{"title":"北阿拉伯-努比亚盾(埃及南西奈)碰撞后的Ferani火山:岩石成因及其对埃迪卡拉纪(607-593 Ma)地球动力学演化的启示","authors":"Mabrouk Sami, M. Azer, A. Abdel-Karim","doi":"10.1086/724335","DOIUrl":null,"url":null,"abstract":"The Ediacaran (607–593 Ma) Ferani volcanic rocks are exposed in South Sinai, at the extreme northern tip of the Arabian-Nubian Shield (ANS). The studied volcanics constitute a cogenetic continuous intermediate (andesite to dacite) to acid (rhyodacite to rhyolite) lava sequence with a high-K calc-alkaline metaluminous to slightly peraluminous nature. They contain a high concentration of large-ion lithophile elements (i.e., Ba, Rb, Pb, and Th), but lower contents of Nb, P, Ti, and Sr. They also have a general enrichment in light rare earth elements ((La/Sm)N=2.66–4.92), compared to heavy rare earth elements ((Gd/Yb)N=1.10–2.29), with a slightly negative Eu anomaly (Eu/Eu*=0.35–0.94). The cooling of the Ferani magma began at ∼1000°–1100°C and went to ∼700°C at low pressure (<5.1 kbar) and shallow crustal levels (<17 km), according to thermobarometric modeling. The low degree of partial melting of the mafic lower-crustal rocks could have produced the andesitic-dacitic magmas that ascended through the crust and fractionated, leading to the production of the early intermediate Ferani lavas. Progressive fractional crystallization of the intermediate melts could consequently have formed the rhyodacite and rhyolite melts, which were later erupted to form the upper acidic Ferani volcanic sequence. Petrological and geochemical features support a postcollisional setting of the Ferani volcanics. Lithospheric delamination is the main geodynamic process responsible for the formation of the Ferani volcanics during the postcollisional extensional stage in the northern ANS crust.","PeriodicalId":54826,"journal":{"name":"Journal of Geology","volume":null,"pages":null},"PeriodicalIF":1.5000,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"7","resultStr":"{\"title\":\"Postcollisional Ferani Volcanics from North Arabian–Nubian Shield (South Sinai, Egypt): Petrogenesis and Implication for Ediacaran (607–593 Ma) Geodynamic Evolution\",\"authors\":\"Mabrouk Sami, M. Azer, A. Abdel-Karim\",\"doi\":\"10.1086/724335\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The Ediacaran (607–593 Ma) Ferani volcanic rocks are exposed in South Sinai, at the extreme northern tip of the Arabian-Nubian Shield (ANS). The studied volcanics constitute a cogenetic continuous intermediate (andesite to dacite) to acid (rhyodacite to rhyolite) lava sequence with a high-K calc-alkaline metaluminous to slightly peraluminous nature. They contain a high concentration of large-ion lithophile elements (i.e., Ba, Rb, Pb, and Th), but lower contents of Nb, P, Ti, and Sr. They also have a general enrichment in light rare earth elements ((La/Sm)N=2.66–4.92), compared to heavy rare earth elements ((Gd/Yb)N=1.10–2.29), with a slightly negative Eu anomaly (Eu/Eu*=0.35–0.94). The cooling of the Ferani magma began at ∼1000°–1100°C and went to ∼700°C at low pressure (<5.1 kbar) and shallow crustal levels (<17 km), according to thermobarometric modeling. The low degree of partial melting of the mafic lower-crustal rocks could have produced the andesitic-dacitic magmas that ascended through the crust and fractionated, leading to the production of the early intermediate Ferani lavas. Progressive fractional crystallization of the intermediate melts could consequently have formed the rhyodacite and rhyolite melts, which were later erupted to form the upper acidic Ferani volcanic sequence. Petrological and geochemical features support a postcollisional setting of the Ferani volcanics. Lithospheric delamination is the main geodynamic process responsible for the formation of the Ferani volcanics during the postcollisional extensional stage in the northern ANS crust.\",\"PeriodicalId\":54826,\"journal\":{\"name\":\"Journal of Geology\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.5000,\"publicationDate\":\"2022-11-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"7\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Geology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1086/724335\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1086/724335","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOLOGY","Score":null,"Total":0}
Postcollisional Ferani Volcanics from North Arabian–Nubian Shield (South Sinai, Egypt): Petrogenesis and Implication for Ediacaran (607–593 Ma) Geodynamic Evolution
The Ediacaran (607–593 Ma) Ferani volcanic rocks are exposed in South Sinai, at the extreme northern tip of the Arabian-Nubian Shield (ANS). The studied volcanics constitute a cogenetic continuous intermediate (andesite to dacite) to acid (rhyodacite to rhyolite) lava sequence with a high-K calc-alkaline metaluminous to slightly peraluminous nature. They contain a high concentration of large-ion lithophile elements (i.e., Ba, Rb, Pb, and Th), but lower contents of Nb, P, Ti, and Sr. They also have a general enrichment in light rare earth elements ((La/Sm)N=2.66–4.92), compared to heavy rare earth elements ((Gd/Yb)N=1.10–2.29), with a slightly negative Eu anomaly (Eu/Eu*=0.35–0.94). The cooling of the Ferani magma began at ∼1000°–1100°C and went to ∼700°C at low pressure (<5.1 kbar) and shallow crustal levels (<17 km), according to thermobarometric modeling. The low degree of partial melting of the mafic lower-crustal rocks could have produced the andesitic-dacitic magmas that ascended through the crust and fractionated, leading to the production of the early intermediate Ferani lavas. Progressive fractional crystallization of the intermediate melts could consequently have formed the rhyodacite and rhyolite melts, which were later erupted to form the upper acidic Ferani volcanic sequence. Petrological and geochemical features support a postcollisional setting of the Ferani volcanics. Lithospheric delamination is the main geodynamic process responsible for the formation of the Ferani volcanics during the postcollisional extensional stage in the northern ANS crust.
期刊介绍:
One of the oldest journals in geology, The Journal of Geology has since 1893 promoted the systematic philosophical and fundamental study of geology.
The Journal publishes original research across a broad range of subfields in geology, including geophysics, geochemistry, sedimentology, geomorphology, petrology, plate tectonics, volcanology, structural geology, mineralogy, and planetary sciences. Many of its articles have wide appeal for geologists, present research of topical relevance, and offer new geological insights through the application of innovative approaches and methods.