniques. We welcome any criticism that is constructive, and remain open to any further data that could refine or challenge our interpretations.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"59 12","pages":"3381-3384"},"PeriodicalIF":1.4,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142762619","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":"Fabrics and Origin of Troctolites in the Keketoukeleke Ultramafic–Mafic Complex, South Altyn Tagh, Northwest China","authors":"Guojian Geng,&nbsp;Liang Liu,&nbsp;Haijun Xu","doi":"10.1002/gj.5054","DOIUrl":"https://doi.org/10.1002/gj.5054","url":null,"abstract":"<div>\u0000 \u0000 <p>Troctolite is relatively rare compared with other ultramafic–mafic rocks, but its origins and rheological deformation are significant for understanding melt–rock interactions and fractional crystallization of mafic magmas. The Keketoukeleke ultramafic–mafic complex in the South Altyn Tagh, northwest China, consists mainly of dunite, coarse- and fine-grained troctolite. Based on petrographic observations, major and trace element variations of the dunites and troctolites, and low olivine Zr/Y and Ti/Y ratios, we propose that the troctolites were formed by fractional crystallization and late localized water-bearing melt injection. In addition, the olivine in the dunites has A- and E-type fabrics, whereas the olivine in the troctolites has a weak fabric and plagioclase has a pronounced fabric with the [010] axes aligned subnormal to the foliation and [100] axes subparallel to the lineation. The results suggest that the troctolite rheological deformation was concentrated mainly in plagioclase, and the olivine only underwent grain rotation or grain boundary slip. Furthermore, the dating of baddeleyite in troctolite suggests they crystallized at 378.6 ± 2.3 Ma, suggesting the Keketoukeleke ultramafic–mafic complex emplaced the continental crust extension after deep subduction–exhumation process of South Altyn.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"59 12","pages":"3362-3376"},"PeriodicalIF":1.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142762735","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":"Serpentinised Dunites of the Neoarchean Shimoga Greenstone Belt, Western Dharwar Craton, India: Insights on Ni-PGE Mineralisation and Genesis","authors":"Th. Dhanakumar Singh,&nbsp;C. Manikyamba,&nbsp;G. Harshitha,&nbsp;M. Lingadevaru,&nbsp;K. S. V. Subramanyam,&nbsp;Arijit Pahari","doi":"10.1002/gj.5071","DOIUrl":"https://doi.org/10.1002/gj.5071","url":null,"abstract":"<div>\u0000 \u0000 <p>Ultramafic rocks of the Archean greenstone belts worldwide are potential hosts for Cu-Ni, precious metal deposits like platinum group elements (PGEs) and gold. This study highlights the geochemical evidence and genesis of Ni-PGE mineralisation in the ultramafic rocks of Shimoga greenstone belt of the Western Dharwar Craton, India. Petrographically, the studied rocks are identified to be serpentinised dunites, while their geochemical signatures indicate komatiitic affinity. Presence of disseminated sulphides and pronounced serpentinisation in these rocks suggest a combination of Type II (disseminated sulphides) and Type IV (post-magmatic alterations) komatiite-related Ni–Cu-PGE deposits. Chondritic Al₂O₃/TiO₂ (9.65–16.38) ratios, superchondritic Gd/Yb_N (1.3–1.6), depleted high-field-strength elements (HFSEs) (Zr, Hf), enrichment of LREE over HREE and negative Nb–Ta anomalies reflect the generation of parental melts from plume-sourced Al-depleted komatiites with significant crustal contamination during their emplacement. The major, trace element and PGE relationships (FeO vs. MgO, Cu vs. Pd, Ni/Cu vs. Pd/Ir) infer the origin of sulphur undersaturated primary melts through moderate to higher degrees of partial melting followed by crustal assimilation that led to PGE enrichment. These observations suggest their formation from melts derived from greater depths of the upper mantle (&gt; 400 km) at high pressure (&gt; 10 GPa), wherein, the mantle residue retained majorite garnet. The high Ni (avg. Ni = 6511 ppm) substantiated by high Kambalda ratio ([Ni:Cr] × [Cu:Zn] = 5.6), Ni/Cr ratios (&gt; 1) with high concentration of PGEs (avg. ∑PGE = 3078 ppb) confirm the fertile/mineralised nature of the komatiitic source and potential Ni-PGE mineralization in the ultramafic rocks of the Shimoga greenstone belt.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 1","pages":"45-63"},"PeriodicalIF":1.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143117762","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":"Basin–Orogen Coupling-Driven Meso-Cenozoic Deformation Along the Southern Margin of the Junggar Basin, NW China: Insights From Integrated Multidisciplinary Analysis","authors":"Feiyu Zhao,&nbsp;Yanhui Suo,&nbsp;Sanzhong Li,&nbsp;Juzhi Deng,&nbsp;Ke Chen,&nbsp;Ian D. Somerville,&nbsp;Mengxue Dai,&nbsp;Xiao Chen,&nbsp;Bin Hu","doi":"10.1002/gj.5079","DOIUrl":"https://doi.org/10.1002/gj.5079","url":null,"abstract":"<div>\u0000 \u0000 <p>The southern margin of the Junggar Basin (SMJB) represents the typical intra-continental basin–orogen coupling structure of the Central Asian Orogenic Belt and is a key area to study the deformation mechanisms and the geodynamic evolution processes of the North Tianshan Orogen. Herein, we compiled data from boreholes, gravity and magnetism, seismicity- and magnetotellurics-derived geological profiles and field data to recover the sedimentary history of the SMJB and discuss the intra-continental deformation driven by the basin–orogen coupling mechanism. The results show that the sedimentary and tectonic evolution of the SMJB were both profoundly controlled by the intra-continental orogeny of the North Tianshan Orogen and its coupling with the Junggar Basin during the Meso-Cenozoic period. Consequently, the SMJB is dominated by thick-skinned thrust nappes accompanied with strike-slip faulting and thrusting. The foreland thrust belt of the SMJB is characterised by three structural belts, from south to north, including the basement-involved thrust belt, the cover-detached foreland thrust-fold belt and the thrusted foreland basement uplifts, respectively. Meanwhile, as indicated by the geometry of the basement thrusts, the thickness of décollements and the structure of the foreland basement, the stress field in the SMJB is obviously stronger in the west and weaker in the east. The sedimentation and deformation migrated northwards into the basin area in a stepwise process, that corresponded to the pace of the overthrusting of the North Tianshan Orogen onto the Junggar Block. Intense regional compression induced the rapid uplifting of the North Tianshan and the significant crustal shortening of the Junggar Block, driving the three structural belts to form accordingly during the Late Jurassic to the Neogene. There are at least one or two décollements within the SMJB, representing one of the main features of basin–orogen coupling structure in most cases. The décollement of some layers represents the decoupling of the sedimentary cover with the basement, which helps to accommodate the lateral crustal shortening of the SMJB by a translation into vertical uplift. As a result, the detached foreland thrust-fold belts in the shallow level of the upper crust overthrusted upon the basement-involved nappes of the mountain's side, forming the opposite thrust system. Coevally, the basement of the basin, in the deep level of the upper crust keeps underthrusting beneath the North Tianshan Orogen, forming a typical crocodile mouth-like structure. In general, both the shallow and deep deformation in the SMJB have been formed by the intense intra-continental compression during the Meso-Cenozoic, which were driven by the basin–orogen coupling mechanism.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"59 12","pages":"3214-3239"},"PeriodicalIF":1.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142762738","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":"A Comprehensive Review of Remote Sensing Technologies for Improved Geological Disaster Management","authors":"Sheetal Kumari,&nbsp;Smriti Agarwal,&nbsp;Nitin Kumar Agrawal,&nbsp;Animesh Agarwal,&nbsp;Manoj Chandra Garg","doi":"10.1002/gj.5072","DOIUrl":"https://doi.org/10.1002/gj.5072","url":null,"abstract":"<div>\u0000 \u0000 <p>Over the past two decades, the frequency of natural hazard incidents has steadily risen, leading to substantial human casualties, infrastructure destruction, societal and economic disruption. The occurrence of disasters, both of natural and human origin, has exhibited an upward trend in frequency over the past few decades on a global scale, posing a significant threat to diverse populations. Over time, remote sensing technologies have proven to be effective in analysing and monitoring diverse natural disasters, including but not limited to droughts, earthquakes, tsunamis, landslides and cyclones. The significant extent of its coverage capacity and the ability to repeat observations make its application economically efficient. This paper aims to elucidate the fundamental contributions and role of remote sensing in disaster management applications. In a comprehensive analysis, this study explores recent practical applications in the context of disaster events. The utilisation of diverse methodologies and functions of remote sensing in disaster monitoring and control is further expanded to encompass the domain of disaster risk management, employing cutting-edge sensors and satellites from emerging technological advancements. This paper also addresses challenges related to disaster monitoring, detection and management. Emergencies, particularly during typical catastrophe scenarios, often witness partial disruptions in communication networks. Consequently, the role of alternative networks becomes paramount in enabling effective disaster detection and management strategies. Emerging issues are highlighted, and potential directions for future research are outlined and also support sustainable development goal 13 (climate action).</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 1","pages":"223-235"},"PeriodicalIF":1.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143117763","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":"Comment on “Singh R, Vadlamani R, Bajpai S, Maurya AS (2024) Strontium Isotope Stratigraphy of Marine Oligocene–Miocene Sedimentary Successions of Kutch Basin, Western India. Geological Journal, 1–20. DOI: 10.1002/gj.4961”","authors":"Pratul Kumar Saraswati,&nbsp;Gianluca Frijia,&nbsp;György Less","doi":"10.1002/gj.5069","DOIUrl":"https://doi.org/10.1002/gj.5069","url":null,"abstract":"<div>\u0000 \u0000 <p>This is a comment on the paper of Singh et al. (<i>Geological Journal</i>, 2024:1–20) on Strontium isotope stratigraphy of marine Oligocene–Miocene sedimentary successions of Kutch Basin, western India. Kutch hosts stratotypes of some lithostratigraphic and chronostratigraphic units of India. In this study, the Sr-isotope estimated ages of the studied formations deviate significantly from their known ages based on biostratigraphy. The authors have not validated the interpreted ages with biostratigraphy. We believe a scrupulous screening of samples and validation of Sr-isotope data with biostratigraphy are two essential requirements of Sr-isotope stratigraphy. Unfortunately, Singh et al. made a new contribution to Kutch stratigraphy that falls short of meeting both conditions, leading to incorrect ages of the regional chronostratigraphic units of India.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"59 12","pages":"3377-3380"},"PeriodicalIF":1.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142762736","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 Ordovician Bentonites From the Southern Ordos Basin: Response to the Subduction of the Proto-Tethys Ocean","authors":"Zuochen Li,&nbsp;Xianzhi Pei,&nbsp;Lei Pei,&nbsp;Youxin Chen,&nbsp;Hao Wang,&nbsp;Hao Lin,&nbsp;Li Qin,&nbsp;Yajie Yang,&nbsp;Shang Ji,&nbsp;Liang'e Chen,&nbsp;Weiyi Hou,&nbsp;Irshad Hussain,&nbsp;Gang Zhang","doi":"10.1002/gj.5077","DOIUrl":"https://doi.org/10.1002/gj.5077","url":null,"abstract":"<div>\u0000 \u0000 <p>The connection between the Ordovician bentonites on the southern margin of the Ordos Basin and the Early Palaeozoic volcanic rocks of the North Qinling Orogenic Belt is crucial for understanding the subduction and collisional closure of the Shangdan Ocean during the Early Palaeozoic. This paper investigates zircon U–Pb ages, geochemistry and Lu–Hf isotopic compositions of zircons in the Upper Ordovician Zhaolaoyu Formation bentonites located on the southern margin of the Ordos Basin. U–Pb dating of zircon indicates a coeval age of 453.3 ± 1.4 Ma (MSWD = 0.99), which represents the crystallisation age during the Late Ordovician Katian stage. The bentonites exhibit higher SiO₂ (57.94–77.95 wt.%) and Al₂O₃ (9.21–14.33 wt.%), classifying them within the low-potassium alkali basalt to medium-potassium calc-alkaline series. The parent rock of the bentonites is likely intermediate to felsic volcanic rocks. The rare earth element partitioning curves of the bentonites are right-dipping, with a more pronounced negative Eu anomaly (<i>δ</i>Eu = 0.48–0.67). The zircons in the bentonites yield two-stage model ages ranging from 546 to 956 Ma, along with <i>ε</i>\u0000 _Hf(<i>t</i>) values between 5.56 and 13.55. These results indicate that the bentonites are products of volcanic arc magma formed in a subduction–collision environment. The interbedded bentonites in the Upper Ordovician limestones of the southern margin of the Ordos Basin may be associated with the northward subduction of the Shangdan Oceanic crust, reflecting the subduction and consumption of the Proto-Tethys Ocean along the southern margin of the North China Block.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 1","pages":"104-132"},"PeriodicalIF":1.4,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143117622","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":"Distribution and Controlling Factors of the Contourites on the Northern Continental Slope of the South China Sea","authors":"Hairong Wang,&nbsp;Chengqian Yu,&nbsp;Xianglan Chen,&nbsp;Xianglin Li,&nbsp;Hongfang Gao","doi":"10.1002/gj.5067","DOIUrl":"https://doi.org/10.1002/gj.5067","url":null,"abstract":"<div>\u0000 \u0000 <p>The northern continental margin of the South China Sea (SCS) is an important component of deep-water circulation, providing excellent conditions for studying bottom currents in a marginal sea. Seismic data were employed to discern the sedimentary patterns prevalent in the deep-water continental slope sediments on the northern continental margin of the SCS, encompassing gravity flow, contourite and mixed depositional systems. The contourite depositional system includes various types of deposits (such as separated mounded drifts, patch or channel-related drifts, deformed sheeted drifts, composite drifts, bottom current sediment waves, plastered contourite drifts) and various morphologic erosional features eroded by the bottom current (such as moats, non-depositional surfaces, troughs and scarps). These contourite features are related to the continental slope's morphology and its sources. The Dongsha slope exhibits distinctive characteristics marked by intense bottom current erosion and deposition, featuring separated mounded drifts and deformed sheeted drifts along its lower slope. The lower slope of the Pearl River showcases a spectrum of bottom current-induced features, including sediment wave fields, erosion fields and contourite drifts. The southern flank of the Shenhu slope is characterised by a bottom current erosion field, a non-depositional surface, a sediment wave field and isolated mounded drifts. On the Yingqiong slope, the contourite drifts are limited to its southern flank where gravity flow action is absent, and the complex geomorphology interacts with the bottom current, forming a complex contourite depositional system. The results of this study serve as a foundational framework for further global research on bottom current circulation and hydrodynamics.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 1","pages":"1-18"},"PeriodicalIF":1.4,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143115603","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":"Activity History of the Gangga Graben in the Southern Segment of Kung Co Rift in Southern Tibet Constrained by ESR and U-Series Dating","authors":"Xuejian Dai,&nbsp;Songtao Yan,&nbsp;Hu Li,&nbsp;Junfeng Hu,&nbsp;Tao Liu,&nbsp;Hongrui Dai,&nbsp;Yangchun Wei,&nbsp;Yushi Lei,&nbsp;Wangchuan Guo,&nbsp;Chongyang Xin","doi":"10.1002/gj.5068","DOIUrl":"https://doi.org/10.1002/gj.5068","url":null,"abstract":"<p>Characterising the spatial and temporal distribution of the S-N-trending rift in southern Tibet is crucial for elucidating the dynamics of E-W extension within the Tibetan Plateau since the Miocene. The Kung Co–Tangra Yumco rift, located in the central part of the rift system, was initiated at the peak of rifting development. While the initiation of rifting has been ascertained through low-temperature thermochronology, direct timing constraints remain absent for the Gangga Graben in the southernmost region. Utilising the quartz electron spin resonance (ESR) dating technique, we ascertained the onset age of the eastern boundary fault of the Gangga Graben to be 12.00 ± 1.80 Ma, with an accelerated activity phase at 9.17 ± 1.19 Ma, and an activity age for the western boundary fault at 2.22 ± 0.24 Ma. U-series dating conducted on the western boundary disclosed a time span of 20–13 ka for hot spring fissure activity. Seismic evidence, inclusive of those from the Gongdapu Horst, indicates persistent activity of the Gangga Graben since the Pleistocene. Comparative analysis of age data from the Kung Co–Tangra Yumco rift suggests that it commenced almost synchronously along its strike at ~14.5–12 Ma. Considering the rifts trending from west to east in southern Tibet and the genetic mechanism of leucogranite, we propose an E-W extension mechanism in southern Tibet. At ~26–14 Ma, the lithosphere experienced weakened delamination and asthenosphere upwelling, leading to a series of magmatic activities and onset of E-W extension in southern Tibet. At ~17–7 Ma, as the basal shearing of the underthrusting Indian Plate increased, it marked the peak phase of rifting in southern Tibet.</p>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"60 1","pages":"19-32"},"PeriodicalIF":1.4,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/gj.5068","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143115604","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":"Serpentinised Mantle Section of Neoproterozoic Ophiolite at Al-Barramiya District, North Arabian-Nubian Shield: Tectono-Magmatic Evolution and Metamorphism","authors":"Bassam A. Abuamarah,&nbsp;Amany M. A. Seddik,&nbsp;Mokhles K. Azer,&nbsp;Yi-Xiang Chen,&nbsp;Mahmoud H. Darwish","doi":"10.1002/gj.5066","DOIUrl":"https://doi.org/10.1002/gj.5066","url":null,"abstract":"<div>\u0000 \u0000 <p>This research focuses on the field observations, petrography, mineral chemistry and geochemistry of the serpentinised peridotite of Al-Barramiya ophiolitic sequence to place constraints on their magmatic history and their geodynamic evolution. Al-Barramiya ophiolitic rocks are a dismembered ophiolite which was strongly deformed and metamorphosed under greenschist to lower amphibolite facies. They comprise a mantle section dominated by highly serpentinised peridotite with less metapyroxenite and chromitite, as well as a crustal portion represented by metagabbros. Along shear zones, the ophiolite sequence was affected by several types of alteration. Extensive carbonate alteration is common in the ultramafic section, resulted in talc carbonates, listvenites and magnesite, while rodingitisation is common in the metagabbro resulted in rodingite. Despite the extensive serpentinisation, some fresh relics of primary mantle minerals such as Cr-spinel, olivine and pyroxenes are preserved sporadically in the serpentinised peridotite. Few Cr-spinel crystals are sometimes surrounded by subhedral flakes of Cr-chlorite (kämmererite) that was formed due to replacement of Cr-spinel during later alteration or regional metamorphism. The serpentinite samples are depleted in the total REE (0.56–1.19 ppm) with slightly negative to slightly positive Eu anomalies (0.89–1.28). The fresh cores of Cr-spinel have Cr# mostly &gt; 60, and the relics of pyroxenes and olivine are Mg-rich suggesting that the Al-Barramiya serpentinites are residual to high degrees of melt extraction. The estimated degrees of partial melting range between 18.2% and 20.7%. All the mineralogical and geochemical characteristics of the ultramafic section of the Al-Barramiya ophiolites are most consistent with its formation in a fore-arc setting.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"59 12","pages":"3335-3361"},"PeriodicalIF":1.4,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142762643","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}