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首页> 外文期刊>Journal of geodynamics >Volcanism on the Eggvin Bank (Central Norwegian-Greenland Sea, latitude ～71°N): age, source, and relationship to the Iceland and putative Jan Mayen plumes
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Volcanism on the Eggvin Bank (Central Norwegian-Greenland Sea, latitude ～71°N): age, source, and relationship to the Iceland and putative Jan Mayen plumes

机译：埃格文河岸（挪威中部格陵兰海，北纬〜71°N）的火山活动：年龄，来源，与冰岛的关系以及推测的扬·马延羽状流

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摘要

The Eggvin Bank (Central Norwegian-Greenland Sea, latitude ～71°N) is a topographically anomalous shallow area with scattered volcanic peaks extending between the island of Jan Mayen and East Greenland and straddling the northern segment of the mid-Atlantic Kolbeinsey Ridge axis. Basalts dredged from the Eggvin Bank range from variably depleted, tholeiitic, near-axis lavas to enriched, transitional-to-alkaline, off-axis seamount lavas. In terms of normalised incompatible element patterns, the most depleted, near-axis tholeiite is similar to neighbouring Kolbeinsey Ridge basalts, whereas the off-axis, transitional-to-alkaline lavas are similar to other alkaline basalts occurring close to the Eggvin Bank region, e.g., those of Jan Mayen. ~(40)Ar/~(39)Ar step heating data indicate that the off-axis seamount lavas are coeval with other alkaline lavas erupted in the Central Norwegian-Greeland Sea at ca. 0.6-0.7 Ma. In contrast, the Eggvin near-axis tholeiites are <0.1 Ma. Volcanic peaks west and north of Jan Mayen show no indication of a systematic age progression. Therefore, the Jan Mayen hot spot hypothesis is not supported by the available radiometric age data. Sr, Nd, and Pb isotope compositions of near-axis and off-axis Eggvin Bank lavas are distinct, implying differences in their mantle sources. Isotope ratios of the off-axis basalts (~(87)Sr/~(86)Sr = 0.70344-0.70352, ~(143)Nd/~(144)Nd = 0.51283-0.51288, ~(206)Pb/~(204)Pb = 18.82-18.85) resemble those of neighbouring alkali basalt occurrences, however, isotope ratios of the near-axis tholeiites correspond to lavas erupting in the south-eastern volcanic zone of Iceland, e.g., at Vestmannaeyjar. The near-axis tholeiites are generated by an unusual source with highly radiogenic Pb (~(206)Pb/~(204)Pb = 18.95) together with relatively radiogenic Nd (~(143)Nd/~(144)Nd = 0.51295) and low-radiogenic Sr (~(87)Sr/~(86)Sr = 0.70314), respectively, representing an unique composition in the mantle north of central Iceland. The overlap in isotope compositions between Eggvin Bank near-axis tholeiites and south-east Iceland alkaline lavas could be an indication that the Eggvin Bank tholeiite source was derived from the Iceland plume and that it was emplaced in the upper mantle by the original Iceland plume head during the Early Tertiary as suggested by Tronnes et al. [Tronnes, T., Planke, S., Sundvoll, B., Imsland, P., 1999. Recent volcanic rocks from Jan Mayen: low degree melt fractions of enriched north-east Atlantic mantle. J. Geophys. Res. 104, 7153-7167]. Isotope and trace element data indicate an abrupt change in source composition along the Kolbeinsey Ridge axis at latitude ca. 70.6°N, apparently reflecting a boundary between two chemically distinct mantle domains with limited interaction. Based on Pb versus Pb isotope diagrams, no dispersion of enriched material is observed adjacent to the hypothetical Jan Mayen/Jan Mayen Platform plume, neither to the north-east along the Southern Mohns Ridge nor to the south along the Central Kolbeinsey Ridge.
机译：Eggvin银行（挪威中部格陵兰海，北纬〜71°N）是一个地形异常的浅层区域，在Jan Mayen岛和East Greenland岛之间延伸并横跨大西洋中部Kolbeinsey Ridge轴线的北部，散布着火山峰。从埃格文河岸挖出的玄武岩范围从贫乏的，变质的，近轴的熔岩到富集的，过渡到碱性的离轴海山熔岩。就归一化的不相容元素模式而言，最耗竭的近轴黄铁矿类似于邻近的Kolbeinsey Ridge玄武岩，而离轴过渡至碱性熔岩类似于发生在Eggvin Bank地区附近的其他碱性玄武岩，例如Jan Mayen的那些。 〜（40）Ar /〜（39）Ar阶跃加热数据表明，离轴海山熔岩与挪威中部-格陵兰中部约200摄氏度爆发的其他碱性熔岩同时期。 0.6-0.7毫安。相比之下，Eggvin近轴冲孔石的硬度小于0.1 Ma。 Jan Mayen西部和北部的火山峰没有显示出系统的年龄发展迹象。因此，可用的辐射年龄数据不支持Jan Mayen热点假设。 Eggvin Bank熔岩的近轴和偏轴的Sr，Nd和Pb同位素组成是不同的，这意味着它们的地幔来源也不同。离轴玄武岩的同位素比（〜（87）Sr /〜（86）Sr = 0.70344-0.70352，〜（143）Nd /〜（144）Nd = 0.51283-0.51288，〜（206）Pb /〜（204 ）（Pb = 18.82-18.85）与邻近的碱性玄武岩出现相似，但是，近轴冲长岩的同位素比率对应于冰岛东南部火山区（例如在Vestmannaeyjar）喷出的熔岩。近轴黄铁矿是由具有高放射原性Pb（〜（206）Pb /〜（204）Pb = 18.95）和相对放射原性Nd（〜（143）Nd /〜（144）Nd = 0.51295）的不寻常来源产生的和低放射性Sr（〜（87）Sr /〜（86）Sr = 0.70314）分别代表了冰岛中部北部地幔的独特组成。 Eggvin Bank近轴冲孔岩和冰岛东南部碱性熔岩之间的同位素组成重叠可能表明Eggvin Bank冲孔岩来源是来自冰岛羽状流，并且被原始的冰岛羽状流头安置在上地幔中如Tronnes等人所述，在第三纪初期。 [Tronnes，T.，Planke，S.，Sundvoll，B.，Imsland，P.，1999。JanMayen最近的火山岩：富集的东北大西洋地幔的低度熔融组分。 J.地球物理。 Res。 104，7153-7167]。同位素和痕量元素数据表明，沿纬度ca沿Kolbeinsey Ridge轴的源组成突然变化。 70.6°N，显然反映了相互作用有限的两个化学性质不同的地幔区域之间的边界。根据Pb与Pb同位素图，在假设的Jan Mayen / Jan Mayen平台羽流附近，无论是沿南部Mohns岭的东北方向，还是沿中部Kolbeinsey脊的南部均未观察到富集物质的分散。

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