More than 30 mafic dykes crop out in the Sergeevka belt in the coastal South Primorye, Far East Russia, of which geologic settings have been unclear for years. This study conducted major- and trace elements characterization, Sr–Nd isotope analyses, and Ar–Ar amphibole and U–Pb zircon datings for these rocks in order to identify their origin. The results demonstrated that all dykes are characterized by high Ba/Yb and low Nb/Y, Zr/Y, and Th/Yb ratios, which suggest their origin from arc melts derived from thin wedge mantle and shallow-dipping slab. These dykes are clearly separated into two distinct age/geochemistry suites; that is, the Paleogene and Early Cretaceous one with dolerites/basalts and adakitic rocks, and the Permian–Triassic one with high-Mg and high-Al gabbro-dolerite varieties. Their geochemistry suggests that the older suite was sourced from a primitive depleted MORB mantle (DMM)-type mantle, whereas the younger suite from an enriched mantle II (EM2)-type mantle domain. The transition in source type from DMM to EM2 occurred during the Jurassic-earliest Cretaceous time, probably by a strong influence of a mantle plume onto the long-continuing subduction-related magmatism. The plume influence reached the maximum when the unique meimechite-picrite complex formed in the region.

中文翻译：

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环日本域晚中生代活动边缘岩浆来源的重大变化：俄罗斯滨海南部谢尔盖夫卡带晚古生代至古近纪基性岩脉的地球化学约束

俄罗斯远东南滨海边疆区的 Sergeevka 带出现了 30 多座镁铁质岩脉，多年来一直不清楚其地质背景。本研究对这些岩石进行了主量和微量元素表征、Sr-Nd 同位素分析以及 Ar-Ar 闪石和 U-Pb 锆石测年，以确定它们的来源。结果表明，所有岩脉都具有高 Ba/Yb 和低 Nb/Y、Zr/Y 和 Th/Yb 比的特征，这表明它们起源于薄楔形地幔和浅倾板片的电弧熔体。这些岩脉清楚地分为两个不同的年龄/地球化学组；即，古近纪和早白垩世具有辉绿岩/玄武岩和埃达克岩的岩层，以及具有高镁和高铝辉长辉长岩品种的二叠纪-三叠纪岩层。他们的地球化学表明，较旧的套件来自原始的耗尽 MORB 地幔 (DMM) 型地幔，而年轻的套件来自富集地幔 II (EM2) 型地幔域。源类型从 DMM 到 EM2 的转变发生在侏罗纪 - 最早的白垩纪时期，可能是由于地幔柱对长期持续的俯冲相关岩浆作用的强烈影响。当该地区形成独特的 meimechite-picrite 复合体时，羽流影响达到最大。