Age of Alpine Corsica ophiolites revisited: Insights from in situ zircon U-Pb age and O-Hf isotopes
Age of Alpine Corsica ophiolites revisited: Insights from in situ zircon U-Pb age and O-Hf isotopes
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重新审视科西嘉高山蛇绿岩的年龄：原位锆石 U-Pb 年龄和 O-Hf 同位素的见解
DOI：
10.1016/j.lithos.2015.02.006
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发表时间：
2015-04
期刊：
影响因子：
3.5
通讯作者：
Lahondere, Didier
中科院分区：
文献类型：
--
作者：
Faure, Michel;Rossi, Philippe;Lin, Wei;Lahondere, Didier
蛇绿岩序列的年龄和时间的知识是了解板块构造机制的必要条件。阿尔卑斯山科西嘉的Lustrés和上推覆体中的蛇绿岩代表了利古里亚-皮埃蒙特洋盆的残余，该洋盆是在中生代西阿尔卑斯特提斯开启期间形成的中大西洋海盆的分支。尽管有大量的同位素和古生物学研究，但Lustrés推覆体中蛇绿岩的年龄和时间仍然存在争议。本文对东科西嘉Lustrés推覆体中三个地点的蛇绿辉长岩和斜长花岗岩进行了锆石U-Pb年龄和O-Hf同位素的综合原位分析。我们的新结果表明，这些岩石在~ 159 Ma，约10百万年同步结晶。比巴拉格尼上推覆体中的蛇颈龙还要年轻辉长岩和斜长花岗岩中的锆石具有较高的εHf（t）正值（+ 15.0 ~+ 15.9）和类地幔δ 18 O值（5.2-5.4‰）。因此，这些蛇绿岩是同生的，并从亏损的N-MORB型地幔部分熔融产生的岩浆结晶。与此相反，在Balagne上推覆体中，~ 169 Ma蛇绿岩中含有大量继承自大陆地壳的捕虏晶锆石。我们目前的同位素年代学和地球化学知识支持古地理重建，其中Balagne推覆体中最早的蛇绿岩在约169 Ma时侵位在大陆边缘附近，而Lustrés推覆体中的N-MORB型蛇绿岩可能形成于约10百万年。后来在利古里亚-皮埃蒙特洋盆的中部。讨论了Lustrés和Balagne上推覆体相对于大陆边缘的相对位置。
Knowledge of the age and timing of ophiolite sequences is essential for understanding the mechanisms of plate tectonics. The ophiolites in the Schistes Lustrés and the Upper nappes of Alpine Corsica represent remnants of the Liguria-Piemonte ocean basin that formed as a branch of the Central Atlantic basin during the opening of the Mesozoic Western Alpine Tethys. Despite numerous isotopic and paleontological studies, the age and timing of the ophiolites in the Schistes Lustrés nappe are still controversial. This study presents integrated in situ analyses of zircon U-Pb age and O-Hf isotopic data for ophiolitic gabbros and plagiogranites from three localities in the Schistes Lustrés nappe of Eastern Corsica. Our new results demonstrate that these rocks crystallized synchronously at ~ 159 Ma, approximately 10 m.y. younger than the ophiolites in the Balagne Upper nappe. Zircons from the gabbros and plagiogranites are characterized by highly positive εHf(t) (+ 15.0 to + 15.9) and mantle-like δ18O (5.2-5.4‰) values. Thus, these ophiolitic rocks were cogenetic, and crystallized from magmas produced by partial melting of a depleted, N-MORB type mantle. By contrast, in the Balagne Upper nappe, the ~ 169 Ma ophiolites contain numerous xenocrystic zircons inherited from a continental crust. Our current knowledge of isotopic geochronology and geochemistry supports a paleogeographic reconstruction, in which the earliest ophiolites in the Balagne nappe were emplaced close to a continental margin at ~ 169 Ma, whilst the N-MORB type ophiolites in the Schistes Lustrés nappe were likely formed approximately 10 m.y. later in the central part of the Liguria-Piemonte oceanic basin. The relative location of the Schistes Lustrés and Balagne Upper nappes with respect to continental margins is discussed.
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影响因子：
3.5
作者：
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通讯作者：
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影响因子：
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影响因子：
2.3
作者：
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