Journal of the Geological Society最新文献_第5页

Geochemistry, mineral chemistry and Re–Os isotopes of refractory peridotites of the North Balkhash ophiolite zone in the West Central Asian Orogenic Belt (Central Kazakhstan): multi–stage melt evolution of a Late Precambrian forearc mantle 中亚西部造山带北巴尔喀什蛇绿岩带难熔橄榄岩的地球化学、矿物化学及Re-Os同位素:晚前寒武纪弧前地幔多期熔融演化

3区地球科学

Journal of the Geological Society Pub Date : 2023-09-27 DOI: 10.1144/jgs2023-091

Aleksandra Milyukova, Anfisa Skoblenko, Yildirim Dilek, Kuo-Lung Wang, Valentina Batanova, Kirill E. Degtyarev

{"title":"Geochemistry, mineral chemistry and Re–Os isotopes of refractory peridotites of the North Balkhash ophiolite zone in the West Central Asian Orogenic Belt (Central Kazakhstan): multi–stage melt evolution of a Late Precambrian forearc mantle","authors":"Aleksandra Milyukova, Anfisa Skoblenko, Yildirim Dilek, Kuo-Lung Wang, Valentina Batanova, Kirill E. Degtyarev","doi":"10.1144/jgs2023-091","DOIUrl":"https://doi.org/10.1144/jgs2023-091","url":null,"abstract":"In this study we report on the petrography, major, trace element and mineral chemistry, platinum group elements (PGE), and Re–Os isotope systematics of depleted ultramafic rock suites from the Itmurundy Block in the North Balkhash ophiolite zone (NBOZ) in Kazakhstan. Represented mainly by variably serpentinized harzburgites and dunites, our samples are characterized by low whole-rock Al2O3 (0.33–0.86 wt.%), CaO (0.51–0.86 wt%), and Na2O (0.07–0.25 wt.%) concentrations, and high-Mg olivine (Fo = 91–92) and orthopyroxene (Mg# = 92–93) contents, together with moderately high-Cr spinel numbers (Cr# = 63–68). They are depleted in incompatible elements (ΣREE, Nb, Sc) and enriched in compatible elements, such as Cr (up to 2817 ppm) and Ni (up to 2327 ppm), representing highly refractory mantle residues derived from a forearc mantle wedge. They underwent 19–23% hydrous partial melting to produce boninitic melts. 187Os/188Os values vary from 0.1202 to 0.12599, and 187Re/188Os ratios from 0.230 to 0.316. The Re–Os model ages (TMA) and maximum Re depletion model age (TRD) were calculated based on the obtained data. Re–Os isotope systematics suggest that the analysed peridotites formed in two stages: first stage around 1.5 Ga, and a later stage around 668 to 589 Ma. Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists Supplementary material: https://doi.org/10.6084/m9.figshare.c.6845683","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135536644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Direct dating of deposition and rift-related alteration of fossil barren red bed units in the North Sea 北海赤层单元化石沉积与裂谷蚀变的直接定年

3区地球科学

Journal of the Geological Society Pub Date : 2023-09-27 DOI: 10.1144/jgs2023-052

Malcolm S.W. Hodgskiss, Nick M.W Roberts, Päärn Päiste, Niels Rameil, Erik Hammer, Harald Brunstad, Aivo Lepland

{"title":"Direct dating of deposition and rift-related alteration of fossil barren red bed units in the North Sea","authors":"Malcolm S.W. Hodgskiss, Nick M.W Roberts, Päärn Päiste, Niels Rameil, Erik Hammer, Harald Brunstad, Aivo Lepland","doi":"10.1144/jgs2023-052","DOIUrl":"https://doi.org/10.1144/jgs2023-052","url":null,"abstract":"Many fossil-barren or poorly fossiliferous red bed units are found in the North, Norwegian, and Barents seas. Due to the near-absence of biostratigraphic markers in these units, and the possibility of unconformities at their upper and lower boundaries, determining their depositional ages and stratigraphic assignment can be challenging. We apply in-situ U-Pb carbonate dating on North Sea samples, including plant-root related carbonates (rhizoliths) from paleosols and calcite veins crosscutting clasts in a conglomeratic red bed unit, to constrain their respective ages. Our data indicate that one of the studied units was deposited ca. 260 to 250 Ma (Ma – millions of years ago) and may represent an early development of the Skagerrak Formation. The second unit yielded an oldest age of 180.2 ± 9.7 Ma, interpreted to represent a late diagenetic event rather than deposition. High Mn/Sr and low δ 13 C values in many cements dated between ca. 180 to 100 Ma are interpreted to represent precipitation of diagenetic carbonates and reprecipitation of root carbonates, potentially related to Jurassic-Cretaceous volcanism and uplift during rifting of the North Sea. These new data point to U-Pb carbonate geochronology as an effective tool for directly dating red bed units and subsequent diagenetic events. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6850741","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"728 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135538076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Superposed Variscan and Alpine deformation in the basement rocks of southern Andorra, Central Pyrenees 中比利牛斯山脉安道尔南部基底岩石中叠加的瓦里斯坎和阿尔卑斯山脉变形

3区地球科学

Journal of the Geological Society Pub Date : 2023-09-27 DOI: 10.1144/jgs2023-099

A. Margalef, P. Granado, J.M. Casas

{"title":"Superposed Variscan and Alpine deformation in the basement rocks of southern Andorra, Central Pyrenees","authors":"A. Margalef, P. Granado, J.M. Casas","doi":"10.1144/jgs2023-099","DOIUrl":"https://doi.org/10.1144/jgs2023-099","url":null,"abstract":"Detailed mapping, structural analysis and cross-section constructions yield new data on the geometry and chronology of Variscan and Alpine deformations in the central Pyrenees of southern Andorra. The studied area is characterized by polyphase deformation and strain partitioning due to the presence of an efficient décollement level within Silurian black shales. Variscan macrostructures gave rise to a minimum shortening of ca. 22% for Cambrian-Ordovician and Upper Ordovician units below the décollement level and of ca. 35% for Silurian and Devonian units above it. Variscan structures are cut by out-of-sequence thrusts, presumably developed after late Variscan igneous intrusions, and extensional faulting. Those thrusts cut previous Variscan D 2 (main-phase) folds and originate additive and subtractive contacts. We propose an Alpine age for most of these thrusts which, together with the Variscan structures, are affected by subsequent Alpine deformation, which causes changes in their orientation around the intrusions, and a progressive steepening of the cleavage from south to north. We discuss the usefulness and limitations of balanced cross-sections in polydeformed areas and propose that the technique is valid to construct regional sections and to obtain geologically reasonable pre-deformational configurations.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135536786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Surface rupture history and 18-ka-long slip rate along the Pazarcık segment of the East Anatolian Fault 东安纳托利亚断层Pazarcık段地表破裂历史和18 ka长的滑动速率

3区地球科学

Journal of the Geological Society Pub Date : 2023-09-27 DOI: 10.1144/jgs2023-056

Önder Yönlü, Volkan Karabacak

{"title":"Surface rupture history and 18-ka-long slip rate along the Pazarcık segment of the East Anatolian Fault","authors":"Önder Yönlü, Volkan Karabacak","doi":"10.1144/jgs2023-056","DOIUrl":"https://doi.org/10.1144/jgs2023-056","url":null,"abstract":"We investigate the paleo earthquakes and slip-rate on the Pazarcık segment of East Anatolian Fault which has involved surface rupture of 6 February 2023 Pazarcık-Kahramanmaraş earthquake (Mw:7.7) and provided insights of the long-term behavior of this major continental fault. Paleoseismologic data from two trench sites, reveal evidence for at least five surface ruptures in the Holocene Period. The historical earthquake of 1114AD is verified at both trench sites but the following event of 1513AD is only identified at one site. In addition, the age difference of the older events shows historical activity are separated by much longer periods of relative quiescence that range from 500 years to 1000 years which suggest quasiperiodic earthquake occurrence on sub-segments of the Pazarcık segment. Our fault parallel trenches revealed 101±5 m offset in the last 18 ka and 51±1 m offset in the last 9 ka on a buried stream channel and the actual channel of the same stream respectively. The correlation of the maximum and abandonment age of the channel with measured offsets revealed 5.6 mm a -1 long-term slip rate of the fault. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6850786","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"300 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135472716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Early Paleozoic ductile deformation of the South China Block: the polyphase shear zones in the Eastern Jiangnan Belt 华南地块早古生代韧性变形:东江南带多相剪切带

3区地球科学

Journal of the Geological Society Pub Date : 2023-09-26 DOI: 10.1144/jgs2023-062

Jun Hu, Xinqi Yu, Wei Li, Nianwei Liu

{"title":"Early Paleozoic ductile deformation of the South China Block: the polyphase shear zones in the Eastern Jiangnan Belt","authors":"Jun Hu, Xinqi Yu, Wei Li, Nianwei Liu","doi":"10.1144/jgs2023-062","DOIUrl":"https://doi.org/10.1144/jgs2023-062","url":null,"abstract":"Three parallel east–west (E–W)-trending shear zones are components of the polyphase shear zones in the eastern Jiangnan belt. The meso- and microstructural characteristics and the estimates of deformation temperatures, vorticities, and geochronology of these shear zones provide significant information regarding the tectonic evolution of the South China Block (SCB) during the early Paleozoic. Most shear sense indicators (e.g., asymmetric folds, S-C fabrics, and rotating porphyroclasts) reveal that the kinematics were characterized by E–W dextral shear. Finite strain measurements indicate an oblate strain ellipsoid shape with S-type and SL-type tectonites. The rotated rigid porphyroclasts and Mohr circle methods yield vorticity (Wk) values of 0.58–0.80 and 0.66–0.89, respectively, indicating that the flow was generally shear-dominated with almost equal proportions of simple and pure shear. Both mineral deformation thermometers and quartz c-axis fabrics indicate that the deformation occurred at medium temperature conditions of 400–550℃. Combined with our new age and regional geological data, the E–W-trending shear zones might represent an increment of deformation during the last period of the early Paleozoic orogeny in the SCB.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135718742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The seismotectonic role of transversal structures in the Plio-Quaternary evolution of the External Marche Apennines (Italy) 横向构造在意大利外亚平宁丘陵上第三纪-第四纪演化中的地震构造作用

3区地球科学

Journal of the Geological Society Pub Date : 2023-09-18 DOI: 10.1144/jgs2023-002

M. Costa, C. Invernizzi, G. Penza, S. Teloni, P.P. Pierantoni

{"title":"The seismotectonic role of transversal structures in the Plio-Quaternary evolution of the External Marche Apennines (Italy)","authors":"M. Costa, C. Invernizzi, G. Penza, S. Teloni, P.P. Pierantoni","doi":"10.1144/jgs2023-002","DOIUrl":"https://doi.org/10.1144/jgs2023-002","url":null,"abstract":"The seismotectonic setting of external Marche Apennines (Central Italy) was defined integrating geomorphological, structural, and seismological data. Strong historical earthquakes characterized the area, but geometries and kinematics of the seismogenic sources are not well defined. Plio-Quaternary Apennine compressional NW-SE structures are segmented by NE-SW oriented transversal faults, whose origin and role are still debated. We characterize the geometry, kinematics, and activity of four main transversal faults to better define their seismogenic potential. These high-angle and deeply rooted transversal fault systems have been mapped; they separate the external Apennine sector into blocks and sub-blocks with different structural and evolutionary features. The integrated dataset revealed that some inherited fault segments have recently been reactivated displacing Quaternary deposits. Spatial distribution of seismicity indicates that some clusters of hypocentres are located within the basement. Stress field analysis using available focal mechanism solutions confirms the prevalence of left-lateral kinematics on roughly SW–NE oriented structures. The transversal structures thus contribute to the longitudinal segmentation of the Apennine structures and, more in general, they are involved in the northern part of Adria plate kinematics toward N and NNW. Assessing seismic hazard and planning to mitigate risk in populated areas close to the Adriatic coast should consider these potentially active faults evidenced by the instrumental seismicity and important historical earthquakes.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135152932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The continuation of the Mull Dyke Swarm into the Southern North Sea 马尔堤防的延续进入北海南部

IF 2.7 3区地球科学

Journal of the Geological Society Pub Date : 2023-08-25 DOI: 10.1144/jgs2023-039

F. Carver, J. Cartwright, A. Mcgrandle, C. Kirkham, Evan Pryce

引用次数: 0

Double arc–continent collision record in the Latest Mesozoic–Cenozoic tectonic history of the Himalayan–Tibetan orogenic belt in Western Pakistan 巴基斯坦西部喜马拉雅-西藏造山带中新生代构造史上的双弧-大陆碰撞记录

IF 2.7 3区地球科学

Journal of the Geological Society Pub Date : 2023-08-25 DOI: 10.1144/jgs2023-076

Inayat Ullah, Chuandong Xue, Tiannan Yang, H. Furnes, Y. Dilek, Wen Wang, Abdul Ghaffar

{"title":"Double arc–continent collision record in the Latest Mesozoic–Cenozoic tectonic history of the Himalayan–Tibetan orogenic belt in Western Pakistan","authors":"Inayat Ullah, Chuandong Xue, Tiannan Yang, H. Furnes, Y. Dilek, Wen Wang, Abdul Ghaffar","doi":"10.1144/jgs2023-076","DOIUrl":"https://doi.org/10.1144/jgs2023-076","url":null,"abstract":"Our recent field investigations in western Pakistan have revealed that serpentinized peridotites here are crosscut by numerous intrusions of gabbro and tonalite. New zircon U–Pb dating of these plutons indicates Late Cretaceous–Early Eocene ages of their crystallization. They have arc-like geochemical signatures and constitute the middle crust of an island arc complex. Together with their extrusive counterparts they form the RasKoh island arc (RIA), defined for the first time in this study. The RIA and the Chaiga continental arc to the north represent the manifestations of two separate subduction zone systems within Neotethys, developed between India and Eurasia. We posit that this Neotethyan domain contained two oceanic plates. Subduction of the leading plate beneath Eurasia generated the Jurassic–Late Oligocene Chaiga continental arc, and the northward subduction of the trailing plate resulted in the development of the Late Cretaceous–Oligocene, ensimatic RasKoh arc. Arrival of the Indian subcontinent at the latitude of the RasKoh arc in the earliest Miocene caused the emplacement of the RasKoh arc onto India via oblique arc–continent collision. The subsequent collision of this composite Indian plate with Eurasia resulted in extensive deformation of Late Cretaceous flysch deposits and the ophiolitic arc basement.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Ophiolites, melanges and blueschists collection available at:\u0000 https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6795686\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41901921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Incomplete vascular ring of the aortic arch presenting with dysphagia in an adult: case report. 成人主动脉弓血管环不完整伴吞咽困难一例报告。

IF 1.2 3区地球科学

Journal of the Geological Society Pub Date : 2023-08-25 eCollection Date: 2023-01-01 DOI: 10.11604/pamj.2023.45.183.38569

Ndubueze Ezemba, Augustine Chukwudi Onuh, Uchenna Simon Onoh

{"title":"Incomplete vascular ring of the aortic arch presenting with dysphagia in an adult: case report.","authors":"Ndubueze Ezemba, Augustine Chukwudi Onuh, Uchenna Simon Onoh","doi":"10.11604/pamj.2023.45.183.38569","DOIUrl":"10.11604/pamj.2023.45.183.38569","url":null,"abstract":"<p><p>Anomalies of the arterial branches of the arch of the aorta are rare, with the aberrant right subclavian artery being the most common of this anomaly. Majority of the anomalies are asymptomatic and often discovered as incidental findings. In the great majority of the symptomatic cases, the presentation may be either with breathlessness or dysphagia or both. This is in addition to the nature of the intrinsic arterial disease of the aberrant vessel, especially in adult patients; and unless borne in mind, the diagnosis is often missed leading to delays and wrong treatment. In this report we present a case of dysphagia in an adult male Nigerian initially diagnosed as œsophageal stricture from herbal potion ingestion but review of his imaging investigations gave a final diagnosis of dysphagia lusoria from an aberrant right subclavian artery. The difficulty in making a diagnosis and the need for a multidisciplinary review of the imaging investigations are highlighted. The patient was successfully treated by a combined trans-thoracic and cervical approach with division and re-implantation of the aberrant vessel unto the right common carotid artery. He has remained symptom-free for 2 years after surgery. Although the great majority of these anomalies are often asymptomatic, it is important they are borne in mind both in imaging investigations as well as in procedures involving structures in the upper visceral mediastinum. Various surgical approaches have been documented in the management of symptomatic ones; it is however recommended that options that ensure revascularization of the affected limb be selected.</p>","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"164 1","pages":"183"},"PeriodicalIF":1.2,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10656587/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85978356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Mineral & whole–rock geochemistry of high-Al podiform chromitites in the Fizh Massif of the Cretaceous Oman ophiolite: Origin of hydrous, N–MORB melts in a nascent forearc setting 白垩纪阿曼蛇绿岩Fizh地块高铝脚状铬铁矿的矿物及全岩地球化学:新生弧前环境中含水N-MORB熔体的成因

IF 2.7 3区地球科学

Journal of the Geological Society Pub Date : 2023-08-23 DOI: 10.1144/jgs2023-047

Ronge Bo, Y. Dilek, S. Nasir, Weiwei Wu, Peng-Jie Cai, Yu-Xiao Lu, D. Lian, Jing S. Yang

{"title":"Mineral & whole–rock geochemistry of high-Al podiform chromitites in the Fizh Massif of the Cretaceous Oman ophiolite: Origin of hydrous, N–MORB melts in a nascent forearc setting","authors":"Ronge Bo, Y. Dilek, S. Nasir, Weiwei Wu, Peng-Jie Cai, Yu-Xiao Lu, D. Lian, Jing S. Yang","doi":"10.1144/jgs2023-047","DOIUrl":"https://doi.org/10.1144/jgs2023-047","url":null,"abstract":"The Oman ophiolite is one of the largest and best-exposed ophiolites in the world with >450 chromitite deposits. We report here a newly identified chromitite deposit in the Wadi Rajmi in Oman. This deposit occurs within a dunitic envelope, which is surrounded by harzburgite, and consists of massive and disseminated chromitite types. The Rajmi peridotites represent depleted upper mantle rocks, which underwent >20% of partial melting and which experienced metasomatism by melts and fluids derived from a subducting slab. They demonstrate geochemical affinities similar to those of the Izu-Bonin-Mariana forearc peridotites, supporting their formation in a forearc environment. The Rajmi chromitites have low Cr# values and are classified as high-Al type. They have geochemical compositions comparable to those of chromitites crystallized from mid-ocean ridge basalt (MORB)-type melts. However, the chromites in these high-Al chromitites contain various silicate inclusions (i.e. amphibole, mica), indicating a hydrous and atypical MORB nature of their parental magmas. Combined with the mineralogical and geochemical characteristics of the country rocks, we posit that the parental melts of the Rajmi high-Al chromitites had a MORB-like affinity, derived from partial melting of a nascent forearc mantle.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Ophiolites, melanges and blueschists collection available at:\u0000 https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6795689\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43015083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0