Geological Magazine最新文献_第10页

Petrogenesis and geochemical characteristics of Plio-Quaternary alkali basalts from the Qorveh–Bijar volcanic belt, Kurdistan Province, NW Iran 伊朗库尔德斯坦省Qorveh-Bijar火山带上第三纪—第四纪碱性玄武岩的岩石成因及地球化学特征

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-17 DOI: 10.1017/S0016756823000018

N. Salehi, A. Torkian, T. Furman, P. L. le Roux

{"title":"Petrogenesis and geochemical characteristics of Plio-Quaternary alkali basalts from the Qorveh–Bijar volcanic belt, Kurdistan Province, NW Iran","authors":"N. Salehi, A. Torkian, T. Furman, P. L. le Roux","doi":"10.1017/S0016756823000018","DOIUrl":"https://doi.org/10.1017/S0016756823000018","url":null,"abstract":"Abstract The Pliocene–Quaternary volcanic rocks which outcrop between Qorveh and Bijar are part of post-collisional within-plate volcanic activity in northern Iran. These mafic alkaline rocks form part of the northern arm of the Sanandaj–Sirjan (Hamedan–Tabriz) zone. Thermobarometry on equilibrium clinopyroxene – whole-rock pairs yields pressures and temperatures of 4–6 (±1.8) kbar and 1182–1213 (±27) °C, respectively; olivine – whole-rock (melt) equilibrium thermometry yields crystallization temperatures of 1212–1264 (±27) °C. Field relationships, including the presence of pyroxenitic xenoliths, and geochemical evidence (e.g. high FeO/MnO, and low CaO compared to lavas derived from peridotite sources) suggest a pyroxenitic mantle source for the studied rocks. Variation of trace elements and isotopic ratios (i.e. Ce/Pb, Ba/La, 87Sr/86Sr) indicate that this pyroxenite mantle source was generated by interaction between melted sediments of the subducted Neo-Tethys slab with ambient peridotitic lithospheric mantle. The resulting metasomatized lithosphere is denser and has a lower viscosity than the peridotitic mantle, and tectonic disturbance can cause it to fall into the depths of the mantle. The descending volatile-rich material starts to melt with increasing temperature. Modelling of rare earth element (REE) abundances suggests that <1 % partial melting of the descending pyroxenite could create the Plio-Quaternary alkali basaltic magma of the Qorveh–Bijar. The geochemical evidence for lithospheric foundering, and hence drip magmatism, in the Qorveh–Bijar volcanic belt is supported by seismographic studies indicating thinned lithosphere beneath the study area.","PeriodicalId":12612,"journal":{"name":"Geological Magazine","volume":"160 1","pages":"888 - 904"},"PeriodicalIF":2.3,"publicationDate":"2023-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43366465","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

Mantle transition zone-derived eclogite xenolith entrained in a diamondiferous Mesoproterozoic (∼1.1 Ga) kimberlite from the Eastern Dharwar Craton, India: evidence from a coesite, K-omphacite, and majoritic garnet assemblage 印度东Dharwar克拉通中元古代(~ 1.1 Ga)含金刚石金伯利岩中地幔过渡带衍生的榴辉岩包体:来自铜辉岩、钾辉岩和多数石榴石组合的证据

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-15 DOI: 10.1017/S0016756822001315

A. Chatterjee, N. C. Chalapathi Rao, R. Pandey, Ashutosh Pandey

{"title":"Mantle transition zone-derived eclogite xenolith entrained in a diamondiferous Mesoproterozoic (∼1.1 Ga) kimberlite from the Eastern Dharwar Craton, India: evidence from a coesite, K-omphacite, and majoritic garnet assemblage","authors":"A. Chatterjee, N. C. Chalapathi Rao, R. Pandey, Ashutosh Pandey","doi":"10.1017/S0016756822001315","DOIUrl":"https://doi.org/10.1017/S0016756822001315","url":null,"abstract":"Abstract Subduction-related kimberlite-borne eclogite xenoliths of the Precambrian age may provide significant information about the evolution and recycling of a subducting crust as exhumed/orogenic eclogites of the pre-Mesoproterozoic time-frame are globally rare. In this paper, we report a kimberlite-borne eclogite xenolith from the diamondiferous Kalyandurg kimberlite cluster of the Eastern Dharwar Craton, India, which contains a plethora of ultra-high-pressure minerals such as coesite, majoritic garnet, and supersilicic K-rich omphacite. The presence of these ultra-high-pressure minerals is confirmed by in situ X-ray diffractometry, laser Raman spectra and electron probe microanalysis. The presence of coesite undisputedly pinpoints a subduction origin for the eclogite at ∼2.8 GPa pressure, which corresponds to ∼100 km depth. The geothermobarometric estimations involving garnet–omphacite–kyanite–coesite reveal that such an eclogitic assemblage equilibrated at ∼5–8 GPa (∼175–280 km) pressure during ultra-deep subduction. The textural relationship between omphacite, coarse-grained garnet and majoritic garnet coupled with the laser Raman spectra and geobarometric estimations obtained from the majoritic garnet demonstrate that the majoritic garnet formed at ∼8–19 GPa (∼280–660 km) owing to disassociation of omphacite and coarse-grained garnet to majoritic garnet during increment of pressure up to the mantle transition zone. Thus, the mineralogical and geothermobarometric data suggest that the studied eclogite possibly travelled down to the mantle transition zone before it was rapidly carried up by a pre-Mesoproterozoic mantle plume, and subsequently entrained as a xenolith by the Mesoproterozoic (∼1.1 Ga) kimberlite.","PeriodicalId":12612,"journal":{"name":"Geological Magazine","volume":"160 1","pages":"874 - 887"},"PeriodicalIF":2.3,"publicationDate":"2023-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43109172","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: 2

Gill grooming in middle Cambrian and Late Ordovician trilobites 中寒武世和晚奥陶世三叶虫的鳃理染

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-15 DOI: 10.1017/S001675682300002X

Jin-bo Hou, N. Hughes, M. Hopkins

引用次数: 1

Weak and intermittent anoxia during the mid-Tournaisian (Mississippian) anoxic event in the Montagne Noire, France 法国黑山地区中图尔纳期(密西西比期)缺氧事件期间的弱间歇缺氧

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-14 DOI: 10.1017/S0016756822001297

M. Rakociński, Daria Książak, Agnieszka Pisarzowska, M. Zatoń, M. Aretz

{"title":"Weak and intermittent anoxia during the mid-Tournaisian (Mississippian) anoxic event in the Montagne Noire, France","authors":"M. Rakociński, Daria Książak, Agnieszka Pisarzowska, M. Zatoń, M. Aretz","doi":"10.1017/S0016756822001297","DOIUrl":"https://doi.org/10.1017/S0016756822001297","url":null,"abstract":"Abstract The mid-Tournaisian black radiolarian cherts of the Lydiennes Formation are exposed in deep-shelf successions of the Puech de la Suque and Col des Tribes sections of the Mont Peyroux Nappe area in the Montagne Noire, southern France. This interval represents the mid-Tournaisian anoxic event that is also termed the Lower Alum Shale Event. This event is associated with a global marine transgression that was characterized by increased productivity and drastic facies changes from pelagic carbonate sedimentation to the widespread deposition of black organic-rich siliceous shales and radiolarites in many parts of the world. In the present study, high-resolution inorganic geochemistry and framboidal pyrite analyses were employed to decipher changes in depositional conditions during the mid-Tournaisian anoxic event in the Montagne Noire. The results show that the total organic carbon contents of sediments associated with the Lower Alum Shale Event vary from 0.09 to 1.9 wt %. These low to moderate total organic carbon contents, high U/Th, low Corg/P and intermediate V/Cr ratios, enrichment in redox-sensitive trace elements, such as U, Mo and V, as well as varying sizes of pyrite framboids, indicate periodic dysoxic to anoxic bottom-water conditions during deposition of the studied sediments. Anomalous Hg spikes (>500 ppb) are also reported in the mid-Tournaisian deep-water marine succession of the Montagne Noire in the present study, which confirm a possible influence of increased regional volcanic activity during this environmental turnover.","PeriodicalId":12612,"journal":{"name":"Geological Magazine","volume":"160 1","pages":"831 - 854"},"PeriodicalIF":2.3,"publicationDate":"2023-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41705398","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: 2

Hydroclimatic conditions and sediment provenance in the northeastern Arabian Sea since the late Miocene: insights from geochemical and environmental magnetic records at IODP Site U1457 of the Laxmi Basin 晚中新世以来阿拉伯海东北部水文气候条件和沉积物物源:Laxmi盆地IODP U1457点地球化学和环境磁记录的启示

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-10 DOI: 10.1017/S0016756822001273

Mahboob Alam, Tripti Muguli, G. P. Gurumurthy, M. Arif, Y. Sohrin, A. Singh, T. Radhakrishna, D. Pandey, Komal Verma

{"title":"Hydroclimatic conditions and sediment provenance in the northeastern Arabian Sea since the late Miocene: insights from geochemical and environmental magnetic records at IODP Site U1457 of the Laxmi Basin","authors":"Mahboob Alam, Tripti Muguli, G. P. Gurumurthy, M. Arif, Y. Sohrin, A. Singh, T. Radhakrishna, D. Pandey, Komal Verma","doi":"10.1017/S0016756822001273","DOIUrl":"https://doi.org/10.1017/S0016756822001273","url":null,"abstract":"Abstract Palaeo-monsoon and palaeoclimate conditions over Southeast Asia are a matter of debate despite notable studies on the continental and oceanic sedimentary record. The present study investigates the environmental magnetic and geochemical records preserved in the deep marine sediments of the northeastern (NE) Arabian Sea to elucidate the erosion history of the western Himalayas and its link with the prevailing hydroclimatic conditions since the late Miocene. For this, the sediment core retrieved during International Ocean Discovery Program (IODP) Expedition 355 at Site U1457 in the NE Arabian Sea has been explored. The results reveal that the hydroclimatic conditions were predominantly arid during the late Miocene, except for humid intervals from 6.1 Ma to 5.6 Ma. Humid climate conditions in the Indus River Basin returned during the mid-Pliocene and continued to the Pleistocene with an intense chemical weathering regime from 1.9 Ma to 1.2 Ma. The dominant sediment source to the NE Arabian Sea at Site U1457 during the late Miocene and the Pliocene was the Indus River, while during the Pleistocene, mixed sediments brought by the Indus River and the Peninsular Indian rivers were observed. The sediment contribution from a chemically less altered mafic source (the Deccan basalts) increased between 1.2 Ma and 0.2 Ma, possibly linked to a weak Indian Summer Monsoon. The summer monsoon wind strength and associated shift in the Inter-Tropical Convergence Zone (ITCZ) influenced the dominant sediment provenance at Site U1457 of the Laxmi Basin.","PeriodicalId":12612,"journal":{"name":"Geological Magazine","volume":"160 1","pages":"813 - 829"},"PeriodicalIF":2.3,"publicationDate":"2023-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46078224","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

Malformed individuals of the trilobite Estaingia bilobata from the Cambrian Emu Bay Shale and their palaeobiological implications 寒武纪鸸鹋湾页岩三叶虫的畸形个体及其古生物学意义

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-08 DOI: 10.1017/S0016756822001261

R. Bicknell, J. D. Holmes, D. García‐Bellido, J. Paterson

{"title":"Malformed individuals of the trilobite Estaingia bilobata from the Cambrian Emu Bay Shale and their palaeobiological implications","authors":"R. Bicknell, J. D. Holmes, D. García‐Bellido, J. Paterson","doi":"10.1017/S0016756822001261","DOIUrl":"https://doi.org/10.1017/S0016756822001261","url":null,"abstract":"Abstract Malformed trilobite specimens present important insight into understanding how this extinct arthropod group recovered from developmental or moulting malfunctions, pathologies, and injuries. Previously documented examples of malformed trilobite specimens are often considered in isolation, with few studies reporting on multiple malformations in the same species. Here we report malformed specimens of the ellipsocephaloid trilobite Estaingia bilobata from the Emu Bay Shale Konservat-Lagerstätte (Cambrian Series 2, Stage 4) on Kangaroo Island, South Australia. Ten malformed specimens exhibiting injuries, pathologies, and a range of teratologies are documented. Furthermore, five examples of mangled exoskeletons are presented, indicative of predation on E. bilobata. Considering the position of malformed and normal specimens of E. bilobata in bivariate space, we demonstrate that the majority of malformed specimens cluster among the larger individuals. Such specimens may exemplify larger forms successfully escaping predation attempts, but could equally represent individuals exhibiting old injuries that were made during earlier (smaller) growth stages that have healed through subsequent moulting events. The available evidence from the Emu Bay Shale suggests that this small, extremely abundant trilobite likely played an important role in the structure of the local ecosystem, occupying a low trophic level and being preyed upon by multiple durophagous arthropods. Furthermore, the scarcity of malformed E. bilobata specimens demonstrates how rarely injuries, developmental malfunctions, and pathological infestations occurred within the species.","PeriodicalId":12612,"journal":{"name":"Geological Magazine","volume":"160 1","pages":"803 - 812"},"PeriodicalIF":2.3,"publicationDate":"2023-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46127235","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: 3

The Ladinian–Carnian conodont fauna at Yize, Yunnan, southwestern China, with implications for conodont palaeoecology and palaeogeography 云南宜泽拉甸-卡尼期牙形刺动物群及其古生态学和古地理学意义

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-06 DOI: 10.1017/S0016756822001236

Zaitian Zhang, Yadong Sun

{"title":"The Ladinian–Carnian conodont fauna at Yize, Yunnan, southwestern China, with implications for conodont palaeoecology and palaeogeography","authors":"Zaitian Zhang, Yadong Sun","doi":"10.1017/S0016756822001236","DOIUrl":"https://doi.org/10.1017/S0016756822001236","url":null,"abstract":"Abstract Subdivisions of Ladinian–Carnian boundary beds and the lower Carnian strata in South China are challenging owing to a paucity of west Tethyan ammonoids. We investigated a conodont fauna in a continuous section at Yize in eastern Yunnan Province to provide a biostratigraphic solution. Five genera and 24 conodont species are recognized, and five conodont zones are established. The zones are, in ascending order, the Paragondolella inclinata Zone, the Quadralella polygnathiformis Zone, the Quadralella praelindae Zone, the Quadralella auriformis Zone and the Quadralella robusta Zone. The Ladinian–Carnian boundary is provisionally defined by the first occurrences of Quadralella polygnathiformis and Quadralella intermedia in the cherty limestone member of the Zhuganpo Formation. Regional correlations via conodont biostratigraphy indicate that the Zhuganpo Formation is probably diachronous, with a maximal range spanning the upper Ladinian to the lower Carnian. Amongst all common late Ladinian – early Carnian conodont genera, Paragondolella, Quadralella and Mazzaella are probably cosmopolitan. Budurovignathus was restricted to a few basins and probably preferred offshore or deep-water environments.","PeriodicalId":12612,"journal":{"name":"Geological Magazine","volume":"160 1","pages":"776 - 793"},"PeriodicalIF":2.3,"publicationDate":"2023-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45621185","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

Late Permian to early Triassic gabbro in North Lhasa, Tibet: evidence for plume - subduction-zone interaction of the Palaeo-Tethys ocean – RETRACTION 西藏拉萨北部晚二叠世至早三叠世辉长岩:古特提斯洋退缩的羽流-俯冲带相互作用证据

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-01 DOI: 10.1017/S0016756823000171

Meng-long Duan, Chao-Ming Xie, Bin Wang, Yuhang Song, Wen-qing Li, Y. Hao

引用次数: 0

GEO volume 160 issue 2 Cover and Front matter GEO第160卷第2期封面和封面

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-01 DOI: 10.1017/s0016756823000201

引用次数: 0

GEO volume 160 issue 2 Cover and Back matter GEO第160卷第2期封面和封底

IF 2.3 3区地球科学

Geological Magazine Pub Date : 2023-02-01 DOI: 10.1017/s0016756823000213

引用次数: 0